Derivation of copolymer hydrogel from Salvia hispanica mucilage and its utilization in adsorption of Reactive Black-5

Chia mucilage-grafted-acrylamide was designed using a microwave-assisted method for removal of hazardous azodyes from aquatic environments. After testing different batches, batch with highest grafting efficiency and water retention capacity (50% ± 1.25 and 500% ± 2.5, respectively) was chosen for characterization and adsorption analysis. Fourier transform infrared spectroscopy confirmed the presence of functional groups corresponding to both Chia mucilage and Acrylamide in the hydrogel. Scanning electron microscopic images showed transition of initially smooth fibrillar structure of chia mucilage to comparatively rougher and granular copolymer arrangement. Hydrogel was found thermally stable up to 480 °C whereas dynamic light scattering analysis exhibited hydrodynamic size of 593.8 nm and zeta potential of 30 mV, indicating moderate stability of hydrogel. Upon optimization, maximum adsorption efficacies were observed at 50 mg/l Reactive Black-5 concentration, 50 mg hydrogel, pH-4 and 25 °C. Adsorption results showed slightly greater inclination towards Pseudo-first order kinetic model due to close proximity between experimental and calculated values of adsorbed amount at equilibrium i.e. q_e and q_cal values (19.30 and 20.71 mg/g respectively). Maximum monolayer adsorption capacity obtained from Langmuir isotherm was found as 100 mg/g. Additionally, adsorption behavior of Reactive Black-5 onto chia-based copolymer was more in line with the Freundlich isotherm (R² = 0.99) compared to Langmuir (R² = 0.92) and Sips (R² = 0.83) models, as shown by linear plots. Repeated experiments demonstrated that prepared hydrogel could be a sustainable adsorbent, offering an economical and swift solution for successful remediation of Reactive Black-5 from contaminated water bodies.