Optimization of carboxymethyl cellulose hydrogels beads generated by an anionic surfactant micelle templating for cationic dye uptake: Swelling, sorption and reusability studies

Abstract

Carboxymethyl cellulose hydrogels beads were synthesized by ionotropic gelation in Al3+ solutions with or without sodium n-dodecyl sulfate (SDS) surfactant as a pore-forming micelle templating and NaCl as porogen agent. FTIR spectroscopy and EDX analysis evidenced the formation of hydrogels. The morphology observed by Scanning Electron Microscopy (SEM) showed rough porous surfaces. The swelling properties in various media were studied. The addition of SDS optimized the capacity and initial rate of swelling. The porous beads were assessed as adsorbents to remove methylene blue (MB) dye from aqueous solutions by varying parameters: pH medium, adsorbent dose, initial MB concentration, and contact time. The kinetics obeyed well to pseudo-second-order model and the isotherms data followed Langmuir model with a maximum of adsorption capacity of 82mgg−1. Thermodynamic studies showed spontaneous and endothermic nature of the process. From reusability study, all beads are well regenerated and displayed unexpected increase in removal efficiency compared to starting ones, with an optimal capacity of 350mgg−1. This fact is due to dye entrapped in the desorbed beads that favored subsequent dye access to internal sites. In view of effectiveness of adsorption and regeneration, the optimized hydrogels are promising as low cost dyes adsorbents.