Removal of Arsenic from Groundwater by Industrial Byproducts and Its Comparison with Zero-Valent Iron

A byproduct of the steel industry, basic oxygen furnace slag (BOFS) is used to remove As(III) from groundwater, and its adsorption efficiency is compared with commercially available zero-valent iron (ZVI). Batch experiments were performed to determine their feasibility as adsorbents and to investigate different experimental parameters such as adsorption kinetics, adsorption isotherms, anionic effects, and desorption. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscope (HR-TEM), and X-ray diffraction (XRD) were used to characterize particle size, the surface morphology of pristine materials and As(III)-treated products. As(III) adsorption kinetics occurred on a scale of hours following a pseudo-first-order rate constants ($k_{\mathrm{obs}}$) $0.15–0.85{\min }^{-1}$ and $0.080–0.52{\mathrm{h}}^{-1}$ (at varied adsorbents concentration) of BOFS and ZVI, respectively. The As(III) adsorption affinity by BOFS and ZVI were 0.96 and $1.2\mathrm{mg}\mathrm{As}(\mathrm{III}){\mathrm{g}}^{-1}$ of adsorbents at $1\mathrm{mg}{\mathrm{L}}^{-1}$ As(III) initial concentration, 15°C, which was calculated using Langmuir isotherm, respectively. Interestingly, there was no interference of bicarbonate (${\mathrm{HCO}}_3^{-}$) for both BOFS and ZVI, whereas an increase in anions (${\mathrm{H}}_4{\mathrm{SiO}}_4^0$ and ${\mathrm{H}}_2{\mathrm{PO}}_4^{2-}$) up to 100 mM for As(III) adsorption on BOFS decreased the As(II) adsorption on ZVI and BOFS to 1 and 14–23%, respectively. There was no desorption of arsenic while desorbing with deionized water. However, in the presence of phosphate (100 mM), there was $\sim 20$ and 18% desorption for BOFS and ZVI, respectively. This study shows that BOFS has great potential for in situ remediation, which is $\sim 20$ times cheaper and highly efficient than ZVI for arsenic removal from aqueous solution.