有机酸对针铁矿和膨润土吸附Cd^(2+)、Pb^(2+)的影响

EFFECTS OF ORGANIC ACIDS ON ADSORPTION OF Pb^(2+) AND Cd^(2+) BY GOETHITE AND BENTONITE

用平衡吸附法研究了不同浓度的有机酸(乙酸、酒石酸和柠檬酸)对针铁矿和膨润土吸附Cd2+、Pb2+的影响。结果表明:(1)低浓度(<0.6 mmol L-1)有机酸促进供试矿物吸附Cd2+和Pb2+,随着有机酸浓度增加,吸附逐渐被抑制。高浓度(>1.0 mmol L-1)有机酸对Pb2+吸附的抑制作用比对Cd2+的强。有机酸浓度的变化对针铁矿Cd2+、Pb2+吸附率的影响大于对膨润土的。(2)不同Cd2+浓度下,有机酸对膨润土Cd2+吸附强度的影响大于针铁矿。加入高浓度Cd2+(8.0 mmol L-1)时,低浓度有机酸对膨润土吸附Cd2+的促进作用比加入低浓度Cd2+(0.4 mmol L-1)时明显,高浓度有机酸对膨润土吸附Cd2+的抑制作用与低浓度Cd2+时相近。(3)低浓度有机酸(<0.6 mmol L-1)时,酒石酸、柠檬酸对针铁矿吸附Cd2+的促进作用大于乙酸,而它们对膨润土吸附Cd2+的促进作用相似;在三种有机酸高浓度(>1.0 mmol L-1)时,针铁矿对Cd2+的吸附都趋于稳定,而柠檬酸对膨润土吸附Cd2+的抑制作用比乙酸和酒石酸的明显。不同种类有机酸下,矿物对Pb2+吸附率大小的变化基本一致。

Effects of organic acids （acetic acid, tartaric acid and citric acid） on adsorption of Cd^2＋ and Pb^2 ＋ by goethite and bentonite were studied with the batch method. The results show that Cd^2＋ and Pb^2＋ adsorption by the tested minerals was promoted by organic acids low in concentration （ 〈 0.6 mmol L^- 1 ）, whereas the adsorption was inhibited with the concentration of the organic acids rising. The inhibiting effect of the organic acids on Pb^2 ＋ adsorption by goethite and bentonite were stronger than on Cd^2＋ adsorption when the concentration was 〉 1.0 mmol L^-1. The effect of change in concentration of the organic acids on Cd^2＋ and Pb^2＋ adsorptions varied with minerals, and was more obvious on goethite than on bentonite. The effect of the organic acid on Cd^2 ＋ adsorption intensity on bentonite was greater than on goethite even if the concentration of added Cd^2 ＋ varied. The effect of low concentration organic acid promoting Cd^2 ＋ adsorption by bentonite was more obvious when the concentration of Cd^2 ＋ was high （8.0 mmol L^-1） than when it was low （0.4 mmol L^-1） , but the inhibiting effect of high concentration organic acids on Cd^2 ＋ adsorption by bentonite remain approximate whether the concentration of Cd^2 ＋ was high or low. The Cd^2 ＋ adsorption by goethite was more obviously promoted by tartaric acid and citric acid than by acetic acid when they were low in concentration （ 〈 0.6 mmol L^-1） , but the promoting effects of the three organic acids on Cd^2 ＋ adsorption by goethite were similar. When the concentrations （ 〉 1.0 mmol L^-1） of the organic acids were high, their effects on Cd^2 ＋ adsorption by goethite were stable, but the Cd^2 ＋ adsorption by bentonite was more obviously restricted by citric acid than by acetic acid or tartaric acid. The effects of the three kinds of organic acids on Pb^2＋ adsorption on two minerals were almost the same.