FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
A process for recovering liquid bromine from industrial waste
Hardik Anilsinh Jadeja, 1727/A, "Swapnil’’, Shiv park, Kalyabid, Bhavnagar-364002, Gujarat, India
Prashant Navinchandra Bhatt, 2236/6, green park, Hill drive, Bhavnagar-364002, Gujarat, India
Upendra Harishbhai Pandya, 1528/H, theosophicai society, Near Rupani Cereal, Bhavnagar-364001, Gujarat, India
Yashodhar Navnitrai Bhatt, 22, Nalanda tenement, Hill drive, Bhavnagar-364002, Gujarat, India
The following specification particularly describes the invention and the manner in which it is to be performed.

BACKGROUND OF INVENTION
The present invention relates to a process for recovering liquid bromine from industrial waste.
The primary use of elemental bromine is in the manufacture of bromine compounds that have chemical and biological activity, high density or fire retarding and extinguishing properties. Bromine products are well represented in such use areas as gasoline additives, flame retardants, agricultural chemicals, drilling fluids, photographic chemicals, sanitizers, dyes, pharmaceuticals, water disinfection, desizing of cotton, bleaching of pulp and paper, air conditioning absorption fluids, hair waving compositions and others.
It is understood that when bromine is being reacted, half of the bromine molecule takes part in the main reaction and the other half normally passes out as hydrobromic acid gas. This acidic gas in turn is being absorbed in an alkali to form alkali bromide having some lower boiling impurities of the main reaction. In other words only 50% of the bromine fed to the reaction is utilized in the reaction and the rest 50% goes out as effluent stream, normally referred by the bromine consumer as a by product These typical reaction patterns disturb the bromine economics on a greater extent and make the bromine compounds more costly in the global market.
In view to over come this hurdle one needs to brain storm and come out with a cyclic utilization partem wherein the bromine passed out in an effluent stream is recovered and recycled.
In principle, bromine is manufactured from sea bittern / water by acidifying followed by treatment with chlorine.
Basic Reaction
2 X - Br + Cl2 → 2 X - C1 + Br2
Where, X = Alkali metal
Several industrial processes for recovering bromine, including the well-known Kubierschky's and Dow process have been proposed and widely used for commercial
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practice. Techniques for recovering bromine from various wastes liquid also have been known, since long.
US Patent No. 3379506 has disclosed a method for recovering liquid bromine from gas mixtures obtained from the bromination of fluorohydrocarbons wherein the hydrogen of the fluorohydrocarbons is substantially substituted by bromine with formation of hydrogen bromide. Brominated gas mixture together with oxygen at a temperature of 250 to 500 ° C was passed over a Deacon catalyst comprising a porous support like alumina, silica gel, clay etc impregnated with solution of bromides or chlorides of metals viz. Cu, Fe, Ti, Va, Cr, Mn etc. In this process, pure oxygen was used in an excess of 5 to 20% over the stoichiometric amount thereby oxidizing selectively HBr to Br2. The Deacon catalyst used was initially dried at 120 ° C and then activated by heating at 450 ° C. The drawback of the process is that the catalyst is to be initially heated and activated prior to it use and for the oxidation to happen with higher selectively needs higher temperature and excess amount of pure oxygen over stoichiometric amount.
US Patent No. 3705010 has disclosed a process for the recovery of bromine and hydrogen bromide from organic bromides such as ethylene dibromide, which comprises reacting an organic bromide with oxygen at a temperature within the range of 200 to 1200 ° C in the presence of metal oxide catalysts like Cr203, A1203, V203, V205, Mo3Og, M02O5, M0O2, W02, W205, CeO2 or U3O8 wherein the molar ratio of 02/organic bromide is within the rang of from 2/1 to 10/1. The residence time, wherein the reactants remain in the heated zone, is in the range of 0.1 to 30 seconds and will very inversely with reaction temperature. The drawback of the process is that the reaction is feasible only at very high temperature. Moreover the residence time in very critical and difficult to maintain. Higher time will induce formation of organic tars in the reaction zone.
US Patent No. 3875293 has disclosed a process for the recovery of bromine as hydrogen bromide which comprises reacting an aliphatic bromide up to 6 carbon atoms or an aromatic bromide containing 9 carbon atoms with hydrogen gas at a temperature within the range 300 to 600 ° C in the presence of catalyst such as one or more of the oxides of chromium, vanadium, tungsten, cerium, molybdenum or aluminium. For almost complete conversion of bromide to HBr, an excess of
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hydrogen about 0.55 mole hydrogen per mole of bromine in organic bromide has to be used. By process HBr can be separated from the reaction product The drawback of the process is that it involves high temperature whereby the formation of carbon particles increases making frequent regeneration of catalyst necessary. Regeneration of catalyst is done at high temperature, which makes the process cost sensitive.
US Patent No. 4105753 has disclosed a process for the preparation of bromine and/or HBr from ammonium bromide, wherein vaporised ammonium bromide is reacted with molecular oxygen in presence of an inorganic oxidation catalyst containing at least one element selected from the group consisting of copper, vanadium, chromium, molybdenum, uranium, manganese, iron, cobalt and rare earth elements and mixtures thereof, at about ambient pressure and a temperature of from 200 to 800 ° C and a reaction time of more than 0.1 second to produce a reaction gas product consisting of bromine, nitrogen and H2O and recovering the bromine from gaseous reaction product. The drawback of the process is that the catalytic conversion takes place at high temperature.
US Patent NO. 3961033 has disclosed a process for preparing liquid bromine by reacting chlorine gas with ethylene dibromide in the presence of an aluminium halide catalyst like aluminium chloride, aluminium bromide and aluminium chlorobromides under anhydrous condition. In this process, for the isolation of product from the reaction mixture, first aluminium containing material was removed from reaction mixture by washing with water, resulting washed fraction was dried by sulfuric acid, layers of reaction mixture and sulfuric acid was separated by gravity and finally bromine and ethylene dichloride was distilled out from the dried reaction mixture. The drawbacks of the process are that the reaction of chlorine gas with ethylene dibromide in the presence of an aluminium halide catalyst is exothermic which requires cooling to keep the reaction within the desirable temperature and during distillation, decomposition of organic product occurs in the presence of aluminium halide catalyst. More unit operations involve which make the process cost sensitive.
US Patent NO. 4044113 has disclosed a process for preparing liquid bromine by reacting chlorine gas with ethylene dibromide in the presence of an anhydrous catalytic viz. iron halide selected from ferric chloride, ferric bromide and ferric chlorobromides at a temperature maintained in the range of 35 to 50 ° C. In this
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process 0.5 to 0.6 moles of chlorine is added per mole of ethylene dibromide for a period of from one-half to 3 hours. The catalyst weight percent varies in the range of 0.6 to 2.0 weight percent based on the weight of ethylene dibromide. The drawbacks of the process are that the reaction is to be carried out in almost anhydrous conditions. More than 0.1% water has deleterious effect on bromine recovery. Beside, the addition of chlorine gas is to be critically controlled as the reaction is exothermic and precautions are to be taken to maintain a low temperature.
US Patent No. 3437444 has disclosed a process wherein the hot saline brine having bromide, calcium, magnesium and sulphate is sprayed from the top of the reactor column, concurrently HC1 and HNO3 are discharged simultaneously in the molar ratio of 1: 3. At the same time steam is countercurrently introduced from the bottom of the reactor which expels the resulting nitrosyl tribromide into the fractionation column where it is decomposed thermally. The liquid bromine along with residual water is heated to give bromine and the nitrogen oxide is converted to HNO3 and recycled. The drawbacks of the process are that the rate of saline brine, hydrochloric and nitric acid are to be maintained critically, and slight variation may affect the yield of bromine. The decomposition of nitrosyl tribromide is done at high temperature and this makes the process uneconomical.
US Patent No. 4029732 has disclosed a method for preparing bromine by reacting 0.1 to 1 mole of hydrogen peroxide with 1 mole of bromide ions of aqueous solution like bromo sulfuric acid solution, vaporising and removing the bromine produced from the aqueous medium substantially as rapidly as it produced to prevent the bromine from reacting with the hydrogen peroxide. The drawback of the process is that adequate arrangement be made to effect the separation of bromine produced as rapidly as it is formed, thereby preventing the bromine to come in contact with more hydrogen peroxide. This type of equipment/ arrangement makes the process complex.
US Patent No. 4131626 has disclosed a process for producing bromine wherein the alkali and alkaline earth metal bromide salts are heated with oxidation catalysts selected from the group of B203, CaO, Fe2O3, AI2O3, Na2B407, ZnO, MgO, Mn02, Ti02, NaNC2, Si02 etc and passing oxygen containing gas at a temperature in the range 500 to 1000 ° C. In this process a siliceous by-product is obtained. Here, the oxidation reaction at high temperature is followed by volatilization of molten bromide
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salt and sintering of mixture, both trends to lower the yield of bromine. The drawbacks of the process are that, the catalytic oxidation of bromide salts takes place at very high temperature. Moreover due to insitu volatilization and sintering process the yield of bromine is reduced.
US Patent No. 3959450 has disclosed a method for producing liquid bromine. In the process, an aqueous mother liquor containing hydrogen bromide in contiontration range of 0.12 to 0.15 kilograms/litre is acidified with an acid like hydrochloric acid or sulfuric acid followed by pre-chlorination with about 80 to about 90 % of the amount of chlorine stoichiometrically equivalent to the bromide present in mother liquor in pre-chlorinator whereby, 20% bromine of the total yield is separated by passing through primary and secondary gravity separator. The resulting mother liquor containing unreacted hydrogen bromide and chlorine and dissolve bromine is reacted with remaining 10 to 20% chlorine at 100 ° C by passing steam into steaming-out tower to distil out crude bromine which is further purified. The drawbacks of the process are that more number of unit operations makes the process complex. Moreover the process requires special design of the equipment which are resistant to liquid bromine and aqueous hydrobromic acid.
US Patent No. 4124693 has disclosed a process for recovery, manipulation and storage of bromine. In the process, sea water is acidified with an acid such as hydrobromic or hydrochloric acid (pH 3 to 4) and reacted with molecular chlorine to produce molecular bromine which is absorbed in an aqueous absorbing solution of certain asymmetrical quaternary ammonium halide at temperature range of 10 to 20 ° C whereby a liquid, water immiscible bromine complex is formed that can be stored, manipulated and readily handled. In this process the condensation of the bromine by the absorbing solution is an exothermic reaction and it is quite essential to maintain the temperature between 15 to 25 ° C by same external cooling. The drawbacks of the process are that it requires large volume of steam or air to separate bromine from sea water and the absorption of bromine vapour in an aqueous absorbing solution is exothermic which requires cooling to keep the reaction within the desirable temperature range of 10 to 20 ° C.
US Patent No. 4125595 has disclosed a process for the production of liquid bromine. In the process, salt solution containing 5.3 gm/lit of bromine is preheated at 94 ° C
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and injected into a bromine column having a re-boiler which have a liquid zone and gaseous zone wherein chlorine and steam is introduced and reacted with the salt solution counter currently to form crude bromine which is purified by primary and secondary distillation. The drawbacks of the process are that it imbibes multisteps which make the process complex and difficult to control at each stage. Moreover for the recovery of purified bromine from the mixture it required to undergo several distillation steps which make the process uneconomical.
US Patent No. 4317919 has disclosed a process for the oxidation of substituted aromatic compounds to an aromatic carboxylic acid by means of molecular oxygen using a lower aliphatic mono carboxylic acid as solvent and in the presence of a catalyst viz. heavy metal compounds, bromine or bromine containing compound, a Pd or Pt mounted on zeolite, silica, alumina etc. at a temperature in the range of 80 to 270 ° C and a pressure in the range of 1 to 50 bar. The drawback of the process is that oxidation of aromatic compounds is carried out at high temperature and pressure. This makes the process uneconomical.
US Patent No. 4356159 discloses a method of recovering bromine from methyl bromide. In this process, in the first stage a substituted aromatic compound is oxidised to a carboxylic acid in the presence of catalyst containing a source of bromine, to form methyl bromide in a gas stream. This effluent gas stream containing HBr is contacted with a platinum catalyst presence of oxygen at a temperature in the range of 200 to 800 ° C. This converts methyl bromide to elemental bromine, hydrogen bromide of mixtures thereof. The drawback of the process is that it involves the oxidation of methyl bromide at high temperature and moderate pressure. This will in turn make the method uneconomical.
US Patent No. 4324665 has disclosed a process for the recovering bromine from a waste liquid obtained in the production of anilines by ammonolysis of nuclear substituted bromobenzenes with at least one halogen atom. The waste liquid is made alkaline (pH>10) and then chlorine gas passed until the oxidation-reduction potential of liquid is 100 mv. This precipitates the aniline derivatives which are removed by filtration. The alkaline filtrate is subjected to distillation to remove trace of ammonia and aniline derivatives. The filtrate having pH <3 is allowed to flow down through a vertical tower and chlorine gas and steam are countercurrently introduced from the
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bottom to distil out bromine. The drawback of the process is that it multi-steps are involved till the final recovery of liquid bromine. Besides the process involves chlorination initially in alkaline medium and finally in acidic medium. At this stage it is cumbersome to critically control the milli volt (mv) at each stage.
US Patent No. 5385650 has disclosed a process for the recovery of bromine from an acidic solution containing bromide ions. In this process an electric current is passed through the solution between an anode and a cathode in a dilute electrolytic cell that contains a cation exchange membrane kept between the anode and a cathode. Thereby bromine is generated at the anode to produce an anolyte product containing bromine and hydrogen is generated at cathode. Bromine is separated from the anolyte product under negative pressure. The drawback of the process is that the process involves electrochemical oxidation which requires more energy and the process becomes uneconomical. Beside, it is essential to add acid and maintained the pH between 2 to 6 in order to prevent formation of bromate in the electrolyzate.
Great Britain Patent No. 1546768 has disclosed a process for the recovery of bromine from a gaseous iron bromide produced by the bromination of iron containing titaniferous ore. In this process gaseous ion bromide is oxidised with oxygen at a temperature range of 750 to 1100 ° C to prevent condensation of iron bromide to produce particles of iron oxide and bromine gas. The drawback of the process is that it involves oxidation of gaseous iron bromide to generate bromine at very high temperature.
WO Patent No. 1993/06038 has disclosed a process for producing bromine from sea water. In this process, seawater is acidified with sulfuric acid and reacted with chlorine gas to produce bromine which is separated from acidified seawater by blowing air and reacted with SO2 in presence of water to form an acid stream comprising HBr and H2SO4. Resulting HBr is oxidised with O2 containing gas at 125 to 500 ° C in a molar ratio of HBr: 02 between about 3.25 and 4.1 in the presence of a catalyst like copper bromide, lanthanum oxide, lanthanum bromide, lanthanum oxybromide or mixture thereof and zircorria catalyst to produce bromine. The drawback of the process is that it involves catalytic oxidation of hydrogen bromide with O2- containing gas at high temperature. More number of process steps makes the process complex.
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WO Patent No. 1993/06039 has disclosed process for producing bromine from inorganic bromide salt. In this process, inorganic bromide salt is acidified with a strong acid, preferably sulphuric acid, to produce a gaseous HBr stream. The HBr stream is then mixed with 02- containing gas and passed to an oxidation reactor where it is catalytically oxidized at 230-250 ° C to produce bromine and water The hot effluent is quenched and liquid bromine is separated from water. The recovered bromine is contacted with H2SO4 acid to remove the water/ moisture content. The drawback of the process is that, the catalytic oxidation of hydrogen bromide is carried out at higher temperature. Beside, liquid bromine needs drying to remove water/moisture content.
WO Patent No. 1996/00696 and European patent No. 715601 has disclosed a method for recovering bromine from a liquid effluent by high-temperature pressurised combustion of the liquid effluent in a combustion chamber, maturation of the flue gases at medium temperature in a chamber, hetero-azeotropic distillation of the gases in a distillation column such that the gaseous water/bromine mixture produced by distillation is condensed and separation of the bromine in a settling tank by demixing the water and bromine at a temperature of around 5 ° C, the resulting liquid bromine being distilled again in a column and purified to 99.9%. The drawback of the process is that it involves combustion of liquid effluent at high temperature and pressure.
Japanese Patent No. 13%09427 has disclosed a process for recovering bromine in a high yield from a printed substrate as a part of recycle by leaching an incinerated ash dust containing 1-15 % bromine with a water or an alkali such as sodium hydroxide or potassium hydroxide or an acid such as sulfuric acid, neutralizing the leached liquid and filtering the neutralized liquid. Bromine is obtained by blowing. The drawback of the process is that it involves absorption of volatilized bromine.
Japanese Patent No. 2002030003 has disclosed a method for recovering bromine from an organic bromine compound by subjecting the organic bromine compound to a mechano-chemical treatment in the presence of an alkali metal hydroxide. The drawback of the process is that it involves mechano-chemical treatment of organic bromine compound.
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Japanese Patent No. 57129804 has disclosed a process for recovering bromine from brine containing 1-15 gm/lit free bromine by treating the brine with a strongly basic anion exchange resin at 10 to 40 ° C to allow the bromine to be absorbed on the resin and treating the resin with 1/5-5 times as much water as the resin by volume and contacting with steam at 60 to 130 ° C to recover liquid bromine by desorption. The drawback of the process is that it involves absorption of volatilized bromine on the resin.
Japanese Patent No. 58167403 has disclosed a process for the preparation of bromine from aqueous solution containing bromine by blowing air or inert gas at 50-300Nm<3>/m<3>H flow rate through an acidic aqueous solution of bromine containing chlorine of specific pH to 4 or below to generate bromine gas which is recovered by absorption method with an alkali, sulphurous acid gas etc. The drawback of the process is that it involves absorption of bromine gas with an alkali, sulphurous acid gas etc.
Japanese Patent No. 54120292 has disclosed a process for recovering bromine from aqueous solution containing bromine compound such as salt of NH3 or NH4 by treating an aqueous solution containing bromine compound with NaOH at above 60 ° C and at pH 11-13 to remove ammonia, blowing chlorine gas into resulting aqueous solution to remove a trace amount of ammonia and treating ammonia free aqueous solution again with chlorine and steam to recover bromine. The drawbacks of the process are that it involves decomposition of salt of ammonia and removal of ammonia from the aqueous solution.
Japanese Patent No. 58041703 has disclosed a process for the recovery of bromine from sea water by treating acidic sea water with chlorine to form free bromine solution, contacting this solution with an aqueous solution of an alkali hydroxide through a hydrophobic high polymer film such as a polyolefin film and absorbing bromine in the alkali solution. The drawback of the process is that it involves absorption of volatilized bromine on a hydrophobic high polymer film.
Japanese Patent No. 62265102 has disclosed a process to obtain bromine withought using chlorine from aqueous solution containing bromine by passing the ozone gas through aqueous solution containing bromine at pH 4 or less and blowing air or inert
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gas into the aqueous solution to liberate bromine. The drawback of the process is that it involves ozone gas as an oxidizing agent which makes the process expensive.
Japanese Patent No. 4170302 has disclosed a process for recovering bromine from aqueous solution containing bromine by passing an aqueous solution containing bromine at pH 4 or less with air and chlorine through liquid dispersion plate of the packed tower, contacting air and aqueous solution containing bromine with the wetted shelf having 20-50 mm H2O pressure drop in the lower part of the packed tower to extract bromine. The drawback of the process is that it involves absorption of volatilized bromine on dispersion plate of the packed tower.
Japanese Patent No. 55109201 has disclosed a process for recovering bromine from a gas containing bromine in lower contiontration by contacting gas with a porous, strongly basic anion exchange resin like quarternary ammonium anion resin at 40 ° C to adsorb bromine on the resin, heating the resin containing bromine at 60 to 130 ° C by direct contact with steam to disorbe bromine. The drawback of the process is that it involves absorption of volatilized bromine on a strongly basic anion exchange resin and desorption of bromine.
Japanese Patent No. 56059603 has disclosed a process for recovering bromine from a free bromine solution containing 1-15 gm/lit free bromine by contacting free bromine solution with a strongly basic anion exchange resin at 10 to 40 ° C to adsorb bromine on the resin, contacting resin with steam at 60-130 ° C to allow the bromine to be desorbed. The drawback of the process is that it involves absorption of volatilized bromine on a strongly basic anion exchange resin and desorption of bromine.
OBJECTIVE OF THE INVENTION
The main object of the present invention is to provide a process for recovering liquid bromine from industrial waste containing quaternary ammonium salt which obviates the drawbacks as detailed above.
Another object of the present invention is to provide an industrially advantageous process for recovering bromine from an industrial waste to reduce pollution in the environment.
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Still another object of the present invention is to evaporate the liquid effluent by solar evaporation in solar ponds to separate undesired impurities present in liquid effluent in most economical way.
Yet another object of the present invention is to treat the liquid effluent with alkali such as hydroxides and carbonates of alkali metals or lime.
Yet another object of the present invention is to oxidize the acidic effluent with chlorine gas and steam in a column reactor.
Yet another object of the present invention is to eliminate/solve the problem of the industrial waste containing bromide salt.
Yet another object of the present invention is to recycle the excess of the chlorine gas used for oxidation.
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DESCRIPTION OF THE DRAWING
In the drawing accompanying this specification
Figure A represents the liquid effluent.
Figure B represents the alkali such as hydroxides and carbonates of alkali metals or
lime.
Figure C represents the chlorine gas.
Figure D represents the steam.
Figure E represents preheated acidic effluent.
Figure F represents effluent coming out from the bottom of the column after
debromination.
Figure G represents pure bromine coming out from the striping tower and product
cooler after removal of impurity of chlorine.
Figure H represents mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or
similar spent acid.
Figure 1 represents the reactor in which liquid effluent is treated with alkali.
Figure 2 represents the reactor in which alkaline liquid effluent is neutralized by
mineral acid.
Figure 3 represents the pre-heater.
Figure 4 represents the vertically long gas-liquid contact chamber.
Figure 5 represents the primary condenser.
Figure 6 represents the secondary condenser.
Figure 7 represents the gravity separator.
Figure 8 represents the receiving pot of the crude bromine.
Figure 9 represents the condenser.
Figure 10 represents the scrubber in which excess chlorine is scrubbed in a part of
liquid effluent.
Figure 11 represents the rectification column for chlorine removal from crude
bromine.
Figure 12 represents the product cooler.
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STATEMENT OF INVENTION
In this invention the liquid effluent to be treated contains a quarternary ammonium salt (bromide), which being highly soluble in aqueous media passes out into an effluent stream of pesticide industry.
In this invention, at first the liquid effluent is evaporated by solar evaporation in solar ponds to separate undesired impurities. These impurities are removed by various mechanical processes viz. filtration, decantation, gravity separation etc.
The resulting liquid effluent is treated with an alkali such as hydroxides and carbonates of alkali metals -or lime to decompose quarternary ammonium salt. The liberated low boiling amine is scrubbed into an acid to convert it into acid salt of amine.
The resulting strongly alkaline effluent is then neutralized by using mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or similar spent acid. The resulting liquid after neutralization was filtered to remove the precipitate formed, if any.
The above pre-treated liquid effluent is acidified to adjust the pH range of 1 to 4 by adding mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or similar spent acid and preheated in the temperature range of 50 ° C to 100 ° C. preheated acidic effluent is reacted with chlorine gas by allowing the acidic liquid effluent to flow from the top of the vertically long gas-liquid contact chamber, chlorine gas and steam to pass from the bottom of the vertically long gas-liquid contact chamber whereby bromine is distilled out.
The bromine and water layers are separated in a gravity separator, the water layer is returned to the vertically long gas-liquid contact chamber, while the bromine layer flows to the refining section. The chlorine coming out from striping tower is condensed and scrubbed in a part of the acidic liquid effluent and returned immediately to the vertically long gas-liquid contact chamber. The effluent from the bottom of the vertically long gas-liquid contact chamber is sent to effluent treatment plant.
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In an embodiment of the present invention, the industrial liquid waste containing quarternary ammonium salt (bromide) may be used in the concentration range of 15 to 40% (w/w) as sodium bromide.
In another embodiment of the present invention, the liquid effluent may be solar evaporated in the temperature range of 25 to 43 ° C for a period in the range of 1 to 15 days.
In yet another embodiment of the present invention, the solid precipitated impurities may be separated either by filtration or decantation method.
In still another embodiment of the present invention, the impurities free effluent may be treated with alkali metal salt solution in the concentration range of 25 to 50% (w/w) in liquid form or 75 to 100% in solid form for a period in the range of 30 to 120 minutes.
In still another embodiment of the present invention, the liberated quarternary amine may be scrubbed into acid solution in the concentration range of 20 to 98% (w/w) for a period in the range of 30 to 120 minutes.
In still another embodiment of the present invention, the alkaline effluent may be neutralized with mineral acid in the concentration range of 20 to 98% (w/w) under continuous agitation at ambient temperature.
In still another embodiment of the present invention, the pH of the effluent may be adjusted in the range of 1 to 4 by adding acid in tile concentration range of 20 to 98% (w/w).
In still another embodiment of the present invention, the acidic effluent may be heated in the temperature range of 50 to 100 ° C.
In still another embodiment of the present invention, the heated acidic effluent may be allowed to flow from the top of the vertically long gas-liquid contact chamber at a rate in the range of 50 to 200 litres per hour.
In still another embodiment of the present invention, the chlorine gas may be passed from the bottom of the vertically long gas-liquid contact chamber at a rate in the range of 10 to 50 kg/hour.
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In still another embodiment of the present invention, the steam may also be simultaneously passed from the bottom of the vertically long gas-liquid contact chamber at a rate in the range of 1 to 10 kg/ hour.
In still another embodiment of the present invention, the crude bromine may be separated from the water layer in the gravity separator.
In still another embodiment of the present invention, the upper water layer may be recycled to the vertically long gas-liquid contact chamber.
In still another embodiment of the present invention, the crude bromine may be purified by the distillation process.
In still another embodiment of the present invention, the excess chlorine may be scrubbed in a part of the liquid effluent and recycled.
Accordingly the present invention provides a process for recovering liquid bromine from industrial waste which comprises following steps;
i. evaporating liquid effluent to remove undesired impurities present in liquid effluent in solar ponds in the temperature range of 25 to 43 ° C for a period in the range of 1 to 15 days.
ii. separating undesired impurities obtained in step (i) by filtration, decantation etc.
iii. adding water to adjust the quarternary ammonium salt (bromide) concentration in the range of 15 to 40% (w/w) as sodium bromide, if required.
iv. adding an alkali such as hydroxides and carbonates of alkali metals or lime in the concentration range of 25 to 50% (w/w) in liquid form or 75 to 100% in solid form in an excess of 0 to 10% man the stoichiometric requirement for a period in the range of 30 to 120 minutes.
v. recovering the liberated amine obtained in step (iv) by scrubbing it in to an acid solution in the concentration range of 20 to 98% (w/w) for a period in the range of 30 to 120 minutes to recover amine.
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vi. neutralizing the excess alkaline effluent obtained in step (v) with mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or similar spent acid in the concentration range of 20 to 98% (w/w) under agitation at ambient temperature.
vii. filtering the precipitates obtained, if any, in step (vi).
viii. adjusting the pH of the liquid effluent in the pH range of 1 to 4 by adding acid in the concentration range of 20 to 98% (w/w).
ix. heating the acidic liquid effluent as obtained in step (viii) in the temperature range of 50 to 100 ° C.
x allowing the acidic liquid effluent to flow from the top of the vertically long gas-liquid contact chamber at a rate in the range of 50 to 200 litre/hour.
xi. passing chlorine gas at a rate in the range of 10 to 50 kg/hour from the bottom of the vertically long gas-liquid contact chamber in an excess 0 to 15% then the stoichiometric requirement to the alkali bromide content in liquid effluent.
xii. simultaneously passing steam from the bottom of the vertically long gas-liquid contact chamber at a rate in the range of 1 to 10 kg/hour.
xiii. striping the bromine out from the effluent.
xiv. separating the condensate to recover crude bromine by gravity.
xv. recycling the upper water layer containing dissolved bromine and chlorine obtained in step (xiv) to the vertically long gas-liquid contact chamber.
xvi. purifying the crude bromine obtained in step (xiv) by distillation.
xvii. scrubbing the uncondensed chlorine gas obtained in step (xiv) and (xvi) in a part of the acidic liquid effluent obtained in the step (viii) and recycle.
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DETAILED DESCRIPTION OF THE INVENTION
The process of this invention mainly involves the oxidation of bromide salts of pre-treated liquid effluent to bromine by using chlorine gas as an oxidizing agent.
The liquid effluent to be treated in this invention contains a quarternary ammonium salt (bromide), which being highly soluble in aqueous media passes out into an effluent stream of pesticide industry.
This liquid effluent has the following chemical composition.

Probable chemical composition %
Quarternary ammonium salt (bromide) 15 to 40 % (w/w as sodium bromide)
Other organic impurities 0.5 to 5 % (w/w)
Water 29.5 to 75 % (w/w)
This process obviates the need for huge quantity of energy (fuel, electricity etc.) required in the process wherein sea water or bittern containing bromide ion in the concentration range of 0.065 to 12 gm/lit are used as bromine source.
The liquid effluent may be subjected to the treatment of this invention, directly as it is, or after it has been subjected to a pre-treatment such as solar evaporation, alkali treatment, neutralization, filtration etc.
In the treatment according to this invention, at first, the liquid effluent is evaporated by solar evaporation in solar ponds. It serves to separate undesired impurities present in liquid effluent, which may adversely affect the recovery and purity of bromine. These impurities are removed by various mechanical processes viz. filtration, decantation, gravity separation etc.
The resulting effluent after separation of undesired impurities is subjected to addition of water to adjust the quarternary ammonium salt (bromide) concentration in the range of 15 to 40% (w/w as NaBr) prior to smooth striping of bromine.
Then an alkali is added in the concentration range of 25 to 50% (w/w) in liquid form or 75 to 100% in solid form in an excess of 0 to 10% than the stoichiometric requirement to above concentrated liquid effluent for a period in the range of 30 to 120 minutes. As an alkali, hydroxides and carbonates of alkali metals or lime may be used, and ordinarily sodium hydroxide is most preferable. The liberated low boiling
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amine is then scrubbed into an acid solution in the concentration range of 20 to 98% (w/w) and may be recovered and/or recycled.
Thus, from this process not only bromine is recovered in high yield and purity, but also a tertiary amine can be recovered which is useful as an intermediate in the synthesis of various chemicals.
The resulting strongly alkaline effluent was then neutralized by using mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or similar spent acid in the concentration rang 20 to 98% (w/w) under agitation at ambient temperature. The resulting liquid after neutralization was filtered to remove the precipitate formed, if any.
In the final step of bromine recovery, the above pre-treated liquid effluent is acidified to adjust the pH in the range of 1 to 4 by adding mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or similar spent acid in the concentration range of 20 to 98% (w/w) followed by preheating at 50 ° C to 100 ° C and preheated acidic effluent is brought into contact countercurrently with gaseous chlorine while allowing the acidic liquid effluent to flow from the top of the vertically long gas-liquid contact chamber, chlorine gas and steam to pass from the bottom of the vertically long gas-liquid contact chamber, whereby bromine is distilled out. The heating of the effluent to nearly a boiling is required in order to reduce the partial pressure of bromine in the effluent to nearly zero and in this way to improve stripping efficiency of the effluent of its bromine content.
Preheating is beneficial for boiler operation because returned condensate helps to keep down boiler salinity. If make up water has a high concentration of dissolved matter, this may be an important factor in the operation of boiler and heat economy. The process requires that certain quantities of live steam should be introduced into vertically long gas-liquid contact chamber to distil out the bromine from the effluent. Debromination of effluent in vertically long gas-liquid contact chamber is enhanced by steam condensation and a small, but functionally important, part of the steam helps to move the gaseous bromine product from the vertically long gas-liquid contact chamber on to the condenser.
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Chlorine gas may be introduced in an excess 0 to 15% then the stoichiometric requirement at a rate in the range of 10 to 50 kg/hour. An acidic effluent may be flow from the top of the vertically long gas-liquid contact chamber at a rate in the range of 50 to 200 litre/hour. Steam may be introduced from the bottom of the vertically long gas-liquid contact chamber at a rate in the range of 1 to 10 kg/hour.
The chlorine content of the crude liquid bromine is reported to be up to 4%. The vapours emerging from the product chamber contain more than that but a part of the chlorine is flashed off during condensation and is scrubbed immediately in a part of the acidic liquid effluent and returned immediately to the vertically long gas-liquid contact chamber. After condensation two liquid phases are formed, one composed of liquid bromine containing some chlorine, the other of water saturated with bromine.
The larger the chlorine contents of the liquid bromine phase, the larger also the chlorine content of the water phase. Presence of chlorine in the latter increases bromine solubility and consequently increases the specific gravity and changes the colour of the solution. Due to this the specific gravity and to some extent the colour of the brominated water layer, provide a measure of the chlorine content of the crude bromine and hence also an indication for the operator how to regulate the supply of chlorine to the tower.
The bromine and water layers are separated in a gravity separator, the water layer is continuously decanted. and returned to the vertically long gas-liquid contact chamber, while the bromine layer flows to the refining section. According to practice observed a reflux ratio of 5:1 is sufficient to reduce the chlorine content from about 1 to 0.2% when a column 1 metre height packed with 1 inch raschigs rings is used. The chlorine coming out from striping tower is condensed and scrubbed in a part of the acidic liquid effluent and returned immediately to the vertically long gas-liquid contact chamber. The effluent from the bottom of the vertically long gas-liquid contact chamber is sent to effluent treatment plant.
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CHARACTERISATION OF THE PRODUCT
The analytical test procedures to be used for determining bromine percent by mass, chlorine (as CI) percent by mass, non-volatile matter percent by mass, iodine (as I) percent by mass and sulphates (as SO4) percent by mass in liquid bromine of this invention are as follows.
Determination of bromine
1. Reagents
Potassium iodide
Standard sodium thiosulphate solution-0.1 N.
Starch indicator solution
2. Procedure
Dissolve about 10 g of potassium iodide in 30 ml of water and transfer the solution to a clean 100 ml volumetric flask. Weigh the flask accurately. Add about 0.5 ml of the material to the flask, stopper immediately and weigh again. Dilute the contents of the flask to 100 ml and mix well. Pipette out 25 ml of the solution from the flask into a comical flask and titrate with standard sodium thiosulphate solution using freshly prepared starch indicator solution.
3. Calculation
Bromine, percent by mass = 31.97 V N / M
Where,
V = volume, in ml, of standard sodium thiosulphate solution used in the
titration; N = normality of the standard sodium thiosulphate solution; and M = mass in g of the material taken for the test.
In the value of bromine percentage as obtained, make a correction for the chlorine percent by subtracting the percentage result for chlorine obtained multiplied by 2.25.
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Determination of chlorine
1. Reagents
Zinc filings
Concentrated nitric acid
Standard silver nitrate solution- 0.1 N
Nitrobenzene
Standard ammonium thiocyanate solution- 0.1 N
Ferric alum indicator- saturated solution
2. Procedure
Add 50 ml of water to a 250 ml volumetric flask fitted with a stopper and weigh (Mi). To this add about 3 ml of liquid bromine and weigh again (Mb). The difference between M2 and Mi gives the exact amount (M) of the material taken for the test. Add about 0.5 g of zinc dust and shake thoroughly for 10 minutes. Heat the flask on a steam-bath to remove the excess of bromine. Dissolve the residue in 75 ml of water and 25 ml of concentrated nitric acid. Heat the resulting solution to boiling on a water bath for 5 minutes. Pass a gentle stream of air for 20 minutes through a tapered in-let tube extending to the bottom of the flask to completely remove bromine. Allow the flask to cool and add 20 ml of standard silver nitrate solution. To this add 10 drops to nitrobenzene and shake vigorously for one minute. Titrate the excess silver nitrate with standard sodium thiocyanate solution using ferric alum indicator, shaking well between successive additions of the titrant. Carry out a blank determination using the same quantities of all the reagents.
3. Calculation
Chlorine (as CI) percent by mass = 3.546 (V, - V2) N / M
Where,
V1 = volume, in ml, of standard ammonium thiocyanate solution used in the
blank determination;
V2= volume, in ml, of standard ammonium thiocyanate solution used in test
with the material;
N = normality of standard ammonium thiocyanate solution; and
M = mass in g of the material taken for the test.
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Determination of non-volatile matter
1. procedure
Transfer exactly 5 ml of the material to a weighed silica dish. Volatilize the material on a steam-bath under hood and dry the dish for one hour at 105 ± 5 ° C. cool in a desiccator and weigh again.
2. Calculation
Non-volatile matter, percent by mass = 100 M / V D
Where,
M = mass in g of the residue;
V = volume in ml of the material taken for the test; and
D = relative density of the material.
Test for iodine
1. Apparatus
Nessler cylinders - 50 ml capacity.
2. Reagents
Zink dust
Ferric chloride solution - 10 percent (m/v)
Chloroform
Standard potassium iodide solution
3. Procedure
Shake 1 ml of the material with 50 ml of water and 3 g of zinc dust until all the bromine is decolorized. Filter the contents into a nessler cylinder. Add to the filtrate 1 ml of ferric chloride solution, 5 ml of chloroform and shake well. In another nessler cylinder, take 1 ml of standard potassium iodide solution and to this add 50 ml of water, 1 ml of ferric chloride solution, and 5 ml of chloroform and shake thoroughly. Compare the colour of the cylinders.
The material shall be taken as not having exceeded the limit prescribed in specification if the intensity of pink or violet colour of the chloroform layer in the first cylinder is not deeper than that of the colour of the chloroform layer
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in the second cylinder. This colour intensity corresponds to 0.05 percent iodine in the sample.
Test for sulphates
1. Apparatus
'Nessler cylinders - 50 ml capacity.
2. Reagents
Dilute ammonium hydroxide solution - 10 percent (v/v) Dilute hydrochloric acid -IN
Barium chloride solution - approximately 10 percent m/v Standard sulphate solution
3. procedure
Take 1.3 ml of the material in a 100 ml porcelain evaporating dish with 30 ml of water. Add slowly 15 ml of dilute ammonium hydroxide solution and evaporate to dryness. Dissolve the white residue obtained in 80 ml of dilute hydrochloric acid. Take 40 ml of this solution in a nessler cylinder and add 1 ml or barium chloride solution; mix well and allow to stand for 1 hour. Similarly, on another nessler cylinder take 3 ml of standard sulphate solution, 40 ml of dilute hydrochloric acid and 1 ml of barium chloride solution; mix and set aside for 1 hour.
The material shall be taken as not having exceeded the limit prescribed in specification if the turbidity producer with the material is not greater than that produce with the standard sample. This standard turbidity corresponds to 0.015 percent sulphate content in the material.
Typical industrial product specifications for bromine are given as under.

Parameter Value
1. Bromine % by mass 98.5 min.
2. Chlorine (as CI) % by mass 0.5 max.
3. Non volatile matter % by mass 0.05 max.
4. Iodine (as I) % by mass 0.05 max.
5. Sulfates (as S04) % by mass 0.015 max.
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Liquid bromine, in accordance with the present invention can be recovered from quarternary ammonium salt (bromide) present in the effluent stream of pesticide industry. Prior to alkali (sodium hydroxide or carbonate) solution treatment the liquid effluent is solar evaporated to separate out the undesired impurities. The alkaline effluent obtained after the removal of liberated amine is treated with mineral acid to neutralize the excess alkali and also to adjust the pH between 1 to 4. The heated acidic effluent is allowed to react with chlorine gas and steam in a vertical reactor, whereby bromine is stripped and further purified by distillation. The prior art does not divulge nor teach how liquid bromine can be recovered from the effluent of pesticide industry containing quarternary ammonium salt (bromide). It is reported for the first time in the present invention how liquid bromine can be recovered from quarternary ammonium salt (bromide) present in the pesticide industry. In the hitherto known process, the source of bromine is sea-water, organic and inorganic bromo compounds which are easily available. In this invention, we have alleviated problem of throwing away the hazardous waste as effluent and have generated a potential source of bromine.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLE 1
In this example, the liquid effluent obtained by the pre-treatment such as solar evaporation and addition of water was used.
To a stirred solution of 1 kg liquid effluent containing 30% (w/w as sodium bromide) quarternary ammonium salt, 0.125 kg sodium hydroxide was added. Strongly alkaline effluent was neutralized by 98% sulfuric acid. The resulting liquid after neutralization was filtered to remove any precipitate formed.
The pH of the above liquid was adjusted to 1.5 by adding 98% sulphuric acid and then it was preheated up to 85 ° C in pre-heater before it was subjected to the bromine recovery. The bromine recovery was conducted in glass packed tower which had a diameter of 4 inch, a height of 54 inch with a liquid fed inlet at the top and a gaseous chlorine inlet, a steam inlet and drain outlet at the bottom and a bromine distillate outlet at upper middle portion of the tower.
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The preheated acidic effluent was fed from the tower top at a rate of 54 litre/ hour and gaseous chlorine was fed from the tower bottom in an excess of 8% than the stoichiometric requirement to the sodium bromide content at a rate of 6.6 kg/hour. At the bottom of the tower, steam was introduced at a rate of 1.75 kg/hour and the liberated bromine was distilled and collected by condensation. Plugging of the tower was not observed at all. The imreacted 8% excess chlorine was scrubbed in a part of the acidic effluent and recycled.
The crude bromine obtained from previous step was rectified, which showed 99.75% purity. In the present experimentation, bromine recovery is 93.50%.
EXAMPLE-2
In this example, the direct liquid effluent without subjecting to pre-treatment such as solar evaporation and addition of water was used.
0.10 kg sodium hydroxide was added to 1 kg liquid effluent containing 22% (w/w as sodium bromide) quarternary ammonium salt, in the same way as given in preceding example. The strong alkaline effluent was neutralized by 98% sulphuric acid and the precipitates formed were removed and thereafter the pH of the resulting liquid adjusted to 2 using 98% sulphuric acid. Further an acidic preheated liquid was brought into contact with gaseous chlorine and steam in the same way as reported in the previous experimentation to liberate bromine. The flow rate of acidic preheated effluent was 56 litre/ hour. Steam was introduced at a rate of 2.00 kg/hour. Chlorine was introduced in an excess of 9.5% than the stoichiometric requirement at a. rate of 5 kg/hour. Bromine obtained in this experimentation is 99.57% in purity and the present recovery is 91.25%.
EXAMPLE-3
In this example, the liquid effluent, directly as it is without subjecting to pre-treatment such as solar evaporation and addition of additional water, alkali treatment and neutralization is used.
To liquid effluent containing 20% (w/w as sodium bromide) quarternary ammonium salt, was added 30% hydrochloric acid to adjust the pH to 1. Thereafter an acidic preheated liquid was brought into contact with gaseous chlorine and steam in the same way as reported in the previous experimentation to liberate bromine. Chlorine
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was introduced in an excess of 10.5% than the stoichiometric requirement at a flow rate of 9 kg/hour. The flow rate of acidic preheated effluent was 145 litres/ hour. Steam was introduced at a flow rate of 5.5 kg/ hour. The excess 10.5% chlorine was scrubbed in a part of the acidic effluent and recycled. Bromine obtained in this experimentation is 99.45% in purity and the present recovery is 89.85%.
EXAMPLE-4
In this example, the direct liquid effluent without subjecting to pre-treatment such as solar evaporation and addition of water was used.
0.15 kg lime was added to 1 kg liquid effluent containing 25%( w/w as sodium bromide) quarternary ammonium salt, in the same way as given in preceding example. The strong alkaline effluent was neutralized by 98% sulphuric acid and the precipitates formed were removed and thereafter the pH of the resulting liquid adjusted to 1 using 98% sulphuric acid. Further an acidic preheated liquid was brought into contact with gaseous chlorine and steam in the same way as reported in the previous experimentation to liberate bromine. The flow rate of acidic preheated effluent was 100 litre/ hour. Steam was introduced at a rate of 3.5 kg/hour. Chlorine was introduced in an excess of 8% than the stoichiometric requirement at a rate of 9.175 kg/hour. Bromine obtained in this experimentation is 99.60% in purity and the present recovery is 92.50%. The excess 8% chlorine was scrubbed in a part of the acidic effluent and recycled.
EXAMPLE-5
In this example, the direct liquid effluent without subjecting to pre-treatment such as solar evaporation and addition of water was used.
0.085 kg sodium carbonate was added to 1 kg liquid effluent containing 16% (w/w as sodium bromide) quarternary ammonium salt, in the same way as given in preceding example. The strong alkaline effluent was neutralized by 98% sulphuric acid and the precipitates formed were removed and thereafter the pH of the resulting liquid adjusted to 1 using 98% sulphuric acid. Further an acidic preheated liquid was brought into contact with gaseous chlorine and steam in the same way as reported in the previous experimentation to liberate bromine. The flow rate of acidic preheated effluent was 75 litre/ hour. Steam was introduced at a rate of 2.5 kg/hour. Chlorine
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was introduced in an excess of 10 % than the stoichiometric requirement at a rate of 4.25 kg/hour. Bromine obtained in this experimentation is 99.67% in purity and the present recovery is 91.00%. The excess 10% chlorine was scrubbed in a part of the acidic effluent and recycled.
EXAMPLE-6
In this example, the liquid effluent, directly as it is without subjecting to pre-treatment such as solar evaporation and addition of additional water, alkali treatment and neutralization is used.
To liquid effluent containing 27.5% (w/w as sodium bromide) quarternary ammonium salt, was added 85% sulfuric acid to adjust the pH to 1. Thereafter an acidic preheated liquid was brought into contact with gaseous chlorine and steam in the same way as reported in the previous experimentation to liberate bromine. Chlorine was introduced in an excess of 9.5% than the stoichiometric requirement at a flow rate of 19 kg/hour. The flow rate of acidic preheated effluent was 200 litres/ hour. Steam was introduced at a flow rate of 7 kg/ hour. The excess 9.5% chlorine was scrubbed in a part of the acidic effluent and recycled. Bromine obtained in this experimentation is 99.61% in purity and the present recovery is 90.05%.
The main advantages of the present invention are:
1. As described above, the process of this invention is useful to recover liquid bromine from quarternary ammonium salt (bromide) present in the effluent stream of pesticide industry.
2. This invention provides an industrially advantageous eco-friendly process for recovering bromine from a liquid effluent, which is safe, smooth, suitable for industrial practice and economically viable in operation.
3. This invention makes it possible to avoid detrimental effect of the waste on environment.
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We claim
1. A process for recovering liquid bromine from industrial waste which comprises steps:
i. evaporating liquid effluent to remove undesired impurities present in liquid effluent by solar ponds in the temperature range of 25 to 43 ° C for a period in the range of 1 to 15 days.
ii. separating undesired impurities obtained in step (i) by filtration, decantation etc.
iii. adding water to adjust the quarternary ammonium salt (bromide) concentration in the range of 15 to 40% (w/w) as sodium bromide, if required.
iv. adding an alkali such as hydroxides and carbonates of alkali metals or lime in the concentration range of 25 to 50% (w/w) in liquid form or 75 to 100 % in solid form in an excess of 0 to 10% than the stoichiometric requirement for a period in the range of 30 to 120 minutes.
v. recovering the liberated amine obtained in step (iv) by scrubbing it in to an acid solution in the concentration range of 20 to 98% (w/w) for a period in the range of 30 to 120 minutes to recover amine.
vi. neutralizing the excess alkaline effluent obtained in step (v) with mineral acid viz. hydrochloric acid/ sulphuric acid/nitric acid or similar spent acid in the concentration range of 20 to 98% (w/w) under agitation at ambient temperature.
vii. filtering the precipitates obtained, if any, in step (vi).
viii. adjusting the pH of the liquid effluent in the pH range of 1 to 4 by adding acid in the concentration range of 20 to 98% (w/w).
ix. heating the acidic liquid effluent as obtained in step (viii) in the temperature range of 50 to 100 ° C.
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x. allowing the acidic liquid effluent to flow from the top of the vertically long gas-liquid contact chamber at a rate in the range of 50 to 200 litre/hour.
xi. passing chlorine gas at a rate in the range of 10 to 50 kg/hour from the bottom of the vertically long gas-liquid contact chamber in an excess 0- 5% then the stoichiometric requirement to the alkali bromide content in liquid effluent.
xii. simultaneously passing steam from the bottom of the vertically long gas-liquid contact chamber at a rate in the range of 1 to 10 kg/hour.
xiii. _ striping the bromine out from the effluent.
xiv. separating the condensate to recover crude bromine by gravity.
xv. recycling the upper water layer containing dissolved bromine and chlorine obtained in step (xiv) to the vertically long gas-liquid contact chamber.
xvi. purifying the crude bromine obtained in step (xiv) by distillation.
xvii. scrubbing the uncondensed chlorine gas obtained in step (xiv) and (xvi) in a part of the acidic liquid effluent obtained in the step (viii) and recycle.
2. A process for recovering liquid bromine from industrial waste as claimed in claim 1, wherein the contiontration of quarternary ammonium salt (bromide) is maintained in the range of 15 to 40% (w/w) as sodium bromide in liquid waste.
3. A process for recovering liquid bromine from industrial waste as claimed in claim 1 & 2, wherein the liquid effluent waste is evaporated by maintaining the temperature in the range of 25 to 43 ° C for a period in the range of 1 to 15 days.
4. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 3, wherein the solid precipitated impurities are separated by filtration, decantation and the like methods.
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5. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 4T wherein the impurities free effluent is treated with an alkali such as hydroxides and carbonates of alkali metals or lime in the concentration range of 25 to 50% (w/w) in liquid form or 75 to 100% in solid form in an excess of 0 to 10% than the stoichiometric requirement for a period in the. range of 30 to 120 minutes.
6. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 5, wherein the liberated amine is scrubbed in an acid solution while maintaining the contiontration in the range of 20 to 98% (w/w) for a period maintained in the range of 30 to 120 minutes.
7. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 6, wherein the alkaline effluent is neutralized with mineral acid while maintaining the concentration in the range of 20 to 98% (w/w) under continuous agitation and at ambient temperature.
8. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 7, wherein the pH of the effluent is maintained in the range of 1 to 4 by adding acid and maintaining the concentration in the range of 20 to 98% (w/w).
9. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 8, wherein the acidified effluent is heated and the temperature is maintained in the range of 50 to 100 ° C.
10. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 9, wherein the heated acidified effluent is allowed to flow from the top of the vertically long gas-liquid contact chamber at a rate maintained in the range of 50 to 200 litres per hour.
11. A process for recovering liquid bromine from industrial waste as claimed in claim 1 to 10, wherein the chlorine gas is passed from the bottom of the vertically long gas-liquid contact chamber at a rate maintained in the range of 10 to 50 kg/hour.
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12. A process for recovering liquid bromine from industrial waste as claimed in
claim 1 to 11, wherein the steam is simultaneously passed from the bottom of
the vertically long gas-liquid contact chamber at a rate maintained in the range
of l to 10 kg/hour.
13. A process for recovering liquid bromine from industrial waste substantially as
herein described with reference to the examples and drawing accompanying
this specification.

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ABSTRACT
A new process is described for the recovery of liquid bromine from quarternary ammonium salt (bromide) present in the effluent stream of pesticide industry. The process comprises of solar evaporation to separate the undesired impurities, treating with hydroxides and carbonates of alkali metals or lime, adjusting the pH and carrying out the oxidation of bromide anions using chlorine gas as an oxidizing agent. The distilled bromine is useful in preparation of numerous organo-inorganic bromo compounds.
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