Adsorptive removal of phosphate from aqueous solutions by thermally modified copper tailings

In this study, thermally modified copper tailings (TMCT) were used to adsorb phosphate in aqueous solutions through experiments. The characterization of TMCT and unmodified copper tailings (UMCT) was done by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The effects of pH, adsorbent dosage, contact time, and initial phosphate concentrations on phosphate adsorption were investigated. We studied the adsorption ability of TMCT and UMCT at 298 K, and the Langmuir isotherm model closely described the adsorption isotherm data, indicating that the maximum adsorption capacity (Q_max) of the TMCT and UMCT was 14.25 mg g^-1 and 2.08 mg g^-1, respectively. In addition, the adsorption isotherms of TMCT were analyzed at 288 K, 298 K, and 308 K, and the calculated Q_max of phosphate were 9.83 mg g^-1 at 288 K, 14.25 mg g^-1 at 298 K, and 11.55 mg g^-1 at 308 K. Finally, the concentration of copper in the effluent was checked, and the content was 130 mg L^-1. Then, the effluent was adsorbed by Eichhornia crassipes stem biochar; after adsorption, the concentration of the secondary effluent was 0.7 mg L^-1, which is lower than the grade II classification (1.0 mg L^-1) of the integrated wastewater discharge standard (GB8978-1996). The results suggest that the TMCT can be effectively and environmentally friendly used to adsorb phosphate from aqueous solutions.