Microwave biochars produced with activated carbon catalyst: Characterization and sorption of volatile organic compounds (VOCs)

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.

Automated summary

This study produced a series of microwave biochars derived from wheat straw using a granulated activated carbon (GAC) catalyst, and tested their adsorption capacity for benzene series volatile organic compounds (VOCs). The results showed that microwave biochars with larger specific surface area, total pore volume, and micropore volume had higher adsorption capacities, and the adsorption process was influenced by both physical partitioning and chemisorption mechanisms.