Formation of persistent free radicals in sludge biochar by hydrothermal carbonization

Abstract

The uses of biochar as soil fertilizer can offset global warming and reduce dependence on limited mineral resources in the future circular economy, yet biochar may contain contaminants that can ultimately enter the food chain. In particular, persistent free radicals are emerging contaminants previously detected in biochar but underlying mechanisms of radical formation are not yet established. Here we studied radical generation during hydrothermal carbonization of waste sludge at 160-220 ºC for 0.5-2 h with solid weight ratios of 10%w-40%w using electron paramagnetic resonance and Fourier transform infrared spectrometry. Results reveal that radical concentration increases with temperature, reaction time, and weight ratio in sludge biochars, reaching a content of 47.2 × 10 15 spins/g for 220 ºC, 2 h heating, and 40%w solid ratio. Moreover, low temperature of about 160 ºC favors the production of oxygen-centered radicals, whereas higher temperature of 220 ºC produces carbon-centered radicals. Our findings imply that biochar ecotoxicity should be assessed prior applications to prevent adverse health effects.

Quantitative lipidomics analysis of changes in egg yolk lipids during spray-drying and subsequent accelerated storage

“…In addition, significant increases in the abundance of lysophospholipid species such as LPA (18:1), LPA (20:4), LPC (0:0/16:0), LPC (22:6), LPE (18:0/0:0), LPE (0:0/16:0), and LPE (0:0/18:0) were found during the spray-drying treatment in the present study. Some studies have reported an increase in the abundance of some lysophospholipid species in spray-dried processed food fractions, but the corresponding mechanisms of occurrence remain unclear ( Ali et al, 2018 ; Tang et al, 2021 ). Egg yolk is rich in endogenous lipases such as phospholipase and neutral lipase ( Parchem and Bartoszek, 2016 ; Wang et al, 2017 ).…”

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

“…Compared to EPFRs in biochars derived from lignocellulosic biochars (Table S1 †), data in biochars derived from non-lignocellulosic biomass are very limited. [19][20][21] Sludge is a typical non-lignocellulosic biomass and sludge-based biochars receive widely attention in soil remediation, wastewater treatment, chemical catalysis, and so on, 22,23 but there were limited investigations on EPFRs in sludge-based biochars. 24 For example, the g-values of PFRs in sludge-based pyrobiochars were reported, but the spin concentrations of PFRs were not offered.…”

Optimized Oxygen Reduction Reaction of Sm0.7La0.3Mn2O5 Nanorods by a Lanthanum Dopant for Zinc–Air Batteries

“…However, the low activity of Mn-based mullite has been the main problem limiting the application of zinc–air batteries. In the current study, increasing oxygen defects, controlling morphology, metal ion doping, and compounding with carbon materials , are commonly used to optimize the performance of catalysts. It has been reported that Zhao et al introduced a perovskite structure in SmMn 2 O 5 by a one-step co-precipitation method, using the interfacial effect between SmMn 2 O 5 and perovskite to increase electron transport for improving the catalytic performance of the catalyst.…”