Influence of Monovalent Cations on the Efficiency of Ferrous Ion Oxidation, Total Iron Precipitation, and Adsorptive Removal of Cr(VI) and As(III) in Simulated Acid Mine Drainage with Inoculation of Acidithiobacillus ferrooxidans

Abstract

Acid mine drainage is highly acidic and contains large quantities of Fe and heavy metal elements. Thus, it is important to promote the transformation of Fe into secondary iron minerals that exhibit strong heavy-metal removal abilities. Using simulated acid mine drainage, this work analyzes the influence of monovalent cations (K + , NH 4 + , and Na + ) on the Fe 2+ oxidation and total Fe deposition efficiencies, as well as the phases of secondary iron minerals in an Acidithiobacillus ferrooxidans system. It also compares the Cr(VI) (K 2 Cr 2 O 7 ) and As(III) (As 2 O 3 ) removal efficiencies of different schwertmannites. The results indicated that high concentrations of monovalent cations (NH 4 + ≥ 320 mmol/L, and Na + ≥ 1600 mmol/L) inhibited the biological oxidation of Fe 2+ . Moreover, the mineralizing abilities of the three cations differed (K + > NH 4 + > Na + ), with cumulative Fe deposition efficiencies of 58.7%, 28.1%, and 18.6%, respectively [n(M) = 53.3 mmol/L, cultivation time = 96 h]. Additionally, at initial Cr(VI) and As(III) concentrations of 10 and 1 mg/L, respectively, the Cr(VI) and As(III) removal efficiencies exhibited by schwertmannites acquired by the three mineralization systems differed [n(Na) = 53.3 > n(NH 4 ) = 53.3 > n(K) = 0.8 mmol/L]. Overall, the analytical results suggested that the removal efficiency of toxic elements was mainly influenced by the apparent structure, particle size, and specific surface area of schwertmannite.

Impact of Fulvic Acid and Acidithiobacillus ferrooxidan Inoculum Amount on the Formation of Secondary Iron Minerals

“…For example, schwertmannite possesses hydroxyl groups, sulfate groups, and a large specific surface area. It has been reported in the literature that the adsorption capacity of As by schwertmannite has a good adsorption effect on both As and Cr [ 17 , 18 ]. Cu 2+ and Pb 2+ also exist in the form of ternary complexes on the surface of schwertmannite [ 19 ], which plays an important role in the migration of heavy metals and has a potential application value.…”

The Important Role of Dissolved Oxygen Supply Regulated by the Hydraulic Shear Force during the Biosynthesis of Iron Hydroxysulfate Minerals

“…The primary factors controlling the formation of iron hydroxysulfate minerals are the reaction time, temperature, acidity, Fe 2+ concentration and the monovalent cation type and concentration (K + , Na + , NH 4 + , etc.) [21][22][23][24]. In an extremely acidic environment, the A. ferrooxidans-mediated biomineralization involves the biologic oxidation of Fe 2+ and thus facilitate Fe hydrolysis.…”