Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, China.
Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-environmental Science & Technology, Guangzhou 510650, China.
J Environ Manage. 2018 Jul 1;217:747-753. doi: 10.1016/j.jenvman.2018.04.023. Epub 2018 Apr 24.
Much attention has been paid to the relationship between microbial iron reduction and the behavior of cadmium (Cd) recently, but most previous research has employed unrealistically high Cd concentrations (e.g., 2-55 mg L) and has failed to consider the effects of iron oxides and microbial cells together. We investigated the reduction of lepidocrocite by Shewanella oneidensis MR-1 in the presence of a low concentration of Cd using batch reactor systems. The results showed that with 422 μg L added dissolved Cd, an initial 137 μg L decrease in aqueous Cd occurred due to adsorption onto lepidocrocite and that the further removal of remaining aqueous Cd occurred only in the system containing bacteria. This further decrease in aqueous Cd was unlikely to be caused by mineral transformation because the microbial reduction of lepidocrocite resulted in particle-size-increased (thus, specific-surface-area-decreased) lepidocrocite, and unlikely to be caused by the pH increase to 7.4 induced by iron reduction either because a pH-adsorption edge suggested that at pH 7.4, less than 60% of aqueous Cd can be adsorbed by lepidocrocite in the reactors. An adsorption isotherm showed a significant Cd adsorption capacity by S. oneidensis MR-1 cells, and we therefore attributed the further Cd removal to adsorption by S. oneidensis MR-1 cells. The results suggest that a realistically low concentration of Cd can be immobilized during microbial iron reduction by adsorption on iron oxides and microbial cells.
最近，人们对微生物还原铁与镉（Cd）行为之间的关系给予了极大关注，但大多数先前的研究都采用了不切实际的高 Cd 浓度（例如，2-55mg/L），并且没有考虑到铁氧化物和微生物细胞的共同作用。我们使用批式反应器系统研究了 Shewanella oneidensis MR-1 在低浓度 Cd 存在下对纤铁矿的还原作用。结果表明，在添加了 422μg/L 的溶解 Cd 的情况下，由于吸附到纤铁矿上，最初的 137μg/L 的水溶液 Cd 减少了，并且只有在含有细菌的系统中才会进一步去除剩余的水溶液 Cd。这种水溶液 Cd 的进一步减少不太可能是由于矿物转化引起的，因为微生物还原纤铁矿导致粒径增大（因此，比表面积减小）的纤铁矿，也不太可能是由于铁还原引起的 pH 增加到 7.4 引起的，因为 pH 吸附边缘表明在 pH 7.4 时，不到 60%的水溶液 Cd 可以被反应器中的纤铁矿吸附。吸附等温线显示出 S. oneidensis MR-1 细胞对 Cd 的显著吸附能力，因此，我们认为进一步去除 Cd 是由于 S. oneidensis MR-1 细胞的吸附作用。研究结果表明，在微生物还原铁的过程中，通过吸附在铁氧化物和微生物细胞上，可以固定真实的低浓度 Cd。
