基于铁屑铁细菌与硫酸盐还原菌协同治理锑矿废水的作用及机理研究

Antimony(Sb) is detected in water with elevated concentration due to a variety of industrial applications and mining activities. Remediation of Sb mine drainage by adsorption has gained widely attention. Iron oxides has better absorption performance for Sb(III) and Sb(V) than other adsorbents. However, these mineral sorbents prepared by chemical methods is cost-prohibitive and a high concentration of sulphate can decrease the absorption of Sb. Sulfate-reducing bacteria can reduce sulphate to hydrogen sulfide and precipitate with Sb. However, dissolved oxygen is poisonous to sulfate-reducing bacteria, and lack of organic matter can result in low activity of sulfate-reducing bacteria. In this project, scrap iron is used to treat Sb mine drainage, and biomineralized iron oxides by autotrophic iron bacteria is an efficiency adsorbent for Sb, then the commensal sulfate-reducing bacteria can also reduce sulphate to hydrogen sulfide in this micro environment. The main operations of this project include: iron bacteria and sulfate-reducing bacteria is screened from soil which is polluted by Sb, and then the bacteria is cultured in the presence of scrap iron. The composites material of activated iron bacteria, sulfate-reducing bacteria and scrap iron are constructed and this material is used to treat Sb(V). By optimizing scrap iron mass, iron bacteria and sulfate-reducing bacteria biomass, the optimal parameters of composites for Sb removal are obtained. Based on dynamic experiment, products morphology analysis and variation of microbial community, the principle and key process of Sb(V) removal by composites material are obtained. The continuous treatment of practical Sb mine drainage by composite material is studied using dynamic analog instruments, meanwhile recycling Sb from precipitate is conducted. Finally, an environment-friendly and highly efficient technique for treating the Sb mine drainage is obtained through the above studies.

针对化学法合成铁氧化物治理锑矿废水成本高、且大量硫酸盐产生竞争吸附，而硫酸盐还原菌(SRB)法去除锑又面临着营养源匮乏，溶解氧抑制微生物活性的问题。本项目采用廉价铁屑处理锑矿废水，充分利用化能自养型铁细菌生物成因铁氧矿物高效吸附锑，并考虑铁屑与铁细菌共存所构成的微环境下SRB生物沉淀除锑能力。实施过程为：从受锑矿废水污染环境筛选出铁细菌和SRB，驯化培养，使其能够腐蚀铁屑生存；构建铁细菌-SRB-铁屑三者共存体系，优化铁屑质量、铁细菌与SRB生物量，提出去除Sb(V)的最佳体系构成参数；通过批实验研究共存体系对污染物的去除，测定产物化学组成与微生物群落结构动态变化，阐明铁细菌和SRB协同铁屑去除锑的作用机理和关键过程；通过模拟装置研究铁细菌-SRB-铁屑在动态条件下对实际锑矿废水去除情况，以明确共存体系的适用范围，回收沉淀物中的金属锑，为锑矿废水治理提供一种新的思路。

项目采用廉价铁屑处理锑矿废水，充分利用化能自养型铁细菌生物成因铁氧矿物高效吸附锑，并考虑铁屑与铁细菌共存所构成的微环境下SRB生物沉淀除锑能力。研究发现零价铁去除Sb(V)的主要机理为铁腐蚀生成铁的氧化物/氢氧化物然后吸附Sb(V)。微米级铁粉对Sb(V)去除效果较高，浮游球衣菌可对Fe3+离子起到生物矿化作用，但该生物成因铁氧矿物在Sb(V)去除中并没有发挥重要作用，反而抑制了微米级铁粉对Sb(V)的去除率。这表明应从环境中筛选对Fe0的氧化能力更强的兼性好氧铁氧化菌，同时选用颗粒较粗的废铁屑作为修复材料。项目从污水厂污泥中筛选出了一株自养型铁氧化细菌，该铁菌株在24h内可将溶液中60%的 Fe2+氧化生成铁氧化物。经富集分离得到一株硫酸盐还原菌，该菌株为脱硫弧菌属（Desulfovibrio）的一个分支。筛选所得的铁氧化细菌、硫酸盐还原菌自身对Sb(V)的吸附能力较低。中性条件下单独铁屑对溶液中Sb(V)的去除率为50%，共存硫酸盐降低了去除效果。构建铁屑-铁氧化细菌共存体系，尽管酸性条件下单独铁屑除锑效果较好，但是pH对该共存体系除锑影响不明显，这是因为酸性环境下铁细菌生长状况不好，铁细菌不能高效氧化Fe0。重要的是铁屑-铁氧化细菌除锑反应48h后出现了二次释放现象，反应7d后去除率在60%左右。构建铁屑-铁细菌-硫酸盐还原菌共存体系，该三者共存体系除锑效果最佳，高达87%，并且微生物生命力顽强，在反应7d后，除锑效果仍然上升。一般来说，化学反应在24h内达到稳定，而三者共存体系反应7d仍有效果，这说明了在反应后期微生物发生了显著的作用。将收集的锑矿废水通过蠕动泵向密闭反应装置下部进液，发现出水中Sb(V)浓度变化趋势和SO42-并不同步，相对来说体系对Sb(V)吸附作用更强，反应前20天出水中几乎不含Sb(V)，但是随着反应的进行去除效果逐渐降低，反应100天后，硫酸盐还原菌的活性基本失效，但是整个体系仍具有一定的除锑能力。总之，废铁屑价格低廉来源丰富，且可达到了以废治废，应用于锑矿废水治理前景广泛。