Red mud regulates arsenic fate at acidic pH via regulating arsenopyrite bio-oxidation and S, Fe, Al, Si speciation transformation

Fe(II) bio-oxidation mediates red mud transformations to form Fe(III)/Al (hydr)oxide adsorbent for efficient As(V) removal under acidic conditions

“…In comparison, the maximum As(V) and As(III) adsorption capacities of the original RM were only 5.7 and 1.4 mg/g, respectively. The As(V) adsorption capacity of the biogenic composite Fe(III)/Al (hydr)oxide@cell based adsorbent formed under [Fe(II)]ini of 1 g/L (89.9 mg/g) was significantly higher than that of an RM-based adsorbent (48.5 mg/g) previously prepared by a direct modification with 1 g/L of Fe(III) (in the form of Fe2(SO4)3) [37]. The comparison with other adsorbents (summarized in Table S6) shows that Fe(III)/Al (hydr)oxide adsorbents generated during Fe(II) bio-oxidation are suitable sorbent materials for As(V) removal under acidic conditions.…”

“…Zhang et al recently reported that in the presence of the acidophilic Fe/S-oxidizing bacterium Sulfobacillus (Sb.) thermosulfidooxidans, a small amount of RM can affect the As fate by regulating FeAsS biooxidation and As, Fe, S, Al, and Si speciation transformations, implying there is potential to apply RM as a control for As pollution in acidic environments [37]. However, to date, detailed data are missing particularly on the effects of Fe(II) concentration and the presence of RM on the transformations and As removal capacity of Fe(III) (hydr)oxides, formation of which is catalyzed by AIOP in acidic environments.…”

Biochar Promotes Arsenopyrite Weathering in Simulated Alkaline Soils: Electrochemical Mechanism and Environmental Implications

“…In the biochar and Fe­(III) systems, the shift of peak from 1035 to 1130 cm –1 suggests the formation of biochar-Fe complexes and the bending mode of Fe–OH . In addition, a new peak appears at 600 cm –1 , which may be attributed to the formation of Fe–O bonds . The peak at 1600 shifted slightly to 1615 cm –1 in the biochar and Fe­(III)/As­(V) systems, which may be due to the formation of biochar–Fe-As complexes via carboxyl groups.…”

“…50 In addition, a new peak appears at 600 cm −1 , which may be attributed to the formation of Fe−O bonds. 51 The peak at 1600 shifted slightly to 1615 cm −1 in the biochar and Fe(III)/As(V) systems, which may be due to the formation of biochar−Fe-As complexes via carboxyl groups. The appearance of a new peak at 827 cm −1 indicates the presence of As−O− Fe, 51,52 which could be the formation of amorphous iron arsenate or arsenate adsorbed on iron (oxyhydr)oxide.…”

Efficient dealkalization of red mud and recovery of valuable metals by a sulfur-oxidizing bacterium

“…thermosulfidooxidans is an acidophile (with a pH optimum of 1.9–2.4; Karavaiko et al, 1990 ) that is often abundant in low-pH, sulfur-rich environments, showing a high sulfur oxidation activity at elevated temperatures (Dopson and Lindström, 2004 ). Additionally, the strain YN-22 has a high tolerance for potentially toxic metals and has been shown to be able to oxidize sulfur even under relatively high pH conditions (up to 4.5; Zhang et al, 2021 ). The basal salts medium (BSM) for cultivation comprised (in g/L): (NH 4 ) 2 SO 4 , 3.0; MgSO 4 , 0.5; K 2 HPO 4 , 0.5; KCl, 0.1; Ca(NO 3 ) 2 , 0.01 and yeast extracts 0.2.…”