Facile and fast synthesis of nitrogen-doped biochar-supported nanoscale ferrous sulfide composite for efficient removal of aqueous Cr(VI)

Abstract

In this work, a novel nitrogen-doped biochar-supported nanoscale ferrous sulfide composite (nFeS@NBC) was fabricated by pyrolyzing corn straw pretreated with Mohr’s salt through a one-step carbothermic reduction process, which was applied in the efficient disposal of hexavalent chromium (Cr(VI))-containing wastewater. The key effects of impregnation ratio and pyrolysis temperature on the properties and removal performance of nFeS@NBC for Cr(VI) were subsequently investigated. The properties of nFeS@NBC were characterized through a series of techniques. It indicated that FeS nanoparticles were successfully loaded and –NH₂ functional groups effectively formed on the biochar surface, which enhanced the removal performance of nFeS@NBC for Cr(VI) from wastewater. The removal performance of nFeS@NBC for Cr(VI) was systemically evaluated at different experimental conditions and in the presence of major co-existing ions. Adsorption kinetics was best suited to the pseudo-second-order model. Additionally, Langmuir isotherms model could well explain the adsorption experiment data for the removal of Cr(VI) by nFeS@NBC with the highest adsorption capacity of 373.85 mg·g^–1. According to the thermodynamic study, nFeS@NBC dominated the adsorption of Cr(VI) through an endothermic and spontaneous process. The adsorption and reduction served as the main removal mechanisms of nFeS@NBC for aqueous Cr(VI). nFeS@NBC could be used repetitively for its regeneration. Thus, the above results showed that it was feasible and efficient to remove Cr(VI) by nFeS@NBC, providing a potential green material for environmental remediation.

Graphical abstract

Keywords

nanoscale ferrous sulfide / nitrogen-doped biochar / hexavalent chromium / removal performance / adsorption and reduction

References

[1] Yao L , Hu Y , Zou Y , Ji Z , Hu S , Wang C , Zhang P , Yang H , Shen Z , Tang D . . Selective and efficient photoextraction of aqueous Cr(VI) as a solid-state polyhydroxy Cr(V) complex for environmental remediation and resource recovery. Environmental Science & Technology, 2022, 56(19): 14030–14037

[2] Wang Y , Lan G , Qiu H , Pu K , Liu X , Chen L , Xu B . PAD resin: an intelligent adsorbent for solving Cr(VI) pollution with real-time feedback and high efficiency. Journal of Hazardous Materials, 2025, 483: 136563

[3] Ge Q , Feng X , Wang R , Zheng R , Luo S , Duan L , Ji Y , Lin J , Chen H . Mixed redox-couple-involved chalcopyrite phase CuFeS₂ quantum dots for highly efficient Cr(VI) removal. Environmental Science & Technology, 2020, 54(13): 8022–8031

[4] Tang L , Yang J , Liu X , Kang L , Li W , Wang T , Qian T , Li B . Biodegradation of phenanthrene-Cr(VI) co-contamination by Pseudomonas aeruginosa AO-4 and characterization of enhanced degradation of phenanthrene. Science of the Total Environment, 2024, 918: 170744

[5] Bayuo J , Rwiza M J , Choi J W , Njau K N , Mtei K M . Recent and sustainable advances in phytoremediation of heavy metals from wastewater using aquatic plant species: green approach. Journal of Environmental Management, 2024, 370: 122523

[6] Ma R , Xu X , Zhang Y , Zhang D , Xiang G , Chen Y , Qian J , Yi S . Synergistic effects of adsorption and chemical reduction towards the effective Cr(VI) removal in the presence of the sulfur-doped biochar material. Environmental Science and Pollution Research International, 2024, 31(6): 8538–8551

[7] Liu Y , Gan H , Tian L , Liu Z , Ji Y , Zhang T , Alvarez P J J , Chen W . Partial oxidation of FeS nanoparticles enhances Cr(VI) sequestration. Environmental Science & Technology, 2022, 56(19): 13954–13963

[8] Pan Y , Sun L , Yu Z , Guo X , Chen L , Huang M . The performance of mordenite-dispersed and stabilized ferrous sulfide composites for the removal of Cr(VI) from aqueous solutions. Separation and Purification Technology, 2025, 353: 128279

[9] Liu Z , Yang Q , Zhu P , Liu Y , Tong X , Cao T , Tomson M B , Alvarez P J J , Zhang T , Chen W . Cr(VI) reduction and sequestration by FeS nanoparticles formed in situ as aquifer material coating to create a regenerable reactive zone. Environmental Science & Technology, 2024, 58(16): 7186–7195

[10] Mao W , Li Y , Zhang L , Shen X , Liu Y , Guan Y . Synergistic adsorption removal of heavy metal oxoanions and cations from aqueous solution by a polyacrylate-coated ferrous sulfide and layered double hydroxide nanocomposite. Chemical Engineering Journal, 2024, 487: 150518

[11] Han M , Wei X , Wang R , Li J , Sun W , Zhang C . Recycling Cu(II) from complexing copper wastewater using ferrous sulfide stabilized by carboxymethyl cellulose: efficiency and mechanism insights. Separation and Purification Technology, 2024, 330: 125209

[12] Mao W , Li Y , Zhang L , Shen X , Liu Y , Li R , Guan Y . Photoexcitation-induced efficient detoxification and removal of arsenite in contaminated water by a layered double hydroxide-supported polyacrylate stabilized ferrous sulfide composite. Journal of Hazardous Materials, 2024, 474: 134812

[13] Liu Z , Li F , Miao Y , Zhang G , Pang Z , Zhang C , Lin X . Encapsulating carboxymethyl cellulose stabilized nanoscale ferrous sulfide with layered magnesium hydroxide shell for controlled reactivity release and long-term sequestration of Cr(VI). Separation and Purification Technology, 2024, 340: 126836

[14] Ma Y , Jiang S , Zhong J , Chen X , Shu Y . Reactivity enhancement of ferrous sulfide by poly-sodium acrylate cryogels on aqueous Cr(VI) removal: performance and mechanism. Journal of Environmental Chemical Engineering, 2022, 10(6): 108783

[15] Ravindiran G , Rajamanickam S , Janardhan G , Hayder G , Alagumalai A , Mahian O , Lam S S , Sonne C . Production and modifications of biochar to engineered materials and its application for environmental sustainability: a review. Biochar, 2024, 6(1): 62

[16] Zhu S , Huang X , Yang X , Peng P , Li Z , Jin C . Enhanced transformation of Cr(VI) by heterocyclic-N within nitrogen-doped biochar: impact of surface modulatory persistent free radicals (PFRs). Environmental Science & Technology, 2020, 54(13): 8123–8132

[17] Zhang Y , Tang Y , Jin B , Yan R , Zhang L , Li Y , Li J , Liang S . Urea-modified hazelnut shell biochar (N-HSB) for efficient Cr(VI) removal: performance and mechanism insights. Journal of Contaminant Hydrology, 2024, 266: 104414

[18] Chen D , Du X , Chen K , Liu G , Jin X , Song C , He F , Huang Q . Efficient removal of aqueous Cr(VI) with ferrous sulfide/N-doped biochar composites: facile, in-situ preparation and Cr(VI) uptake performance and mechanism. Science of the Total Environment, 2022, 837: 155791

[19] Liu G , Hu D , Song C , Chen K , Du X , Chen D , Jin X , He F , Huang Q . Pyrolysis of different biomass feedstocks impregnated with Mohr’s salt to prepare ferrous sulfide-loaded nitrogen-doped biochar composites for sequestration of aqueous Cr(VI) ions. Journal of Analytical and Applied Pyrolysis, 2022, 164: 105545

[20] Tang Y , Zhang Y , Yan R , Zhang L , Li Y , Li J , Liang S , Yang Y . Enhanced removal of aqueous Cr(VI) by mango kernel biochar supported polysulfide-green synthesized-nanoscale zero valent iron: performance and mechanism. Chemical Engineering Science, 2024, 35: 121108

[21] Ye Z , Jiang M , Yan F , Cao B , Wang F . Chemical aging of biochar-zero-valent iron composites in groundwater: impact on Cd(II) and Cr(VI) co-removal. Environmental Research, 2024, 263: 120022

[22] Li J , Wu S , Zhang W , Pan B , Hua M . Enhanced anaerobic digestion for energy recovery from brewery wastewater employing nano zero-valent iron loaded biochar prepared by residual sludge. Chemical Engineering Journal, 2024, 499: 156466

[23] Zhao Z . Efficient removal of Cr(VI) containing tunnel wastewater by sludge biochar loaded with ferrous sulfate. Desalination and Water Treatment, 2024, 320: 100786

[24] Xue Y , Kamali M , Costa M E V , Thompson I P , Huang W , Rossi B , Appels L , Dewil R . Activation of peroxymonosulfate by Fe, N co-doped walnut shell biochar for the degradation of sulfamethoxazole: performance and mechanisms. Environmental Pollution, 2024, 355: 124018

[25] Chen D , Bai X , Chen Y , Wang Y , Zhu Y . Efficient removal of sulfamethoxazole by activated peroxodisulphates using Fe/N co-doped biochar: the minimal role of high-valent iron species. Separation and Purification Technology, 2024, 343: 127078

[26] Zhu X , Xu L , Wang C , Qi Y , Shi J , Jin X , Bai X , Yan W , Jin P . Insights into the enhanced simultaneous adsorption and catalytic removal of antibiotics by a novel Fe/B co-doped biochar. Separation and Purification Technology, 2025, 360: 130888

[27] Kong W , Li X , Li F , Zimmerman A R , Gao B , Wang J . Iron-modified coal gangue/rice husk biochar composites for enhanced removal of aqueous As(V). Separation and Purification Technology, 2025, 360: 131028

[28] Guo P , Gu X , Li Z , Xu X , Cao Y , Yang G , Kuang C , Li X , Qing Y , Wu Y . A novel almond shell biochar modified with FeS and chitosan as adsorbents for mitigation of heavy metals from water and soil. Separation and Purification Technology, 2025, 360: 130943

[29] Deng W , Wang G , Wang B , Deng N . Sulfur modified biochar supported ferrous sulfide composite for the immobilization of cadmium in contaminated soil. Water, Air, and Soil Pollution, 2024, 235(8): 495

[30] Wei Y , Zhang K , Cheng T , Zhou G . Characteristics and mechanisms of Cr(VI) removal from aqueous solution by FeS_m/BC composite. Water, Air, and Soil Pollution, 2023, 234(2): 68

[31] Cong Y , Shen L , Wang B , Cao J , Pan Z , Wang Z , Wang K , Li Q , Li X . Efficient removal of Cr(VI) at alkaline pHs by sulfite/iodide/UV: mechanism and modeling. Water Research, 2022, 222: 118919

[32] Zhou Z , Liu P , Wang S , Finfrock Y Z , Ye Z , Feng Y , Li X . Iron-modified biochar-based bilayer permeable reactive barrier for Cr(VI) removal. Journal of Hazardous Materials, 2022, 439: 129636

[33] Wan Y , Luo H , Cai Y , Dang Z , Yin H . Selective removal of total Cr from a complex water matrix by chitosan and biochar modified-FeS: kinetics and underlying mechanisms. Journal of Hazardous Materials, 2023, 454: 131475

[34] Qu J , Zhang W , Bi F , Yan S , Miao X , Zhang B , Wang Y , Ge C , Zhang Y . Two-step ball milling-assisted synthesis of N-doped biochar loaded with ferrous sulfide for enhanced adsorptive removal of Cr(VI) and tetracycline from water. Environmental Pollution, 2022, 306: 119398

[35] Qiao H , Hu J , Xu H , Zhao Y . Study of the nano zero-valent iron stabilized by carboxymethyl cellulose loaded on biochar for remediation of Cr(VI)-contaminated groundwater. Separation and Purification Technology, 2025, 353: 128494

[36] Tian H , Huang C , Wang P , Wei J , Li X , Zhang R , Ling D , Feng C , Liu H , Wang M . . Enhanced elimination of Cr(VI) from aqueous media by polyethyleneimine modified corn straw biochar supported sulfide nanoscale zero valent iron: performance and mechanism. Bioresource Technology, 2023, 369: 128452

[37] Wang B , Zhao C , Feng Q , Lee X , Zhang X , Wang S , Chen M . Biochar supported nanoscale zerovalent iron-calcium alginate composite for simultaneous removal of Mn(II) and Cr(VI) from wastewater: sorption performance and mechanisms. Environmental Pollution, 2024, 343: 123148

[38] Kumar Mondal A , Hinkley C , Kondaveeti S , Vo P H N , Ralph P , Kuzhiumparambil U . Influence of pyrolysis time on removal of heavy metals using biochar derived from macroalgal biomass (Oedogonium sp.). Bioresource Technology, 2024, 414: 131562

[39] Yang Z , Wang J , Zhao N , Pang R , Zhao C , Deng Y , Yang D , Jiang H , Wu Z , Qiu R . A novel biochar-based 3D composite for ultrafast and selective Cr(VI) removal in electroplating wastewater. Biochar, 2024, 6(1): 46

[40] Ke Z , Mei M , Liu J , Du P , Zhang B , Wang T , Chen S , Li J . Deep eutectic solvent assisted facile and efficient synthesis of nitrogen-doped magnetic biochar for hexavalent chromium elimination: mechanism and performance insights. Journal of Cleaner Production, 2022, 357: 132012

[41] Jiang F , Wei C , Yu Z , Ji L , Liu M , Cao Q , Wu L , Li F . Fabrication of iron-containing biochar by one-step ball milling for Cr(VI) and tetracycline removal from wastewater. Langmuir, 2023, 39(51): 18958–18970

[42] Gao J , Yang L , Liu Y , Shao F , Liao Q , Shang J . Scavenging of Cr(VI) from aqueous solutions by sulfide-modified nanoscale zero-valent iron supported by biochar. Journal of the Taiwan Institute of Chemical Engineers, 2018, 91: 449–456

[43] Rong K , Li X , Yang Q , Liu Z , Yao Q , Zhang Z , Li R , Zhao L , Zheng H . Removal of aqueous Cr(VI) by green synthesized sulfide iron nanoparticles loaded corn straw biochar: performance, mechanism, and DFT calculations. Applied Surface Science, 2024, 670: 160729

[44] Ma Y , Lu N , Yan S , Wang H , Cao X , Feike T , Guan J . Hydrochar supported strategy for nZVI to remove bisphenol A and Cr(VI): performance, synergetic mechanism, and life cycle assessment. Separation and Purification Technology, 2025, 358: 130423

[45] Li S , You T , Guo Y , Yao S , Zang S , Xiao M , Zhang Z , Shen Y . High dispersions of nano zero valent iron supported on biochar by one-step carbothermal synthesis and its application in chromate removal. RSC Advances, 2019, 9(22): 12428–12435

[46] Sun Y , Lyu H , Gai L , Sun P , Shen B , Tang J . Biochar-anchored low-cost natural iron-based composites for durable hexavalent chromium removal. Chemical Engineering Journal, 2023, 476: 146604

[47] Ahmad S , Gao F , Lyu H , Ma J , Zhao B , Xu S , Ri C , Tang J . Temperature-dependent carbothermally reduced iron and nitrogen doped biochar composites for removal of hexavalent chromium and nitrobenzene. Chemical Engineering Journal, 2022, 450: 138006

[48] Hu S , Liu C , Bu H , Chen M , Tang J , Jiang B , Ran Y . Reduced sulfur compounds and carboxylic acid groups in dissolved PFRs of iron-biochar enhance Cr(VI) reduction in anaerobic conditions. Biochar, 2024, 6(1): 13

[49] Cheng H , Zheng X , Zhu Y , Wang P , Zhu J , Wei J , Liu Z , Huang C . Stabilization of sulfidated nano zerovalent iron with biochar: enhanced transport and application for hexavalent chromium removal from water. Journal of Environmental Management, 2024, 371: 123045

Competing interests

The authors declare that they have no competing interests.

Acknowledgements

This study was financially supported by the Shandong Province Young Taishan Scholar, China (Grant No. tsqn202312155), the National Natural Science Foundation of China (Grant No. 42471081), the Shandong Provincial Natural Science Foundation (Grant No. ZR2021YQ22), and the Shandong Province Colleges and Universities Youth Innovation Science and Technology Teams Support Program (Grant No. 2021KJ015).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at http://doi.org/10.1007/s11705-025-2558-x and is accessible for authorized users.

RIGHTS & PERMISSIONS

2025 Higher Education Press