Surface modification of sodium alginate-polyvinyl alcohol hydrogel beads using low-pressure cold plasma and application for methylene blue removal from water

This study examines the adsorption efficiency of methylene blue (MB) from aqueous solutions using sodium alginate-polyvinyl alcohol (SA/PVA) hydrogel beads modified through low-pressure cold plasma (LPCP) treatment. The LPCP process significantly enhanced the surface properties of the hydrogel beads, improving their adsorption capacity (P<0.05). Experimental results revealed that plasma-treated beads exhibited substantially higher MB removal compared to untreated beads, with optimal performance observed under the P5 treatment condition (5 minutes of LPCP exposure). FTIR and SEM analyses confirmed structural modifications after adsorption in all samples. Adsorption kinetics adhered to a pseudo-second-order model, indicating chemisorption as the primary mechanism. Thermodynamic analysis demonstrated that the adsorption process was spontaneous and endothermic. Furthermore, the hydrogel beads showed excellent reusability, maintaining efficient dye removal across multiple cycles. These findings highlight the potential of LPCP-treated hydrogel beads as an effective and sustainable solution for MB removal in wastewater treatment applications.