Enhancement of Pb(ii) adsorptive removal by incorporation of UiO-66-COOH into the magnetic graphitic carbon nitride nanosheets

Abstract

Efficient elimination of Lead (Pb(II)) from aqueous solutions has become a crucial area of focus in the wastewater treatment industry. In this study, novel mesoporous magnetic g-C₃N₄/Fe₃O₄/UiO-66-COOH was synthesized by combining the acid-functionalized metal–organic framework (MOF) of UiO-66-COOH via a facile novel solvothermal method with magnetic graphitic carbon nitride (g-C₃N₄/Fe₃O₄) sheets to enhance Pb(II) adsorption in water. The study investigated various influential adsorption parameters, including pH, dosage, contact time, ion concentration, and temperature. The Langmuir model, which depicts monolayer adsorption on a uniform surface, was a more suitable fit for the adsorption isotherms. The kinetics conformed to the pseudo-second-order model, indicating a chemical adsorption mechanism. According to the Langmuir model, the adsorption capacity of g-C₃N₄/Fe₃O₄/UiO-66-COOH is expected to reach a maximum of 285.8 mg L⁻¹. This value is 2.6 times higher than g-C₃N₄/Fe₃O₄ and 1.6 times higher than UiO-66-COOH. The enhanced adsorption capacity of g-C₃N₄/Fe₃O₄/UiO-66-COOH is attributed to its superior characteristics, such as abundant functional groups and high surface area which is 2.16 times higher than g-C₃N₄/Fe₃O₄. The adsorption thermodynamics indicated that the adsorption occurred spontaneously and was characterized as exothermic. g-C₃N₄/Fe₃O₄/UiO-66-COOH material exhibited good recyclability for up to five runs.