Activated Hydrochar Prepared from Longan Fruit (Dimocarpus longan Lour.) Peel via Hydrothermal Carbonization-NaOH Activation for Cationic Dyes Removal

Abstract

Hydrothermal carbonization is recognized as a method of processing biomass into carbon-rich products due to its energy-saving and environmental-friendly advantages. In this study, two types of hydrochar were prepared from Longan Fruit (Dimocarpus longan Lour.) Peel via hydrothermal carbonization at temperatures of 190°C and 250°C and activated using NaOH (HC-ACT 190 and HC-ACT 250) for removal of malachite green (MG) and rhodamine B (RhB) dyes. The maximum capacity for MG dye removal using HC-ACT 190 and HC-ACT 250 materials was 172.414 mg/g and 250 mg/g, while for RhB dye was 111.111 mg/g and 151.515 mg/g, respectively. The optimum pH was obtained at pH 6 for MG and pH 3 for RhB with adsorption equilibrium time occurring at 90 minutes. The kinetic study shows that the adsorption process follows pseudo-second-order kinetics, while the isotherm model was determined by the Langmuir isotherm model. Materials can be reused effectively for at least 3 cycles with an adsorption percentage of MG dye removal using HC-ACT 190 and HC-ACT 250 materials was 69.91% and 83.15% respectively, while for RhB dye was 35.79% and 55.6% respectively. The material is more selective on MG dye compared to RhB dye based on the selectivity test on the adsorption of the dye mixture.

Layered Double Hydroxide Coated by Carbon-Based Material for Environmental Dye Pollutant

“…However, malachite green contributes to environmental pollution due to its toxic effect on various organisms' organs, including animal and fish poisonings (Jaffari et al, 2023). Because of the large scale of aquaculture nowadays and using malachite green at the rates from 0.1 to 10.0% of the aquatic culture mass per day, appropriate methods for the determination of this dye and other water pollutants are extremely required (Palapa et al, 2023a).…”