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Effect of heating temperature and time on the phosphate adsorption capacity of thermally modified copper tailings.

In the present study, copper tailings were treated at different temperatures (50-650 °C) and for various times (0.5-6 hours) and their phosphate adsorption capacity was investigated. The results showed that heating temperature significantly affected adsorption capacity. The highest capacity was observed in treatments at 310-350 °C. Heating time did not influence phosphate adsorption ability of copper tailings. Scanning electron microscopy, Barrett-Joyner-Halenda (BJH), and Fourier transform infrared spectroscopy (FTIR) were employed to characterize untreated copper tailings (raw CT) and copper tailings heated at 340 °C (CT340). The results showed that CT340 had a rougher surface, more and smaller pores, a larger surface area and higher FTIR transmittance than raw CT. These changes in texture might explain the increased phosphate adsorption of thermally modified copper tailings. Mathematical modeling showed that the Langmuir nonlinear model was the best fit to the current data. The maximum adsorption capacities of raw CT and CT340 were predicted as 2.08 mg/g and 14.25 mg/g at 298 K, pH 6.0, respectively.