Phosphate adsorption characteristics of CeO2-loaded, Eucommia ulmoides leaf residue biochar.

In this study, a Ce-loading biochar (Ce-BC) was synthesized by the optimal modification method of pre-pyrolysis impregnation, a pyrolysis temperature at 600 °C, and a CeCl3 concentration of 1.00 mol L-1 for efficient adsorption phosphorus (P) from wastewater. The results revealed that Ce-BC could achieve a maximum P removal rate of 100% under specific conditions: an adsorbent concentration of 2.00 g L-1, an initial solution pH of 3.00, an adsorption temperature of 25 °C, and an initial P concentration of 20.00 mg L-1. The adsorption process followed the quasi-secondary kinetic model, suggesting the Ce-BC was particularly effective in acidic environments. Meanwhile, Ce-BC has a strong resistance to anion interference and good cycling performance (the P adsorption capacity of Ce-BC was 59.77% of its initial value after four cycles). Field emission scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) indicated that Ce-BC contained a porous structure and rich functional groups (hydroxyl and carboxyl), and compounds of CeO2 and MgCeO3 were formed. The Ce loading favored the exchange with P through ligands, inner-sphere complexation, ion exchange, and electrostatic interaction to form inner-sphere complex-cerium P (CePO4), and the surface complex of Ce-O-P replaced O-H. In addition, the Ce-BC adsorption columns substantially affected P removal in actual wastewater. Overall, Ce-BC is a promising material for the treating P-containing acidic wastewater.