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Biochar derived from corn stalk doping with activated carbon was produced by microwave-assisted pyrolysis and applied to sorb volatile organic compounds (VOCs: benzene and o-xylene). Specific surface area (SSA), total pore volume (TPV) and micropore volume (MV) of microwave biochar increased with increasing microwave power with the maximum values 325.2 m 2 ·g -1 , 0.181 mL·g -1 and 0.1420 mL·g -1 , respectively. Adsorption capacities of benzene and o-xylene on microwave biochar ranged 6.82-54.75 mg·g -1 and 7.43-48.73 mg·g -1 , which were separate positively related with SSA, TPV, and MV. Benzene adsorption was mainly dominated by surface interaction and partition mechanisms, while o-xylene adsorption was governed by pore filling. The adsorption capacities of microwave biochar for benzene and o-xylene decreased by only 0.30% and 0.99% on the 5th cycle that illustrated the reasonably good reusability of microwave biochar. The results of this research demonstrate that microwave biochar is a promising adsorbent for VOCs removal., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

A series of microwave biochars derived from wheat straw in the presence of a granulated activated carbon (GAC) catalyst, using a range of microwave conditions, were produced, characterized and tested as sorbents of three benzene series volatile organic compounds (VOCs). The microwave biochar with the greatest specific surface area (SSA), total pore volume (TPV), and micropore volume (312.62 m 2  g -1 , 0.2218 cm 3  g -1 , and 0.1380 cm 3  g -1 , respectively), were produced with 1:3 biomass:GAC catalyst mass ratio, 10 min microwave irradiation time, and at 500 W power level (WB500). Maximum adsorption capacities of WB500 to benzene, toluene and o-xylene were 53.9 mg g -1 , 75.8 mg g -1 and 63.0 mg g -1 , respectively, and were directly correlated to microwave biochar properties such as SSA, TPV or micropore volume, but were also influenced by VOC properties such as molecular polarity and boiling point. Kinetic modeling suggested that adsorption was governed by both physical partitioning and chemisorption mechanisms. In addition, microwave biochars maintained 79% to 92% of their initial adsorption capacity after ten adsorption/desorption cycles. These results suggest that microwave biochars produced with an GAC catalyst have excellent potential for efficient use in the removal of VOCs from waste gas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Pristine biochar (CN600), ball-milled biochar (CN600-BM), H 2 O 2 modified BM-biochar (CN600-O), and NH 4 OH modified BM-biochar (CN600-N) derived from corn stalk were applied to adsorb phenyl volatile organic compounds (VOCs). H 2 O 2 and NH 4 OH modification of BM-biochar significantly improved its physicochemical characteristics and adsorption abilities. The specific surface area of CN600-O increased 2.05 and 1.23 times compared to CN600 and CN600-BM, respectively; while CN600-N increased 2.41 and 1.45 times, respectively. In addition, the ball milled biochars, especially CN600-O, showed higher acidity and polarity than CN600. The VOC adsorption amount onto biochars was 10.96-130.21 mg/g. CN600-O and CN600-N had high uptake of the VOCs and reached 100.07-111.79 mg/g and 110.49-130.21 mg/g, respectively. CN600-N showed the best performance with P-xylene adsorption up to 130.21 mg/g. VOC adsorption onto the CN600-O and CN600-N were mainly governed by surface adsorption and associated with morphology characteristics of the biochars as well as VOC properties such as boiling point and molecular size. Five cycles of adsorption-desorption experiments showed that CN600-O and CN600-N had good reusability with the reuse efficiencies of 88.01 %-92.21 % and 92.19 %-95.39 %, respectively. The results indicate that O- and N-doped ball-milled biochars are promising in adsorption for effective and sustainable VOC removal., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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 (50.57-159.66 mg⋅g -1 ) were greater than that of the nonactivated hydrochars (15.98-25.36 mg⋅g -1 ), which was mainly caused by the enlargement of surface area. The significant linear correlation (R 2  = 0.984 on acetone, and R 2  = 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 decreased by 6.2% and 7.8%, respectively. The slight decline in adsorption capacity confirmed the reusability of activated hydrochar as a VOC sorbent., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Volatile organic compounds (VOCs) severely threaten human health and the ecological environment because most of them are toxic, mutagenic, and carcinogenic. The persistent increase of VOCs together with the stringent regulations make the reduction of VOC emissions more imperative. Up to now, numerous VOC treatment technologies have emerged, such as incineration, condensation, biological degradation, absorption, adsorption, and catalysis oxidation et al. Among them, the adsorption technology has been recognized as an efficient and economical control strategy because it has the potential to recover and reuse both adsorbent and adsorbate. Due to their large specific surface area, rich porous structure, and high adsorption capacity, carbonaceous adsorbents are widely used in gas purification, especially with respect to VOC treatment and recovery. This review discusses recent research developments of VOC adsorption onto a variety of engineered carbonaceous adsorbents, including activated carbon, biochar, activated carbon fiber, carbon nanotube, graphene and its derivatives, carbon-silica composites, ordered mesoporous carbon, etc. The key factors influence the VOC adsorption are analyzed with focuses on the physiochemical characters of adsorbents, properties of adsorbates as well as the adsorption conditions. In addition, the sources, health effect, and abatement methods of VOCs are also described., (Copyright © 2017 Elsevier B.V. All rights reserved.)