The state analysis of carbon in ore and the phase analysis method of various forms of carbon in ore have not been reported at home and abroad.
In this paper, how to determine carbon in various states is systematically explored and experimented, and the quantitative analysis methods of carbon in carbonate, organic compound carbon, amorphous element carbon and graphite are preliminarily drawn up. Select phosphoric acid samples to determine carbon in carbonate. A single sample was burned at 500℃ to remove organic compounds and amorphous element carbon, and then graphite was determined. The separated samples were treated with X reagent to remove the organic compound carbon, and the amorphous elements carbon and graphite were determined. Total carbon is determined by combustion method, and carbon in organic matter and amorphous element carbon are obtained by differential alkali method. Non-aqueous titration was used for determination.
Methods Through comprehensive addition recovery test, the recovery rate of each phase was greater than 95%.
Experimental part
1. Reference materials and main reagents
Calcium carbonate: used as carbonate standard material, containing C 12.0%.
Tannin: used as the reference substance of organic compounds, containing C46.0%.
Amorphous element carbon: take carbonaceous slate and grind it to 0.075mm, treat it with HCl and HF for 2-3 times, wash it with water and acid, then filter it with sand core funnel, wash it, dry it and grind it fine. Used as carbon reference for amorphous elements, containing C4.77%.
Graphite: prepared by grinding with spectrally pure electrode, containing 99.9% carbon.
Chromium trioxide: analytically pure.
Ammonium metavanadate: analytically pure.
Phosphoric acid: analytically pure.
Non-aqueous solution: 1000mL absolute ethanol, 1gKOH (or 4gKOH), 30mL ethanolamine, 200mg thymolphthalein, and shake well for later use.
2. Instruments and equipment
Use the traditional non-drop setting device.
3. Experimental methods
Take an appropriate amount of reference substance, and determine CO2 by the usual acid-soluble nonaqueous titration, or burn it at a certain temperature, or treat it with X reagent, and then determine carbon by the combustion nonaqueous titration.
Results and discussion
1. Measure the dissolution rate of carbon, amorphous element carbon and graphite in organic compounds under CO2 condition.
Appropriate amount of tannin, amorphous element carbon and graphite are respectively weighed, and 20 ml of H3PO4 (1+1) is added according to the conditions of measuring CO2, and the heating time is 15min. The results are shown in table 1.2.
Table 1.2 Measure the effects of carbon, amorphous carbon and graphite in organic compounds under CO2 conditions.
It can be seen from Table 1.2 that their dissolution rates are all less than 0. 1%.
2. Determine the dissolution rate of graphite under the condition of organic compound carbon.
Weigh a proper amount of graphite, according to the conditions of determining carbon in organic compounds, add 2gCrO3, 30 ~ 50mgNH4VO3, bath in boiling water for 25min, and determine carbon by non-aqueous titration. The results are shown in table 1.3.
Table 1.3 Effect of graphite on determination of carbon content in organic compounds
It can be seen from table 1.3 that the dissolution rate of graphite is less than 0. 1%.
3. Separation of organic compound carbon and amorphous element carbon
(1) combustion temperature condition test
The recovery rates of organic compound carbon, amorphous element carbon and graphite at different temperatures are shown in table 1.4.
Table 1.4 Carbon recovery rate in three states at different temperatures
It can be seen from Table 1.4 that at 500℃, the recovery rate of graphite is 98.5%, the recovery rate of amorphous element carbon is only 1.5%, and the recovery rate of organic compound carbon is zero. Therefore, graphite can be separated from organic compound carbon and amorphous element carbon at 500℃.
(2) Experiment on separation conditions of organic compound carbon and amorphous element carbon.
When H2O2 is used, it is found that the oxidation ability of H2O2 is weak. When concentrated nitric acid is used for oxidation, the carbon loss of amorphous elements is great. After many tests, X reagent is better. See table 1.5 for the results.
Table 1.5 carbon dissolution rate of amorphous elements in organic compounds
It can be seen from the table 1.5 that after repeated treatment with X- 1 or X-2 for 3 ~ 4 times, the residual carbon rate of organic compounds is 5% ~ 7%, and the carbon recovery rate of amorphous elements is more than 90%, which can basically meet the phase separation requirements of phase analysis. Because of their similar chemical properties, it is difficult to separate them quantitatively. This separation condition needs further study and experiment to improve the clarity of phase separation.
Analytical method
(1) First, check whether the device system leaks, add non-water droplets at the glass baffle about 1cm, weigh a proper amount of CaCO3 and put it in a test tube, and adjust the solution to light blue 1 ~ 2 min according to the analysis method.
(2) Weigh 0. 1 ~ 0.5g of sample into a test tube, cover the rubber plug with a separatory funnel, a thermometer and an air duct, close the piston of the separatory funnel, add 20ml of H3PO4 (1+1) along the small opening of the separatory funnel, plug the small opening of the funnel with a rubber plug with an air duct, open the piston and introduce O2, after the phosphoric acid enters the test tube. After the sample is decomposed, the color of the absorption cup turns pale, and immediately titrate with non-water droplets to light blue 1 ~ 2 min as the end point, and count the readings, which is carbon in carbonate.
(3) Weigh the sample 0. 1 ~ 0.5g in a porcelain boat, burn it 1h in a muffle furnace at 500℃, cool it, add10ml H3PO4 (1+1), and open it to complete the reaction (. Add 10mL concentrated H3PO4 along the opening of the separating funnel, heat it, and treat it at 140 ~ 160℃ for 20min. The carbon determined by non-water droplets is graphite carbon.
(4) Weigh 0. 1 ~ 0.5g of sample into a small beaker, add X- 1 or X-2 reagent 1 ~ 2ml (depending on the sample amount), heat and dry at low temperature, repeat for 3 ~ 4 times, transfer to a porcelain boat with a small amount of water, and dry. Put that porcelain boat into a combustion furnace with the temperature raise to 65438 0000℃, introducing O2, measure the carbon as the sum of graphite and amorphous element carbon by non-water drop method, and subtracting graphite carbon as amorphous element carbon.
(5) Weigh 0. 1 ~ 0.5g of sample into a porcelain boat, put it into a combustion furnace at 1000℃, introduce O2, conduct water-free determination to obtain total carbon, and obtain organic compound carbon by subtraction.
Comprehensive recovery test
Different amounts of carbonate, organic compounds, amorphous element carbon and graphite were added to 1 ~ 4 sample, and the carbon amounts in various states were determined according to the analysis method. The results are listed in table 1.6.
Table 1.6 Carbon recovery rate in four states
It can be seen from the table 1.6 that the recovery rate of carbon in four states is 97% ~ 104%.
label
The phase analysis methods of various carbon states (carbonate, organic compound carbon, amorphous element carbon and graphite) in ores were studied. It is proposed for the first time that the carbon that affects gold leaching by wet method is mainly amorphous element carbon and its quantitative determination method, which will provide key detection technology for the characterization of refractory gold ore containing carbon and the improvement of gold leaching process.