A Study on the Application of Coffee Waste Biochar with Hydrothermal Carbonization and Adsorption Performance of Toluene

In this study, biochar was created from coffee wastes with a high moisture content by applying a hydrothermal carbonization (HTC) method. Environmental problems during the treatment and optimal conditions were derived based on the adsorption performance of biochar. In addition, we compared biochar and activated biochar to evaluate their potential as adsorbents for VOCs by chemical activation using KOH to activate micro-secessions of biochar. The highest yield was obtained at 260^oC for 1 h and the iodine adsorption performance at approximately 687.11 mg/L. Therefore, the HTC optimal reaction conditions using coffee wastes increased its potential for use as an adsorbent. KOH was used as a chemical activator to activate the biochar under optimal generative conditions. A second batch test was conducted and analyzed for yield and iodine adsorption performance. The second batch test showed that the optimal activation temperature was about 700^oC, the optimal mixing ratio of biochar and KOH was 1: 0.5, and the optimal activation time was 1 h for 1,105.33 mg/g iodine adsorption performance. Toluene adsorption experiments were conducted to evaluate the VOC adsorption potential of coffee wastes, biochar, activated biochar, and GAC (Granular Activated Charcoal, Untreated). As a result, activated biochar, which was adsorbed at 240 minutes, was considered a more efficient adsorbent than coffee wastes, biochar, and GAC. Therefore, this study conducted an adsorbent evaluation of activated biochar produced from the HTC process. The resultant biochar showed higher efficiency in a shorter period and was sufficient to be used as an adsorbent.