Efficient removal of phosphorus and nitrogen from aquatic environment using sepiolite-MgO nanocomposites: preparation, characterization, removal performance, and mechanism

Excessive phosphorus will lead to eutrophication in aquatic environment; the efficient removal of phosphorus is crucial for wastewater engineering and surface water management. This study aimed to fabricate a nanorod-like sepiolite-supported MgO (S-MgO) nanocomposite with high specific surface area for efficient phosphate removal using a facile microwave-assisted method and calcining processes. The impact of solution pH, adsorbent dosage, contact time, initial phosphate concentrations, Ca²⁺ addition, and N/P ratio on the phosphate removal was extensively examined by the batch experiments. The findings demonstrated that the S-MgO nanocomposite exhibited effective removal performance for low-level phosphate (0 ~ 2.0 mM) within the pH range of 3.0 ~ 10.0. Additionally, the nanocomposite can synchronously remove phosphate and ammonium in high-level nutrient conditions (> 2.0 mM), with the maximum removal capacities of 188.49 mg P/g and 89.78 mg N/g. Quantitative and qualitative analyses confirmed the successful harvesting of struvite in effluent with high-phosphate concentrations, with the mechanisms involved attributed to a synergistic combination of sorption and struvite crystallization. Due to its proficient phosphate removal efficiency, cost-effectiveness, and substantial removal capacity, the developed S-MgO nanocomposite exhibits promising potential for application in phosphorus removal from aquatic environments.