Water-washing treatment can change biochar microstructure: microwave pyrolysis of biomass

ABSTRACT

In this study, biochar was produced in a microwave pyrolysis reactor and three microwave reaction conditions were introduced. They were pyrolysis temperatures (500, 600, 700, 800, and 900°C), microwave powers (600, 650, 700, 750, and 800 W), and pyrolysis times (30, 40, 50, 60, and 70 min), respectively. The produced biochar was mixed with deionized water and then treated with water washing in a shaker. The yields and microstructure of biochar obtained from the microwave reactor were detailed and the pore structure of washed biochar was also studied. Results showed that the corn stover biochar yield ranged between 44.71 wt.% and 59.92 wt.% depending on the conditions used. The pores in biochar were dominated by macropores and mesopores. As the three reaction conditions were elevated, nanoscale pores appeared, pores were clogged, the pore structure became more obvious and the biochar structure got fragile. Water-washing treatment enlarged the pore sizes, cleaned the clogged pores, and removed water-soluble salts. At longer pyrolysis times, the action of water flow can cause biochar to collapse This study can provide guidance for future microstructure regulation of biochar.

Graphical abstract

KEYWORDS:

• Biochar
• microwave pyrolysis
• yield
• microstructure
• washing treatment

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Financial support was provided by the National Natural Science Foundation of China [52076049], Heilongjiang Province “Double First-class” Discipline Collaborative Innovation Achievement Project [LJGXCG2023-080], and Heilongjiang Provincial Key R&D Program “Unveiling the Leader” Project [2023ZXJ02C04].

Notes on contributors

Chaoyue Liu

Chaoyue Liu is an undergraduate student at the School of Energy Science and Engineering of Harbin Institute of Technology (HIT) in China. His research interests are biomass, plastic, and thermochemistry.

Tianhao Qiu

Tianhao Qiu is a Ph. D. candidate at the School of Energy Science and Engineering of Harbin Institute of Technology (HIT) in China. He received his bachelor’s degree from Beijing Institute of Technology and his master’s degree from University of Chinese Academy of Sciences. His research interests are production and application of biochar.

Weitao Cao

Weitao Cao is a master student at the School of Energy Science and Engineering of Harbin Institute of Technology (HIT) in China. He received his bachelor’s degree from Qingdao University (China). His research interests are preparation and characterization of carbon-based electrode materials.

Hui Liu

Hui Liu is full professor at the School of Energy Science and Engineering of Harbin Institute of Technology (HIT) in China. He received his bachelor’s and master’s degrees from Northeast Electric Power University and his Ph.D. from Harbin Institute of Technology. He is mainly engaged in teaching and research on combustion and clean and high-value utilization of carbon-based fuels. He has published more than 60 papers as the first or corresponding author in journals such as Combusion and Flame, Energy, and Fuel. He has developed and supervised over 20 Masters and 4 PhDs.

Wenke Zhao

Wenke Zhao is a full assistant professor at the School of Energy Science and Engineering of Harbin Institute of Technology (HIT) in China. He received his B.S., M.S., and Ph.D. degrees from Harbin Institute of Technology. He has led and participated in several research projects. His research interests are heat pumps, thermodynamics and porous materials.

Ehab Mostafa

Ehab Mostafa is a professor at Agricultural Engineering Department, Faculty of Agriculture, Cairo University in Egypt. He received his Bachelor’s and Master’s degrees from Cairo University (Egypt) and his PhD from the University of Bonn (Germany). He has published more than 20 SCI papers with a H index of 10. His research interests is utilization of agricultural waste.

Yaning Zhang

Yaning Zhang is a full professor at the School of Energy Science and Engineering of Harbin Institute of Technology (HIT) in China. He received his Ph.D. degree from Harbin Institute of Technology. He worked as a visiting scholar (2011-2012) and postdoctoral fellow (2013) at the Department of Process Engineering and Applied Science of Dalhousie University in Canada, and also a postdoctor (2016-2018) at the Department of Bioproducts and Biosystems Engineering of University of Minnesota Twin Cities in the USA. He has been conducting both fundamental and applied research in the areas of exergy, thermodynamics, biomass, thermochemical processes and energy systems. He has published 5 books, 10 book chapters, and more than 100 SCI indexed papers with a H index of 41.