嗜酸性氧化亚铁硫杆菌介导的次生铁矿物形成的影响因素分析

酸性矿山废水(AMD)具有酸度高并含有大量可溶性Fe、硫酸根及重(类)金属的特点,采用生物矿化法促使AMD中Fe向羟基硫酸铁次生矿物转变,对AMD后期石灰中和减少氢氧化铁和废石膏的产生,提高中和效率具有实际意义.本研究模拟AMD,考察了初始pH、Fe~(2+)浓度、Fe/Na摩尔比对嗜酸性氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)体系中Fe~(2+)氧化率、总Fe沉淀率、次生铁矿物矿相的影响.结果表明,高浓度Na~+会抑制A.ferrooxidans的氧化能力,当Na~+浓度在A.ferrooxidans耐受范围内时,其不影响Fe~(2+)氧化及总Fe沉淀去除效果,表现在160、80、20 mmol·L~(-1)的Fe~(2+)分别在72、48、48 h内被完全氧化,培养至终点时平均总Fe沉淀率分别为20.04%、16.43%、0.99%.此外,在Fe~(2+)浓度为160mmol·L~(-1)体系中,当Fe/Na摩尔比为1.0、2.0时,pH为2.0~2.6时获得次生铁矿物均为纯净施氏矿物.而当Fe/Na摩尔比降至0.5时,次生铁矿物的合成途径开始向黄钠铁矾转移,且其特征衍射峰随着Na~+浓度提高而愈加显著.本研究结果可为生物合成次生铁矿物工艺的优化及其在AMD治理领域的有效应用提供必要的参数支撑.

Factors affecting the formation of secondary iron minerals mediated by Acidithiobacillus ferrooxidans

Acid mine drainage (AMD) is characterized typically by high acidity, soluble Fe, sulfate, and toxic metals. Thus, it is of practical significance to promote the transformation of soluble Fe and sulfate into secondary iron hydroxysulfate minerals by biomineralization of Acidithiobacillus ferrooxidans, which is helpful in enhancing subsequent lime neutralization efficiency of AMD and reducing the production of ferric hydroxide and waste gypsum. In the study, we investigated that the influence of initial pH, Fe²⁺ concentration, molar ratio of Fe/Na on the bio-oxidation rate of Fe²⁺, total Fe deposition efficiency, and phases of secondary iron minerals in simulated AMD containing Acidithiobacillus ferrooxidans. The results indicate that a higher concentration of Na⁺ significantly inhibited the biological oxidation of Fe²⁺. However, when Na⁺ concentration was lower than tolerance concentration for Acidithiobacillus ferrooxidans, Fe²⁺ oxidation and total Fe removal through precipitation were not influenced. Results show that 160, 80 and 20 mmol·L^-1 of Fe²⁺ could be completely oxidized within 72, 48 and 48 h, with average total Fe removal efficiency being 20.04%, 16.43% and 0.99%, respectively. In addition, when the molar ratio of Fe/Na was 1 and 2, the secondary iron minerals obtained in pH range between 2.0~2.6 were still pure schwertmannites, with initial Fe²⁺ at 160 mmol·L^-1. When The molar ratio of Fe/Na drops to 0.5, natrojarosite begin to occur the characteristic diffraction peak in XRD analysis become strong with the increase of Na⁺ concentration. The resutls of this study can provide a novel approach and optimization strategy in improving the biosynthesis of secondary iron minerals in AMD.