CO2 as a reaction medium for pyrolysis of lignin leading to magnetic cobalt-embedded biochar as an enhanced catalyst for Oxone activation

Ming-Tong Yang; Wai-Chi Tong; Jechan Lee; Eilhann Kwon; Kun-Yi Andrew Lin

doi:10.1016/j.jcis.2019.02.090

CO₂ as a reaction medium for pyrolysis of lignin leading to magnetic cobalt-embedded biochar as an enhanced catalyst for Oxone activation

J Colloid Interface Sci. 2019 Jun 1:545:16-24. doi: 10.1016/j.jcis.2019.02.090. Epub 2019 Feb 28.

Authors

Ming-Tong Yang¹, Wai-Chi Tong¹, Jechan Lee², Eilhann Kwon³, Kun-Yi Andrew Lin⁴

Affiliations

¹ Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung, Taiwan.
² Department of Environmental and Safety Engineering, Ajou University, Suwon 16499, Republic of Korea. Electronic address: jlee83@ajou.ac.kr.
³ Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gunja-dong, Gwangjin-gu, Seoul, Republic of Korea. Electronic address: ekwon74@sejong.ac.kr.
⁴ Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung, Taiwan. Electronic address: linky@nchu.edu.tw.

PMID: 30861478
DOI: 10.1016/j.jcis.2019.02.090

Abstract

Carbonaceous materials have been proven as advantageous supports for anchoring cobalt (Co) nanoparticles (NPs) to formulate Co/carbon composite catalysts for Oxone activation in degrading pollutants in water. While Co/carbon composites represent attractive catalysts, most carbonaceous supports are usually sophisticatedly fabricated using fine chemicals and immobilization of Co on carbon supports requires complicated post-modifications. As biochar appears as a versatile but easily-accessible carbon, pyrolysis of Co/lignin can result in a promising Co/biochar (CoBC) catalyst for Oxone activation. Especially, when CO₂ is used to replace N₂ as a reaction medium for pyrolysis of Co/lignin, the syngas production from pyrolysis can be enhanced and a magnetic CoBC is also obtained. This CoBC appears as a micro-sized composite of Co nanoparticles (NPs) well-distributed and embedded within carbon matrices, and exhibits several advantageous properties, such as high porosity, large surface area and magnetism, making it an advantageous catalyst for activating Oxone in water. As decolorization of Amaranth (AMR) dye is employed as a model test, CoBC successfully activates Oxone to fully decolorize AMR within 60 min with a rate constant of 0.33 min^-1. CoBC also exhibits a much higher catalytic activity than CoBC prepared from pyrolysis in N₂, and Co₃O₄, revealing its promising advantages. The activation energy of AMR decolorization by CoBC-activated Oxone is 48 kJ/mol, which is also lower than those reported in other studies. CoBC can be also re-used to activate Oxone over multiple cycles. These findings validate that CoBC is certainly a promising heterogeneous catalyst, which can be simply prepared from pyrolysis of Co/lignin in CO₂ with concomitant enhanced syngas production.

Keywords: Amaranth; Biochar; CO(2); Cobalt; Oxone; Pyrolysis.