Enrichment of lanthanides in aqueous system by cellulose based silica nanocomposite

Synthesis of cellulose based silica (CLx/SiO₂) nanocomposite was successfully carried out and employed for the removal of Eu(III), La(III) and Sc(III). Nanocomposite was characterized by TEM, AFM, SEM, XRD, FTIR and BET. TEM analysis indicated that the particle diameter of nanocomposite was in the range of 9–15 nm and silica particles was uniformly distributed throughout the nanocomposites. The presence of mixed phases of cellulose and SiO₂ was observed by FTIR and XRD. Experimental results showed that CLx/SiO₂ nanocomposite produced by sulfuric acid modification possess higher surface area than that of citric acid modified. Various parameters including contact time, pH, nanocomposite dosage, initial concentration, and temperature were optimized to achieve maximum adsorption capacity. The kinetics results revealed that the surface chemical sorption for Eu(III) and La(III) and physisorption for Sc(III). Also, the film diffusion was the rate-determining step of the adsorption process. Importantly, the isotherms fitted better to Langmuir for Eu(III) and La(III) than Freundlich. The positive values of ΔH⁰ indicates that the adsorption process was endothermic and negative value of ΔG⁰ indicates the feasibility of Eu(III), La(III) and Sc(III) removal by adsorption on CLN/SiO₂ nanocomposite and suggests the spontaneous nature of adsorption on nanocomposite. Desorption of adsorbate loaded on nanocomposite during adsorption process was easily carried out up to three cycles. The results indicate that the nanocomposite is an efficient adsorbent with good adsorption capacity for Eu(III), La(III) and Sc(III).