Engineering sodium alginate-SiO2 composite beads for efficient removal of methylene blue from water

The lack of sufficient active binding sites in commonly reported sodium alginate (SA)-based porous beads hampers their performances in adsorption of water contaminants. To address this problem, porous SA-SiO2 beads functionalized with poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) are reported in this work. Due to the porous properties and the existence of abundant sulfonate groups, the obtained composite material SASiO2-PAMPS shows excellent adsorption capacity toward cationic dye methylene blue (MB). The adsorption kinetic and adsorption isotherm studies reveal that the adsorption process fits closely to pseudo-second-order kinetic model and Langmuir isotherm model, respectively, suggesting the existence of chemical adsorption and monolayer adsorption behavior. The maximum adsorption capacity obtained from Langmuir model is found to be 427.36, 495.05, and 564.97 mg/g under 25, 35, and 45 degrees C, respectively. The calculated thermodynamic parameters indicate that MB adsorption on SA-SiO2-PAMPS is spontaneous and endothermic.