Effect of Adsorption on the Biodegradation of Nitrilotriacetate by Chelatobacter heintzii

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• 作者：Harvey Bolton ; Jr. and Don C. Girvin
• 刊名：Environmental Science & Technology
• 出版年：1996
• 出版时间：June 1996
• 年：1996
• 卷：30
• 期：6
• 页码：2057 - 2065
• 全文大小：597K
• 年卷期：v.30,no.6(June 1996)
• ISSN：1520-5851

文摘

Nitrilotriacetic acid (NTA) is a synthetic chelatingagent that was used to decontaminate nuclear reactorsand was disposed at Department of Energy wastesites. NTA may influence the mobility and fate of radionuclides in soils and sediments if it is notbiodegraded. Because it was unclear how adsorptionof NTA would influence its degradation, experimentswere conducted in a model system containinggibbsite and Chelatobacter heintzii with⁶⁰CoNTA atpH 7 and NTA at pH 6 and 8. The rates of NTAdesorption from gibbsite were pH dependent (desorptionhalf-lives at pH 6, 7, and 8 were 80, 16, and 1 h,respectively, while that of Co at pH 7 was 2.5 h forequal molar CoNTA). Degradation rates of NTA insolution by C. heintzii decreased as pH decreasedanddepended on the dominant form of NTA in solution(e.g., biodegradation rates for HNTA^2- >AlOHNTA^-> CoNTA^-). The degradation of NTA wassignificantly slower when NTA was adsorbed to gibbsite. Thisdifference was observed at pH 6 and 8 with NTAand at pH 7 with NTA and equal molar cobalt. Acoupledprocess model successfully simulated NTA desorptionand degradation at all pHs. Both experimental dataand simulations demonstrated that adsorbed NTAwas unavailable for biodegradation and that the rateof desorption limited the rate of biodegradation.Only a fraction of the total⁶⁰Co (i.e., 4%) wasassociatedwith C. heintzii cells after NTA had beendegradedin the presence of gibbsite. Therefore, the biodegradation of NTA by microorganisms similar to C.heintziishould not significantly alter⁶⁰Co sorptiontoaluminum oxides or⁶⁰Co transport where NTAand⁶⁰Co have been co-disposed.