One-step Synthesis of Sodium Hydroxide-assisted Hydrochar from Spent Coffee for Enhanced Adsorption Performance
Main Article Content
Abstract
Modification is a common method to enhance the physicochemical properties of hydrochar. In this work, hydrochar was synthesized from spent coffee grounds (SCG) with the presence of NaOH during the hydrothermal treatment in a one-step process. The adsorption of methylene blue (MB) in aqueous solution using SCG, SCG-derived hydrochar (HC-W), and NaOH-activated hydrochar (HC-S) as adsorbents was studied. The results showed that hydrochar can effectively remove MB with a high removal rate of above 90%. Among these materials, HC-S exhibited the highest MB adsorption capacity and the shortest time to reach the adsorption equilibrium. The MB adsorption kinetics and isotherm of hydrochar were well fitted by the pseudo-second-order kinetic model and the Langmuir model, respectively. The maximum adsorption capacity of HC-S for MB was 30.17 mg/g. The synergic effect between hydrothermal carbonization and NaOH activation plays a crucial role in enhancing of hydrochar adsorption performance, which is favorable for the adsorption of MB onto the surface of hydrochar.
Keywords:
Hydrochar; Activation; NaOH; One-pot synthesis.
References
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[31] S. Fan, M. Zhao, J. Luo, W. Li, X. Fan, N. Zhou, H. Xu, Y. Shi, Facile preparation of N/P co-doped mesoporous biochar for efficient removel of methylene blue from aqueous solutions: A 2D-FTIR-CÓ, adsorption mechanism analysis, and fixed-bed column study, J. Water Process Eng. 72 (2025) 107479.
https://doi.org/10.1016/j.jwpe.2025.107479
[2] B. Kamenicka, A critical review on applications of microreactors for the treatment of polluted water with organic dyes, Sci. Total Environ. 969 (2025) 178897. https://doi.org/10.1016/j.scitotenv.2025.178897
[3] K.F. Kayani, Mimetallic metal-organic frameworks (BMOFs) for dye removal: a review, RSC Adv. 14 (2024) 31777-31796.
https://doi.org/10.1039/d4ra06626j
[4] H.B. Slama, A.C. Bouket, Z. Pourhassan, F.N. Alenezi, A. Silini, H. Cherif-Silini, Diversity of synthetic dyes from textile industries, discharge impacts and treatment methods, Appl. Sci. 11 (2021) 62555. https://doi.org/10.3390/app11146255
[5] H. Nawaz, M. Umar, A. Ullah, H. Razzaq, K.M. Zia, X.Q. Liu, Polyvinylidene fluoride nanocomposite super hydrophilic membrane integrated with polyaniline-graphene oxide nano fillers for treatment of textile effluents, J. Hazard. Mater. 403 (2021) 123587. https://doi.org/10.1016/j.jhazmat.2020.123587
[6] B.L. Alderete, J. da Silva, R. Godoi, F.R. da Silva, S.R. Taffarel, L.P. da Silva, Evaluation of toxicity and mutagenicity of a synthetic effluent containing azo dye after Advanced Oxidation Process treatment, Chemosphere 263 (2021) 128291. http://doi.org/10.1016/j.chemosphere.2020.128291
[7] J.E. Gaayda, F.E. Tichou, R. Oukhrib, P.S. Yap, T.Q. Liu, M. Hamdani, Natural flocculants for the treatment of wastewater containing dyes or heavy metals: a state-of-the-art review, J. Environ. Chem. Eng. 9 (2021) 106060.
https://doi.org/10.1016/j.jece.2021.106060
[8] O.A. Bin-Dahman, T.A. Saleh, Synthesis of polyamide grafted on biosupport as polymeric adsorbents for the removal of dye and metal ions, Biomass Convers. Biorefin. 14 (2024) 2439-2452.
https://doi.org/10.1007/s13399-022-02382-8
[9] H.M. Mohd Noor Hazrin, A. Lim, C. Li, J.J. Chew, J. Sunarso, Adsorption of 2,4-dichlorophenoxyacetic acid onto oil palm trunk-derived activated carbon: Isotherm and kinetic studies at acidic, ambient conditions, Mater. Today Proc. 64 (2022) 1557–1562. https://doi.org/10.1016/j.matpr.2021.09.461
[10] J. Wang, S. Wang, Preparation, modification and environmental application of biochar: a review, J. Cleaner Prod. 227 (2019) 1002–1022. https://doi.org/ 10.1016/j.jclepro.2019.04.282
[11] A.U. Rajapaksha, S.S. Chen, D.C.W. Tsang, M. Zhang, M. Vithanage, S. Mandal, B. Gao, N.S. Bolan, Y.S. Ok, Engineered/designer biochar for contaminant removal/immobilization from soil and water: potential and implication of biochar modification, Chemosphere 148 (2016) 276–291.
https://doi.org/10.1016/j.chemosphere.2016.01.043
[12] W. Yu, T. Ren, Y. Duan, S. Huai, Q. Zhang, Z. Cai, C. Lu, Mechanism of Al toxicity alleviation in acidic red soil by rice-straw hydrochar application and comparison with pyrochar, Sci. Total Environ. 877 (2023) 162849.
https://doi.org/10.1016/j.scitotenv.2023.162849
[13] N. Chen, S. Cao, L. Zhang, X. Peng, X. Wang, Z. Ai, L. Zhang, Structural dependent Cr (VI) adsorption and reduction of biochar: hydrochar versus pyrochar, Sci. Total Environ. 783 (2021) 147084.
https://doi.org/10.1016/j.scitotenv.2021.147084
[14] M. Cavali, H. Benbelkacem, B. Kim, R. Bayard, N.L. Junior, D.G. Domingos, A.L. Woiciechowski, A.B.C. Junior, Co-hydrothermal carbonization of pine residual sawdust and non-dewatered sewage sludge – effect of reaction conditions on hydrochar characteristics, J. Environ. Manage. 340 (2023) 117994.
https://doi.org/10.1016/j.jenvman.2023.117994
[15] A. Amado-Fierro, T.A. Centeno, J.L.R. Gallego, R. Forján, Critical assessment of biowaste-derived hydrochars for remediating contaminated soils, Environ. Technol. Innovation 38 (2025) 104183.
https://doi.org/10.1016/j.eti.2025.104183
[16] Y. Chen, S.A. Huang, K. Yu, J.Z. Guo, Y.X. Wang, B. Li, Adsorption of lead ions and methylene blue on acrylate-modified hydrochars, Bioresour. Technol. 379 (2023) 129067. https://doi.org/10.1016/j.biortech.2023.129067
[17] M. Zulfajri, M. Adlim, N. Andalia, A. Rasool, S. Sudewi, G.G. Huang, Preparation of magnesium acetate-modified pineapple crown waste hydrochar via co-hydrothermal carbonization for a specific azo dye adsorption, Bioresour. Technol. Rep. 30 (2025) 102127. https://doi.org/10.1016/j.biteb.2025.102127
[18] Z. Zhang, X. Rao, Q. Wu, S. Wang, Y. Chen, X. Yang, X. Sun, Q. Zhou, P. Lu, Preparationg of FeCl3 modified wood chips hydrochar for gas phase mercury removal from flue gas, Fuel, 391 (2025) 134802.
https://doi.org/10.1016/j.fuel.2025.134802
[19] K. Sathish, S. Saraswat, Screening and characterization of thermally modified biowaste-derived hydrochars for slow-release fertilizer for alkaline soil reclamation, Cleaner Waste Syst. 11 (2025) 100257.
https://doi.org/10.1016/j.clwas.2025.100257
[20] X. Zhang, W. Xiang, B. Wang, J. Fang, W. Zou, F. He, Y. Li, D.C.W. Tsang, Y.S. Ok, B. Gao, Adsorption of acetone and cyclohexane onto CO2 actived hydrochars, Chemosphere 245 (2020) 125664.
https://doi.org/10.1016/j.chemosphere.2019.125664
[21] J. Qu, F. Meng, F. Bi, Z. Jiang, M. Wang, Q. Hu, Y. Zhang, H. Yu, Y. Zhang, Nitrogen-doped porous hydrochar for enhanced chromium (VI) and bisphenol A scavenging: Synergistic effect of chemical activation and hydrothermal doping, Environ. Res. 267 (2025) 120667. https://doi.org/10.1016/j.envres.2024.120667
[22] Y.X. Gan, M. Yusuf, H. Ibrahim, Preparation and characterization of potassium hydroxide activated hydrochar, Mater. Lett. 376 (2024) 137328. https://doi.org/10.1016/j.matlet.2024.137328
[23] M.J. Lilian, R. Bissessur, K. Kang, Q.S. He, Y. Hu, Study of KOH-activated hydrochar for CO2 adsorption, J. Ind. Eng. Chem. 143 (2025) 240-251.
https://doi.org/10.1016/j.jiec.2024.08.026
[24] F. Zhou, K. Li, F. Hang, Z. Zhang, P. Chen, L. Wei, C. Xie, Efficient removal of methylene blue by activated hydrochar prepared by hydrothermal carbonization and NaOH activation of sugarcane bagasse and phosphoric acid, RSC Adv. 12 (2022) 1885. https://doi.org/10.1039/d1ra08325b
[25] A. Rani, M. Rongpipi, A. Bhardwaj, K. Hussain, M. Arora, J.N. Babu, Improved carboxylate density hydrochar by alkylation of surface phenol for adsorption of cationic dye in aqueous solution, Surf. Interfaces 56 (2025) 105511. https://doi.org/10.1016/j.surfin.2024.105511
[26] W. Yan, H. Zhang, K. Sheng, A. M. Mustafa and Y. Yu, Evaluation of engineered hydrochar from KMnO4-treated bamboo residues: Physicochemical properties, hygroscopic dynamics, and morphology, Bioresour. Technol. 250 (2018) 806–811. https://doi.org/10.1016/j.biortech.2017.11.052
[27] A.C. Martins, O. Pezoti, A.L. Cazetta, K.C. Bedin, D.A.S. Yamazaki, G.F.G. Bandoch, T. Asefa, J.V. Visentainer, V.C. Almeida, Removal of tetracycline by NaOH-activated carbon produced from macadamia nut shells: Kinetic and equilibrium studies, Chem. Eng. J. 260 (2015) 291–299.
https://doi.org/10.1016/j.cej.2014.09.017
[28] T. Zhang, X. Wu, S. M. Shaheen, Q. Zhao, X. J. Liu, J. Rinklebe, Ammonium nitrogen recovery from digestate by hydrothermal pretreatment followed by activated hydrochar sorption, Chem. Eng. J. 379 (2020) 122254.
https://doi.org/10.1016/j.cej.2019.122254
[29] G. Prasannamedha, P. S. Kumar, R. Mehala, T. J. Sharumitha and D. Surendhar, Enhanced adsorptive removal of sulfamethoxazole from water using biochar derived from hydrothermal carbonization of sugarcane, J. Hazard. Mater. 407 (2021) 124825.
https://doi.org/10.1016/j.jhazmat.2020.124825
[30] X. Xiao, B. Chen, L. Zhu, Transformation, morphology, and dissolution of silicon and carbon in rice straw-derived biochars under different pyrolytic temperatures, Environ. Sci. Technol. 48 (2014) 3411–3419.
https://doi.org/10.1021/ es405676h
[31] S. Fan, M. Zhao, J. Luo, W. Li, X. Fan, N. Zhou, H. Xu, Y. Shi, Facile preparation of N/P co-doped mesoporous biochar for efficient removel of methylene blue from aqueous solutions: A 2D-FTIR-CÓ, adsorption mechanism analysis, and fixed-bed column study, J. Water Process Eng. 72 (2025) 107479.
https://doi.org/10.1016/j.jwpe.2025.107479