Green-synthesized cerium oxide/coconut shell nanocomposites for adsorptive detoxification of hexavalent chromium from water

Water is essential component of life; thus access to clean and safe water is crucial for human consumption, agriculture and other life-sustaining activities. However, water contamination remains a major global concern. Among various pollutants, heavy metals pose significant threat to environment and health due to their high toxicity and carcinogenic nature which has attracted considerable attention of researchers. In this study, CeO2/coconut shell nanocomposites were synthesized and characterized using X-ray Diffraction, Scanning electron microscopy, Energy Dispersive X-ray Spectroscopy, Fourier Transform Infrared Spectroscopy, TGA, and UV-Visible spectroscopy to investigate their structural, morphological, and chemical properties. The objective of this study is to investigate efficiency of the synthesized nanocomposites as an economical and environmental friendly adsorbent to eliminate Cr(VI) from water. Adsorption experiments in batch mode were conducted to determine the effect of key parameters including initial Cr(VI) concentration, pH, adsorbent dosage, and contact time. The analysis of Cr(VI) was performed using UV-Visible Double Beam Spectrophotometer. The synthesized nanocomposites exhibited significant Cr(VI) elimination efficiency. Equilibrium adsorption data were best described by the Langmuir isotherm model, indicating monolayer adsorption on a relatively homogeneous surface, while the Freundlich model suggested the presence of limited surface heterogeneity. To understand the adsorption behavior, five kinetic models (pseudo first order, pseudo second order, intraparticle diffusion, fractional power, and Elovich) were used to analyze the experimental results. Among these, pseudo second order showed the best correlation with the experimental data (R2 = 0.96088) indicating that chemisorption was the dominant mechanism governing Cr(VI) uptake. The Elovich model also demonstrated a reasonably high correlation (R2 = 0.88706), further supporting the presence of heterogeneous surface interactions and activation energy barriers. The findings suggest that CeO2/coconut shell nanocomposites offer an efficient, eco-friendly and cost-effective solution for Cr(VI) removal from water.