Hydrothermal synthesis of CuO/biochar from longan seeds for effective adsorption of methyl orange in water

Abstract

This study presents the synthesis of CuO/biochar adsorbent from Dimocarpus longan (longan) seeds using a hydrothermal method for the removal of methyl orange (MO) from aqueous solutions. The material was characterized using SEM, EDX, XRD, FT-IR, and BET analyses. The results confirmed the uniform distribution of CuO nanoparticles on the biochar surface, significantly increasing the specific surface area and adsorption capacity. Adsorption performance was investigated on contact time, solution pH, MO concentration, and adsorbent dosage. The adsorption process followed the Langmuir isotherm model, with a maximum adsorption capacity of 227.27 mg/g at pH 3 and an equilibrium time of 90 minutes. The pseudo-second-order kinetic model best described the adsorption behavior, indicating chemisorption as the dominant mechanism. These findings suggest that CuO/biochar derived from longan seeds is a promising and environmentally friendly material for removing anionic dyes from wastewater.