Application of Green Novel NiO/ZSM-5 for Removal of Lead and Mercury ions from Aqueous Solution: Investigation of Adsorption Parameters

Consistent with the US Environmental Protection Agency, heavy metals are classified as carcinogenic to humans. Their numerous agricultural, industrial, domestic, medical, and technical requirements have resulted in their widespread dissemination in the environment. This article examines a new green adsorbent for the removal of two hazardous heavy metals, lead, and mercury. The impact of contact time, pH, initial concentration, and temperature on the adsorption capacity of Pb^2+ and Hg^2+ were evaluated. Experimental data were analyzed by adsorption models. The equilibrium data were well adapted to the Langmuir adsorption model. The results show that the adsorption is homogeneous and localized in a monolayer. In addition, the maximum adsorption capacity was 277.78 mg/g for Pb^2+ and 64.52 mg/g for Hg^2+ from Langmuir isotherm. Thermodynamic data, including free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) variations were also considered. The important point is that the negative value of ΔG° signifies the spontaneity of the adsorption process of the heavy metals−NiO/ZSM-5 system.