| Abstract:A novel process of extracting vanadium from stone coal which came from Hunan Province was proposed in this paper. A study of the differences between the blank roasting and mixing soda roasting for the effect on vanadium leaching was carried out. The leaching solution was obtained by leaching the calcine with dilute soda solution as leaching agent and N263was used to extract vanadium from the leaching solution. The process was mainly composed of blank roasting, leaching with soda, extracting vanadium with transformed N263, stripping with NaOH, subsiding vanadium with ammonium salt, etc. The results indicate this simplified and environment-friendly process has good prospects.The main contents and conclusions are as follows:(1) The roasting of stone coalThe influences of roasting style, roasting time, roasting temperature and the roasting additive on leaching rate of vanadium were studied. The experimental results show that, under the same leaching with water condition, the leaching rate of vanadium from the calcine which was added soda for roasting was higher than that of blank roasting. The leaching rate was33%for blank roasting and53%for soda roasting. The optimal conditions for roasting were roasting at800℃, roasting for2h and the amount of soda was2%of the ore.(2)Leaching of vanadiumCalcine was leached by soda solution. The factors of soda addition, leaching temperature, leaching time, the ratio of liquid to solid were studied. The results show that the suitable conditions were leaching for30min, leaching at85℃, the liquid to solid ratio from2/1to3/1, and the soda occupies3%of the ore, and the leaching rate of vanadium can reach up to60%. Comparative leaching experiments of NaOH and Na2CO3shows that the leaching rate of vanadium increased from60.35%to63.15%with NaOH leaching while the concentration of impurities increased greatly. (3) Direct solvent extraction of vanadium from alkaline-leaching liquor The saturated concentration of V2O5in organic phase was34.67g/L, when the organic solution consisted of0.919mol/LN263+20%ec-caprylic+30%kerosene, the concentration of V2O5in feed liquid was4.205g/L and pH was12.6. In addition, a series of saturated capacity of V2O5of different concentration of N263in organic phase were obtained. The mechanism of extracting vanadium by carbonate quaternary ammonium salt proved by saturated capacity method can be expressed as below: V2O74-(aq)+2(R3R’N)2CO3(org)=(R3R/N)4V2O7(org)+2CO32-(aq) HVO42-(aq1)+(R3R’N)2CO3(org)=(R3R’N)2HVO4(org)+CO32-(aq)The thermodynamic analysis shows that the extraction reaction was slightly exothermic. So raising the reaction temperature is thermodynamically adverse. The extraction rate of V2O5reaches99.7%and the concentration of V2O5in raffinate was less than0.02g/L after extracted by countercurrent with the organic solution consisted of0.919mol/LN263+20%ec-caprylic+30%kerosene for three times, and the concentration of V2O5in feed solution was5.3825g/L under the conditions of temperature at31℃, leaching for5min, phase ratio(O/A)1/1.The stripping agent was NaOH solution. The concentration of V2O5could be about50g/L in strip liquor and is below0.3g/L after7-stage countercurrent stripped in the unloaded organic phase. When the concentration of V2O5in the loaded organic was27.18g/L, the concentration of NaOH was3mol/L, temperature at30℃, phase ratio(O/A) of2/1, time for5min. The sediment was got after adding ammonium salt to strip liquor, and then washing the sediment and drying it at80℃, taking it to a roasting furnace and keeping temperature at500℃for2h. Then the red powdery product was obtained, and the concentration of V2O5in the product was99.1%by chemical analysis. |
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