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 × 1015 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.
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References
Arangio AM, Tong H, Socorro J, Pöschl U, Shiraiwa M (2016) Quantification of environmentally persistent free radicals and reactive oxygen species in atmospheric aerosol particles. Atmospheric Chem Phys 16(20):13105–13119. https://doi.org/10.5194/acp-16-13105-2016
Brindhadevi K, Anto S, Rene ER, Sekar M, Mathimani T, Chi NTL, Pugazhendhi A (2021) Effect of reaction temperature on the conversion of algal biomass to bio-oil and biochar through pyrolysis and hydrothermal liquefaction. Fuel 285:119106. https://doi.org/10.1016/j.fuel.2020.119106
Chen N, Huang Y, Hou X, Ai Z, Zhang L (2017) Photochemistry of hydrochar: reactive oxygen species generation and sulfadimidine degradation. Environ Sci Technol 51(19):11278–11287. https://doi.org/10.1021/acs.est.7b02740
Coronella C, Hiibel SR, Vahed Qaramaleki S, Román S, Silva N (2017) Hydrothermal carbonization of wastes for simultaneous nutrient recovery and energy capture. AlChE Annual Meeting, Sustainable Engineering Forum. https://www.aiche.org/conferences/aiche-annual-meeting/2017/proceeding/paper/314a-hydrothermal-carbonization-wastes-simultaneous-nutrient-recovery-and-energy-capture
dela Cruz AL, Cook RL, Dellinger B, Lomnicki SM, Donnelly KC, Kelley MA, Cosgriff D (2014) Assessment of environmentally persistent free radicals in soils and sediments from three Superfund sites. Environ Sci Process Impacts 16(1):44–52. http://doi.org/https://doi.org/10.1039/c3em00428g
dela Cruz AL, Cook RL, Lomnicki SM, Dellinger B (2012) Effect of low temperature thermal treatment on soils contaminated with pentachlorophenol and environmentally persistent free radicals. Environ Sci Technol 46(11):5971–5978. https://doi.org/10.1021/es300362k
dela Cruz AL, Gehling W, Lomnicki S, Cook R, Dellinger B (2011) Detection of environmentally persistent free radicals at a superfund wood treating site. Environ Sci Technol 45(15):6356–6365. http://doi.org/https://doi.org/10.1021/es2012947
Dellinger B, Lomnicki S, Khachatryan L, Maskos Z, Hall RW, Adounkpe J, McFerrin C, Truong H (2007) Formation and stabilization of persistent free radicals. Proc Combust Inst 31(1):521–528. https://doi.org/10.1016/j.proci.2006.07.172
Demirbaş A (2000) Mechanisms of liquefaction and pyrolysis reactions of biomass. Energ Convers Manag 41:633–646. https://doi.org/10.1016/S0196-8904(99)00130-2
Devi P, Saroha AK (2017) Utilization of sludge based adsorbents for the removal of various pollutants: A review. Sci Total Environ 578:16–33. https://doi.org/10.1016/j.scitotenv.2016.10.220
Fang G, Gao J, Liu C, Dionysiou DD, Wang Y, Zhou D (2014) Key role of persistent free radicals in hydrogen peroxide activation by biochar: implications to organic contaminant degradation. Environ Sci Technol 48(3):1902–1910. https://doi.org/10.1021/es4048126
Fang G, Liu C, Gao J, Dionysiou DD, Zhou D (2015) Manipulation of persistent free radicals in biochar to activate persulfate for contaminant degradation. Environ Sci Technol 49(9):5645–5653. https://doi.org/10.1021/es5061512
Gao Y, Wang X-H, Yang H-P, Chen H-P (2012) Characterization of products from hydrothermal treatments of cellulose. Energy 42(1):457–465. https://doi.org/10.1016/j.energy.2012.03.023
Gao P, Xu W, Sontag P, Li X, Xue G, Liu T, Sun W (2016a) Correlating microbial community compositions with environmental factors in activated sludge from four full-scale municipal wastewater treatment plants in Shanghai. China Appl Microbiol Biot 100(10):4663–4673. https://doi.org/10.1007/s00253-016-7307-0
Gao P, Zhou Y, Meng F, Zhang Y, Liu Z, Zhang W, Xue G (2016b) Preparation and characterization of hydrochar from waste eucalyptus bark by hydrothermal carbonization. Energy 97:238–245. https://doi.org/10.1016/j.energy.2015.12.123
Gao P, Yao D, Qian Y, Zhong S, Zhang L, Xue G, Jia H (2018) Factors controlling the formation of persistent free radicals in hydrochar during hydrothermal conversion of rice straw. Environ Chem Lett 16(4):1463–1468. https://doi.org/10.1007/s10311-018-0757-0
GEP Research (2018). Research reports on the sludge treatment and disposal industry (in Chinese). http://www.gepresearch.com/99/view-767612-1.html. Accessed 2 Nov 2020
He C, Giannis A, Wang J-Y (2013) Conversion of sewage sludge to clean solid fuel using hydrothermal carbonization: hydrochar fuel characteristics and combustion behavior. Appl Energ 111:257–266. https://doi.org/10.1016/j.apenergy.2013.04.084
He J, Xiao Y, Tang J, Chen H, Sun H (2019) Persulfate activation with sawdust biochar in aqueous solution by enhanced electron donor-transfer effect. Sci Total Environ 690:768–777. https://doi.org/10.1016/j.scitotenv.2019.07.043
HTCycle. Hydrothermal carbonisation for a clean-running world. Retrieved January 21, 2021. https://htcycle.ag/en/process_40
Hu J, Shen D, Wu S, Zhang H, Xiao R (2014) Effect of temperature on structure evolution in char from hydrothermal degradation of lignin. J Anal Appl Pyrol 106:118–124. https://doi.org/10.1016/j.jaap.2014.01.008
IshizakiI C, Martí I (1981) Surface oxide structures on a commercial activated carbon. Carbon 19(6):409–412. https://doi.org/10.1016/0008-6223(81)90023-3
Jia H, Nulaji G, Gao H, Wang F, Zhu Y, Wang C (2016) Formation and stabilization of environmentally persistent free radicals induced by the interaction of anthracene with Fe(III)-modified clays. Environ Sci Technol 50(12):6310–6319. https://doi.org/10.1021/acs.est.6b00527
Jia H, Zhao S, Nulaji G, Tao K, Wang F, Sharma VK, Wang C (2017) Environmentally persistent free radicals in soils of past coking sites: distribution and stabilization. Environ Sci Technol 51(11):6000–6008. https://doi.org/10.1021/acs.est.7b00599
Khachatryan L, Vejerano E, Lomnicki S, Dellinger B (2011) Environmentally persistent free radicals (EPFRs). 1. Generation of reactive oxygen species in aqueous solutions. Environ Sci Technol 45:8559–8566. https://doi.org/10.1021/es201309c
Lichtfouse E, Albrecht P, Behar F, Hayes JM (1994) A molecular and isotopic study of the organic matter from the Paris basin, France. Geochim Cosmochim Acta 58:209–221. https://doi.org/10.1016/0016-7037(94)90458-8
Lichtfouse E, Sappin-Didier V, Denaix L, Caria G, Metzger L, Amellal-Nassr N, Schmidt J (2005) A 25-year record of polycyclic aromatic hydrocarbons in soils amended with sewage sludges. Environ Chem Lett 3:140–144. https://doi.org/10.1007/s10311-005-0010-5
Lieke T, Zhang XC, Steinberg CEW, Pan B (2018) Overlooked risks of biochars: persistent free radicals trigger neurotoxicity in Caenorhabditis elegans. Environ Sci Technol 52(14):7981–7987. https://doi.org/10.1021/acs.est.8b01338
Lu X, Pellechia PJ, Flora JR, Berge ND (2013) Influence of reaction time and temperature on product formation and characteristics associated with the hydrothermal carbonization of cellulose. Bioresour Technol 138:180–190. https://doi.org/10.1016/j.biortech.2013.03.163
Ogunsola OM, Berkowitz N (1995) Removal of heterocyclic S and N from oil precursors by supercritical water. Fuel 74:1485–1490. https://doi.org/10.1016/0016-2361(95)00099-Q
Peccia J, Westerhoff P (2015) We should expect more out of our sewage sludge. Environ Sci Technol 49(14):8271–8276. https://doi.org/10.1021/acs.est.5b01931
Qin Y, Zhang L, An T (2017) Hydrothermal carbon-mediated fenton-like reaction mechanism in the degradation of alachlor: direct electron transfer from hydrothermal carbon to Fe(III). ACS Appl Mater Int 9(20):17115–17124. https://doi.org/10.1021/acsami.7b03310
Qin Y, Li G, Gao Y, Zhang L, Ok YS, An T (2018) Persistent free radicals in carbon-based materials on transformation of refractory organic contaminants (ROCs) in water: a critical review. Water Res 137:130–143. https://doi.org/10.1016/j.watres.2018.03.012
Raheem A, Sikarwar VS, He J, Dastyar W, Dionysiou DD, Wang W, Zhao M (2018) Opportunities and challenges in sustainable treatment and resource reuse of sewage sludge: a review. Chem Eng J 337:616–641. https://doi.org/10.1016/j.cej.2017.12.149
Reed JR, dela Cruz ALN, Lomnicki SM, Backes WL (2015) Inhibition of cytochrome P450 2B4 by environmentally persistent free radical-containing particulate matter. Biochem Pharmacol 95:126–132. https://doi.org/https://doi.org/10.1016/j.bcp.2015.03.012
Rouxhet and Robin (1978) Infrared study of the evolution of kerogens of different origins during catagenesis and pyrolysis. Fuel 57(9):533–540. https://doi.org/10.1016/0016-2361(78)90038-8
Ruan X, Sun Y, Du W, Tang Y, Liu Q, Zhang Z, Doherty W, Frost RL, Qian G, Tsang DCW (2019) Formation, characteristics, and applications of environmentally persistent free radicals in biochars: a review. Bioresour Technol 281:457–468. https://doi.org/10.1016/j.biortech.2019.02.105
Sabio E, Alvarez-Murillo A, Roman S, Ledesma B (2016) Conversion of tomato-peel waste into solid fuel by hydrothermal carbonization: influence of the processing variables. Waste Manag 47:122–132. https://doi.org/10.1016/j.wasman.2015.04.016
Saravia J, Lee GI, Lomnicki S, Dellinger B, Cormier SA (2013) Particulate matter containing environmentally persistent free radicals and adverse infant respiratory health effects: a review. J Biochem Mol Toxic 27(1):56–68. https://doi.org/10.1002/jbt.21465
Seleiman MF, Santanen A, Mäkelä PSA (2020) Recycling sludge on cropland as fertilizer: advantages and risks. Resour Conserv Recy 155:104647. https://doi.org/10.1016/j.resconrec.2019.104647
Tasca AL, Puccini M, Gori R, Corsi I, Galletti AMR, Vitolo S (2019) Hydrothermal carbonization of sewage sludge: a critical analysis of process severity, hydrochar properties and environmental implications. Waste Manage 93:1–13. https://doi.org/10.1016/j.wasman.2019.05.027
Tissot BP, Welte DH (1984) Diagenesis, catagenesis and metagenesis of organic matter. In: Petroleum formation and occurrence. Springer, Berlin. https://doi.org/https://doi.org/10.1007/978-3-642-87813-8_6
Vejerano EP, Rao G, Khachatryan L, Cormier SA, Lomnicki S (2018) Environmentally persistent free radicals: insights on a new class of pollutants. Environ Sci Technol 52(5):2468–2481. https://doi.org/10.1021/acs.est.7b04439
Volpe R, Bermudez Menendez JM, Ramirez Reina T, Volpe M, Messineo A, Millan M, Titirici M-M (2019) Free radicals formation on thermally decomposed biomass. Fuel 255:115802. https://doi.org/10.1016/j.fuel.2019.115802
Wang H, Guo W, Yin R, Du J, Wu Q, Luo H, Liu B, Sseguya F, Ren N (2019) Biochar-induced Fe(III) reduction for persulfate activation in sulfamethoxazole degradation: Insight into the electron transfer, radical oxidation and degradation pathways. Chem Eng J 362:561–569. https://doi.org/10.1016/j.cej.2019.01.053
Xu X, Jiang E (2017) Treatment of urban sludge by hydrothermal carbonization. Bioresour Technol 238:182–187. https://doi.org/10.1016/j.biortech.2017.03.174
Xu M, Wu T, Tang Y, Chen T, Khachatryan L, Rameshlyer P, Guo D, Chen A, Lyu M, Li J, Liu J, Li D, Zuo Y, Zhang S, Wang Y, Meng Y, Qi F (2019) Environmentally persistent free radicals in PM2.5: a review. Waste Dispos Sustain Energy 1:177–197. https://doi.org/10.1007/s42768-019-00021-z
Yang L, Liu G, Zheng M, Jin R, Zhu Q, Zhao Y, Wu X, Xu Y (2017) Highly elevated levels and particle-size distributions of environmentally persistent free radicals in haze-associated atmosphere. Environ Sci Technol 51(14):7936–7944. https://doi.org/10.1021/acs.est.7b01929
Zhang K, Sun P, Faye MCAS, Zhang Y (2018) Characterization of biochar derived from rice husks and its potential in chlorobenzene degradation. Carbon 130:730–740. https://doi.org/10.1016/j.carbon.2018.01.036
Zhang Z, Zhu Z, Shen B, Liu L (2019) Insights into biochar and hydrochar production and applications: a review. Energy 171:581–598. https://doi.org/10.1016/j.energy.2019.01.035
Zhang Y, Yin M, Sun X, Zhao J (2020) Implication for adsorption and degradation of dyes by humic acid: Light driven of environmentally persistent free radicals to activate reactive oxygen species. Bioresour Technol 307:123183. https://doi.org/10.1016/j.biortech.2020.123183
Zhao S, Gao P, Miao D, Wu L, Qian Y, Chen S, Sharma VK, Jia H (2019) Formation and evolution of solvent-extracted and nonextractable environmentally persistent free radicals in fly ash of municipal solid waste incinerators. Environ Sci Technol 53(17):10120–10130. https://doi.org/10.1021/acs.est.9b03453
Zhu Y, Wei J, Liu Y, Liu X, Li J, Zhang J (2019) Assessing the effect on the generation of environmentally persistent free radicals in hydrothermal carbonization of sewage sludge. Sci Rep 9(1):17092. https://doi.org/10.1038/s41598-019-53781-3
Acknowledgements
This work was financially supported by the Guangxi Innovation Drive Development Fund (Grant Number AA17204076); the GDAS’ Project of Science and Technology Development (Grant Number 2020GDASYL-20200102014); the National Key R&D Program of China (Grant Number 2019YFD1100502); and the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China (Grant Number 51888103).
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Tang, Z., Zhao, S., Qian, Y. et al. Formation of persistent free radicals in sludge biochar by hydrothermal carbonization. Environ Chem Lett 19, 2705–2712 (2021). https://doi.org/10.1007/s10311-021-01198-8
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DOI: https://doi.org/10.1007/s10311-021-01198-8