硫酸/硫酸钠复合淋洗剂对铬渣的淋洗效果研究

CHROMIUM LEACHING BY SULFURIC ACID/SODIUM SULFATE COMPOSITE ELUENT FROM CHROMIUM SLAG

以湖南长沙某铬盐厂铬渣为研究对象,通过室内模拟实验,采用振荡淋洗方法研究了硫酸-硫酸钠复合淋洗剂对铬渣污染场地Cr的淋洗效果,探讨了淋洗剂浓度、液固比和淋洗时间等对淋洗效果的影响,以及淋洗前后重金属形态的变化,并通过对比试验研究了硫酸钠、柠檬酸、草酸、Na2-EDTA、硫酸、柠檬酸-柠檬酸三钠以及盐酸-氯化钠作为淋洗剂对总铬和六价铬的淋洗效果。结果表明:硫酸/硫酸钠复合淋洗剂在浓度为0.4 mol/L,液固比为20∶1,反应时间为6 h,常温条件下可以达到最佳淋洗效果,总铬和六价铬的浸出效率分别为70.35%和71.56%;另外,重金属形态分析表明,该复合淋洗剂有效减少了铬渣中弱酸可提取态和有机物结合态Cr的百分比,使得残渣态Cr的百分比增加,从而降低了Cr的活性,达到修复目的。淋洗剂对比试验结果表明,与其他淋洗剂相比,硫酸-硫酸钠淋洗效果最好,其中的氢离子能与Cr^(3+)进行离子交换,而硫酸根能够有效地将钙与六价铬分离,对此高钙铬渣的处理更具针对性和有效性。

In this study,laboratory simulation tests were conducted to evaluate the effect of sulfuric acid/sodium sulfate on extracting Cr from the contaminated soils by surrounding chromium residue,which were discarded from a chromic salt factory in Changsha,Hunan province. The effects of reagent concentration,liquid-solid ratio and reaction time on the efficiency were investigated. The form distribution of Cr in slag before and after the composite eluant treatment was tested as well. And by contrast tests,we analyzed the total chromium and Cr（ Ⅵ） ＇s removal rate by different leaching reagents（ Na2SO4、CTA、OA、Na2-EDTA、H2SO4、citric/sodium citrate and HCl/NaCl）. The results indicated that the best effect of sulfuric acid/sodium sulfate were obtained at the concentration of 0. 4 mol/L under room temperature,and the optimum liquid-solid ratio and reaction time were 20∶ 1 and 6 h,respectively; the removal rates of the total chromium and Cr（ Ⅵ） in slag can reach 70. 35%and 71. 56%,respectively; besides,heavy metal speciation analysis showed that the composite eluant could effectively reduce the percentage of acid extractable fraction and organic combined fraction,but increase the percentage of residual form of Cr.Therefore,the activity of Cr was decreased,and the purpose of remediation was achieved. The results of the contrast test showed that sulfuric acid/sodium sulfate was verified as the best leaching agent. As a conclusion,this kind of composite eluant contains hydrogen ion which could exchange with Cr^3＋,and sulfate radical ion could effectively separated calcium and Cr（ Ⅵ）,which was more targeted and efficient for the treatment of awkward chromium slag with high calcium content.