High efficiency removal of methylene blue dye using κ-carrageenan-poly(acrylamide-co-methacrylic acid)/AQSOA-Z05 zeolite hydrogel composites

Abstract

This work reports the preparation of zeolite hydrogel composite (ZHC) based on κ-carrageenan (KC) and AQSOA-Z05 zeolite and its potential use in water remediation applications for methylene blue (MB) dye adsorption. The ZHC was synthesized via the graft-copolymerization technique using the crosslinked hydrogel of KC as polymer matrix. Effects of incorporating zeolite particles within the hydrogel matrix on the properties were studied using different characterization techniques such as TEM, X-ray diffraction, SEM and FTIR. The hydrogel composite with 8% loading of zeolite exhibited maximum swelling capacity (3.481%) among the synthesized ZHCs. For MB removal, ZHC adsorbed 99% dye with 0.4 g L−1 adsorbent dose in the neutral pH solution. Furthermore, the adsorption of MB onto ZHC followed pseudo-second-order and Langmuir isotherm models. The ZHC exhibited maximum adsorption capacities of 661.91 at 298.18 K, 674.05 at 308.15 K and 682.67 mgdye gads−1 at 318.15 K. Dye diffusion mechanism partially followed both liquid film and intra-particle diffusion mechanisms. Results obtained from thermodynamics experiments suggested the endothermic nature of the MB adsorption on ZHC. MB was selectively adsorbed from the binary dye mixtures having MB and methyl orange in different concentration ratio. In addition, the ZHC showed excellent adsorption behavior for six continuous adsorption–desorption cycles. Therefore, the synthesized ZHC has all the properties to be used as a potential adsorbent for the treatment of cationic dyes contaminated wastewater.