Valorization of Stipa tenacissima Biomass into Functional Carboxymethylcellulose Hydrogel beads for Eco-Friendly Dye Removal

In this study, sodium carboxymethyl cellulose (CMC-Na) with a high degree of substitution was synthesized via chemical modification of cellulose extracted from Stipa tenacissima. The obtained CMC-Na served as a base material for preparing hydrogel beads through a drop-addition method, where a mixture of polyvinyl alcohol (PVA) and CMC was added to a boric acid solution containing calcium chloride. Two hydrogel bead types were formulated: PC (PVA-CMC) and PCA (PVA-CMC-NH₄Cl), with the goal of evaluating their capacity to adsorb methylene blue (MB) from aqueous solutions. The water retention capacity of the beads was evaluated by measuring their swelling in a neutral medium, after 72 hours, PCA beads exhibited a swelling of 1250%, while PC beads reached 936.5%. Batch adsorption experiments examined the effects of contact time and initial MB concentration. Kinetic analysis indicated that MB adsorption followed a pseudo-first-order model and occurred via a three-step intraparticle diffusion mechanism. Isotherm analysis showed that the Langmuir model best described the adsorption behavior, with a maximum adsorption capacity of 16.72 mg/g and a removal efficiency of 88.66%. These findings demonstrate the promising potential of PCA hydrogel beads as eco-friendly and efficient adsorbents for dye removal from wastewater.