Performance and Mechanism of Modified Orange Peel as a Highly Efficient Adsorbent for Lead(II) and Mercury(II) Removal from an Aqueous Solution

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Abstract This research involves evaluating the use of modified orange peel (MOP) in the removal of Pb 2+ and Hg 2+ from wastewater. For the modification process, certain concentrations of ethanol, NaOH, and CaCl 2 solution were added to the washed and dried orange peel and kept at room temperature for 24 hours. The mixture was then subjected to filtration and rinsed with distilled water until the pH level reached 7. For this reason, the effects of Pb 2+ and Hg 2+ on the adsorption efficiency were examined by performing batch experiments. The surface properties of MOP were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT‐IR) techniques. The results revealed that, among the various models, the Langmuir isotherm model provided the best fit to the isotherm data for Hg 2+ and Pb 2+ ions. Based on the kinetic data of adsorption, the pseudo‐second‐order kinetic model provided a more accurate description of the adsorption process for Pb 2+ and Hg 2+ ions. According to thermodynamic analyses, both metal ions bind to MOP spontaneously and endothermally. MOP was determined to be a reliable and valid alternative material for the removal of Pb 2+ and Hg 2+ from aqueous environments based on its qualities such as high adsorption capacity, ease of availability, low cost, use of agricultural waste, recycling potential, and no environmental impact.