Surface Modification of Graphite with Phenyl Isocyanate for Effective Adsorption of Nickel and Cadmium from Industrial Wastewater

Abstract

Industrial wastewater contamination by heavy metals represents a serious environmental concern due to the toxicity and persistence of elements like nickel and cadmium. This research focused on modifying graphite surfaces with phenyl isocyanate to improve their adsorption performance for Ni²⁺ and Cd²⁺ ions. The functionalized graphite was thoroughly characterized using advanced spectroscopic and microscopic methods. Studies on batch adsorption were carried out in various settings, taking into account variations in the starting metal ion concentration, contact duration, pH, and dose of the adsorbent. Adsorption kinetics, besides the equilibrium isotherm models, had been employed to assess the removal process's effectiveness and clarify the adsorption mechanism. Comparing the changed graphite to the unmodified version, the results showed a significant increase in adsorption capacity. Optimal removal efficiency was achieved within a pH range of 6–8, with the adsorption process best described by the pseudo-second-order kinetic model and conforming to the Langmuir isotherm, suggesting monolayer chemisorption. Regeneration tests confirmed the adsorbent's reusability over multiple cycles without substantial loss of efficiency. These findings indicate that phenyl isocyanate-functionalized graphite is a promising, economical, and environmentally beneficial adsorbent for treating wastewater polluted with heavy metals.