Preparation of new modified O-carboxymethylchitosan terminated with phenyl phosphonic acid-amide moiety for adsorption of cerium from aqueous solutions by batch and fixed bed column methods

The increasing demand for rare earth elements and the environmental concerns associated with their release into aquatic systems have created a growing need for efficient and sustainable adsorbent materials for cerium recovery from wastewater. This work aimed to develop a modified O-carboxymethylchitosan (O-CMC) terminated phenyl phosphonic acid-amide moieties (O-CMC-PPA) to extract cerium (Ce(III)) via both techniques (batch and fixed-bed column). Characterization of O-CMC-PPA was carried out using scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), FT-IR, X-ray Diffraction (XRD), and thermal analysis through TGA and DTG. Batch experimentations tested various parameters pH, Ce(III) concentration, adsorbent dosage, contact time, and temperature, showing an optimal adsorption capacity of 339 mg/g at pH 3 and an initial Ce(III) concentration of 400 mg/L at 25°C. Isotherm models indicated monolayer adsorption according to the Langmuir model, while the kinetics followed a pseudo-second-order model. The experiments conducted at temperatures ranging from 25°C to 45°C demonstrated that the adsorption process is spontaneous and endothermic, becoming more favorable at elevated temperatures. Kinetic models, including Nelson-Yoon and Thomas, were employed to assess column efficiency. Additionally, desorption of loaded Ce(III) was effectively achieved using 0.2 M HNO3. The modified O-CMC-PPA was successfully reused for five adsorption-desorption cycles.