Comparative Adsorptive Removal of Arsenate From Water Systems Using Iron Phosphate (FePO ₄ ), Unmodified, and Iron‐Impregnated Activated Carbons From Water Systems

ABSTRACT Arsenic contamination in aquatic systems presents severe environmental and health hazards and can result from both human activities and natural occurrences. The focus of the current study was to investigate arsenate adsorption onto FePO 4 , unmodified activated carbon (VAC), and iron‐impregnated activated carbon (Fe‐AC) to create an efficient arsenic‐removal adsorbent. BET surface area analysis showed the highest surface area for VAC (525 m 2 g −1 ), followed by Fe‐AC (140 m 2 g −1 ) and FePO 4 (80 m 2 g −1 ) surface area, which decreased with increasing calcination temperatures owing to particle agglomeration. FTIR spectra confirmed the formation of Fe–O and Fe–OH bonds in Fe‐AC, while XRD analysis confirmed that VAC exhibited amorphous behavior, and the calcination at 750 °C transformed the crystalline phase of FePO 4 and Fe‐AC. The point of zero charge (PZC) trend followed Fe‐AC > FePO 4 > VAC, in comparison to arsenate adsorption. The kinetic data best fitted to the pseudo‐second order (PSO) model, suggesting chemisorption‐controlled mechanisms, and the sharp equilibrium data fitted the Langmuir isotherm for monolayer adsorption. The adsorption capacities ( q m) and Langmuir constants ( K L ) decreased with increasing pH but were enhanced considerably with an increase in temperature. The thermodynamic parameters (Δ H ° > 0, Δ G ° < 0, Δ S ° < 0) confirmed that the process was endothermic, spontaneous, and feasible. Activation energy values complement the stronger adsorption affinity of Fe‐AC compared with FePO 4 . Both adsorbents removed almost 100% of arsenic from real water samples; however, as Fe‐AC was able to show higher performance based on enhanced surface reactivity and better iron dispersion, it would be favorable in adsorption. The overall findings suggest that Fe‐AC holds a good promise as a sustainable and regenerable adsorbent for arsenic remediation in water treatment applications.