Simultaneous oxidation and adsorption of phosphite by magnetic La2(CO3)3/CoFe2O4/biochar composite with peroxymonosulfate

Phosphite [P(III)], an emerging eutrophication pollutant, has attracted limited attention in recent years. Owing to the higher solubility and resistance to biotransformation of P(III), oxidation of P(III) to phosphate [P(V)] is considered to be necessary to enhance P(III) removal. Herein, an efficient and regenerable magnetic La2(CO3)3/CoFe2O4/biochar composite (LCB) was constructed through a facile one-pot hydrothermal method to treat phosphite-laden wastewater. LCB coupled with peroxymonosulfate (PMS) exhibited satisfactory P(III) removal performance through a one-step process for simultaneous oxidation and adsorption of P(III). The adsorption capacity of LCB/PMS for P(III) (71.94 mg/g) was much higher than that of LCB. LCB/PMS system showed high P(III) removal efficiency of 96.62 %, wide pH ranging from 4.0 to 9.0, and good reusability. It also worked well in the existence of anions and humic acid. The quenching experiments and electron spin resonance tests (ESR) revealed the critical role of SO4•- in the P(III) oxidation process. Characterization results demonstrated that electrostatic attraction and ligand exchange were responsible for P(III)/P(V) adsorption. Moreover, LCB/PMS system presented desirable performance in eliminating a series of typical organic and inorganic phosphorus. The LCB/PMS system provides a promising and sustainable technology for the purification of P(III)-contaminated water.