Effective RhB Dye Removal Using Sustainable Natural Bioadsorbents Synthesized from Avocado Seed and Skin

Abstract

Managing waste generated by the food industry is a pressing environmental challenge, and traditional disposal methods such as landfilling or incineration are no longer viable solutions. However, by recovering and valorizing waste in wastewater treatment, we can address the waste management issue and the energy-intensive nature of conventional treatment methods with processes compatible with renewable energy technologies. In this work, avocado skin and seed are valorized for their application in removing Rhodamine B (RhB) dye. Avocado skin (ASk) and seed (ASe) were recovered and recycled separately to develop natural bioadsorbents. Biomaterials were characterized by XRD, XPS, ICP-MS, ATR-FTIR spectroscopy, TGA, N2 adsorption/desorption, and SEM. The ASk and ASe bioadsorbents were employed to remove RhB at four experimental conditions: pH, RhB concentration, bioadsorbent concentration, and temperature. RhB removal was followed by UV–Vis spectroscopy. The results show that at pH 3, the highest percentages of dye removal are achieved, using ASk and ASe, with 88 and 92% removal, respectively. ASe bioadsorbent is more effective for removing RhB dye, reaching 92% after 4 h of contact with 2 g L−1 of bioadsorbent and at 30 °C. Experimental results better fit a pseudo-second-order kinetic model and the Langmuir adsorption model, with maximum adsorption capacities of 13.1240 and 17.9998 mg g−1 for ASk and ASe, respectively. The results show that natural bioadsorbents are suitable options for environmental remediation.