Efficient organic-MgO matrix as adsorbent for heavy metal uptake: Spectroscopic, adsorption isotherms, kinetic and thermodynamic analysis

Abstract

In this study, a new adsorbent has been developed by modifying a low-cost and readily available waste, namely the dried orange (Citrus aurantium Linn) peel (CiR). The removal of heavy metals pollutants by binding of magnesium oxides (MgO) on the peel represents a simple, economical, and faster method. Various analysis, including X-ray diffraction, Fourier transforms infrared spectroscopy and application of mathematical models, have been performed on the modified adsorbent (dried Citrus reticulata peel + MgO; CiR-MgO matrix). The abundant free functional groups present in the biomass and metal oxides collectively exert interactive forces leading to the sorption of Zn²⁺ heavy metals. The Langmuir isotherm and pseudo-first order kinetic models are confirmed as the best fitted model of the adsorption process through chi-analysis. The rate-limiting step of intra-particle diffusion governs the adsorption process. This method is best suited for fixed-bed column application due to its fast kinetics, hydrophilic nature, and regeneration process with 0.005 M HCl.