In this study, adsorption behaviors and mechanisms of Sb(III) ions onto Fe(III)-treated humus sludge adsorbent (FTHSA) from aqueous solutions was investigated using batch adsorption techniques, Fourier transform infrared (FT-IR) spectra and scanning electron microscopy were coupled to an energy-dispersive spectrometer (EDS). FTHSA was prepared via immersion with 1 mol/L FeCl 3. The effects of dosage, contact time, Sb(III) initial concentration, and pH on the adsorption of Sb(III) onto FTHSA were investigated. Sb(III) adsorption was favored at pH with 2.0 and decreased dramatically with increasing pH. The description of equilibrium data of Sb(III) adsorption by Langmuir, Freundlich, and Dubbin-Radushkevich isotherm models showed that Langmuir model provided the best fit for Sb(III) adsorption with maximum adsorption amount of 9.433 mg/g. Pseudo first-order, pseudo second-order, Elovich, and intraparticle diffusion model were applied to describe the adsorption process of Sb(III) ions onto FTHSA. The results showed that the pseudo second-order model described well how Sb(III) adsorption and chemical adsorption played a dominant role in the adsorption process. The FT-IR spectra also indicated that the chemical interactions as ion exchange among the metal ions and N-H, O-H, C=O, COO, and CO were mainly involved in the adsorption process. Therefore, FTHSA has a suitable potential removal for Sb(III) ions in the practical process.

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Elevated soil concentrations of antimony (Sb) and co-contaminants are frequently encountered where antimony has been mined on a large scale. For instance, the Xikuangshan antimony mine in central South China has sustained, over many centuries, dispersed and spatially variable input of toxic elements into the soil ecosystem. We utilized this unique environment to assess the impact of geochemical conditions on soil microbiology. Geochemical conditions were assessed by monitoring absolute and available fractions of toxic elements and disrupted soil properties. Soil microbiology was studied by high-throughput sequencing and statistical analysis, including principle component analysis and canonical correspondence analysis. Results show that Sb concentrations were ranged from 970 to more than 24,000 mg/kg. As concentrations were three times higher than the regional background values and ten times higher for Pb, 590 times higher for Cd and 30 times higher for Hg. About 5-10% of the total soil Sb was environmentally mobile. Microbial diversity was high, and soil properties such as pH, organic matter, iron and sulfate controlled the absolute microbial activity. We identified strong positive and negative correlations with specific bacterial taxonomic groups which show: (1) an intolerance of available fractions for all elements, e.g., Gemmatimonas, Pirellula, Spartobacteria; (2) a good tolerance of available fractions for all elements, e.g., Povalibacter, Spartobacteria; and (3) a mixed response, tolerating available Sb, Hg and Cd and inhibition by As, Pb, e.g., Escherichia/Shigella and Arthrobacter, and in reverse, e.g., Gemmatimonas and Sphingomonas. The site hosts great diversity dominated by Gram-negative organisms, many with rod (bacillus) morphologies but also some filamentous forms, and a wide range of metabolic capabilities: anaerobes, e.g., Saccharibacteria, metal oxidizing, e.g., Geobacter, chemoautotrophs, e.g., Gemmata, and sulfur reducing, e.g., Desulfuromonas. The bioremediation potential of Arthrobacter and Escherichia/ Shigella for Sb control is highlighted.

Environmental pollution caused by excessive Sb(III) in the water environment is a global issue. We investigated the effect of processing parameters, their interaction and mechanistic details for the removal of Sb(III) using an iron salt-modified biosorbent (Fe(III)-modified Proteus cibarius (FMPAs)). Our study evaluated the optimisation of the adsorption time, adsorbent dose, pH, temperature and the initial concentration of Sb(III). We use response surface methodology to optimize this process, determining optimal processing conditions and the adsorption mechanism evaluated based on isotherm model and adsorption kinetics. The results showed that—(1) the optimal conditions for the adsorption of Sb(III) by FMPAs were an adsorption time of 2.2 h, adsorbent dose of 3430 mg/L, at pH 6.0 and temperature 44.0 °C. For the optimum initial concentration of Sb(III) 27.70 mg/L, the removal efficiency of Sb(III) reached 97.60%. (2) The adsorption process for Sb(III) removal by FMPAs conforms to the Langmuir adsorption isotherm model, and its maximum adsorption capacity (qmax) is as high as 30.612 mg/g. A pseudo-first-order kinetic model provided the best fit to the adsorption process, classified as single layer adsorption and chemisorption mechanism. (3) The adsorption of Sb(III) takes place via the hydroxyl group in Fe–O–OH and EPS–Polyose–O–Fe(OH)2, which forms a new complex Fe–O–Sb and X≡Fe–OH. The study showed that FMPAs have higher adsorption capacity for Sb(III) than other previously studied sorbents and with low environmental impact, it has a great potential as a green adsorbent for Sb(III) in water.