FIELD OF INVENTION:

The present innovation relates to the synthesis of novel flotation reagents for enhanced iron
ore-gangue separation. Guanidine derivatives have been synthesized and their applicability as flotation collectors has been investigated. Amphiphilic guanidine derivatives and their salts such as 1-dodecyl guanidine, 1 -(2-(2-(2-aminoethoxy) ethoxy) ethyl) guanidine and (2-(2-hydroxyethoxy) ethyl) guanidine showed better selectivity for the gangue mineralsAl2O3 and SiO2. Furthermore, the yield of concentrate produced was high in all cases.

BACKGROUND OF THE INVENTION:

Iron ores containing high Al2O3/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 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 SiO2and Al2O3can 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. 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. In our present
invention, the reagents are not only selective towards alumina but also produce low alumina
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.

BRIEF DESCRPTION OF THE INVENTION:
This invention relates to a method for the synthesis of novel guanidine flotation reagent for
enhanced iron ore-gangue separation comprising:
methylating thiourea to produce 2-methylisothiouronium iodide(2),
reacting said 2-methylisothiouronium iodide with corresponding amines(4a, 4b) to produce 1-
dodecyl guanidine hydroiodide (Ga) and
(2-(2-hydroxyethoxy)ethyl)guanidine(Gb) respectively,
protecting amino group of 2-methylisothiouronium iodide(2) with Boc anhydride produced
N,N,-bis(tert-butoxycarbonyl)-S-methylisothiourea(3)
reacting said N,N'-bis(tert-butoxycarbonyl)-S-methylisothiourea(3) with amin(Gc) to
produce amphihlic 1 -(2-(2-aminoethoxy)ethoxy)ethyl)guanidine(Gc).
DETAILED DESCRIPTION OF THE INVENTION:
Guanidine is one of the strongest bases (pKa =13.6) with strong hydrogen bonding
capabilities and chemical stability. In an effective flotation process, mineral-reagent
interaction should be as good as the air bubble reagent interaction. 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.
Using guanidine as base the following reagents has been synthesised:
1. 1-dodecyl guanidine (Ga)
2. (2-(2-hydroxyethoxy) ethyl) guanidine(Gb)
3. l-(2-(2-(2-aminoethoxy) ethoxy) ethyl) guanidine (Gc)
These aliphatic guanidine derivatives were prepared in two to four steps synthetic procedure
from thiourea 1 as shown in step 1. Methylation of thiourea 1 using methyl iodide in
methanol as solvent gave 2-methylisothiouronium iodide2 in 90 % yield.1 Reaction of this 2-
methylisothiouronium iodide 2 with corresponding amines (4a and 4b) afforded desired
guanidines Ga and Gb in moderate yields. Boc protection of amino groups of 2-
methylisothiouronium iodide 2 with Boc anhydride in presence of sodium bicarbonate as base
gav N,N'-bis(tert-butoxycarbonyl)-S-methylisothiourea 3 as a white solid. The amphiphilic
guanidine derivative Gc was synthesized by the reaction of N,N'-bis(tcrt-butoxycarbonyl)-S-
methylisothiourea 3 with the amine 4c followed by Boc deprotection.


2-Methylisothiouronium iodide 2 and dodecylamine 4a were dissolved in ethanol and stirred
at 90°C for 12 h followed by column purification yielded 1-dodecylguanidine hydroiodide Ga
as a brown solid (Step 2).

Step 2: Synthesis of 1-dodecyl guanidine (Ga)
Next we have synthesized an amphiphilic guanidine derivative (2-(2-
hydroxyethoxy)ethyl)guanidine Gb by reaction of 2-methylisothiouronium iodide 2 with 2-
(2-aninoethoxy)ethanol 4b in ethanol:water (1:1) at 95 °C for 18 h (Step 3).

Step 3: Synthesis of (2-(2-hydroxyethoxy)ethyl)guanidine Gb.
2-(2-(2-aminoethoxy)ethoxy)ethanamine was reacted with N,N'-bis(tert-butoxycarbonyl)-S-
methylisothiourea 3 in CH2Cl2 at room temperature for 12 h gave the Boc protected guanidine
deriveative 5 in 65% yield. Deprotection of Boc groups of 5 using trifluoroacetic acid (TFA)

in dichloromethane afforded amphophilic l-(2-(2-(2-aminoethoxy)ethoxy)ethyl)guanidine Gc
in 85% yield (Step 4).

Step 4: Synthesis of l-(2-(2-(2-aminoethoxy)ethoxy)ethyl)guanidincGc
Flotation experiments:
Next flotation tests were performed on 500 g of iron ore sample (size: -200#, mesh)
using 0.5 g of the guanidine derivatives (Ga, Gb and Gc) as collectors. The feed alumina
range was 2%-4% and silica range was 2.0%-4%. In all the flotation experiments, two
fragments were collected basically that is froth and tailings. In a reverse flotation system, the
froth is the impurity and the tailing which remains behind in the flotation machine is the
product and is called the concentrate. The aliphatic 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%.

Flotation test results:
The test results have been provided for the three collectors and a range is provided to
take into account the variation in the results obtained due to various factors such as feed
variation, water quality, temperature etc.


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 (Ga, Gb, Gc)
4. Frother used: MIBC
5. Depressant used: causticized starch solution (200 ppm / O.lg/10ml)
6. pH regulator: NaOH
7. pH maintained: 8.5-9.5
8. pH meter
9. trays, weighing balance, beakers, droppers, conical flasks, glass rod
Preparation of causticized starch solution
1. 100 mL 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 lg 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 9.5-10.5by 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.

10. The material was raked off after 30secs each till the 5th material and after that the 6th
froth was raked off after 3mins.
11. failings were collected as frothl and froth 2.
12. The products were dried, weighed and sent for chemical analysis.
In summary, amphophilic guanidine derivatives showed good selectivity for minerals like
silica and alumina in reverse floatation process giving high yields of iron ore concentrates.
Characterization of reagents via Nuclear Magnetic Resonance (NMR)
Spectroscopy, Infrared (FTIR) spectra and High resolution mass spectra (HRMS)
(ESI).
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 CDC13, DMSO-d6
and D2O.

Proton (1H) and carbon (l3C) NMR spectra are recorded on a Bruker ADVANCE 500
spectrometer operating at 500 MHz for proton and 125 MHz for carbon nuclei or a Bruker
ADVANCE 400 spectrometer operating at 400 MHz for proton and 100 MHz for carbon
nuclei. NMR spectra are recorded in deuterated solvents as detailed and at ambient probe
temperature (300 K). Chemical shifts are reported in parts per million (ppm) on the δ scale
and were referenced to the appropriate residual solvent peaks: (1H: δ(CDCl3) = 7.26 ppm,
5((CD3)2SO) = 2.50 ppm, (D2O: 8 4.80 ppm) and 13C: δ(CDC13) = 77.26 ppm, δ(CD3)2SO) =
39.50 ppm). Data is reported as: chemical shift (multiplicity, coupling constant if appropriate,
integration). The following notations are used: singlet (s); doublet (d); triplet (t); quartet (q);
multiplet (m); broad (Sbr) The coupling constants (J) are reported in Hertz. Infrared (FTIR)
spectra (vmax) are recorded on a FTIR-8300 spectrophotometer as a thin film (neat) for liquid
samples and arc reported in cm"1. High resolution mass spectra (HRMS) (ESI) are performed
on a Micromass Q-Tof micro (Water Corporation) spectrometer by +ve mode electrospray
ionization.
Spectroscopic characterization of the reagents
Dodecyl guanidine hydro-iodide Ga

1H NMR (400 MHz, CDC13): δ 7.12 (t, J = 5 Hz, 1H), 6.80-6.30 (sbr, 4H), 3.26-3.18 (m, 2H),
1.70-1.60 (m,2H), 1.44-1.38 (m, 2H), 1.34-1.22 (m, 16H), 0.90-0.84 (t, 7=6.5, 3H);
13C NMR (100 MHz, CDCI3): δ 157.0, 42.5, 32.1, 29.8, 29.8, 29.7, 29.5, 29.4, 28.6, 27.0,
22.8, 14.2;

IR(Neat): 3323, 2924, 2852, 1652;
HRMS (ESI) calculated for C13H30N3 [M+H]+: 228.2434; Found 228.2432



(2-(2-hydroxyethoxy) ethyl) guanidine Gb

1H NMR (500 MHz, DMSO-d6): δ 6.58 (sbr, 2H), 5.46 (s, 1H), 4.90-4.19 (sbr, 2H), 3.51-3.48
(m, 4H), 3.40 (m, 2H), 3.28 (t, J = 5.2 Hz, 2H);
13C NMR (100 MHz, DMSO-d6): δ 156.9, 72.2, 72.1, 60.1,41.0;
IR (Neat): 3394,2932,2195, 1651, 1352, 1118;
HRMS (ESI) calculated for CsH14N3O2 [M+H]+: 148.1081; Found 148.1082.

l-(2-(2-(2-aminoethoxy) ethoxy) ethyl) guanidineGc

lH NMR (500 MHz, D2O): δ 3.60-3.51 (m, 8H), 3.23-3.20 (m, 2H), 3.03 (s, 2H);
13C NMR (100 MHz, D2O): δ 161.9 (q, J = 36.7 Hz), 157.3, 114.6 (q, J = 290.3 Hz), 69.7,
69.6,68.8,66.4,41.1,39.1;
IR (Neat): 3440, 2927, 1778, 1660, 1172;
HRMS(ESI)calcd for C7H19N4O2 [M+H]+: 191.1508; Found 191.1505.
1Hand 13CNMR of Gc

WE CLAIM:
1. A method for the synthesis of novel guanidine flotation reagent for enhanced iron ore-
gangue separation comprising:
methylating thiourea to produce 2-methylisothiouronium iodide(2),
reacting said 2-methylisothiouronium iodide with corresponding amines(4a, 4b) to
produce 1 -dodecyl guanidine hydroiodide (Ga) and
(2-(2-hydroxyethoxy)ethyl)guanidine(Gb) respectively,
protecting amino group of 2-methylisothiouronium iodide(2) with Boc anhydride
produced N,N'-bis(tert-butoxycarbonyl)-S-methylisothiourea(3)
reacting said N,N'-bis(tert-butoxycarbonyl)-S-methylisothiourea(3) with amin(Gc) to
produce amphihlic l-(2-(2-aminocthoxy)ethoxy)ethyl)guanidine(Gc).
2. The method as claimed in claim 1, wherein the step of methylation is performed by
using methyl iodide in methanol as solvent.
3. The method as claimed in claim 1, wherein said step of protection of amino groups of
2-methylisothiouronium iodide(2) with Boc anhydride in presence of sodium
bicarbonate as base.

4. The method as claimed in claim 1, wherein said 2- methylisothiouronium iodide(2)
and dodecylamine(4a) were dissolved in ethanol and stirred for 12hrs at 90°C.
5. The method as claimed in claim 1, wherein the said 2- methylisothiouronium
iodide(2) was reacted with (2-aminoethoxy)ethano(Gb) in ethanol: water (1:1) at
95°C for 18hrs.
6. The method as claimed in claim 1, wherein 2-(2-(2-aminoethoxy)ethoxy)ethanamine
was reacted with N,N,-bis(tert-butoxycarbonyl)-S-methylisothiourea(3) in CH2Cl2 at
room temperature for 12 hrs to produce the protected guanidine derivative(5) and the
Boc groups of 5 were deprotected using trifluoroacetic acid in dichloromethane to
yield amphophilic l-(2-(2-(2-aminoethoxy)ethoxy)ethyl)guanidine(Gc)