Study of the Mechanisms of Cadmium Biosorption by Dealginated Seaweed Waste
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- 作者：Marí ; a E. Romero-Gonzá ; lez ; Ceri J. Williams ; and Philip H. E. Gardiner
- 刊名：Environmental Science & Technology
- 出版年：2001
- 出版时间：July 15, 2001
- 年：2001
- 卷：35
- 期：14
- 页码：3025 - 3030
- 全文大小：86K
- 年卷期：v.35,no.14(July 15, 2001)
- ISSN：1520-5851
文摘
The ability of dealginated seaweed waste, a wastematerial derived from the commercial processing ofseaweed for alginate production, to remove cadmiumfrom solution was determined. Cadmium sorption was foundto be rapid (91% removal within 5 min), achieving aresidual concentration of 0.8 mg L-1 after 1-h contacttime from an initial solution concentration of 10 mg L-1.The binding of cadmium by dealginate was found to be pHdependent, optimal sorption occurring at around pH6-8. The mechanism of cadmium ion binding by dealginatewas investigated by a number of techniques. Potentiometrictitration of the dealginate revealed two distinct pKavalues, the first having a value similar to carboxyl groupsand the second comparable with that of saturatedthiols and amines. Esterification of the dealginate resultedin the subsequent reduction in cadmium sorption (95%to 17%), indicating that carboxyl groups are largely responsiblefor sorption. Evidence from FT-IR spectra confirmed thepresence of carboxyl groups in untreated dealginate, whilethe number of carboxyl groups was markedly reduced inthe esterified sample. Furthermore, the FT-IR spectrum fordealginate was found to be similar to that previouslyreported for mannuronic acid-rich calcium alginate.Determination of a molar ratio in the displacement ofcalcium by cadmium on dealginate further supported thepresence of an ion-exchange relationship. The ion-exchangeconstant was calculated to be 0.329 × 10-6. The speciationof cadmium in solution both before and after sorptionwas determined by an ion-selective electrode (ISE) technique.The findings of this study suggest that the sorption ofcadmium by dealginate is mainly due to an ion-exchangemechanism.