Environmentally friendly tetra ethyl orthosilicate crosslinked Chitosan–Guargum hydrogel for methylene blue removal: A sustainable water purification method

The present work aimed to synthesize Tetraethyl orthosilicate (T)- crosslinked chitosan (CS) and Guargum (GG) hydrogels with varying compositions (CS-T@GG1, CS-T@GG0.8, and CS-T@GG0.5) and evaluate their application for the removal of methylene blue (MB) dye from aqueous solution. Adsorption of dye on the fabricated hydrogels was conducted in a batch system. The prepared crosslinked hydrogels were characterized using Raman, EDS, SEM, FTIR, XRD, TGA, and particle size analysis. The swelling response of the synthesized hydrogel was investigated in deionized water at different pH levels and electrolyte concentrations. Equilibrium concentrations of dye in aqueous solution and adsorption capacities of adsorbent at various experimental conditions (Different time intervals in batches, solution pH, and initial adsorbate concentration in solution, thermodynamic study at different temperatures, change in enthalpy, entropy, and Gibbs free energy) were evaluated. At pH 12, the dye adsorption efficiency was 82.10% for a 25 ppm methylene blue solution using a 0.025 g/L adsorbent dose at 300 rpm, whereas at neutral pH, the efficiency decreased to approximately 65%. Various kinetic adsorption isotherms and thermodynamic models were simulated mathematically. The pseudo-first-order kinetic model gave the best agreement with the experimental kinetic data, with R2 .99 and the model qe value. Results confirmed that the synthesized hydrogel may be an efficient adsorbent for dye removal. The correlation between the independent variables associated with methyl blue dye adsorption and the dependent parameters was established by analyzing ChemSketch 3D. The hydrogel remained stable for 5 cycles in the stability test.