{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,11]],"date-time":"2026-10-11T04:46:50Z","timestamp":1791694010813,"version":"4.3.4"},"reference-count":38,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T00:00:00Z","timestamp":1790726400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T00:00:00Z","timestamp":1790726400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004826","name":"Beijing Natural Science Foundation","doi-asserted-by":"publisher","award":["8262014"],"award-info":[{"award-number":["8262014"]}],"id":[{"id":"10.13039\/501100004826","id-type":"DOI","asserted-by":"publisher"}]},{"name":"the Key Project of Research and Development Plan of Jiangxi Province","award":["20232BBG70009"],"award-info":[{"award-number":["20232BBG70009"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>Azo dye wastewater poses a persistent environmental challenge because of its high toxicity, poor biodegradability, and widespread occurrence in textile and dyeing effluents, highlighting the need for efficient and sustainable treatment technologies. In this study, iron-modified sludge biochar (Fe@SBC) was prepared via impregnation\u2013pyrolysis and employed to activate peroxymonosulfate (PMS) for methyl orange (MO) degradation, providing a dual benefit of sludge valorization and pollutant removal. Iron modification increased the specific surface area from 50.93 to 66.54 m2\u00b7g\u22121 and total pore volume from 0.085 to 0.309 cm3\u00b7g\u22121, while introducing Fe3O4, Fe2+\/Fe3+ redox pairs, and oxygen-containing functional groups that significantly enhanced electron transfer. The Fe@SBC\/PMS system achieved 95.2 \u00b1 0.2% MO removal within 25 min under optimal conditions, notably outperforming unmodified biochar (86.0 \u00b1 0.6%). The catalyst exhibited excellent pH adaptability (3\u201311) and maintained 88.0 \u00b1 0.8% removal after five cycles. Quenching experiments and EPR analysis identified singlet oxygen (1O2) as the dominant reactive species (~80% contribution), with sulfate and hydroxyl radicals playing auxiliary roles. LC-MS analysis proposed three parallel degradation pathways involving azo bond cleavage, hydroxylation, and desulfonation. These findings demonstrate that Fe@SBC is an effective PMS activator and provide mechanistic insight into the design of sludge-derived carbon catalysts for advanced oxidation processes, offering a promising approach for simultaneous sludge resource recovery and azo dye wastewater treatment.<\/jats:p>","DOI":"10.3390\/nano16191233","type":"journal-article","created":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T13:01:19Z","timestamp":1790773279000},"page":"1233","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Degradation Performance and Mechanism of Methyl Orange by Iron-Modified Sludge Biochar-Activated Peroxymonosulfate"],"prefix":"10.3390","volume":"16","author":[{"given":"Meng-Yuan","family":"Li","sequence":"first","affiliation":[{"name":"National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiang-Li","family":"Yu","sequence":"additional","affiliation":[{"name":"National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mei-Qi","family":"Ren","sequence":"additional","affiliation":[{"name":"National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tao","family":"Hou","sequence":"additional","affiliation":[{"name":"National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-3988-0601","authenticated-orcid":false,"given":"Dan","family":"Cui","sequence":"additional","affiliation":[{"name":"National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, College of Environmental Science and Engineering, Beijing University of Technology, Beijing 100124, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"785","DOI":"10.1038\/s43017-023-00489-8","article-title":"Environmental impacts and remediation of dye-containing wastewater","volume":"4","author":"Lin","year":"2023","journal-title":"Nat. Rev. Earth Environ."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"127957","DOI":"10.1016\/j.cej.2020.127957","article-title":"A review of the innovations in metal- and carbon-based catalysts explored for heterogeneous peroxymonosulfate (PMS) activation, with focus on radical vs. non-radical degradation pathways of organic contaminants","volume":"411","author":"Kohantorabi","year":"2021","journal-title":"Chem. Eng. J."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"109071","DOI":"10.1016\/j.jwpe.2025.109071","article-title":"Dye pollution and its implications for human health, aquatic ecosystems, and sustainable wastewater treatment: A comprehensive review","volume":"80","author":"Kavitha","year":"2025","journal-title":"J. Water Process Eng."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Jahan, N., Tahmid, M., Shoronika, A.Z., Fariha, A., Roy, H., Pervez, M.N., Cai, Y., Naddeo, V., and Islam, M.S. (2022). A Comprehensive Review on the Sustainable Treatment of Textile Wastewater: Zero Liquid Discharge and Resource Recovery Perspectives. Sustainability, 14.","DOI":"10.3390\/su142215398"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"176426","DOI":"10.1016\/j.scitotenv.2024.176426","article-title":"Bioremediation of azo dye: A review on strategies, toxicity assessment, mechanisms, bottlenecks and prospects","volume":"954","author":"Goswami","year":"2024","journal-title":"Sci. Total Environ."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"55","DOI":"10.1016\/j.jenvman.2014.08.008","article-title":"Remediation of textile effluents by membrane based treatment techniques: A state of the art review","volume":"147","author":"Dasgupta","year":"2015","journal-title":"J. Environ. Manag."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1748","DOI":"10.1007\/s11356-023-31175-3","article-title":"A review on existing and emerging approaches for textile wastewater treatments: Challenges and future perspectives","volume":"31","author":"Kallawar","year":"2023","journal-title":"Environ. Sci. Pollut. Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"111357","DOI":"10.1016\/j.jece.2023.111357","article-title":"Influence of pyrolysis atmosphere, temperature, and particle size co-regulation on the physicochemical properties of bone char","volume":"11","author":"Li","year":"2023","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"62","DOI":"10.1007\/s42773-024-00350-1","article-title":"Production and modifications of biochar to engineered materials and its application for environmental sustainability: A review","volume":"6","author":"Ravindiran","year":"2024","journal-title":"Biochar"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"100387","DOI":"10.1016\/j.dwt.2024.100387","article-title":"Role of advance oxidation processes (AOPs) in textile wastewater treatment: A critical review","volume":"318","author":"Jamil","year":"2024","journal-title":"Desalin. Water Treat."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"100194","DOI":"10.1016\/j.wri.2022.100194","article-title":"Activated persulfate and peroxymonosulfate based advanced oxidation processes (AOPs) for antibiotics degradation\u2014A review","volume":"29","author":"Honarmandrad","year":"2023","journal-title":"Water Resour. Ind."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1039\/D2EY00107A","article-title":"Evolution of singlet oxygen in peroxymonosulfate activation: A review","volume":"1","author":"Dong","year":"2023","journal-title":"EES Catal."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Aljuaid, A., Almehmadi, M., Alsaiari, A.A., Allahyani, M., Abdulaziz, O., Alsharif, A., Alsaiari, J.A., Saih, M., Alotaibi, R.T., and Khan, I. (2023). g-C3N4 Based Photocatalyst for the Efficient Photodegradation of Toxic Methyl Orange Dye: Recent Modifications and Future Perspectives. Molecules, 28.","DOI":"10.3390\/molecules28073199"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"128829","DOI":"10.1016\/j.cej.2021.128829","article-title":"Activation of peroxymonosulfate by biochar-based catalysts and applications in the degradation of organic contaminants: A review","volume":"416","author":"Zhao","year":"2021","journal-title":"Chem. Eng. J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"118919","DOI":"10.1016\/j.envres.2024.118919","article-title":"Recent advances in catalyst design, performance, and challenges of metal-heteroatom-co-doped biochar as peroxymonosulfate activator for environmental remediation","volume":"252","author":"Manickavasagam","year":"2024","journal-title":"Environ. Res."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Li, M., Li, P., Zhou, Q., and Lee, S.L.J. (2022). A Mini Review on Persulfate Activation by Sustainable Biochar for the Removal of Antibiotics. Materials, 15.","DOI":"10.3390\/ma15175832"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"129027","DOI":"10.1016\/j.cej.2021.129027","article-title":"New notion of biochar: A review on the mechanism of biochar applications in advanced oxidation processes","volume":"416","author":"Zhou","year":"2021","journal-title":"Chem. Eng. J."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"111365","DOI":"10.1016\/j.jece.2023.111365","article-title":"Sludge-derived biochar applied in peroxymonosulfate (PMS) activation: Reactive oxygen species (ROS) dominated process and characteristics","volume":"11","author":"Feng","year":"2023","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1016\/j.wasman.2024.08.039","article-title":"Pyrolysis-induced migration and transformation of heavy metals in sewage sludge containing microplastics","volume":"189","author":"Chang","year":"2024","journal-title":"Waste Manag."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"748","DOI":"10.1039\/D5EN00904A","article-title":"Electron-transfer management at carbon\u2013iron\u2013oxidant interfaces: Carbon architectures bridging radical\/non-radical pathways for selective, self-sustained advanced oxidation","volume":"13","author":"Liu","year":"2026","journal-title":"Environ. Sci. Nano"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Gong, Z., Ding, S., Huang, M., Oh, W.-d., Wu, X., and Zhou, T. (2025). One-Step Fe\/N Co-Doping for Efficient Catalytic Oxidation and Selective Non-Radical Pathway Degradation in Sludge-Based Biochar. Catalysts, 15.","DOI":"10.3390\/catal15100934"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"137953","DOI":"10.1016\/j.cej.2022.137953","article-title":"Peroxymonosulfate activation by iron self-doped sludge-derived biochar for degradation of perfluorooctanoic acid: A singlet oxygen-dominated nonradical pathway","volume":"450","author":"Fu","year":"2022","journal-title":"Chem. Eng. J."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"149744","DOI":"10.1016\/j.cej.2024.149744","article-title":"Activation of peroxymonosulfate by sludge-derived magnetic biochar for pollutant removal: Performance, applicability, and synergetic mechanism of iron species and carboxylated biochar","volume":"485","author":"Zeng","year":"2024","journal-title":"Chem. Eng. J."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"121258","DOI":"10.1016\/j.jece.2026.121258","article-title":"Red phosphorus triggers endogenous iron activation of sludge biochar for peroxymonosulfate activation: Unravelling superoxide radical and non-radical degradation mechanisms","volume":"14","author":"Xiang","year":"2026","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"122637","DOI":"10.1016\/j.envres.2025.122637","article-title":"Activation of peroxymonosulfate by Fenton-conditioned sludge-derived biochar for efficient degradation and detoxification of sulfamethoxazole: Reactive oxygen species dominated process","volume":"286","author":"Hu","year":"2025","journal-title":"Environ. Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"178434","DOI":"10.1016\/j.cej.2026.178434","article-title":"Low dose peroxymonosulfate decontaminates organics via non-radical carbon capture: Electron transfer process stimulated by interface of zero-valent iron loaded sludge-derived biochar","volume":"544","author":"Meng","year":"2026","journal-title":"Chem. Eng. J."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2154","DOI":"10.1039\/D5CY01356A","article-title":"Magnesium\u2013iron modified sludge biochar for methyl orange removal via adsorption and periodate-based advanced oxidation","volume":"16","author":"Sun","year":"2026","journal-title":"Catal. Sci. Technol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"108513","DOI":"10.1016\/j.surfin.2026.108513","article-title":"Nitrogen-doped magnetic biochar derived from mulberry branch waste for efficient peroxymonosulfate activation and humic acid degradation via a dominant non-radical pathway","volume":"83","author":"Yang","year":"2026","journal-title":"Surf. Interfaces"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"107236","DOI":"10.1016\/j.jaap.2025.107236","article-title":"Effect of pyrolysis temperature and heating rate on the physicochemical properties of alkali lignin-derived biochar: A comparative study of fast and slow pyrolysis","volume":"191","author":"Song","year":"2025","journal-title":"J. Anal. Appl. Pyrolysis"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"7939","DOI":"10.1021\/es301029g","article-title":"Pyrolysis for Biochar Purposes: A Review to Establish Current Knowledge Gaps and Research Needs","volume":"46","year":"2012","journal-title":"Environ. Sci. Technol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.biortech.2014.04.048","article-title":"Influence of pyrolysis temperature on characteristics and heavy metal adsorptive performance of biochar derived from municipal sewage sludge","volume":"164","author":"Chen","year":"2014","journal-title":"Bioresour. Technol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Wang, J., Wang, Q., Gao, P., Sun, D., Jin, L., Ma, L., Yang, L., and Zhao, J. (2023). Enhanced PMS Activation by Highly Dispersed Mn-Ce Bimetallic Oxide on Carbon Nanotubes for Degradation of Phenol. Water, 15.","DOI":"10.3390\/w15122243"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"119039","DOI":"10.1016\/j.jece.2025.119039","article-title":"Peroxymonosulfate activation by iron-rich biochar derived from sewage sludge digestate for sulfamethoxazole degradation: A rigorous examination of performance and mechanistic insights","volume":"13","author":"Iberache","year":"2025","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1007\/s42773-025-00471-1","article-title":"Peroxydisulfate activation by one-step pyrolysis iron-rich sludge biochar for tetracycline removal in water: Performance, mechanism and degradation pathway","volume":"7","author":"Bao","year":"2025","journal-title":"Biochar"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"141150","DOI":"10.1016\/j.cej.2022.141150","article-title":"Iron-rich sludge biochar triggers sodium percarbonate activation for robust sulfamethoxazole removal: Collaborative roles of reactive oxygen species and electron transfer","volume":"457","author":"Mo","year":"2023","journal-title":"Chem. Eng. J."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"140388","DOI":"10.1016\/j.scitotenv.2020.140388","article-title":"Red mudmodified sludge biochar for the activation of","volume":"857","author":"Wang","year":"2020","journal-title":"Sci. Total Environ."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"129656","DOI":"10.1016\/j.jclepro.2021.129656","article-title":"Iron oxychloride composite sludge-derived biochar for efficient activation of peroxymonosulfate to degrade organic pollutants in wastewater","volume":"329","author":"Li","year":"2021","journal-title":"J. Clean. Prod."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.watcyc.2024.06.003","article-title":"Fe-doped biochars prepared via hydrothermal treatment and low-temperature air calcination to activate peroxymonosulfate for efficient tetracycline degradation","volume":"6","author":"Yang","year":"2025","journal-title":"Water Cycle"}],"container-title":["Nanomaterials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-4991\/16\/19\/1233\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,11]],"date-time":"2026-10-11T04:13:29Z","timestamp":1791692009000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-4991\/16\/19\/1233"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,30]]},"references-count":38,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["nano16191233"],"URL":"https:\/\/doi.org\/10.3390\/nano16191233","relation":{},"ISSN":["2079-4991"],"issn-type":[{"value":"2079-4991","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,30]]}}}