Comparative study of dye adsorption on alginate and functionalized montmorillonite hydrogel beads

This work focused on the development of hybrid hydrogel beads based on sodium alginate and hexadecyltrimethylammonium bromide modified montmorillonite (ALG@Mmt@HTAB) for the adsorption of multiple organic dyes such as methylene blue (MB) and trypan blue (TB) from wastewater. The alginate-based hydrogel beads were first characterized through morphological and spectroscopic analyses. The effects of the contact time, mass dosage, and initial dye concentration were investigated through batch tests, highlighting the advantages offered by the presence of modified montmorillonite. The data proved that the adsorption kinetics reached equilibrium within 20 min for MB and 15 min for TB. The extent of dye adsorption is dependent on both the initial dye concentration and the adsorbent dosage. The adsorption data of MB and TB onto the synthesized beads followed the pseudo-second-order model. The experimental data fitted very well to the Langmuir model, which demonstrated the favourable nature of adsorption. The maximum adsorption capacity reaches 345.88 mg/g for MB and 482.22 mg/g for TB. Finally, phenomenological mass transfer kinetics were studied to assess the effect of chemisorption and physisorption. The reported results revealed that the ALG@Mmt@HTAB beads could be used as a novel natural adsorbent for the removal of multiple dye-based solutions from liquid effluents.