Maggot-modified avocado peel as an innovative adsorbent for crystal violet dye wastewater treatment

The high production of avocado generates large amounts of solid organic waste; however, its utilization remains very limited. his study examines the potential of avocado peel (AP) and maggot-modified avocado peel (APM). The modification process involved dissolving AP and maggot larvae in ethanol, followed by sonication and drying, to obtain adsorbent materials for the treatment of crystal violet (CV) dye contamination in wastewater. Batch adsorption optimization was conducted by examining several parameters, including variations in pH, initial concentration, contact time, and heating of the adsorbent. The reusability study was conducted using three desorption eluents, namely acetic acid, hydrochloric acid, and citric acid, over four adsorption-desorption cycles. The results revealed that APM exhibited a higher adsorption capacity than AP, increasing from 165.16 mg g⁻ 1 to 223.49 mg g⁻ 1 . Characterization results indicate that the modification increased amine functional groups, as observed in Fourier Transform Infrared Spectroscopy (FTIR), altered the mineral composition before and after adsorption, as revealed by X-ray Fluorescence (XRF), and partially covered surface pores, as evidenced by Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy (SEM–EDX) images. Isotherm analysis indicated that the adsorption behavior of AP was well-fitted to the Langmuir model, whereas APM followed the Temkin model. For both adsorbents, the adsorption kinetics were consistent with the pseudo-second order (PSO) model. Meanwhile, thermodynamic studies revealed that the process was spontaneous, exothermic, and accompanied by a decrease in system entropy. Reusability tests confirmed that both adsorbents maintained good performance for up to four consecutive cycles. Remarkably, the removal percentage remained high (97%) even when applied to wastewater containing multiple pollutants. These findings highlight that AP waste has great potential to be developed as an environmentally friendly and cost-effective adsorbent for treating dye-contaminated wastewater.