Efficient removal of volatile organic compound by ball-milled biochars from different preparing conditions

Adsorption is an important technology to deal with volatile organic compounds (VOCs), and biochar has attracted much attention as a new type of adsorbent for VOCs. In this study, rice husk, corn stover and pine wood sawdust biochars from different pyrolysis temperatures (300 °C, 500 °C and 700 °C) were synthesized and treated by ball milling. The pristine and ball-milled biochars were used as adsorbents for acetone and toluene removal. Results showed that wood biochar had higher adsorption capacity for VOCs. After ball milling, the BET specific surface area and the oxygen functional group content of biochars increased. With these changes, all the ball-milled biochars showed higher adsorption rate than the pristine biochars. The ball-milled biochars under pyrolysis temperature of 300 °C showed the best adsorption performance for acetone (304 mg g^-1), which was 1.7-fold greater than that of pristine biochar. Increasing the surface area by ball milling is conducive to the diffusion of hydrophobic VOCs molecules such as toluene to the adsorption sites in the biochar. However, for hydrophilic VOCs such as acetone, higher oxygen functional groups were the main reason for the enhanced adsorption by ball milling. Therefore, ball-milled biochar can be used as a potential adsorbent material in VOCs treatment.