Jia Yongfeng, Demopoulos George P
Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
Environ Sci Technol. 2005 Dec 15;39(24):9523-7. doi: 10.1021/es051432i.
Mineral processing effluents generated in hydrometallurgical industrial operations are sulfate based; hence it is of interest to investigate the effect sulfate matrix solution ("sulfate media") has on arsenate adsorption onto ferrihydrite. In this work, in particular, the influence of media (SO4(2-) vs NO3-), added gypsum, and pH alteration on the adsorption of arsenate onto ferrihydrite has been studied. The ferrihydrite precipitated from sulfate solution incorporated a significant amount of sulfate ions and showed a much higher adsorption capacityfor arsenate compared to nitrateferrihydrite at pH 3-8 and initial Fe/As molar ratios of 2, 4, and 8. Adsorption of arsenate onto sulfate-ferrihydrite involved ligand exchange with SO4(2-) ions that were found to be more easily exchangeable with increasing pH. Added gypsum to the adsorption system significantly enhanced the uptake of arsenate by ferrihydrite at pH 8. Equilibration treatment at acidic pH and addition of gypsum markedly improved the stability of adsorbed arsenate on ferrihydrite when pH was elevated. Comparison of arsenate adsorption onto ferrihydrite to coprecipitation of arsenate with iron(III) showed the latter process to lead to higher arsenic removal.
湿法冶金工业操作中产生的矿物加工废水以硫酸盐为基础；因此，研究硫酸盐基质溶液（“硫酸盐介质”）对砷酸盐吸附到水铁矿上的影响具有重要意义。在这项工作中，特别研究了介质（SO4(2-) 与 NO3-）、添加的石膏以及pH值变化对砷酸盐吸附到水铁矿上的影响。从硫酸盐溶液中沉淀出的水铁矿含有大量硫酸根离子，在pH值为3 - 8且初始铁/砷摩尔比为2、4和8时，与硝酸水铁矿相比，对砷酸盐表现出更高的吸附容量。砷酸盐在硫酸盐 - 水铁矿上的吸附涉及与SO4(2-) 离子的配体交换，发现随着pH值升高，SO4(2-) 离子更易于交换。在吸附体系中添加石膏显著提高了水铁矿在pH值为8时对砷酸盐的摄取量。当pH值升高时，在酸性pH下进行平衡处理并添加石膏显著提高了吸附在水铁矿上的砷酸盐的稳定性。将砷酸盐在水铁矿上的吸附与砷酸盐与铁（III）的共沉淀进行比较，结果表明后者过程导致更高的砷去除率。
