Facile Synthesis of Novel Nanocomposite Consists of β-FeOOH, Chitosan, and Salicylaldehyde for Efficient Removal of Zn(II) Ions from Aqueous Media

This study involves the fabrication of β-FeOOH nanoparticles and a novel β-FeOOH@chitosan@salicylaldehyde nanocomposite, specifically engineered for removal of Zn(II) ions from aqueous solutions. X-ray diffraction (XRD) analysis confirmed the successful synthesis of the β-FeOOH structure and its incorporation into the chitosan@salicylaldehyde matrix, with the composite displaying characteristic peaks of both components. Brunauer-Emmett-Teller (BET) analysis revealed that the nanocomposite exhibited a significantly higher surface area (111.99 m²/g), pore volume (0.09876 cm³/g), and micropore size (1.76 nm), enhancing its adsorption potential compared to β-FeOOH nanoparticles alone. Energy dispersive X-ray analysis (EDX) showed Fe and O peaks in β-FeOOH nanoparticles, while additional C and N peaks in the nanocomposite confirmed the integration of chitosan and salicylaldehyde. Scanning electron microscope (SEM) images revealed a dense structure for β-FeOOH and a porous and interconnected morphology for the nanocomposite. The maximum adsorption capacities of the β-FeOOH nanoparticles and β-FeOOH@chitosan@salicylaldehyde nanocomposite were 109.17 mg/g and 199.20 mg/g, respectively. The adsorption process is exothermic, spontaneous, and follows the pseudo-second-order model and Langmuir isotherm. Adsorption is physical for β-FeOOH and chemical for the nanocomposite. Regeneration studies showed consistent removal efficiencies over five cycles, with near-complete desorption of Zn(II) ions from the nanocomposite at 2 M HCl via protonation of chitosan functional groups (NH₂ and OH). The high protonation capability of HCl effectively disrupts the strong chemical bonds, enabling near-complete desorption.