Hydrothermal Synthesis of Waste Black Tea Pulp and Tomato Stem Hydrochars and Comparison of Their Adsorption Performance of Safranin Dye

In this study, hydrochar prepared from black tea (BT) and tomato stem (TS) using subcritical water (SW) conditions was used as an adsorbent for color removal from Safranin-O (SO-Basic Red 2) dye wastewater. The use of black tea hydrochar (BTH) and tomato stem hydrochar (TSH) was investigated in the removal of Safranin-O dye from aqueous solutions by the adsorption process. In optimization studies, variables impacting the adsorption process such as adsorbent size, pH, dye concentration, adsorbent dosage, and shaking time were examined. As a result of optimization studies, removal efficiencies of 85.15% for BTH and 81.5% for TSH were achieved. In this study, the reuse cycle was also examined. Adsorption isotherm models, adsorption kinetic models, and thermodynamic studies have been studied to explain the relationships between the adsorption processes taking place. Data appropriate for the Freundlich and D-R isotherm models as well as the PSO kinetic model were obtained for TSH while defining the Freundlich isotherm model and the pseudo-second-order (PSO) kinetic model for BTH.