Conversion Mechanism of Biomass to Nano Zero-Valent Iron Biochar: Iron Phase Transfer and in Situ Reduction

Nano zero-valent iron biochar (nZVI-BC), an environmentally-friendly functional material prepared from waste biomass, has attracted extensive attention. This material has potential to solve the problem of bio-mass conversion. However, the lack of a method of converting biomass to the nZVI-BC involved in bio-mass modification and pyrolysis hinders its further production and application. In this study, we introduced the green solvent polyethylene glycol 400 (PEG400) to a biomass (rice straw (RS)) modifica-tion system with FeCl3.6H2O, and activated RS was prepared to nZVI-BC by one-step pyrolysis. The addi-tion of PEG400 promoted the hydrolysis of iron ion and improved the RS surface structure, promoting the attachment of Fe2O3 to the RS surface. The mild activation conditions with temperatures of 60, 80, and 100 degrees C and a time of 0.5 h prevented the excessive loss of the lignin component and were conducive to the formation of carbon skeletons. Amorphous carbon and Fe2O3 were subjected to redox reactions to form nZVI-BC with the assistance of reducing gas produced from pyrolysis. In addition, the prepared nZVI-BC was tested for dye (Congo red) removal, showing rapid absorption (70.60% at 5 min) and high catalysis in advanced oxidation (75.67% at 5 min, 90.00% at 60 min). This work proposed a novel mech-anistic strategy for preparing nZVI-BC and set a foundation for its scaled production and application.(c) 2021 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).