Removal of Cadmium from Wastewaters by Aragonite Shells and the Influence of Other Divalent Cations
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- 作者：Stephan Jü ; rgen Kö ; hler ; Pablo Cubillas ; Juan Diego Rodrí ; guez-Blanco ; Christoph Bauer ; Manuel Prieto
- 刊名：Environmental Science & Technology
- 出版年：2007
- 出版时间：January 1, 2007
- 年：2007
- 卷：41
- 期：1
- 页码：112 - 118
- 全文大小：349K
- 年卷期：v.41,no.1(January 1, 2007)
- ISSN：1520-5851
文摘
The effect of dissolved Zn, Co, Pb, Mg, and Ca on theuptake of cadmium by biogenic aragonite was investigated.Experiments were performed in batch-reactors using metal-cadmium-bearing solutions and shell fragments withdiameters in different ranges, the solid/liquid ratio being10 grams per liter. Different initial concentrations of cadmiumand metals (1.0-0.005 mM) were used. Uptake takesplace via heterogeneous nucleation of metal-bearingcrystallites onto the shell surfaces. Cadmium removaloccurs by surface precipitation of otavite. Under the conditionsused here, Co and Ca as well as Pb 
0.3 mM and Zn 0.3 mM do not have a significant effect on the removalof cadmium. At higher concentrations, Pb and Znoutcompete Cd for the dissolving carbonate ions and thusdecrease significantly the Cd removal rates. In contrast,Mg has a slight enhancing effect. Pb and Zn are removedfaster than Cd, precipitating as PbCO3, Pb3(CO3)2(OH)2,and Zn5(CO3)2(OH)6. Within 24-72 h, the concentrations oflead, cadmium, and zinc decrease until ~0.5 
M, andthe presence of aragonite buffers the solution to a pH above8 avoiding redissolution. The study demonstrates thehigh effectiveness of biogenic aragonite in removing Cdand other metals from polluted waters.
0.3 mM and Zn 0.3 mM do not have a significant effect on the removalof cadmium. At higher concentrations, Pb and Znoutcompete Cd for the dissolving carbonate ions and thusdecrease significantly the Cd removal rates. In contrast,Mg has a slight enhancing effect. Pb and Zn are removedfaster than Cd, precipitating as PbCO3, Pb3(CO3)2(OH)2,and Zn5(CO3)2(OH)6. Within 24-72 h, the concentrations oflead, cadmium, and zinc decrease until ~0.5 M, andthe presence of aragonite buffers the solution to a pH above8 avoiding redissolution. The study demonstrates thehigh effectiveness of biogenic aragonite in removing Cdand other metals from polluted waters.