Study of the adsorbent properties of nickel oxide for phenol depollution

Phenol and its derivatives are considered as dangerous pollutants due to these harmful effects on health and the environment. Treatment of the waters charged by these compounds by adsorption remains very important. For these reasons, this study was designed to prepare nickel oxide by precipitation method in order to remove these pollutants from aquatic environments. Indeed, structural and textural properties of this solid have been determined by various physicochemical methods (X-ray diffraction, Fourier transform in the infrared, N2 adsorption/desorption (BET), ATD / ATG thermal analysis and scanning electron microscopy (SEM)). In addition, several adsorption tests were carried out in order to show the effectiveness of this solid for the elimination of phenol in aqueous solution and to determine the physicochemical parameters which affect adsorption. Our results have shown 5.29 mg·g⁻¹ of adsorption capacity with 98% of yield. Furthermore, it was shown that adsorption process was endothermic. For the kinetic study, it was demonstrated that phenol adsorption on NiO follows the pseudo-second-order and the Langmuir model better adaptable for the isotherm of desorption. Moreover, thermodynamic study shows positive values of ΔS ° (266.6 JK⁻¹·mol⁻¹) suggesting a randomness increase of the solid/liquid interface. ΔH ° (60.41 kJ·mol⁻¹) was also positive confirming the endothermic nature of the adsorption processes. However, ΔG ° (kJ·mol⁻¹) was negative suggesting the spontaneity of the phenol adsorption. In summary, this work suggests that phenol adsorption on NiO was linked to the chemical adsorbate/adsorbent interactions.