Chemically activated hydrochar as an effective adsorbent for volatile organic compounds (VOCs) Xueyang Zhang a, b, c, d , Bin Gao c, * , June Fang c , Weixin Zou b, c, e , Lin Dong b, e , Chengcheng Cao a , Jian Zhang d , Yuncong Li f , Hailong Wang g, h a School of Environmental Engineering, Jiangsu Key Laboratory of Industrial Pollution Control and Resource Reuse, Xuzhou University of Technology, Xuzhou 221018, China b Jiangsu Key Laboratory of Vehicle Emissions Control, Center of Modern Analysis, Nanjing University, Nanjing 210093, China c Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611, USA d Jiangsu Key Laboratory of Environmental Material and Environmental Engineering, Yangzhou University, Yangzhou 225009, China e Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China f Tropical Research and Education Center, University of Florida, Homestead, FL 33031, USA g School of Environment and Chemical Engineering, Foshan University, Foshan, Guangdong 528000, China h School of Environmental and Resource Sciences, Zhejiang A&F University, Hangzhou, Zhejiang 311300, China highlights graphical abstract  Chemically activated hydrochars showed good removal of acetone and cyclohexane.  Sorption capacities of the activated hydrochars were 50.57 e159.66 mg g 1  Surface areas of hydrochars and their adsorption capacities had a strong linear correlation.  Physical adsorption was the domi- nant mechanism.  Activated hydrochar showed good reusability. article info Article history: Received 26 September 2018 Received in revised form 9 November 2018 Accepted 22 November 2018 Available online 23 November 2018 Handling Editor: X. Cao Keywords: Hydrothermal conversion Air pollution control VOC removal Carbon sorbents abstract Hydrochars derived from hickory wood and peanut hull through hydrothermal carbonization were activated with H 3 PO 4 and KOH to improve their performance as a volatile organic compound (VOC) adsorbent. Polar acetone and nonpolar cyclohexane were used as representative VOCs. The VOC adsorptive capacities of the activated hydrochars (50.57e159.66 mg,g 1 ) were greater than that of the nonactivated hydrochars (15.98e25.36 mg,g 1 ), which was mainly caused by the enlargement of surface area. The significant linear correlation (R 2 ¼ 0.984 on acetone, and R 2 ¼ 0.869 on cyclohexane) between BET surface areas of hydrochars and their VOC adsorption capacities, together with the obvious adsorption exothermal peak of differential scanning calorimetry curve confirmed physical adsorption as the dominating mechanism. Finally, the reusability of activated hydrochar was tested on H 3 PO 4 activated hickory hydrochar (HHP), which had higher acetone and cyclohexane adsorption capacities. After five continuous adsorption desorption cycles, the adsorptive capacities of acetone and cyclohexane on HHP * Corresponding author. E-mail address: bg55@ufl.edu (B. Gao). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2018.11.144 0045-6535/© 2018 Elsevier Ltd. All rights reserved. Chemosphere 218 (2019) 680e686