This work reports a physically cross-linked chitosan/sulfated carboxymethyl cellulose (Cs–SCMC) hydrogel reinforced with carbon nanotubes (CNTs) as a sustainable adsorbent for removing tartrazine (an anionic azo dye) from water. Sulfation of CMC introduced stable –SO₃⁻ groups that can form a polyelectrolyte complex (ion-pair/electrostatic interactions) with protonated chitosan, enabling hydrogel formation without chemical cross-linking agents. FT‑IR, CHNS, and FE‑SEM confirmed successful functionalization and revealed a porous network suitable for pollutant uptake; CNT incorporation improved structural uniformity and increased accessible interaction sites. The optimized formulation (Cs–SCMC 4 ) exhibited pH-responsive swelling (higher swelling at acidic pH), with water transport governed by Fickian diffusion (n < 0.5). Kinetic analyses showed that both swelling and tartrazine uptake are well described by a pseudo‑second‑order model. Adsorption equilibrium data followed the Langmuir isotherm (R² = 0.9946), indicating monolayer coverage with a maximum capacity of 434.78 mg g -1 . Thermodynamic parameters ( ΔH ° = +14.68 kJ mol -1 , ΔG ° = −0.55 to −2.12 kJ mol -1 over 298–328 K) indicate a spontaneous and endothermic adsorption process. Overall, the CNT-reinforced Cs–SCMC hydrogel is a low-cost, biodegradable, and cross-linker-free material with strong potential for dye‑contaminated wastewater treatment.
Khorsandi et al. (Fri,) studied this question.