A TiO2-functionalized guar gum/sodium alginate hydrogel as a sustainable adsorbent for crystal violet dye remediation

Abstract

Water contamination from synthetic dyes has emerged as a significant environmental issue in recent years because of their adverse effects and environmental persistence; crystal violet (CV) is one such pollutant. The research work presented in this article introduces a hydrogel nanocomposite named GG-SA@TiO₂, composed of guar gum and sodium alginate as a polymer matrix and TiO₂ nanoparticles as a support material for adsorption. This hydrogel nanocomposite was prepared using a combination of covalent and ionic crosslinking. Adsorption studies of CV dye removal were conducted using the batch method to evaluate the role of adsorbent dose, dye concentration, temperature, pH and interfering ions using a hydrogel nanocomposite. Using the Langmuir adsorption model, the theoretical monolayer adsorption capacity (q_m) was estimated to be 8.589 mg g⁻¹. Isotherm evaluation at equilibrium identified the Freundlich model as the most appropriate description, suggesting adsorption on a non-uniform surface with multilayer coverage. Analysis of the kinetic profiles showed that the adsorption process follows a pseudo-second-order rate model. The adsorption process was enabled through the cumulative action of electrostatic forces, hydrogen bonding and surface interactions. The hydrogel also showed good regeneration capability, supporting its use as a reusable adsorbent in dye-based wastewater remediation.