色氨酸对生物成因铁硫酸盐次生矿物形成的影响

采用氧化亚铁硫杆菌催化合成铁硫酸盐次生矿物,研究不同L-色氨酸添加浓度对矿物合成体系pH、氧化还原电位(ORP)、Fe²⁺氧化率、总Fe沉淀率,以及次生矿物产量、化学组成及矿物相的影响.结果表明,随着体系色氨酸浓度的增加,pH降低幅度越小,ORP上升越不明显.色氨酸对铁硫酸盐次生矿物合成的影响依赖于其浓度,当色氨酸浓度低于1.67 g·L^-1时,色氨酸对铁硫酸盐次生矿物的形成起促进作用,表现为总Fe沉淀率及矿物产量随着色氨酸浓度升高而增加.而当色氨酸浓度升高至6.67 g·L^-1时,Fe²⁺氧化率、总Fe沉淀率和矿物产量远低于对照组,表明高浓度色氨酸会抑制铁硫酸盐次生矿物的形成.次生矿物内Fe/S比介于施氏矿物和黄钾铁矾的理论值之间,表明不同合成体系所得次生矿物均为黄钾铁矾和施氏矿物的混合物.矿物学特征分析表明,随着色氨酸浓度的升高,矿物的合成表现为黄钾铁矾向施氏矿物转移.

Influence of tryptophan on formation of biogenic secondary iron hydroxysulfate minerals

Secondary iron hydroxysulfate minerals were synthesized by A. ferrooxidans in solution with different L-tryptophan concentrations. Trends in pH, oxidation reduction potential (ORP), Fe²⁺ oxidation efficiency and total Fe precipitation efficiency, and the amount, elemental composition and mineral phase of secondary minerals in incubation systems were investigated. The results indicated that the higher the concentration of L-tryptophan in systems, the smaller the decreasing range of pH and the increasing range of ORP. The effect of L-tryptophan on secondary iron hydroxysulfate minerals formation is related to the concentration of L-tryptophan. When the concentration of L-tryptophan was lower than 1.67 g·L^-1, the more L-tryptophan added in systems, the higher total precipitation efficiency and the more amount of biogenic minerals formed, indicating that L-tryptophan could stimulate iron hydroxysulfate mineral formation under a certain concentration. While the L-tryptophan addition was up to 6.67 g·L^-1, Fe²⁺ oxidation efficiency, total precipitation efficiency and the amount of biogenic minerals formed in this system were far below those of the control system, suggesting that high concentration of L-tryptophan would restrain the formation of iron hydroxysulfate mineral. The Fe/S ratios of secondary minerals were between the theoretical value of jarosite and schwertmannite, suggesting that the secondary minerals obtained from the five systems were all mixtures of jarosite and schwertmannite. Mineralogical analyses showed that A. ferrooxidans tended to mediate the formation of schwertmannite from jarosite with the increasing of L-tryptophan concentration.