Influence of Sonication Amplitude on Surface Perforation of Chitosan Macrobeads and Impact on Dye Adsorption

Abstract

Due to industrialisation and globalisation, water sources are increasingly contaminated with dyes. Among the various methods available, adsorption is one of the most widely used techniques for dye removal. This project aimed to develop chitosan macrobeads with a surface-perforated structure and to investigate how these surface alterations influence their dye adsorption efficiency. Here, chitosan macrobeads were formed using the gelation method and subsequently subjected to high-intensity sonication at various amplitudes (20 %, 40 %, 60 %, 80 %, and 100 %) for 5 minutes to induce surface perforation. As anticipated, significant changes in the surface structure were observed via electron microscopic analysis. In particular, the bead surfaces exhibited wavy and corrugated layers, with the presence of cracks and pores following sonication. Nevertheless, macrobeads treated at higher sonication amplitudes (≥ 60 %) experienced surface rupture, resulting in flake-like layers. This suggests that the intense sonication disrupted the internal bonding network of the chitosan macrobeads. The macrobeads were found to retain their key surface functional groups despite being subjected to intense sonication. Subsequently, dye adsorption studies showed a slight improvement in adsorption efficiency when chitosan macrobeads were sonicated at 40 % amplitude compared to non-sonicated samples. However, a detrimental effect was observed at higher sonication amplitudes (≥ 60 %), where a significant reduction in adsorption efficiency occurred. This anomaly could be attributed to the detachment of chitosan from the bead matrix, which resulted in beads that were less solidified and lacked surface integrity, ultimately leading to reduced adsorption performance.