| Summary: | The phosphate waste rocks were valorized to apatite (HA) using a simple dissolution/precipitation method. the achievement of the HA phase was confirmed by the use of a set of characterization methods, namely: X-ray diffraction (XRD), X-ray fluorescence Spectrometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). The potential use of the prepared HA for the removal of cobalt (Co2+) from polluted synthetic water was evaluated in the current study through the adsorption process. The effect of pH, metal concentration, adsorbent dose, contact time and temperature on Co2+ removal were investigated. At ambient temperature, pH initial of the solution, Co2+ initial concentration of 10 mg/L without changing the initial pH of this solution and adsorbent dosage of 1 g/L, the adsorption capacity of 8.64 mg/g was achieved within 40 min, corresponding to an elimination percentage of 85.07%. The experimental data followed the pseudo-second-order kinetic models due to its most sufficient determination, R2 = 0.995. The equilibrium adsorption process of Co2+ onto HA fitted well with Freundlich isotherm, with a determination coefficient of R2 = 0.992. The thermodynamic parameters such as enthalpy(ΔH°), entropy(ΔS°) were calculated as -23.144, -0.054 KJ.mol−1, respectively, and Gibbs free energy (ΔG°) ranging from -7.603 to -5.975KJ.mol−1for Co2+adsorption, the results of this experiment revealed that the adsorption process was spontaneous and exothermic, also they indicate the disorderness of the adsorbent-adsorbate interface during the Co2+adsorption process. These results demonstrated that phosphate waste rocks can be used as efficient materials for the preparation of potential adsorbent for Co2+ removal from contaminated water. This work contributes to environmental management by reducing wastes and wastewater treatment.
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