Hydrochar from Lansium domesticum and Salacca zalacca Peel as Adsorbent on Rhodamine-B Removal: Adsorption Process and Regeneration Studies

Utilization of duku (Lansium domesticum) peel and salak (Salacca zalacca) peel as rhodamine-B adsorbent was investigated by producing it into hydrochar of duku peel and hydrochar of salak peel by hydrothermal carbonization at 150 °C for 6 hours. XRD shows hydrochar was an amorphous solid (angle of 2ϴ at 30 deg (002)). FTIR characterization of hydrochar showed that hydrochar had the main constituent of the raw material biomass with detected functional groups in the form of -OH, -CH, C=O, and C-O. Wavenumber at FTIR was shifted after adsorption indicated adsorption of rhodamine-B by adsorbent with changes in the structure. Duku peel increased surface area after being hydrochar from 12.343 m2/g to 21.019 m2/g, but salak peel had decreased in surface area from 62.676 m2/g to 23.121 m2/g. The maximum adsorption capacity of duku peel is 58.824 mg/g at 30 °C, HC of duku peel is 114.943 mg/g at 70 °C and salak peel is 92.593 at 30 °C, HC of salak peel is 102.041 mg/g at 30 °C. In this study, the adsorption kinetics and isotherm models follow the PSO kinetic model and Langmuir isotherm with an endothermic and spontaneous adsorption process. Adsorption efficiency in the regeneration process increases from fruit peel to hydrochar and can be used repeatedly in the regeneration process for 3 cycles.