Research: Enhanced aqueous phosphate removal using chitosan-modified zirconium-loaded cork biochar
Original article by Nature.com
In this study, a novel adsorbent, CS–CBC–Zr composite beads, was successfully developed for the removal of various concentrations of PO4–P using cork stopper biochar as a support material. The synthesis involved chitosan and biochar gel preparation, followed by chemical crosslinking and subsequent Zr loading. Zirconium loading at 3% was found to be the most effective in enhancing the active sites of the CS–CBC–Zr composite beads, thereby improving adsorption performance. The adsorption of phosphate ions onto CS–CBC–Zr beads was best described by the Sips isotherm (n = 1.124, R2 = 0.94), indicating a certain degree of surface heterogeneity and adsorption behavior approaching monolayer coverage. A mean free energy value of 11.24 kJ/mol suggests that phosphate adsorption onto CS–CBC–Zr is primarily governed by chemisorption, characterized by ion exchange reactions at active sites. The maximum adsorption capacity was calculated to be 33.89 mg/g based on the Sips model, which was very close to the experimental value. The equilibrium time for PO₄–P adsorption onto CS–CBC–Zr beads was 120 min. Stable performance across a wide pH range (4–10) and notable phosphate selectivity were also observed. Structural changes in the composite beads at both physical and chemical levels were confirmed by SEM, XPS, and FTIR analyses. The findings of the study show that CS–CBC–Zr exhibited strong capability in removing various PO4–P concentrations, presenting a promising approach not only for mitigating water eutrophication but also for treating heavily polluted wastewater. Future studies should focus on the application of CS–CBC–Zr composite adsorbents in wastewater treatment for the removal of diverse pollutants. Investigating their potential for adsorbing other inorganic and organic contaminants, such as heavy metals and dyes, could offer valuable insights and significantly advance this research area by broadening the practical applications of these composites.
