Ultrasound treatment of chitosan macrobeads for crack formation and application in column dynamics sorption of methyl orange

This study aimed to utilize low-cost and environmentally friendly sorbents for removing textile dyes, particularly methyl orange (MO) from wastewater. Here, continuous adsorption experiments were conducted by using chitosan macrobeads (CS-MB) as the low-cost sorbent. The CS-MB was further treated with ultrasonication for crack and pore formation. The physicochemical evaluation revealed that the sonicated beads (CS-SMB) developed a rougher surface with cracks and pores, creating additional adsorption sites. Column studies showed that the optimized process variables for the continuous adsorption of MO onto the CS-SMB are 10 mg/L initial MO concentration, 400 mm bed height, and 20 mL/min flow rate. The MO removal percentage achieved under these optimized conditions slightly outperformed that of the unsonicated beads (i.e. CS-MB). However, the performance of the CS-SMB and CS-MB converged after 10 min probably due to the reduction in bead size and the presence of trapped bubbles within the beads after sonication. Breakthrough curve modeling showed that the adsorption data of CS-SMB most closely fitted the Yoon-Nelson model. This study demonstrates that ultrasonication can effectively modify the structural properties of chitosan macrobeads, thereby altering their dye removal performance.