Simultaneous capture removal of phosphate, ammonium and organic substances by MgO impregnated biochar and its potential use in swine wastewater treatment

Metal oxide-biochar composites have been used for removing pollutants from aqueous systems. In this Work, optimized MgO-impregnated porous biochar was prepared using an integrated adsorption pyrolysis method for absorption of phosphate, ammonium and organic matter (humate). Results revealed that the MgO-biochar was comprised of nano-sized MgO flakes and nanotube-like porous carbon. Mg content had significant effects on the development of the nanotube-like porous carbon structure in MgO impregnated biochar and its adsorption capacity for phosphate, ammonium and humate. The adsorption isotherms fitted by Langmuir model illustrated that the optimized adsorbent, 20% Mg-biochar, exhibited maximum adsorption capabilities of more than 398 mg/g for phosphate, 22 mg/g for ammonium, and 247 mg/g for hurnate, respectively. The phosphate adsorption fitted the pseudo second-order kinetic model, while ammonium and humate adsorption were best described by the intra-particle diffusion model. The existence of Cl-, No-3(-), SO42-,k(+),Na+ and Cat} ions had no significant impacts on humate adsorption, but the presence of SO42- and Ca2+ affected the phosphate adsorption, and the presence of K+, Na+ and Ca2+ ions inhibited ammonium adsorption. Characterization of adsorbents by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) before and after treating swine wastewater revealed that struvite crystallization, electrostatic attraction, and pi-pi interactions contributed to the adsorption of phosphate, ammonium and humate. The results demonstrated that the optimized MgO-biochar could be employed as an effective adsorbent for the simultaneous removal and recovery of phosphate, ammonium and organic substances from nutrient-rich livestock wastewaters. (C) 2017 Elsevier Ltd. All rights reserved.