Thiourea-modified chitosan for effective adsorption of Remazol Brilliant Blue R: Synthesis, characterization, adsorption properties, and morphological effects

Abstract

This study explores the adsorption of Remazol Brilliant Blue R (RBBR) dye from aqueous solutions using thiourea-grafted chitosan in powder (TUCTS-P) and film (TUCTS-F) forms. The combination of thiourea and chitosan results in a material with positive charges on the amine and carbonyl groups, making it an effective adsorbent for anionic dyes such as RBBR. Therefore, in the present work, the structure of chitosan was modified by chemically grafting thiourea to chitosan chains, forming two different morphologies and using both morphologies for RBBR dye adsorption. Synthesized materials were characterized via FT-IR, XRD, and SEM-EDX. Adsorption efficiencies were optimized at pH 6, with TUCTS-P achieving over 95 % adsorption at 0.45 g L –1 sorbent and 50 minutes, while TUCTS-F required 0.35 g L –1 and 90 minutes. Langmuir isotherms and pseudo-second-order kinetics described the process well, and thermodynamic studies confirmed spontaneity, with ΔG° values of −28.97 kJ mol −1 for TUCTS-P and −28.69 kJ mol −1 for TUCTS-F. Maximum monolayer capacities (qmax) were 580.93 mg g –1 and 675.08 mg g –1 , respectively, emphasizing pore-diffusion's role. Both forms showed promise for removing RBBR from textile effluents effectively.