ABSTRACT

The determination of heavy metals fractionation in the environment is necessary to predict their mobility and bioavailability. This study was carried out to evaluate the effects of rice husk ash (RHA) and iron-coated rice husk ash (Fe-RHA) on As, Cd, Cr, Cu, Mn, Pb and Zn fractionation in gold mine tailings. The tailings were amended with either 0%, 5%, 10%, and 20% (w/w) of RHA or Fe-RHA and the samples were incubated at 60% of field capacity for 80 days. The amount of metals in different fractions at different intervals was determined using a sequential extraction procedure. The results showed that the addition of RHA increased the pH of tailings. The highest pH (9.09) was recorded in samples treated with 20% RHA. However, the addition of Fe-RHA reduced the pH values at all rates and incubation period, compared to the control. The lowest pH (7.17) was recorded in samples treated with 20% Fe-RHA. Both RHA and Fe-RHA increased the easily exchangeable As in the tailings from17.564% to 25.820% at samples treated with 20% RHA and 21.070% at Fe-RHA samples but decreased the carbonate-bound and organic fractions. However, the opposite results were observed for Cd (60.940% to 43.250%), Cr (2.214% to 1.560%), Cu (3.106% to 1.312%), Mn (62.149% to 43.740%), and Zn (9.853% to 1.325%) when tailings amended with 20% RHA. The results suggest that the addition of RHA or Fe-RHA can reduce the availability of cationic heavy metals in the tailings but will increase the availability of anionic metalloids such as As.

摘要

确定环境中重金属的分馏对于预测其迁移率和生物利用度是必要的。本研究旨在评估稻壳灰（RHA）和铁包衣稻壳灰（Fe-RHA）对金矿尾矿中As，Cd，Cr，Cu，Mn，Pb和Zn分离的影响。用0％，5％，10％和20％（w / w）的RHA或Fe-RHA修饰尾矿，并将样品在60％的田间持水量下培养80天。使用顺序萃取程序确定在不同间隔下不同馏分中金属的含量。结果表明，RHA的添加增加了尾矿的pH。在用20％RHA处理的样品中记录到最高pH（9.09）。然而，与对照相比，添加Fe-RHA在所有速率和孵育期间均降低了pH值。最低pH（7。在用20％Fe-RHA处理的样品中记录了17）。RHA和Fe-RHA均将尾矿中易交换的As从使用20％RHA处理的样品中的17.564％增加到25.820％，而在Fe-RHA处理的样品中则为21.070％，但减少了碳酸盐结合和有机物组分。但是，对于Cd（60.940％至43.250％），Cr（2.214％至1.560％），Cu（3.106％至1.312％），Mn（62.149％至43.740％）和Zn（9.853％至9.65％），Cr（2.214％至1.560％），Mn（62.149％至43.740％），Zn（9.853％至9.53％）观察到相反的结果。 1.325％），而尾矿用20％RHA修正。结果表明，添加RHA或Fe-RHA可以减少尾矿中阳离子重金属的利用率，但会增加诸如As等阴离子类金属的利用率。在Fe-RHA样品中为070％，但减少了碳酸盐结合和有机物含量。但是，对于Cd（60.940％至43.250％），Cr（2.214％至1.560％），Cu（3.106％至1.312％），Mn（62.149％至43.740％）和Zn（9.853％至9.65％），Cr（2.214％至1.560％），Mn（62.149％至43.740％），Zn（9.853％至9.53％）观察到相反的结果。 1.325％），而尾矿用20％RHA修正。结果表明，添加RHA或Fe-RHA可以减少尾矿中阳离子重金属的利用率，但会增加诸如As等阴离子类金属的利用率。在Fe-RHA样品中为070％，但减少了碳酸盐结合和有机物含量。但是，对于Cd（60.940％至43.250％），Cr（2.214％至1.560％），Cu（3.106％至1.312％），Mn（62.149％至43.740％）和Zn（9.853％至9.65％），Cr（2.214％至1.560％），Mn（62.149％至43.740％），Zn（9.853％至9.53％）观察到相反的结果。 1.325％）的尾矿用20％RHA修正。结果表明，添加RHA或Fe-RHA可以减少尾矿中阳离子重金属的利用率，但会增加诸如As等阴离子类金属的利用率。