Textile industries in Bangladesh are projected to produce 349 million m3 of wastewater using conventional dyeing practices by the end of 2021. Toxic textile dyes are a major environmental and health hazard, and methylene blue is one of the common components of the textile effluents. Chitosan composites have been shown to have excellent adsorbent properties such as cationic nature and macromolecular structures with high adsorption capacity. Hydrogels are polymeric three-dimensional materials, which can absorb large amounts of water and can be implemented for adsorption applications. Previously, such polymeric three-dimensional composites using chitosan and acryl-based components have been devised to absorb pollutants. Our study proposed that the dye adsorption characteristics of chitosan-polyacrylic acid (chitosan-PAA) composite can be improved by the incorporation of a complexing agent, ethylenediamine tetraacetic acid (EDTA). Two types of chitosan-PAA based composites, one with and the other without EDTA, were prepared using established methods. Comparative studies were carried out to evaluate the applicability of these three-dimensional structures for effective removal of methylene blue dye. The water uptake test showed that up to eight times increase in the swelling ratio of the chitosan-PAA gel occurred, due to EDTA grafting. Fourier transform infrared (FTIR) and thermal analysis experiments confirmed the incorporation of EDTA onto the formed chitosan-PAA hydrogels and also demonstrated thermal stability of both types of composites. Scanning electron microscopy (SEM) images on both hydrogels showed the presence of a highly interconnected macroporous network. The incorporation of EDTA in chitosan-PAA composite increased the dye adsorption performance from 61.65% to 87.88%. The final composite, chitosan-PAA with EDTA incorporated, was further investigated and a maximum absorption capacity, qm of 2000 mg/g was obtained, by fitting to Langmuir isotherm equation. This qm value is higher than most of the dye removal composites qm values reported in literature. Thus, chitosan-PAA hydrogels with EDTA incorporated offers great potential for practical application in the removal of toxic dyes from contaminated textile effluents.

Enhanced encapsulation of cationic dye in EDTA modified chitosan-PAA composite

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.