“Synthesis and characterization of Chitosan-Tamarind Gum-CaO nanoparticle hydrogels for improved adsorption of Alizarin Red-S Dye from aqueous solution: performance assessment and mechanistic insights”

This research investigates the development of highly efficient adsorbents for removal of Alizarin Red-S (ARS) dye from aqueous solutions using chemical crosslinking of chitosan (CH), tamarind gum (TG), and calcium oxide nanoparticles (CaO NPs). Various analytical techniques, including TGA, XRD, SEM, and FTIR, were employed to examine the interactions and morphological changes in the hydrogels. The adsorption capacity of CH-TG and CH-TG-CaO hydrogels was evaluated under different conditions, including adsorbent amount, contact time, pH, and temperature. The data fit well with the Langmuir model, with maximum adsorption capacities (q_max) of 79.05 mg/g for CH-TG and 87.33 mg/g for CH-TG-CaO. A significant increase of approximately 9.38% in ARS adsorption was observed with CH-TG-CaO compared to CH-TG. Optimum adsorption was achieved at pH 7, with 360 min for CH-TG and 160 min for CH-TG-CaO. The highest removal efficiencies were 87.17% for CH-TG and 96.55% for CH-TG-CaO at an adsorbent amount of 0.25 g and 40 mg/L dye concentration at 30 °C and pH 7. The adsorption process followed the pseudo-second-order kinetic model, and thermodynamic results suggest the process is physical, exothermic, and spontaneous. The presence of -NH₂ groups in the hydrogels enhanced affinity for anionic dyes through hydrogen bonding and electrostatic interactions. Thus, CH-TG and CH-TG-CaO hydrogels are promising and efficient adsorbents for environmental remediation.