Effect of pyrolysis conditions on environmentally persistent free radicals (EPFRs) in biochar from co-pyrolysis of urea and cellulose

Nitrogen-Doped Biochar Triggers Oxidative Damage of Wheat (Triticum aestivum L.) and Its Detoxification Strategy

“…As displayed in Table S3 and Figure a, the EPFR content of 400-BC (1.71 ± 0.01 × 10 19 spin g –1 ) was higher than that of 400-N-BC (1.57 ± 0.02 × 10 19 spin g –1 ), while the g-factor for the EPR signals changed from 2.00303 in 400-BC to 2.00333 in 400-N-BC, indicating that the level and type of EPFRs on BC samples changed after N-doping. The decrease of EPFR contents after N-doping might be due to the combination of substituted aromatic compounds with the N element . For N-BC samples prepared at different temperatures, EPFR concentrations showed an increasing trend and reached the maximum for the 400-N-BC sample and then decreased with the enhancement of pyrolysis temperature (Table S4 and Figure S5).…”

Insight into biomass feedstock on formation of biochar-bound environmentally persistent free radicals under different pyrolysis temperatures

“… 36 For example, there were no significant changes on spin concentration of EPFRs of biochars derived from cellulose–urea mixture under the pyrolysis temperatures of 500 °C when the residence times were 5, 10, 15, 20 and 30 min, while they increased significantly from 1 to 5 min. 37 Biochar pyrolyzed for 1–5 h shows that the relative concentration of EPFRs gradually increased, arrived maximum values at 4 h, and decreased at 5 h. 17 …”

“…36 For example, there were no signicant changes on spin concentration of EPFRs of biochars derived from cellulose-urea mixture under the pyrolysis temperatures of 500 C when the residence times were 5, 10, 15, 20 and 30 min, while they increased signicantly from 1 to 5 min. 37 Biochar pyrolyzed for 1-5 h shows that the relative concentration of EPFRs gradually increased, arrived maximum values at 4 h, and decreased at 5 h. 17 Generally, g factor is used to classify an unpaired electron in a different chemical environment. 2 It is generally accepted that g factors of <2.0030 is of carbon-centered radicals, g factors in the range of 2.0030-2.0040 is of carbon-centered radicals with oxygen atoms, and g factors of >2.0040 is of oxygen-centered radicals.…”

“…10 However, PFRs (stable free radicals) can be detected when the pyrolysis of lignin and cellulose without the presence of metal(s). 37,45,46 The pyrolysis of pure cellulose or lignin can form stable organic radicals in the resulting biochars, suggesting that metals are not necessary during the formation of PFRs when the pyrolysis of biomass. 37,45 For example, Liao et al (2014) reported that the hemolytic cleavage of the chemical bonds in the macromolecules during carbonization promoted EPFR generation in biochar.…”

“…37,45,46 The pyrolysis of pure cellulose or lignin can form stable organic radicals in the resulting biochars, suggesting that metals are not necessary during the formation of PFRs when the pyrolysis of biomass. 37,45 For example, Liao et al (2014) reported that the hemolytic cleavage of the chemical bonds in the macromolecules during carbonization promoted EPFR generation in biochar. 11 Odinga et al reviewed the mechanisms of EPFR formation including the interaction between organic precursor molecule and transition metal, and the breaking of chemical bonds in macromolecules.…”