Carbon-Supported Layered Double Hydroxide-Embedded Polymeric Hybrid for Detoxification of Hexavalent Chromium from Water

Cr(VI) is a highly poisonous, mutagenic, and carcinogenic contaminant widely found in industrial wastewater, imposing critical risks to aquatic ecosystems and human health. To address this environmental challenge, an Aegle marmelos shell-derived activated carbon-loaded layered double hydroxide (NiLa-LDH/AC) adsorbent was synthesized via a hydrothermal route and embedded within a chitosan matrix to effectively remove Cr(VI) from aqueous solutions. The chitosan integration provides more active sites for Cr(VI) capture. Critical adsorption parameters, such as pH, point of zero charge, contact time, initial concentration, and adsorbent dosage, were systematically optimized. The composite exhibited a maximum adsorption capacity of 294.5 mg/g at pH 3.0 within 60 min, nearly four times greater than those of the pristine components. The physicochemical characteristics of the composite were thoroughly analyzed using Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, HR-SEM, EDX, BET, zeta potential, and X-ray photoelectron spectroscopy. Adsorption behavior followed the Langmuir isotherm and pseudo-second-order (PSO) kinetic models, indicating monolayer chemisorption. Mechanistic analysis revealed that Cr(VI) removal occurred via surface complexation, electrostatic attraction, ion exchange, and concurrent reduction to Cr(III). The composite also demonstrated excellent selectivity and reusability, highlighting its promise for large-scale water purification and environmental remediation applications.