Synthesis of Fe2O3-modified porous geopolymer microspheres for highly selective adsorption and solidification of F− from waste-water

Abstract

Abstract This study reports the fabrication of slag-based Fe2O3-modified porous geopolymer microspheres composites (Fe2O3@PGMs) having uniform particle size distribution (75–300\u202fμm) and good sphericity by in-situ co-precipitation process. The concentration of Fe3+ as modifier (in Fe2O3) significantly enhanced the resistance of Fe2O3@PGMs against corrosion (leaching concentration of Ca2+ decreased from 95.65 to 30.76\u202fmg/L in 120\u202fmin) and adsorption capacity towards F− of pristine PGMs while 0.2\u202fmol/L (0.2Fe2O3@PGMs) exhibited the best performance. The adsorption data were best fitted with pseudo-second kinetic model and Langmuir isotherm model, indicating the involvement of both, ion exchange and monolayer phenomena during adsorption. 0.2Fe2O3@PGMs delivered outstanding adsorption capacity (59.55\u202fmg/g) and faster reaction kinetics (k2\u202f=\u202f98.11\u202f×\u202f10−4\u202fg\u202fmg−1 min−1) for F− as determined by bath and dynamic experiments. 0.2Fe2O3@PGMs possessed good separation efficiency even at a flow rate of 4\u202fmL/min. The competitive adsorption capabilities of coexisted anions in real seawater, tap water and natural surface water followed an order of: Cl−