فهرست نشریات علمی دسترسی آزاد ایران

Synthetic dyes are toxic, cancer-causing, and mutagenic, which makes water pollution a big environmental problem. This study synthesised a novel xanthan gum-grafted-poly(polyvinylpyrrolidone-co-acrylic acid-acrylamide) [XG-g-poly(PVP-co-AA-AAm)] nanohydrogel for the removal of Brilliant Green (BG) cationic dye using free radical graft copolymerisation. The XRD study showed an amorphous structure with semi-crystalline peaks at 19.18°, 20.68°, and 23.38°. These peaks were linked to xanthan gum, PVP, and polyacrylamide. FTIR confirmed that the grafting worked and found the functional groups (–OH, –CONH₂, –COO⁻) that were responsible for binding the dye. The post-adsorption bands at 1514, 1712, and 1165 cm⁻¹ show that BG was absorbed by electrostatic attraction and hydrogen bonding. Decomposition started at 234.3°C, and TGA/DTA was thermally stable at Tg = 79°C. FESEM indicated that the surfaces changed shape following adsorption, going from smooth (d = 75.4 nm) to spherical dye nanoparticle-covered surfaces (d=29.7–162.7 nm). The nanohydrogel could hold 37.33 mg/g and remove 93.34% of what it was supposed to in 90 minutes when the conditions were just right (C₀ = 200 mg/L, dose = 0.005 g, natural pH, T=30°C). The pseudo-second-order model (R²=1.000) in kinetics proved that chemisorption was real. Weber-Morris forecasted the influence of boundary layer diffusion (C = 36.34 mg/g). The best fit equilibrium data using the Freundlich isotherm indicated heterogeneous multilayer adsorption. Thermodynamic studies showed that adsorption was spontaneous (ΔG° < 0), endothermic (ΔH° > 0), and unexpected (ΔS° > 0). When we used NaCl, KCl, and CaCO₃ to test ionic strength, they all worked well even though there were other electrolytes. These studies indicate that nanohydrogel is an environmentally favourable adsorbent for cationic dye-contaminated wastewater.