Simultaneous ammonium and phosphate removal with Mg-loaded chitosan carbonized microsphere: Influencing factors and removal mechanism

A novel Mg-loaded chitosan carbonized microsphere (MCCM) was prepared for simultaneous adsorption of ammonium and phosphate in this study, through the investigation of preparation procedures, addition ratio, and preparation temperature. Pollutants removals by MCCM were more acceptable with 64.71% for ammonium and 99.26% for phosphorus, compared with chitosan carbonized microspheres (CCM), Mg-loaded chitosan hydrogel beads (MCH) and MgCl2·6H2O. Addition ratio of 0.6:1 (mchitosan: mMgCl2) and preparation temperature of 400 °C in MCCM preparation were responsible for pollutant removal and yield. The effect analysis of MCCM dosage, solution pH, pollutant concentration, adsorption mode and coexisting ions on the removal for both ammonium and phosphate indicated that pollutants removals were increased with increasing MCCM dosages, and achieved the peak at pH 8.5, but presented to be stable with Na+, K+, Ca2+, Cl-, NO3-, CO32- and SO42-, except for Fe3+.Adsorption mechanisms discussion implied that simultaneous ammonium and phosphate removal with MCCM was attributed to struvite precipitation, ion exchange, hydrogen bonding, electrostatic attraction and Mg-P complexation, suggesting that MCCM presents a new way for simultaneous concentrated ammonium and phosphate removal in wastewater treatment.