As(Ⅴ)对嗜酸性氧化亚铁硫杆菌混合培养物氧化性能的影响

通过对pH、Eh、溶液中Fe2+浓度的定期监测以及对实验结束时生成沉淀的XRD、SEM和元素能谱扫描等手段,对比研究了不同初始浓度的As(Ⅴ)对Fe2+的化学氧化和嗜酸性氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)氧化的影响, 同时就As(Ⅴ)在实验体系中固液相之间的分配行为进行了分析.结果表明,Fe2+的化学氧化速率极低,最终氧化率低于8%,As(Ⅴ)的浓度对Fe2+的化学氧化没有影响.有A. ferrooxidans的实验体系,100 mg/L As(Ⅴ)对Fe2+的氧化具有一定的促进作用.当As(Ⅴ)浓度为500 mg～1 g/L时,Fe2+的氧化率在约60 h左右即可达到100%;但4g/L的As(Ⅴ)则会明显抑制Fe2+的氧化,Fe2+的完全氧化大约需要106 h.体系中初始的100 As/(As+S)(摩尔比)会对沉淀物的物相及结晶程度造成一定影响.As(Ⅴ)浓度为0 g/L时,微生物体系中生成的固体沉淀物黄钾铁矾的特征峰明显,随着As(Ⅴ)浓度的提高,沉淀物的结晶程度逐步下降,至4 g/L时沉淀物全部为无定形.元素能谱扫描检测到有大量的As(Ⅴ)存在于固体沉淀物中,表明在Fe2+的氧化过程中,As(Ⅴ)可能会以吸附或共沉淀的形式被固定在固相沉淀物中,这为酸性矿坑水(AMD)地区As(Ⅴ)污染的治理提供了重要的参考.

The effect of As(Ⅴ) on the oxidizing capacity of the mixed culture of Acidithiobacillus ferrooxidans

Comparable studies were conducted between chemical oxidation and microbial oxidation of ferrous sulfate by a mixed culture of Acidithiobacillus ferrooxidans in the presence of different concentrations of As(V). Eh, pH and Fe~(2+) concentration were monitored periodically and the final precipitation was analyzed by X-ray diffraction (XRD) and SEM. The data obtained showed and chemical oxidation of Fe~(2+) was very slow with a final oxidizing ratio of <8% and As(V) had no effect on Fe~(2+) oxidation chemically. Slight enhancement of Fe~(2+) oxidation was observed by 100 mg/ L As( V ) in the microbial system. Complete oxidation of Fe~(2+) could be reached in about 60 hours in the presence of A. ferrooxidans with 500 mg~l g/L As( V ). However, microbial Fe~(2+) oxidation was greatly inhibited by 4 g/L As( V ) and about 106 hours were needed for complete oxidation. Initial mole ratios of 100 As/ (As + S) affected the final solid phase and the crystallization of the precipitation. In the microbial system, typical symmetric peaks of jarostie were clearly distinguished in the precipitates with ≤1g/L As( V ) but the crystallization was decreasing with the increase of As( V ) concentration. Only amorphous solid was observed in the precipitate with 4 g/L As( V ). Elemental mapping indicated that As was evenly distributed in the precipitates either by adsorption or by structural incorporation during the iron oxidation. These results provide important information for the treatment of As contamination in AMD regions.