Microwave-engineered gum ghatti-graft-poly(acrylic acid)/TiO₂ bionanocomposites as reusable high-performance...

Plant-derived polysaccharides have emerged as sustainable matrices for the fabrication of advanced nanocomposite adsorbents for wastewater purification. In the present study, a novel series of gum ghatti-graft-poly(acrylic acid)/TiO₂ (Gg-g-polyAA/TiO₂, GATNC) bionanocomposites were synthesized via a rapid microwave-assisted graft copolymerization technique using ammonium persulfate (APS) as initiator, and N, N'-methylene-bis-acrylamide (MBA) as the crosslinker. The titanium dioxide (TiO₂) nanoparticles were in situ incorporated in varying amounts (25-150 mg) during the polymerization to obtain a series of composites designated as GATNC-1 to GATNC-4. All the GATNCs bionanocomposites were investigated for their dye removal efficiency. Among various tested dyes (cationic and anionic), the GATNCs showed remarkable adsorption efficiency (>90% at pH 7) for the methylene blue (MB). The structural, morphological, and thermal properties of pristine gum ghatti (Gg), unloaded GATNCs, and dye-loaded GATNCs were comprehensively characterized using FTIR, XRD, FESEM, EDS, BET, TGA, DSC and TEM analyses. For all the composites, the adsorption process followed the pseudo-second order kinetics and the Freundlich isotherm, suggesting a chemisorption process on a heterogeneous surface. The Langmuir maximum adsorption capacities (qₘ) were 6042.73, 6314.45, 6656.72, and 6906.76 mg/g for GATNC-1, GATNC-2, GATNC-3, and GATNC-4, respectively. Notably, all GATNCs retained high adsorption performance after multiple successive reuse cycles, with adsorption capacities ranging from 2670.97 to 2719.02 mg/g for GATNC-1 to GATNC-4, respectively, after the tenth repeat cycle. These results highlight the potential of GATNC bionanocomposites as efficient, reusable, and eco-friendly adsorbents for the sustainable remediation of industrial effluents containing toxic cationic dyes.