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

环境中重金属分馏的测定对于预测它们的流动性和生物利用度是必要的。本研究旨在评估稻壳灰 (RHA) 和铁包壳稻壳灰 (Fe-RHA) 对金矿尾矿中 As、Cd、Cr、Cu、Mn、Pb 和 Zn 分馏的影响。尾矿用 0%、5%、10% 和 20% (w/w) 的 RHA 或 Fe-RHA 修正，样品在 60% 的田间容量下孵育 80 天。使用顺序提取程序确定不同时间段不同馏分中的金属量。结果表明，RHA的加入提高了尾矿的pH值。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，Fe-RHA 的添加降低了所有速率和孵育期的 pH 值。最低 pH 值 (7. 17) 记录在用 20% Fe-RHA 处理的样品中。RHA 和 Fe-RHA 都将尾矿中易于交换的砷从 17.564% 增加到 25.820%，在用 20% RHA 处理的样品和 Fe-RHA 样品处理的样品中为 21.070%，但减少了碳酸盐结合和有机部分。然而，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%）观察到相反的结果1.325%) 当尾矿用 20% RHA 修正时。结果表明，添加 RHA 或 Fe-RHA 可以降低尾矿中阳离子重金属的可用性，但会增加阴离子类金属（如 As）的可用性。在 Fe-RHA 样品中为 070%，但减少了碳酸盐结合和有机部分。然而，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%）观察到相反的结果1.325%) 当尾矿用 20% RHA 修正时。结果表明，添加 RHA 或 Fe-RHA 可以降低尾矿中阳离子重金属的可用性，但会增加阴离子类金属（如 As）的可用性。在 Fe-RHA 样品中为 070%，但减少了碳酸盐结合和有机部分。然而，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%）观察到相反的结果1.325%) 当尾矿用 20% RHA 修正时。结果表明，添加 RHA 或 Fe-RHA 可以降低尾矿中阳离子重金属的可用性，但会增加阴离子类金属（如 As）的可用性。