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首页> 外文期刊>Environmental Science & Technology >Removal of Cadmium from Wastewaters by Aragonite Shells and the Influence of Other Divalent Cations
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Removal of Cadmium from Wastewaters by Aragonite Shells and the Influence of Other Divalent Cations

机译：文石壳去除废水中的镉及其他二价阳离子的影响

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The effect of dissolved Zn, Co, Pb, Mg, and Ca on the uptake of cadmium by biogenic aragonite was investigated. Experiments were performed in batch-reactors using metal-cadmium-bearing solutions and shell fragments with diameters in different ranges, the solid/liquid ratio being 10 grams per liter. Different initial concentrations of cadmium and metals (1.0-0.005 mM) were used. Uptake takes place via heterogeneous nucleation of metal-bearing crystallites onto the shell surfaces. Cadmium removal occurs by surface precipitation of otavite. Underthe conditions used here, Co and Ca as well as Pb ≤ 0.3 mM and Zn ≤ 0.3 mM do not have a significant effect on the removal of cadmium. At higher concentrations, Pb and Zn outcompete Cd for the dissolving carbonate ions and thus decrease significantly the Cd removal rates. In contrast, Mg has a slight enhancing effect. Pb and Zn are removed faster than Cd, precipitating as PbCO_3, Pb_3(CO_3)_2(OH)_2, and Zn_5(CO_3)_2(OH)_6. Within 24-72 h, the concentrations of lead, cadmium, and zinc decrease until ～0.5 μM, and the presence of aragonite buffers the solution to a pH above 8 avoiding redissolution. The study demonstrates the high effectiveness of biogenic aragonite in removing Cd and other metals from polluted waters.
机译：研究了溶解的Zn，Co，Pb，Mg和Ca对生物文石吸收镉的影响。使用含金属镉的溶液和直径在不同范围的壳碎片在批反应器中进行实验，固/液比为10克/升。使用了不同的镉和金属初始浓度（1.0-0.005 mM）。吸收是通过将含金属的微晶异质成核到壳表面进行的。去除镉是通过卵石的表面沉淀实现的。在此处使用的条件下，Co和Ca以及Pb≤0.3 mM和Zn≤0.3 mM对镉的去除没有显着影响。在较高的浓度下，Pb和Zn在溶解碳酸根离子方面胜过Cd，因此大大降低了Cd的去除率。相反，Mg具有轻微的增强作用。 Pb和Zn的去除速度比Cd快，沉淀为PbCO_3，Pb_3（CO_3）_2（OH）_2和Zn_5（CO_3）_2（OH）_6。在24-72小时内，铅，镉和锌的浓度降低至〜0.5μM，并且文石的存在使溶液的pH值保持在8以上，从而避免了重新溶解。这项研究证明了生物文石在去除污水中的镉和其他金属方面具有很高的效率。

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