Dithiol-functionalised guar gum-protein aerogel for efficient malachite green removal: Multi-mechanistic adsorption and structural insights.

Abstract

The development of sustainable adsorbents with high structural stability and practical applicability remains a major challenge for dye-contaminated wastewater treatment. This study presents a simple molecular strategy to overcome the structural stability of conventional biopolymer aerogels. A protein-polysaccharide hybrid aerogel composed of guar gum (GG) and bovine serum albumin (BSA) was fabricated using 2,2'-(ethylenedioxy)diethanethiol (EDDT) as a dithiol-assisted supramolecular stabilizer for malachite green (MG) removal. The incorporation of EDDT introduced sulfur-containing functionalities that enhanced network integrity, preserved porosity during freeze-drying, and improved regeneration stability through thiol-mediated interactions and possible partial disulfide formation. Comprehensive characterization (FTIR, PXRD, SEM, TGA, and zeta potential analysis) confirmed the formation of a porous, thermally stable three-dimensional network with favorable surface charge properties. BSA introduced abundant amine and carboxyl groups, enabling multiple adsorption sites. The GG-BSA-EDDT aerogel achieved a Langmuir maximum MG adsorption capacity of 225 mg/g at pH 9.0, following Langmuir and Freundlich isotherms and pseudo-second-order kinetics. Rapid adsorption equilibrium was achieved within 30 min via electrostatic attraction, hydrogen bonding, π-π interactions, pore diffusion, and sulfur-mediated binding. Even after eight cycles, over 90% efficiency was retained, demonstrating excellent reusability. The fully biodegradable composition, facile fabrication strategy, excellent regeneration performance, and multifunctional adsorption mechanism highlight the potential of the GG-BSA-EDDT aerogel as a sustainable adsorbent for practical wastewater remediation.