Hierarchical Al2O3-carbon bio-waste microsphere composite as an effective adsorbent for phosphate recovery: Insights into adsorption kinetics and isotherms

Abstract

Phosphate contamination in aquatic systems is a major environmental concern due to its contribution to eutrophication, thus creating an urgent demand for effective and sustainable removal strategies is essential. This study investigates the phosphate adsorption performance of Al2O3 and Al2O3/biomass-derived carbon composites with varying carbon loadings (10 %, 25 %, and 50 % by mass ratio). The results revealed that incorporating an optimal amount of carbon significantly enhances phosphate adsorption, with the 10 % carbon-loaded composite exhibiting the highest capacity (67.91 mg/g), for exceeding that of pristine Al2O3 and carbon. This improvement is attributed to increased surface area, enhanced pore structure, and synergistic interactions between Al2O3 and carbon functional groups, while excessive carbon loading reduces performance by blocking active sites. The findings offer valuable understandings into designing efficient, low-cost, and sustainable composite adsorbents for advanced phosphate uptake in water treatment applications.