富里酸对生物成因次生高铁矿物形成的影响

为揭示在富硫酸盐环境中富里酸对生物成因次生高铁矿物形成的影响，通过摇瓶试验，研究了嗜酸性氧化亚铁硫杆菌（A. ferrooxidans）参与不同富里酸浓度，对次生高铁矿物合成体系中pH、Fe2+氧化率、TFe沉淀率，以及矿物矿相、官能团、形貌和元素组成的影响。结果表明，pH变化整体呈现先上升后下降的趋势。富里酸浓度0.2-0.4 g/L体系在72h内Fe2+完全氧化，富里酸浓度0.6-1.0 g/L体系在144 h后Fe2+逐渐完全氧化，FA-0.2 g/L体系最高氧化速率（6.69 mmoL/L）是空白组（3.93 mmoL/L）的1.7倍，表明低浓度的富里酸能够促进Fe2+的氧化，提高氧化速率，高浓度的富里酸对A. ferrooxidans活性具有抑制作用，使氧化率降低，Fe2+最高氧化速率延迟。富里酸浓度低于0.4 g/L时，TFe沉淀率与空白组相近；富里酸浓度高于0.6 g/L时，TFe沉淀率比空白组有显著的提高，富里酸浓度的提高促进了Fe3+的水解。随着富里酸浓度提高，次生高铁矿物主衍射峰强度逐渐增强，但其官能团未发生改变，在富里酸浓度0.6-1.0 g/L体系中可以通过SEM察到施氏矿物且其含量逐渐增加，通过EDS分析，试验组K元素含量低于空白组，N和C元素高于空白组，表明富里酸浓度提高抑制黄钾铁矾的生成，有利于黄铵铁矾和施氏矿物的生成且次生高铁矿物对富里酸具有吸附作用

Effect of fulvic acid on biogenic secondary high iron minerals synthesis

To reveal the effect of fulvic acid on the formation of biogenic secondary high iron minerals in sulfate-rich environments, the effects of the involvement of A. ferrooxidans in different fulvic acid concentrations on the pH, Fe2+ oxidation rate, TFe precipitation rate, and mineral phases, functional groups, morphology and elemental composition of the secondary high mineral synthesis system were investigated by shake flask tests. The results show an overall trend of increasing and then decreasing pH changes. The system with fulvic acid concentrations of 0.2-0.4 g/L showed complete oxidation of Fe2+ within 72 h. The system with fulvic acid concentrations of 0.6-1.0 g/L showed gradual complete oxidation of Fe2+ after 144 h. The highest oxidation rate of the FA-0.2 g/L system (6.69 mmoL/L) was 1.7 times higher than that of the control (3.93 mmoL/L), indicating that Low concentrations of fulvic acid can promote the oxidation of Fe2+ and increase the oxidation rate, while high concentrations of fulvic acid have an inhibitory effect on the activity of A. ferrooxidans, resulting in a lower oxidation rate and a delay in the maximum oxidation rate of Fe2+. When fulvic acid concentration was lower than 0.4 g/L, the TFe precipitation rate was similar to that of the control. When the concentration of fulvic acid was higher than 0.6 g/L, the TFe precipitation rate was significantly higher than that of the control, and the increase in fulvic acid concentration promoted the hydrolysis of Fe3+. As the concentration of fulvic acid increased, the intensity of the main diffraction peaks of the secondary high iron minerals gradually increased, but their functional groups did not change. In the system with fulvic acid concentration of 0.6-1.0 g/L, schwertmannite could be observed by SEM and its content gradually increased. By EDS analysis, the content of K element in the experimental group was lower than that in the control, while the content of N and C elements was higher than that in the control. The results showed that the increase of the concentration of fulvic acid inhibited the formation of jarosite, which was beneficial to the formation of ammoniojarosite and schwertmannite, and the secondary minerals had adsorption effect on fulvic acid.