针铁矿对硫酸盐还原菌分解铅矾的影响

铅矾(PbSO_4)是工业生产中释放进入环境的重要含Pb物相,具有潜在的环境风险.采用硫酸盐还原菌(SRB)在厌氧条件下将重金属沉淀形成低溶度积的硫化物是有效固定重金属的方法之一.本研究重点考察了SRB作用下铅矾的转化过程及针铁矿对铅矾分解的影响.结果表明,反应体系中溶液p H和ORP均有所降低;SO_4~(2-)在SRB生长停滞期上升,随后保持稳定;酸可挥发性S浓度随SRB的生长逐渐升高,并最后保持稳定;实验结束后铅矾大部分转化为白铅矿(PbCO_3)和方铅矿.对结果的分析表明,在SRB作用下,铅矾分解转化的机制为:首先转化为白铅矿,其次硫酸盐被还原产生S~(2-),进一步促进铅矾的分解和白铅矿的形成,最后S~(2-)同溶液及新生白铅矿中的Pb~(2+)反应生成溶度积更低的方铅矿;针铁矿的主要作用为:固定溶液中的S~(2-),降低铅矾SRB分解的环境污染风险;通过作为SRB生长的电子受体和降低S~(2-)的生物毒害作用,提高体系中SRB的生物活性.

Effect of goethite on the decomposition of anglesite by sulfate-reducing bacteria

Anglesite (PbSO₄) generated from industrial process is an important Pb-containing substance and has a potential risk of environmental pollution. Transformation of anglesite to galena (PbS) by sulfate-reducing bacteria (SRB) under anaerobic condition is an effective technique for Pb immobilization (formation of met al sulfide with a lower solubility product)). In the current study the transformation process of PbSO₄ with SRB was investigated and the effects of goethite was explored. Results show that pH and redox potential decreased gradually in the batch experiments. Aqueous SO^2-₄increased in the first 40 h when SRB was in the static state. SO^2-₄ was kept stable during the following exponential and steady growth phase of SRB. Protein and acid volatile sulfur increased with the growth of SRB. When the experiment was terminated, it was found that anglesite had been transformed to cerussite (PbCO₃) and PbS. Mechanism for SRB mediated immobilization of Pb is elucidated as follows. Firstly, PbSO₄ reacted with the aqueous carbonate and generated PbCO₃ which has a low solubility. Secondly, S^2- was generated from the reduction of SO^2-₄ which further accelerated the decomposition of PbSO₄ and the generation of PbCO₃. Thirdly, the S^2- reacted with the aqueous Pb²⁺ and Pb²⁺ in PbCO₃ to generate PbS, which has a lower solubility. The role of goethite in the process was attributed to the immobilization of S^2- decrease the risk of pollution caused by PbSO₄ decomposition and to work as the electron acceptors for SRB and reduce the toxic effect on SRB activity.