Application of Mg–Al-modified biochar for simultaneous removal of ammonium, nitrate, and phosphate from eutrophic water

Water eutrophication is a serious environmental problem worldwide. Biochar derived from the thermochemical treatment of biomass, particularly the modified biochar, can be used as a new type of adsorbent for environmental management. In this study, Mg–Al-modified soybean straw biochars (Mg/BC, Al/BC, and Mg–Al/BC) were prepared to remove NH4+, NO3−, and PO43− from eutrophic water. Brunauer–Emmett–Teller analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and Fourier transform infrared techniques were used to characterize the physical and chemical properties of the biochar. The single-solute-adsorption properties and adsorption kinetics of NH4+, NO3−, and PO43− were initially examined. Results showed that the maximum adsorption capacities for NH4+ (0.70 mg/g), NO3− (40.63 mg/g), and PO43− (74.47 mg/g) were achieved on Mg–Al/BC, Al/BC, and Mg/BC, respectively. The bi-solute-coadsorption and tri-solute-coadsorption properties of NH4+, NO3−, and PO43− were then studied to simulate the adsorption in actual eutrophic water. Mg/BC and Al/BC can be used to treat eutrophic water contaminated with PO43− and NO3−, respectively. Mg–Al/BC could effectively improve the quality of water whereNH4+, NO3−, and PO43− coexist. Therefore, the Mg–Al-modified biochars can be used as an excellent adsorbent for the treatment of eutrophic water.