Composite aerogels of alginate/poly(acrylamide)/carbon nanotubes with enhanced performance for cationic dyes adsorption

This study presents the preparation and characterization of a composite aerogel with a double network of alginate (Alg) and poly(acrylamide) (PAM), filled with multi-walled carbon nanotubes (MWCNT). The double network structure was formed by mixing alginate and the PAM network and subsequently cross-linking the polysaccharide with Ca2+ ions. Characterization analyses demonstrated that the inclusion of MWCNT resulted in significant changes to the thermal, morphological, mechanical, and swelling properties of the composite compared to the pristine aerogel (Alg/PAM). Adsorption experiments demonstrated the effectiveness of Alg/PAM/MWCNT in removing cationic dyes (methylene blue, MB, and crystal violet, CV) from aqueous solutions. Notably, the aerogel containing MWCNT exhibited 1.5 times higher adsorption capacity for MB and CV compared to Alg/PAM under similar experimental conditions. Isothermal analyses revealed distinct adsorption behaviors for MB and CV on Alg/PAM/MWCNT, and competitive adsorption was observed when both dyes were present in the solution simultaneously. The composite aerogel also demonstrated excellent reusability, maintaining its performance for at least five cycles, indicating its potential for long-term application.