KOH对富铁富硫酸盐酸性环境中生物成因次生铁矿物合成的影响

生物成因次生铁矿物的高效合成对处理以富铁富硫酸盐为典型环境特征的酸性矿山废水具有重要的工程指导意义.本研究通过细菌培养实验,在富铁富硫酸盐环境(改进型9K液体培养基)中,考察了KOH对嗜酸性氧化亚铁硫杆菌(A.ferrooxidans)催化合成次生铁矿物过程中体系p H、Fe2+氧化率、总Fe沉淀率及次生铁矿物矿相的影响.结果表明,A.ferrooxidans在改进型9K培养基(对照处理)中培养72 h后,p H从原始的2.50下降至2.34,而在对照处理分别加入3.3、6.7与13.4 mmol·L-1KOH的处理体系中培养72 h后,p H却分别降低至2.27、2.15与2.10.同时,KOH的加入能够在一定程度上加速Fe2+的氧化速率及总Fe的沉淀效率.例如,培养至24 h,加入3.3、6.7和13.4 mmol·L-1KOH的处理体系较对照体系Fe2+氧化率分别提高了12.1%、20.3%和23.2%.培养至72 h,加入3.3、6.7和13.4 mmol·L-1KOH的处理体系较对照体系总Fe沉淀率分别增加了26.0%、60.4%和71.8%.通过分析加入6.7 mmol·L-1KOH或3.3 mmol·L-1K2SO4处理体系上述参数的变化情况,可以得出,KOH加速体系酸化、提高Fe2+氧化率及总Fe沉淀率是K+与OH-联合作用所致.本研究不同体系所得次生铁矿物均为黄铁矾与施氏矿物共存的混合物,然而,KOH引入的K+或OH-均有利于体系无定型施氏矿物向晶型黄铁矾类矿物转化.研究结果可为次生铁矿物生物合成及其在酸性矿山废水治理领域的应用提供必要的参数支撑.

Effect of KOH on the formation of biogenic secondary iron minerals in iron- and sulfate-rich acidic environment

Efficient synthesis of biogenic secondary iron minerals facilitated by A. ferrooxidans is of important engineering significance in the treatment of acid mine drainage (AMD), a typical iron- and sulfate-rich acidic effluent. In this study, effect of KOH on pH, Fe²⁺ oxidation rate, total Fe precipitation, and secondary iron minerals phase were investigated during secondary iron minerals formation facilitated by A. ferrooxidans in an iron- and sulfate-rich improved 9K liquid medium through flask experiment. Results showed that pH could decrease from 2.50 at 0 h to 2.34 at 72 h when A. ferrooxidans was incubated in the improved 9K liquid medium as the control treatment. However, the systems pH could decrease to 2.27, 2.15 and 2.10 when A. ferrooxidans was incubated in improved 9K liquid medium with addition of 3.3, 6.7, and 13.4 mmol·L^-1 KOH. Meanwhile, the oxidation rate of Fe²⁺ and the total Fe precipitation rate could be improved by KOH. For example, Fe²⁺ oxidation rate in 3.3, 6.7, and 13.4 mmol·L^-1 KOH-added treatments increased by 12.1%, 20.3%, and 23.2% at 24 h compared with the control treatment, respectively. Total Fe precipitation rates in 3.3, 6.7, and 13.4 mmol·L^-1 KOH-added treatments increased by 26.0%, 60.4%, and 71.8% at 72 h, respectively. In the light of the obtained results, it is found that K⁺ and OH^- jointly result in the decrease of pH, and the increase of Fe²⁺ oxidation and total Fe precipitation rates due to the addition of KOH. In this study, the precipitates formed in different treatments were a mixture of jarosite and schwertmannite. However, schwertmannite could be easily transformed to jarosite when K⁺ or OH^- was added in the system as KOH. The results from this study are helpful in the engineering application of biogenic secondary iron minerals formation for AMD treatment.