Antimonate sequestration from aqueous solution using zirconium, iron and zirconium-iron modified biochars

Abstract

Antimony (Sb) is increasingly being recognized as an important contaminant due to its various industrial applications and mining operations. Environmental remediation approaches for Sb are still lacking, as is the understanding of Sb environmental chemistry. In this study, biosolid biochar (BSBC) was produced and utilized to remove antimonate (Sb(V)) from aqueous solution. Zirconium (Zr), Zirconium-iron (Zr–Fe) and Fe–O coated BSBC were synthesized for enhancing Sb(V) sorption capacities of BSBC. The combined results of specific surface area, FTIR, SEM–EDS, TEM–EDS, and XPS confirmed that Zr and/or Zr–Fe were successfully coated onto BSBC. The effects of reaction time, pH, initial Sb(V) concentration, adsorbate doses, ionic strength, temperature, and the influence of major competitive co-existing anions and cations on the adsorption of Sb(V) were investigated. The maximum sorption capacity of Zr–O, Zr–Fe, Zr–FeCl3, Fe–O, and FeCl3 coated BSBC were 66.67, 98.04, 85.47, 39.68, and 31.54 mg/g respectively under acidic conditions. The XPS results revealed redox transformation of Sb(V) species to Sb(III) occurred under oxic conditions, demonstrating the biochar’s ability to behave as an electron shuttle during sorption. The sorption study suggests that Zr–O and Zr–O–Fe coated BSBC could perform as favourable adsorbents for mitigating Sb(V) contaminated waters.

Adsorption–Desorption Behavior of Arsenate Using Single and Binary Iron-Modified Biochars: Thermodynamics and Redox Transformation

“…The peak close to 2300–2400 cm –1 assigned to the presence of atmospheric CO 2 . 85 These represent stretching and vibration peaks of −O–H and H–O–H, respectively, further indicating the bending and deformation of water molecules. 66 …”

“…Iron chips (Fe) and iron-salt (FeCl 3 ·6H 2 O) were separately used to synthesize Fe-BCs by employing an in situ precipitation method according to Rahman et al (2021b). 85 To this end, 5.58 g Fe-chips [(Fe-chips (99.98% purity) was purchased from Sigma)] was dissolved in 100 mL of HCl (1:1) to prepare 0.1 M Fe-chips solution. Following this, 5.0 g of ground BSBC (<1 mm) was submerged into a 50 mL of Fe-chips or Fe-salt solution (0.1 M FeCl 3 ·6H 2 O) (mass ratio of Fe to BC = 1:1) adjusted at pH 6.5 by adding 0.1 M NaOH.…”

“…A bimetal adsorbent-like Zr–FeCl 3 .6H 2 O BC composite (Zr to Fe molar ratio 1:5) was synthesized following the same method, as described by Rahman et al (2021b). 85 All synthesized BC composites were rinsed 3–4 times with MQ water to remove any impurities followed by centrifugation (5000 rpm for 15 min) and finally dried in an oven at 80 °C. The produced BCs were preserved in a desiccator after being labeled as FeB, FeCl 3 B, and Zr–FeCl 3 B, respectively, for further experiments.…”

“…Iron chips (Fe) and iron-salt (FeCl 3 ·6H 2 O) were separately used to synthesize Fe-BCs by employing an in situ precipitation method according to Rahman et al (2021b) . To this end, 5.58 g Fe-chips [(Fe-chips (99.98% purity) was purchased from Sigma)] was dissolved in 100 mL of HCl (1:1) to prepare 0.1 M Fe-chips solution.…”

“…Thus, the resulting BC suspension was aged for 12 h at room temperature. A bimetal adsorbent-like Zr–FeCl 3 .6H 2 O BC composite (Zr to Fe molar ratio 1:5) was synthesized following the same method, as described by Rahman et al (2021b) . All synthesized BC composites were rinsed 3–4 times with MQ water to remove any impurities followed by centrifugation (5000 rpm for 15 min) and finally dried in an oven at 80 °C.…”