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

Abstract

Highly compressible sewage sludge (SS) derived geopolymer was magnetized with impregnation of magnetite (Fe3O4) 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 ?g 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 ?g g-1, after 3 h) for As(V) than only geopolymer (~9.81 ?g 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: NO3- < Cl- < SO42- < F- < PO43-. The proposed waste derived sustainable composite material was proved to be a promising sorbent for economic As(V) removal under simulated complex environmental conditions.