FIELD OF THE INVENTION
The present invention relates to the synthesis of reverse flotation reagents for enhanced iron ore-gangue separation.
BACKGROUND OF THE INVENTION
Iron ores containing high AI2O3/SiO2 gangue are detrimental to blast furnace and sinter plant operations. Therefore they have to be beneficiated before being fed to the blast furnace for optimum production of steel. Kaolinite is a common gangue mineral frequently found in iron ore deposits. In iron ore flotation, both direct and reverse floatation techniques have been employed. Chemical reagents are the most important part of the flotation process. Based on their function, the reagents are divided into collectors, frothers, regulators and depressants.
In flotation practice, the collector consists of a functional group that is polar and a nonpolar hydrocarbon chain or a polymeric compound. The selectivity of the collector and mineral interaction is determined by the characteristic of the functional group and the nature of the hydrocarbon chain. The capacity of a mineral to adsorb selectively to a particular reagent molecule depends on a wide range of chemical, thermodynamic and steric factors. Iron ore bearing minerals like hematite can be floated by a variety of collectors, such as amines, oleates, sulfonates and sulphates. Beneficiation of iron ore slimes containing significant amount of Fe along with SiO2 and AI2O3 can be concentrated either by reverse cationic flotation of aluminosilicates (Kaolin) or direct anionic flotation of Fe.

The cationic reverse flotation of aluminosilicates seems to be an attractive route for the concentration of low grade ores. However, this is not practiced widely as it is a very difficult task to float alumina or alumina bearing minerals when associated with iron ore. This is because alumina selective reagents are not available as flotation collectors. The collectors available for reverse flotation are mostly silica selective and applicable for ores outside India which have basically silica/quartz as the main impurity. Therefore, it is an important task to design and synthesize cationic collectors for reverse flotation, which can improve the selectivity and floatability of gangue minerals with respect to iron ore.
Primary, secondary and tertiary amines with a carbon chain of varying length have found use in froth flotation of silica and other ores. In case of iron ore flotation, amines have been used for reverse flotation process. But these are effective only when the gangue mineral is basically siliceous in nature. Alumina specific amine based reverse flotation reagents are not very common. Whatever are reported are either not able to give good results with respect to iron ore-gangue separation or produce concentrate with very low yields.
OBJECTS OF THE INVENTION:
In view of the foregoing limitations inherent in the prior-art, the object of the invention is to synthesize new reagents taking guanidine as a base. These reagents should be configured to separate alumina and silica from iron ore resulting concentrate in having 1.8-2.8 % and 1.5-2.7 % respectively. The yield should be around 70% by wt.

SUMMARY OF THE INVENTION
In one aspect, the invention provide a guanidine based reagent comprising a base group, the base group being mono substituted guanidine derivative having chemical structure as



where R' is

In another aspect a method for synthesising a guanidine based reagent is


with
described having steps of reaction of an aniline derivative (8)
a cyanamide solution (NH2CN) in presence of a nitric acid (HNO3) and an
ethanol, wherein the aniline derivative (8) can be anyone of

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
FIGS. 1(a) & 1(b) show 1H and 13C NMR of 1-(4-Methoxyphenyl) guanidine nitrate (GARa).


DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the invention provide a guanidine based reagent for reverse floatation, the guanidine based reagent comprising a base group, the base group being mono substituted guanidine derivative having chemical
In another embodiment, the invention provides a method for synthesising a guanidine based reagent for reverse floatation, the method comprising steps of:
reaction of an aniline derivative (8) with a cyanamide solution
(NH2CN) in presence of a nitric acid (HNO3) and an ethanol, wherein the
aniline derivative (8) is
Guanidine is one of the strongest bases (pKa =13.6) with strong hydrogen bonding capabilities and chemical stability therefore it has been chosen for development of a guanidine based reagent (collector) for effective froth flotation process. Mineral-reagent interaction should be as good as the air

bubble reagent interaction also for effective flotation process. Then only the reagent (collector) can carry the gangue mineral to the top of the flotation cell in the form of froth. This is why guanidine has been chosen as base reagent (high hydrogen bonding capabilities) for good mineral-reagent interaction and guanidine derivatives are synthesised in such a manner that the hydrophobic-hydrophilic balance is maintained for effective flotation process.
Therefore using guanidine as base a base group, which is a mono substituted guanidine derivative, has been synthesised as:



As the reaction proceeds in presence of acid the final
products of guanidine will be in the form of salt of the acid used. This salt may be varied as chloride, iodide, sulphates etc as required for the process and is not a part of GAra, GArb, GARC-



General Information for Nuclear Magnetic Resonance (NMR) Spectroscopy:
All starting materials are obtained from commercial suppliers and used as received. Products are purified by flash chromatography on silica gel (100-200 mesh, Merck). Unless otherwise stated, yields refer to analytical pure samples. NMR spectra are recorded in

1H NMR spectra are recorded at 400 MHz and 500 MHz using Bruker ADVANCE 500 MHz instruments at 300K. Signals are quoted as 5 values in ppm using residual protonated solvent signals as internal standard
ppm). Data is reported as follows: chemical shift , multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, br = broad), coupling constants (Hz) and integration.
spectra are recorded on a Bruker ADVANCE 400 (100 MHz) and 500 MHz (125 MHz) with complete proton decoupling. Chemical shifts (6) are reported in ppm downfield from tetramethylsilane with the solvent as the internal reference and
39.50 ppm).
These reagents developed are best suitable for
iron ore having composition as shown in Table 1. The major iron bearing phase is heamatite with minor amounts of goethite, kaolinite and gibbsite.


is a light blue solid, brown solid and grey solid in nature.
A method for synthesising and is shown by
reaction

Aromatic guanidine compounds can be synthesized by the reaction of an aniline derivative (8) with a cyanamide solution (NH2CN) in the presence of nitric acid and an ethanol. Using this method, 4-methoxyaniline (8a), 4-(heptyloxy) aniline (8b) and 4-nitroaniline (8c) afforded the corresponding guanidine derivatives in
42%, 46% and 54% yields respectively.

It should be noted that the concentration of the cyanamide solution used can be in the range of 40-60% by wt. % in H20. The reaction temperature is maintained at 70- 90° C for a period of 10-14 hrs.
Already stated, as the reaction proceeds in presence of acid the
final products of guanidine will be in the form of salt of the acid used. This salt may be varied as chloride, iodide etc as required for the process and is not a part of Flotation experiments:
Tests were performed on 500 g of iron ore sample as mentioned in Table 1 (size: -200#, mesh) using the guanidine based reagents GAra, The feed alumina range was 2.5%-4% and silica range was 2.0%-4%. In all the flotation experiments, two fragments were collected, cone, and froth. In a reverse flotation system, the froth is the impurity and the cone, which remains behind in the flotation machine is the product.The aromatic guanidine derivatives afforded the final product, which contained alumina and silica in the range of 1.8%-2.8% and 1.5%-2.7% respectively with a yield of around 70%. The results are shown in


Chemical and Materials for the flotation test:
Materials required:
1. Weight of iron ore sample: 500g
2. Size of the iron ore sample: -200# (mesh)
3. Collector used : Synthesized reagents (200-1000 ppm)
4. Frother used: MIBC (if required)
5. Depressant used: causticized starch solution (200 ppm / O.1g/10ml)
6. pH regulator: NaOH
7. pH maintained: 9-9.5
8. pH meter
9. trays, weighing balance, beakers, droppers, conical flasks, glass rod Preparation of causticized starch solution

1. 100mL of water was taken in a beaker.
2. It was heated in a magnetic stirrer up to a temperature of 80 degree centigrade.
3. Then 0.5g of NaOH flakes was added.
4. Then 1g of potato starch was added slowly with continuous stirring for 2 to 5 minutes.
5. Then the solution was cooled as soon as possible.

Procedure Followed:
1. 500g of the sample was weighed and the flotation cell was switched on.
2. 1000mL of water was poured initially in the flotation cell.
3. Then feed sample was added in the cell.
4. The pH was maintained between 9-10 by adding NaOH drop wise
5. After 5mins of conditioning the depressant was added.

6. The collector was added and the sample was conditioned for 3-5mins.
7. Then frother was added.
8. After 2mins the air valve was opened.
9. The material was raked off after 30secs each till the 5th material and after that the 6th froth was raked off after 3mins.
10.The products were dried, weighed and sent for chemical analysis.
Advantages
In summary, aromatic guanidine derivatives showed good selectivity for minerals like silica and alumina in reverse floatation process giving high yields of iron ore concentrates.

We Claim:
1. A guanidine based reagent for reverse floatation, the guanidine
based reagent comprising:
a base group, the base group being mono substituted guanidin derivative having chemical structure as:

2. A method for synthesising a guanidine based reagent for reverse
floatation, the method comprising steps of:
reaction of an aniline derivative (8) with a cyanamide
solution in presence of a nitric acid and an
ethanol, wherein the aniline derivative (8) is


3. The method as claimed in claim 2, wherein concentration of the cyanamide solution is 40-60% by wt. % in H20.
4. The method as claimed in claim 2, wherein the reaction temperature is maintained at 70-90deg. C for a period of 10-14 hrs.