Valorization of mine tailings for the removal of phosphates and ammonium from Wastewater : Toward nutrient recovery

Mine tailings (MT) is an abundant by-product of mining operations that pose environmental and financial challenges. Despite containing minerals valuable for wastewater treatment, research on MT and its valorization strategies remains limited. This study aimed to valorize MT through alkali activation, transforming it into an adsorbent for removing phosphate phosphorus (P) and ammonium nitrogen (N). The alkali-activated MT (AAMT) was spectroscopically analyzed to assess its structural and functional properties, and its adsorptive performance was tested using synthetic solutions and real wastewater. Batch adsorption experiments with synthetic solution showed 97 % P and 86 % N removal at equilibrium, with adsorption capacities of 3.49 mg/g for P and 2.96 mg/g for N. Kinetic modeling indicated that P adsorption occurred through chemisorption involving electrostatic attraction, inner sphere complexation, and precipitation, while N adsorption involved physical adsorption. Adsorption behaviors followed the Sips and Temkin isotherms, with nutrients adsorbed on a heterogeneous surface of different activation energies. The AAMT also performed well in real wastewater, achieving 97 % P and 68 % N removal. This study provides preliminary proof of concept for MT valorization and demonstrates the suitability of AAMT as a low-cost adsorbent for nutrient removal and wastewater treatment.