Phosphate removal from aqueous solutions with a zirconium-loaded magnetic biochar composite: performance, recyclability, and mechanism

Phosphate (P) removal is significant for water pollution control. In this paper, a novel penicillin biochar modified with zirconium (ZMBC) was synthesized and used to adsorb P in water. The results showed that ZMBC had a porous structure and magnetic properties, and the zirconium (Zr) was mainly present in the form of an amorphous oxide. P adsorption displayed strong pH dependence. The Freundlich model described the adsorption process well, and the saturated adsorption capacity was 27.97 mg/g (25 degrees C, pH= 7). The adsorption kinetics were consistent with the pseudo-second-order model, and the adsorption rates were jointly controlled by the surface adsorption stage and intraparticle diffusion stage. Coexisting anion experiments showed that CO32- inhibited P adsorption, reducing the adsorption capacity by 62.63%. The adsorbed P was easily desorbed by washing with a 1 M NaOH solution, and after 5 cycles, the adsorbent had almost the same capacity. The mechanism for P adsorption was inner-sphere complexation and electrostatic adsorption.

Automated summary

A zirconium-modified biochar material was synthesized and used for phosphate adsorption in water. The material exhibited good adsorption performance and stability. The adsorption of phosphate was influenced by pH and coexisting anions, and the adsorption kinetics followed the pseudo-second-order model. This research is of significance for water pollution control.