Preparation and characterization of the linked lanthanum carboxymethylcellulose microsphere adsorbent for removal of fluoride from aqueous solutions

Abstract

Linked carboxymethyl cellulose microspheres loaded with lanthanum(III) (linked-CMC–La) were fabricated with glutaraldehyde, from lanthanum carboxymethyl cellulose microspheres (CMC–La), and used to remove fluoride from aqueous solution. Characterization by SEM, resistance to acid and alkali, TG, pH_pzc and FT-IR was used to distinguish the superiority of the two adsorbents. The results showed that the linked-CMC–La had a higher decomposition temperature (200 °C) than CMC–La (190 °C) and a better resistance to acid and alkali compared with CMC–La. Batch adsorption experiments were also performed, varying factors of pH, initial fluoride concentration, and contact time. The results showed that the maximum removal efficiencies (REs) of CMC–La and linked-CMC–La were about 98.85% and 99.31%, respectively, when the fluoride concentration was 40 mg L⁻¹ at pH 4.0. The adsorption process could be described well using the Langmuir isotherm model. The adsorption kinetics data was fitted well using a pseudo-second-order model. The analysis of the adsorption and desorption of the linked-CMC–La and CMC–La revealed that crosslinking had no obvious effect on the removal efficiency or mechanism of the adsorption and desorption of the two absorbents. The surface adsorption occurred between the linked-CMC–La and fluoride due to Lewis acid–base interaction and supplemented with electrostatic attractions.