Removal of chromium from electroplating wastewater using chitosan-coconut shell composite: kinetics, thermodynamics and artificial neural networks modeling

The electroplating industry releases large volumes of wastewater contaminated with toxic chromium, posing significant risks to both the environment and public health. Although progress has been made in water pollution control, the application of composite adsorbents for chromium removal, combined with simulations for process optimization, remains underexplored. In this study, the effectiveness of a chitosan-coated coconut shell composite in removing chromium from electroplating wastewater was investigated. Under optimal conditions (4 g/L dosage, pH 6.5, 308 K temperature, 200 rpm speed and 60 min time) the composite removed 99% of Cr and outperforming both chitosan and coconut shell. The adsorption process followed pseudo-second-order kinetics (R² = 0.999) and the Langmuir isotherm with a maximum adsorption capacity of 66.66 mg/g. The adsorption efficiency increased with temperature (298–313 K), indicating an endothermic process. The composite retained 98% of its initial capacity after regeneration with HNO₃, demonstrating its cost-effectiveness over multiple cycles. Simulations using artificial neural networks (ANNs) accurately predicted adsorption behavior by achieving a mean square error (MSE) as low as 0.0016. However, despite high Cr removal, the treated effluents did not meet legislative discharge standards, highlighting the need for further biological treatment using activated sludge.