Phosphate removal from wastewater using recycled glass pumice: Performance and mechanisms

Excessive phosphorus discharge into water bodies is a key driver of eutrophication, leading to severe ecological consequences such as oxygen depletion and ecosystem degradation. Consequently, developing efficient, low-cost, and stable methods for phosphorus removal is critical for maintaining water safety. This study investigated glass pumice, a sintered material derived from waste glass, as a novel adsorbent for phosphate removal from wastewater. Batch and dynamic adsorption experiments were conducted to evaluate its performance and reveal the underlying mechanisms. Phosphate adsorption followed pseudo-first-order kinetics and fit the Langmuir isotherm model, with a maximum theoretical adsorption capacity of 166.56 mg/g. Dynamic adsorption experiments revealed that glass pumice maintained consistent adsorption performance for 110 d under a high influent phosphorus concentration (8 mg/L), achieving a total adsorption capacity of 60.38 mg/g. Maintaining a hydraulic retention time (HRT) of at least 6.5 h ensured that the effluent total phosphorus concentration remained below 1 mg/L. Mechanistic analysis revealed that phosphorus is mainly adsorbed via surface calcium salt precipitation (calcium phosphate) and hydroxyl–phosphate exchange and further stabilized by hydrogen bonding. As an inexpensive and highly porous material, glass pumice aggregates exhibit strong potential for efficient and sustainable phosphorus removal, contributing to resource recovery and high-value reuse of waste glass.