Nanobiochar: Production, Properties, and Multifunctional Applications

Abstract

Nanobiochar has received much recent attention among engineered biochars owing to its useful chemical and physical properties. Research efforts have attempted to discover novel methods for nanobiochar preparation and applications. In this review, we summarize all the reported literature on various aspects of nanobiochar preparation, production and use. Often, bulk parent biochar obtained from biomass pyrolysis, mechanically ground using different milling processes to fabricate nanobiochar. Apart from mechanical means, direct fabrication of nanobiochar through flash heating resulting in graphitic nanosheets have been reported. Process conditions applied to the parent biochar directly influence the properties of the resulting nanobiochar. For instance, over 70% out of 33 nanobiochars derived from biomass pyrolyzed above 450 °C demonstrated 32 times greater BET specific surface areas than nanobiochars produced at <450 °C. Nanobiochar has diverse applications, such as wastewater treatment, health care applications, use as an electrode material, and in supercapacitors and sensors, owing to its wide range of physical and chemical properties. However, the toxicity of nanobiochar to human and ecosystem health has not received sufficient research attention. More research should be performed to elucidate the drawbacks, such as high agglomeration potential and low yield, of nanobiochar for practical uses. Furthermore, reported data is insufficient to obtain a clear idea of the nature and behavior of nanobiochar, despite growing interest in the research topic. Hence, future research should be driven towards exploring techniques to improve the yield of nanobiochar, reduce agglomeration, upscale it for electrode supercapacitor production and understanding toxicological aspects.