Ultrasound-assisted abamectin removal using magnetic activated carbon from orange peel embedded in chitosan hydrogel beads

Abamectin is a toxic environmental contaminant posing serious health risks; thus, its removal from water is essential. In this study, chitosan-based hydrogel beads containing varying amounts of magnetic activated carbon were synthesized and utilized for the removal of abamectin from wastewater. Characterization studies confirmed the successful preparation of the composites: FTIR spectra revealed functional groups and MAC-chitosan interactions, XRD confirmed the crystalline features, FESEM showed the uniform dispersion of MAC within the hydrogel matrix, and BET analysis demonstrated that the specific surface area of chitosan hydrogel beads increased from 28.61 m²/g to 43.86 m²/g after MAC incorporation. Batch adsorption studies showed that the chitosan-based hydrogel with 30% magnetic activated carbon achieved nearly 99.95% removal efficiency under Taguchi-optimized conditions (30 mg/L initial concentration, 1.5 g/L adsorbent dosage, pH 5, and 60 min contact time). The nonlinear analysis of adsorption isotherms of different models showed that the adsorption process followed the Toth model when ultrasound was applied and the Sips model in the absence of ultrasound. According to the Langmuir model, the maximum adsorption capacity increased from 71 mg/g to 152 mg/g in the presence of ultrasound, an improvement primarily attributed to the cavitation phenomenon. Moreover, this study is the first to demonstrate that ultrasonication significantly enhances abamectin removal efficiency by considerably shortening the equilibrium time and reducing energy consumption during abamectin adsorption. Also, the evaluation of desorption and reuse revealed that the abamectin adsorption efficiency decreased from 99.95% to 81.8% following eight cycles. This study is the first to demonstrate that ultrasonication significantly enhances abamectin adsorption on MAC-chitosan hydrogel beads. Moreover, the application of ultrasound considerably reduces the adsorption cost, lowering it from 2.9 $/g to 1.5 $/g. However, some limitations, such as partial loss of efficiency after repeated cycles and the need for scale-up studies, remain to be addressed in future research.