Synthesis and Characterization of Alginate/Bentonite Hydrogels

Abstract

The use of bentonite for organic dyes removal in the water system is an economical and highly efficient alternative against the usually applied purification methods. However, during the post-treatment stage bentonite swells and forms highly stable colloidal suspensions, being difficult to separate from the aqueous system. In this work, calcium alginate hydrogels beads with 5 and 10% w/w of bentonite are synthetized and their capacity to adsorb methylene blue, as model dye, from aqueous media is evaluated. Structure and mechanical properties of hydrogels beads are determined, showing that hydrogels beads with bentonite present higher viscosity and hardness. Regarding methylene blue adsorption capacity, the effect the contact time (0–32 h) and the initial cadmium ion concentration (0.2–3.0 mg L−1) are studied employing hydrogel beads. The equilibrium adsorption time is reached at 300 min for all studied hydrogels and experimental data are fitted well with a pseudo-second order kinetic model. As conclusion, alginate/bentonite hydrogel beads are accepted as a promising candidate to remove methylene blue dye from aqueous solutions.