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

This study reports the fabrication of slag-based Fe2O3-modified porous geopolymer microspheres composites (Fe2O3@PGMs) having uniform particle size distribution (75-300 mu m) 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 mg/L in 120 min) and adsorption capacity towards F- of pristine PGMs while 0.2 mol/L (0.2Fe(2)O(3)@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. 0.2Fe(2)O(3)@PGMs delivered outstanding adsorption capacity (59.55 mg/g) and faster reaction kinetics (k(2) = 98.11 x 10(-4) g mg(-1) min(-1)) for F- as determined by bath and dynamic experiments. 0.2Fe(2)O(3)@PGMs possessed good separation efficiency even at a flow rate of 4 mL/min. The competitive adsorption capabilities of coexisted anions in real seawater, tap water and natural surface water followed an order of: Cl- < NO3- < SO42- < PO43-. This study accredited to the low cost and convenient preparation of 0.2Fe(2)O(3)@PGMs, could be envisaged of potential applications for the adsorptive removal and solidification of F- from waste-water.