Effect of iron transformation on Acidithiobacillus ferrooxidans bio-leaching of clay vanadium residue

The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated.Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe^3+/Fe^2+couple and material exchange.The passivation of iron settling correlates with ferrous ion content in bio-leaching solution.In medium containing A.ferrooxidans and Fe(Ⅲ),the increment in Fe(Ⅱ)concentration leads to the formation of jarosite,generating a decline in vanadium extraction efficiency.Analysis of cyclic voltammetry shows that Fe(Ⅱ)ion is apt to be oxidized and translated into precipitate by A.ferrooxidans,which strongly adsorbed to the surface of the residue.Fe(Ⅲ)ion promotes the vanadium extraction due to its oxidizing activity.Admixing A.ferrooxidans to Fe(Ⅲ)medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution.This motivates 3.8%and 21.8%increments in recovery ratio and leaching rate of vanadium compared to the Fe(Ⅲ)exclusive use,respectively.Moreover,Fe(Ⅱ)ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria.

微晶石墨高温焙烧制备高纯石墨研究

以青海都兰某微晶石墨浮选精矿为原料,通过高温焙烧制备高纯石墨。利用XRF、XRD、SEM-EDS等分析原料成分、物相、形貌,系统考查焙烧温度与时间对石墨含碳量和回收率的影响。以含碳量为目标优化了焙烧时间、NaOH/石墨配料比、盐酸浓度、酸浸温度、酸浸时间等参数。结果表明,焙烧温度1 000℃,焙烧时间为20 min,NaOH与石墨矿的质量比为0.75,盐酸浓度为0.6 mol/L,酸浸温度为40℃,酸浸时间为60 min条件下,固定碳含量提高到99.898%,回收率为64.32%。高温碱熔酸浸法是用微晶石墨制备高纯石墨的有效方法,为微晶石墨的高效利用开辟新途径。