Synthesis of corncob biochar with high surface area by KOH activation for VOC adsorption: effect of KOH addition method

BACKGROUND: Carbon materials have been regarded as valuable adsorbents for removal of volatile organic compounds (VOCs) owing to their high specific surface area and abundant pore structure. However, the complexity and high cost of the process used to treat the feedstock to produce commercial activated carbon has limited its application. In this reported study, a series of biochar materials was prepared using the KOH modification method employing corn cob as the raw material. The effects of different potassium hydroxide dosages, various activation temperatures and the activator addition method on the structure, physicochemical properties and VOC adsorption performance of the resulting biochars and their structure-activity relationship were systematically studied. RESULTS: Adsorption performance tests and a series of characterization results showed that the CC-3-700 (corn cob/KOH = 1:3, T = 700 degrees C, two-step dry mixing pyrolysis method) sample had highest toluene dynamic adsorption capacity (up to 573.5 mg g-1) compared to the other prepared samples. This result was attributed to the maximum specific surface area (2349 m2 g-1) and pore volume (1.22 cm3 g-1) of this sample. Moreover, the result suggested that the high specific surface area, abundant pore structure and highly disordered non-graphitizable carbon in sample CC-3-700 were the major reasons for its excellent adsorption performance. The results of a multi-component adsorption performance test showed that corn cob biochar had a strong adsorption capacity for toluene when simultaneously exposed to benzene and toluene. CONCLUSION: The results of this study revealed that the corn cob biochar prepared using a two-step roasting method offers good potential prospects for application in the field of VOC pollution control. (c) 2023 Society of Chemical Industry (SCI).