碳酸钠溶液堆浸-硫酸亚铁还原联合解毒铬渣

以碳酸钠溶液作浸出剂、硫酸亚铁作还原剂,对循环碳酸钠溶液堆浸—硫酸亚铁还原联合解毒铬渣新工艺进行研究。结果表明,在整个解毒过程中,浸出液pH在10～12变化,浸出液经还原后溶液中Cr(VI)的实际浓度略高于其理论值;第一次浸出后,铬渣中钙铁石或水榴石中的Cr(VI)被大量浸出,浸出液中碳酸钠浓度由浸出前的9.3g/L下降至7.98g/L,Cr(VI)浸出率为62.67%;在此后的循环解毒过程中,浸出液中碳酸钠浓度均维持在8g/L左右,Cr(VI)浸出率增加缓慢;循环处理12次后,铬渣中Cr(VI)浸出率达85%,最终解毒渣中残留Cr(VI)主要存在于水滑石中;铬渣粒度显著影响其解毒效果,当粒度小于0.15mm时,最终解毒渣的毒性浸出液中Cr(VI)和总Cr浓度分别为1.98mg/L和2.45mg/L,达到一般工业固体废物填埋的标准。

Detoxification of Chromite Ore Processing Residue by Combination Process of Heap Leaching and Reduction

With Na2CO3 solution as leaching reagent and FeSO4 as reductant, a new combination process of heap leaching and reduction was investigated to detoxify chromite ore processing residue (COPR). The results show that the pH value of leaching solution varies from 10 to 12, and the factual concentration of Cr (VI) in leaching solution after reduction exceeds the theoretic value slightly in the whole process. In the first leaching stage, most of Cr (VI) in brownmillerite or hydrogarnet in COPR may be released, the concentration of Na2CO3 in solution reduces from 9.3 g/L to 7.98g/L, and the leaching rate of Cr (VI) is 62.67%. For the later cycles, the concentration of Na2CO3 maintains about 8 g/L, the leaching rate of Cr (VI) increases slowly. After the twelfth cycle, the leaching rate of Cr (VI) is up to 85%, and the remaining Cr(VI) in final detoxificated COPR may be present in hydrotalcite. Particle size of COPR has a big influence on detoxification effect, and the Cr (VI) and total Cr concentration in leachate of toxicity characteristic leaching procedure (TCLP) of the final detoxificated COPR is 1.98 mg/L and 2.45 mg/L, respectively, meeting the landfill standard for common industrial solid waste when the particle size of COPR is less than 0.15 mm.