Enhanced phosphate removal from aqueous solution using resourceable nano-CaO₂/BC composite: Behaviors and mechanisms

The situation of eutrophication and shortage of phosphorus resources have triggered the development of new methods for the removal and recovery of phosphorus. In this study, a novel and highly efficient composite (nano-CaO₂/BC) was fabricated by using the porous biochar (BC) to load calcium peroxide (CaO₂) nanoparticles. The developed nano-CaO₂/BC was applied to remove and recover phosphate from P-contained sewage. The phosphate removal performance of the composite was examined using the bulk solutions with different pH values, coexisting anions, composite dosages, and initial phosphate concentrations. The phosphate adsorption was a typical chemisorption process that agreed well with the pseudo-second-order kinetic model. Isotherm studies showed that the adsorption matched well with Langmuir-Freundlich and the maximum adsorption capacity at equilibrium was 213.22 ± 13.57 mg g^-1 (298 K). The characterization results demonstrated that the predominant adsorption mechanism was precipitation. Moreover, the composite had good reusability. The seedling growth test confirmed that the P-laden composite can be mixed with soil to promote the growth of seedlings. Therefore, the method of "cycle back to soil" of used composite provided a way of resource utilization and waste disposal.