Utilization of sewage sludge derived magnetized geopolymeric adsorbent for geogenic arsenic removal: A sustainable groundwater in-situ treatment perspective

Highly compressible sewage sludge (SS) derived geopolymer was magnetized with impregnation of magnetite (Fe<inf>3</inf>O<inf>4</inf>) nanoparticles (NPs), and these newly developed and characterized adsorbents were tested in a batch mode for the sorptive removal of metalloid arsenic (As) from a significant potable water resource (groundwater). Various sorption experiments were performed under variable pH (4.0–9.0), magnetized geopolymer dosages (0.1–3 g L⁻¹), contact time (0–180 min), initial As concentrations (10–100 μg L⁻¹) and co–existing anions to develop a critical understanding of the optimal experimental requirements and to assess the sorption kinetics and isotherms. Magnetized geopolymer had better monolayer sorption capacity (∼51.6 μg g⁻¹, after 3 h) for As(V) than only geopolymer (∼9.81 μg g⁻¹, after 3 h) at near neutral pH (∼6.0). The sorption process onto magnetized geopolymer was facilitated by intraparticle diffusion as well as surface complexation mechanisms and was best explained by the pseudo second order kinetic model (R² ≥ 0.95) and Freundlich and Temkin isotherm models (R² ≥ 0.90). The exhausted composite adsorbent was sufficiently regenerated up to five sorption–desorption–regeneration cycles using 0.1 M NaOH. Further, it also displayed an excellent As(V) removal capacity from the cocktail mixture of the common geogenic anions and their antagonistic effect follows the order of: NO<inf>3</inf>⁻ < Cl⁻ < SO<inf>4</inf>²⁻ < F⁻ < PO<inf>4</inf>³⁻. The proposed waste derived sustainable composite material was proved to be a promising sorbent for economic As(V) removal under simulated complex environmental conditions.