Hydrochar Derived from Pennisetum setaceum for Congo Red Adsorption: A Low-Cost Bioadsorbent from Invasive Grass
Abstract
This study investigates the adsorption performance of hydrochar derived from Pennisetum setaceum (PS) through hydrothermal treatment at 250°C for various reaction times (1-4 hours) for the removal of Congo Red (CR) dye from aqueous solutions. The materials were characterized using FTIR, XRD, SEM–EDS, BET, and pHpzc analysis to evaluate changes in functional groups, crystallinity, morphology, elemental composition, and surface charge. FTIR spectra confirmed the presence of oxygen-containing functional groups (O-H, C=O, C-O-C, C-O), while XRD patterns indicated a transition from amorphous to partially crystalline structures, followed by re-amorphization at longer reaction times. SEM images revealed a progressive increase in porosity and surface roughness, accompanied by an increase in carbon content, as shown by EDS. BET analysis of HPS-4 further confirmed its mesoporous structure with a surface area of 9.316 m2/g, which supports enhanced adsorption performance. Adsorption experiments demonstrated that the optimum pH for CR removal by HPS-4 was 5, with a maximum capacity of 51.674 ± 5.468 mg/g. Kinetic studies followed the pseudo-first-order model, and equilibrium data fitted well with the Langmuir isotherm, indicating monolayer adsorption. Thermodynamic analysis showed the process was spontaneous and exothermic (?H° = ?44.07 kJ/mol). The proposed adsorption mechanism involves a combination of electrostatic attraction, hydrogen bonding, and ?–? interactions between CR molecules and the aromatic structure of hydrochar. However, regeneration tests indicated a significant decrease in efficiency after the third cycle. These findings suggest that hydrochar from Pennisetum setaceum is a promising adsorbent for anionic dye removal, with optimal performance achieved under controlled hydrothermal conditions.
References
Adawiyah, R., N. Yuliasari, Y. Hanifah, K. Alawiyah, and N. Rahayu Palapa (2024). Utilizing Areca catechu L. Fruit Peel-Derived Biochar and Hydrochar for Congo Red Adsorption: Kinetic and Thermodynamic Analysis. Indonesian Journal of Environmental Management and Sustainability, 8(4); 135–144.
Ahmad, N., A. R. Marlan, and S. P. J. Negara (2024). Insight of Anionic Dyes Adsorption from Their Aqueous Solutions onto MgAl LDH/Lignin: Characterization and Isotherm Studies. Indonesian Journal of Material Research, 2(2); 40–46.
Ahmad, N., F. Suryani Arsyad, I. Royani, P. Mega Syah Bahar Nur Siregar, T. Taher, and A. Lesbani (2023). High Regeneration of ZnAl/NiAl-Magnetite Humic Acid for Adsorption of Congo Red from Aqueous Solution. Inorganic Chemistry Communications, 150; 110517.
Ahmed, H. M., M. E. Fawzy, and H. F. Nassar (2022). Effective Chemical Coagulation Treatment Process for Cationic and Anionic Dyes Degradation. Egyptian Journal of Chemistry, 65(8); 301–310.
Ahmia, N., M. Benamira, L. Messaadia, R. Masmoudi, D. Horwat, and I. Avramova (2026). Sol-Gel Auto-Combustion Synthesized ZnMn?O? for Efficient Photocatalytic Congo Red Degradation: Structural, Kinetics, Computational, and Ecotoxicity Analyses. Journal of Physics and Chemistry of Solids, 208; 113038.
Akhtar, M. S., S. Ali, and W. Zaman (2024). Innovative Adsorbents for Pollutant Removal: Exploring the Latest Research and Applications. Molecules, 29(18); 4317.
Alegbe, E. O. and T. O. Uthman (2024). A Review of History, Properties, Classification, Applications and Challenges of Natural and Synthetic Dyes. Heliyon, 10(13); e33646.
Alqarni, L. S., M. N. Goda, M. Q. Alfaifi, M. Aleid, A. H. Ahmed, A. Alsulami, and A. Modwi (2025). Congo Red Eradication via Efficient La-NiO-g-C3N4 Nanocomposite from Contaminated Water. Journal of Hazardous Materials Advances, 18; 100751.
Amado-Fierro, A., T. Offermans, J. Jansen, T. A. Centeno, and M. A. Díez (2025). Chemometrics to Connect Feedstock Quality, Process Settings and Calorific Value of Hydrochar Through Infrared Spectra. Fuel Processing Technology, 271; 108201.
Ansone-Bertina, L., L. Arbidans, E. Borska, U. Ozola, O. Purmalis, K. Sarsuns, L. Dobkevica, A. Sarakovskis, M. Klavins, and L. Klavins (2024). Modification and Activation of Hydrochar Obtained by the Hydrothermal Carbonisation Process of Invasive Plant Biomass. Bioresource Technology Reports, 26; 101863.
Asif, F. R., B. Bibi, M. Yasir, I. A. Khan, J. Gul, M. Irfan, S. Javed, and V. Sedlarik (2025). Polyester Waste Activated Carbon Assisted Micropollutant Methylene Blue and Congo Red Dyes Removal from Wastewater: RSM Modeling, Kinetics, Mechanism, and Reusability Study. Journal of Industrial and Engineering Chemistry.
Baaloudj, O., F. Langerame, R. Iunnissi, G. Buttiglieri, D. Del Buono, S. Khadhar, L. Scrano, V. Trotta, and M. Brienza (2025). Biochar-Based Downflow Fixed-Bed Adsorption Systems for Water Treatment: Process Optimization, Reusability, and Techno-Economic Evaluation. Separation and Purification Technology, 377; 134347.
Badaruddin, M., N. Ahmad, E. S. Fitri, A. Lesbani, and R. Mohadi (2022). Hydrochar and Humic Acid as Template of ZnAl Layered Double Hydroxide for Adsorption of Phenol. Science and Technology Indonesia, 7(4); 492–499.
Badran, A. M., U. Utra, N. S. Yussof, and M. J. K. Bashir (2023). Advancements in Adsorption Techniques for Sustainable Water Purification: A Focus on Lead Removal. Separations, 10(11); 565.
Benahdach, K., Y. Aoulad El Hadj Ali, A. Azzouz, M. d. Mar Cerrillo González, A. Chraka, R. El Mail, A. El Laghdach, A. Wahby, and B. Arhoun (2025). Synthesis of Activated Carbon by Microwave-Assisted Sulfuric Acid Activation for the Adsorption of Congo Red in Aqueous Medium: Kinetic, Isotherm, Thermodynamic, Molecular Dynamic, and Functional Theory Studies. Journal of Molecular Liquids, 420; 126821.
Bessaha, F., G. Bessaha, S. Ziane, and A. Khelifa (2023). Adsorption of Methyl Orange on Bentonite: Design, Modeling, and Analysis of Experiments. Iranian Journal of Chemistry and Chemical Engineering, 42(10); 3306–3323.
Bezerra, B. G. P., L. Bieseki, D. R. da Silva, and S. B. C. Pergher (2019). Development of a Zeolite A/LDH Composite for Simultaneous Cation and Anion Removal. Materials, 12; 661.
Bin Mobarak, M., N. S. Pinky, F. Chowdhury, M. S. Hossain, M. Mahmud, M. S. Quddus, S. A. Jahan, and S. Ahmed (2023). Environmental Remediation by Hydroxyapatite: Solid State Synthesis Utilizing Waste Chicken Eggshell and Adsorption Experiment with Congo Red Dye. Journal of Saudi Chemical Society, 27(5); 101690.
Boucherdoud, A., A. Seghier, D. E. Kherroub, O. Douinat, K. Dahmani, B. Bestani, and N. Benderdouche (2025). Autogenous Deposition of Copper Oxide onto Polyaniline Nanocomposite Catalysts for the Photodegradation of Methylene Blue and Congo Red: Experimental Inquiry, RSM Optimization, and DFT Calculation. Materials Science and Engineering: B, 314; 118015.
Cabrera-García, P., M. D. Marrero, A. N. Benítez, and R. Paz (2023). Valorization of Pennisetum setaceum: From Invasive Plant to Fiber Reinforcement of Injected Composites. Plants, 12(9); 1777.
Cavali, M., N. Libardi Junior, J. D. de Sena, A. L. Woiciechowski, C. R. Soccol, P. Belli Filho, R. Bayard, H. Benbelkacem, and A. B. de Castilhos Junior (2023). A Review on Hydrothermal Carbonization of Potential Biomass Wastes, Characterization and Environmental Applications of Hydrochar, and Biorefinery Perspectives of the Process. Science of The Total Environment, 857; 159627.
Chan, K. T., S. T. Ong, and S. T. Ha (2024). Adsorptive Removal of Congo Red Dye from Its Aqueous Solutions by Tetraethylenepentamine Modified Peanut Husks Composite Beads. Desalination and Water Treatment, 317; 100060.
Chen, S., B. Han, X. Chen, F. Xu, and G. Wang (2024). Hydrothermal Synthesis and Morphology Control Mechanism of BaTiO3 from NaTi3O6(OH)(H2O)2 Precursors. Ceramics International, 50(12); 21779–21787.
Chen, Z. L., H. Xu, L. Q. Bai, Y. L. Feng, and B. Li (2023). Protonated-Amino-Functionalized Bamboo Hydrochar for Efficient Removal of Hexavalent Chromium and Methyl Orange. Progress in Natural Science: Materials International, 33(4); 501–507.
Cui, C., W. Qiao, D. Li, and L. J. Wang (2025). Dual Cross-Linked Magnetic Gelatin/Carboxymethyl Cellulose Cryogels for Enhanced Congo Red Adsorption: Experimental Studies and Machine Learning Modelling. Journal of Colloid and Interface Science, 678; 619–635.
Cui, D., B. Zhang, S. Wu, X. Xu, B. Liu, Q. Wang, X. Zhang, and J. Zhang (2024). From Sewage Sludge and Lignocellulose to Hydrochar by Co-Hydrothermal Carbonization: Mechanism and Combustion Characteristics. Energy, 305; 132414.
Da Re, D., E. Tordoni, F. De Pascalis, Z. Negrín-Pérez, J. M. Fernández-Palacios, J. R. Arévalo, D. Rocchini, F. M. Medina, R. Otto, E. Arlé, and G. Bacaro (2020). Invasive Fountain Grass (Pennisetum setaceum (Forssk.) Chiov.) Increases Its Potential Area of Distribution in Tenerife Island Under Future Climatic Scenarios. Plant Ecology, 221(10); 867–882.
da Silva, M. D. C. R., D. M. Druzian, L. F. W. Brum, C. dos Santos, G. Pavoski, D. C. R. Espinosa, Y. P. M. Ruiz, A. Galembeck, and W. L. da Silva (2024). Green Synthesis of ZrO2/PdO-NPs for Photodegradation of Anionic Dyes: Photocatalytic Activity and Machine Learning Modelling. Journal of Molecular Liquids, 410; 125581.
Daer, D., L. Luo, Y. Shang, J. Wang, C. Wu, and Z. Liu (2024). Co-Hydrothermal Carbonization of Waste Biomass and Phosphate Rock: Promoted Carbon Sequestration and Enhanced Phosphorus Bioavailability. Biochar, 6(1); 70.
de Melo, A. N., W. K. L. da Silva, C. C. da Silva, M. C. Ferreira, B. S. Damasceno, and A. C. V. de Araújo (2025). Magnetic Graphite Nanocomposite for the Removal of Reactive Black 5 and Congo Red from Textile Industry Wastewater. Materials Chemistry and Physics, 345; 131230.
Dehghani, M. H., S. Ahmadi, S. Ghosh, A. Othmani, C. Osagie, M. Meskini, S. S. AlKafaas, A. Malloum, W. A. Khanday, A. O. Jacob, O. Gökkus, A. Oroke, O. Martins Chineme, R. R. Karri, and E. C. Lima (2023). Recent Advances on Sustainable Adsorbents for the Remediation of Noxious Pollutants from Water and Wastewater: A Critical Review. Arabian Journal of Chemistry, 16(12); 105303.
Dehingia, B., R. Lahkar, and H. Kalita (2024). Efficient Removal of Both Cationic and Anionic Dyes from Water Using a Single rGO/PSS Nanocomposite Membrane with Superior Permeability and High Aqueous Stability. Journal of Environmental Chemical Engineering, 12(2); 112393.
Deivayanai, V. C., S. Karishma, P. Thamarai, A. Saravanan, P. R. Yaashikaa, and A. S. Vickram (2025). Advanced Modeling of Congo Red Dye Adsorption Using Magnetic Nanoparticles Functionalized with Jackfruit Seed Waste Biomass: A Contemporary Modeling Approach. Materials Chemistry and Physics, 341; 130947.
Ewis, D., M. M. Ba-Abbad, A. Benamor, and M. H. El-Naas (2022). Adsorption of Organic Water Pollutants by Clays and Clay Minerals Composites: A Comprehensive Review. Applied Clay Science, 229; 106686.
Farjadfar, S., M. Ghiaci, S. A. Kulinch, and W. Wunderlich (2022). Efficient Photocatalyst for the Degradation of Cationic and Anionic Dyes Prepared via Modification of Carbonized Mesoporous TiO2 by Encapsulation of Carbon Dots. Materials Research Bulletin, 155; 111963.
Fattahimoghaddam, H., T. Mahvelati-Shamsabadi, and B. K. Lee (2021). Efficient Photodegradation of Rhodamine B and Tetracycline over Robust and Green g-C3N4 Nanostructures: Supramolecular Design. Journal of Hazardous Materials, 403; 123703.
Gao, J., Z. Li, X. Tao, X. Li, and K. Zhu (2025). A Comprehensive Study of Multiscale Pore Structural Characteristics in Deep-Buried Coals of Different Ranks. Scientific Reports, 15(1); 8299.
Guo, W., Z. Zhang, B. Wang, L. Xue, and Y. Feng (2025). Novel Insights into Released Hydrochar Particle Derived from Typical High Nitrogen Waste Biomass: Special Properties, Microstructure and Formation Mechanism. Waste Management, 193; 517–528.
Güleç, F., L. M. G. Riesco, O. Williams, E. T. Kostas, A. Samson, and E. Lester (2021). Hydrothermal Conversion of Different Lignocellulosic Biomass Feedstocks – Effect of the Process Conditions on Hydrochar Structures. Fuel, 302; 121166.
He, J., L. Zhu, S. Guo, and B. Yang (2025). An Effective Strategy for Coal-Series Kaolin Utilization: Preparation of Magnetic Adsorbent for Congo Red Adsorption. Chemical Engineering Science, 304; 120958.
Jefri, J., N. A. Fithri, and A. Lesbani (2024). Enhanced Removal Efficiency of Malachite Green Dye Using Gambir Leaf Extract-Modified NiFe LDH Composites: A Study of Cationic Dye Adsorption. Bulletin of Chemical Reaction Engineering & Catalysis, 19(4); 573–584.
Jefri, J., N. A. Fithri, and N. Ramadhan (2025). Enhanced Selectivity of Ni/Al LDH for Cationic Dye Adsorption via Gambier Leaf Extract Modification. Indonesian Journal of Material Research, 3(1); 1–7.
Kannivelan, S. and K. Rajappan (2025). Design and Development of Ni MOF Nanosheet-Infused CA-Modified PEI Membrane for Enhanced Congo Red Adsorption. Inorganic Chemistry Communications, 178; 114550.
Kazak, O., G. K. Akkaya, and A. Tor (2023). Sustainable and Efficient Removal of Cationic, Anionic and Neutral Dyes from Water by Pre-Deposited Vinasse Biochar Membrane. Journal of Environmental Chemical Engineering, 11(3); 110042.
Khan, M. A., S. Kuldeep, Yadav, N. Singh, and G. A. Basheed (2025). Enhanced Adsorption of Congo Red Dye Using Dried Chitosan Functionalized MnFe?O? Viscoelastic Fluid. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 709; 136166.
Khanzada, A. K., H. E. Al-Hazmi, T. A. Kurniawan, J. Majtacz, G. Piechota, G. Kumar, P. Ezzati, M. R. Saeb, N. Rabiee, H. Karimi-Maleh, E. C. Lima, and J. Makinia (2024). Hydrochar as a Bio-Based Adsorbent for Heavy Metals Removal: A Review of Production Processes, Adsorption Mechanisms, Kinetic Models, Regeneration and Reusability. Science of The Total Environment, 945; 173972.
Kloster, M., N. E. Marcovich, and M. A. Mosiewicki (2025). Microcrystalline Cellulose Modified Chitosan Aerogels To Enhance Congo Red Dye Adsorption. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 707; 135823.
Kohzadi, S., N. Marzban, K. Godini, N. Amini, and A. Maleki (2023). Effect of Hydrochar Modification on the Adsorption of Methylene Blue From Aqueous Solution: An Experimental Study Followed by Intelligent Modeling. Water, 15(18); 3220.
Kousar, S., K. Javed, B. Begum, M. M. Naeem, S. Zhang, and X. Hu (2025). Organic Solvent Assisted Hydrothermal Processing of Cooked Rice To Get Insights Into the Evolution of Chemical Structure of Hydrochar. Waste Management, 205; 115007.
Kumari, U. (2024). Textile Dyes and Their Impact on the Natural Environment. In P. Singh (Ed.), Dye Pollution From Textile Industry: Challenges and Opportunities for Sustainable Development. Springer Nature Singapore, pp. 17–30.
Le, T. T. U., T. G. Ngo, N. A. Hoang, V. H. Nguyen, V. D. Nguyen, L. P. Hoang, T. D. Pham, and T. T. Truong (2025). Adsorption Characteristics of Single and Binary Mixture of Methylene Blue and Rhodamine B on Novel Hydrochar Derived From Lemongrass Essential Oil Distillation Residue. Journal of Molecular Liquids, 425; 127205.
Li, H. Z., Y. N. Zhang, J. Z. Guo, J. Q. Lv, W. W. Huan, and B. Li (2021). Preparation of Hydrochar With High Adsorption Performance for Methylene Blue by Co-Hydrothermal Carbonization of Polyvinyl Chloride and Bamboo. Bioresource Technology, 337; 125442.
Li, K., S. Yu, F. Han, C. Xu, Q. Li, Y. Zhang, and H. Zhou (2025). Decoupled Temperature and Pressure Strategies in Hydrothermal Process of Cellulose: A Comprehensive Study. Fuel, 381; 133304.
Li, Z., W. Yi, Z. Li, C. Tian, P. Fu, Y. Zhang, L. Zhou, and J. Teng (2020). Preparation of Solid Fuel Hydrochar Over Hydrothermal Carbonization of Red Jujube Branch. Energies, 13(2); 480.
Marouani, I., W. H. Hassan, N. S. S. Singh, M. Hasan, A. Abduvokhidov, M. Karimov, A. Abilkasimov, I. Mahariq, and M. A. Diab (2025). Preparation of a Novel Reusable 2D-MXene With Flower-Like LDH Composite for Ultra-High Adsorption of Congo Red and Doxycycline: Stability and Environmental Application. Journal of Water Process Engineering, 76; 108288.
Mohadi, R., N. Juleanti, N. Normah, P. M. S. B. N. Siregar, A. Wijaya, N. R. Palapa, and A. Lesbani (2022). Low-Cost Yet High-Performance Hydrochar Derived From Hydrothermal Carbonization of Duku Peel (Lansium domesticum) for Cr(VI) Removal From Aqueous Solution. Indonesian Journal of Chemistry, 22(6); 1523–1533.
Mortezapour, F., N. Shadjou, and M. Mahmoudian (2025). Effective Removal of Anionic Dyes From Aqueous Solution Using Polyethersulfone Based Membrane Reinforced by Montmorillonite. BMC Chemistry, 19(1); 1–10.
Munonde, T. S., N. Madima, R. Ratshiedana, P. Nosizo Nomngongo, L. E. Mofokeng, and R. S. Dima (2025). Synergistic Adsorption-Photocatalytic Remediation of Methylene Blue Dye From Textile Industry Wastewater Over NiFe LDH Supported on Tyre-Ash Derived Activated Carbon. Applied Surface Science, 679; 161205.
Nabil, G. M., R. H. Althomali, and M. E. Mahmoud (2025). Decorated Gelatin Polymer onto Copper Aluminum Layered Double Hydroxides for Superior Removal of Congo Red: Optimization and Adsorption Evaluation of Kinetics, Isotherms, and Thermodynamics. Journal of Molecular Structure, 1319; 139303.
Ojewumi, M. E. and G. Chen (2024). Hydrochar Production by Hydrothermal Carbonization: Microwave versus Supercritical Water Treatment. Biomass, 4(2); 574–598.
Pasipanodya, D., N. Seedat, B. Patel, and R. Roopchund (2025). Production of Hydrochar from the Hydrothermal Carbonisation of Food Waste Feedstock for Use as an Adsorbent in Removal of Heavy Metals from Water. Biomass Conversion and Biorefinery, 15(8); 11819–11833.
Phan, K. A., D. Phihusut, and N. Tuntiwiwattanapun (2022). Preparation of Rice Husk Hydrochar as an Atrazine Adsorbent: Optimization, Characterization, and Adsorption Mechanisms. Journal of Environmental Chemical Engineering, 10(3); 107575.
Prasannamedha, G., P. S. Kumar, S. R. Balasubramani, V. Parthasarathy, A. D. Deehen, E. Jananie, V. Lokesh, S. Shivani, S. Keerthana, I. Shivani, and G. Rangasamy (2025). Engineering Properties of Hydrochar Fabricated from Hydrothermal Carbonization of Lignocellulosic Biomass: Practice as Adsorbent and Catalyst in Water Treatment. Journal of Water Process Engineering, 74; 107739.
Rianjanu, A., T. Haloho, J. L. Pasaribu, A. G. Fahmi, E. Nurfani, W. S. Sipahutar, H. T. Yudistira, and T. Taher (2025). Electrospun Rare-Earth Metal Oxide (CeO?) Nanofiber for the Degradation of Congo Red Aqueous Dyes. Science and Technology Indonesia, 10(1); 123–130.
Saha, N., K. McGaughy, and M. T. Reza (2020). Elucidating Hydrochar Morphology and Oxygen Functionality Change with Hydrothermal Treatment Temperature Ranging from Subcritical to Supercritical Conditions. Journal of Analytical and Applied Pyrolysis, 152; 104965.
Saha, N., A. Saba, and M. T. Reza (2019). Effect of Hydrothermal Carbonization Temperature on pH, Dissociation Constants, and Acidic Functional Groups on Hydrochar from Cellulose and Wood. Journal of Analytical and Applied Pyrolysis, 137; 138–145.
Satyam, S. and S. Patra (2024). Innovations and Challenges in Adsorption-Based Wastewater Remediation: A Comprehensive Review. Heliyon, 10(9); e29573.
Seemab, S., S. Muhammad, S. Nawaz, S. Ahmad, R. Ullah, and A. Khan (2025). Exploring the Adsorption Potential of Waste Graphite Obtained from Spent Dry Cells for Congo Red Dye from Aqueous Solutions. Chemical Engineering Science, 306; 121224.
Selvaraj, P. S., P. Ettiyagounder, K. Sabarish, K. Periasamy, B. Rengasamy, D. Veeraswamy, T. Karchiyappan, and S. Kathirvel (2025). Hydrothermal Carbonization Approach for Transforming Biomass Waste to Value Added Hydrochar and Its Applications in Water Remediation. Desalination and Water Treatment, 322; 101199.
Shanavas Laila, L. and K. M. Sambasivam (2025). Enhancing the Efficiency of Mortar Mixes by Rice Husk Hydrochar Using Response Surface Methodology: An Experimental Study for Property Improvement and Sustainable Construction Applications. Results in Engineering, 27; 106019.
Shukla, A. K., J. Alam, and M. Alhoshan (2025). Trimesoyl Chloride Crosslinked Chitosan: An Efficient Adsorbent for Congo Red Dye Removal from Water - Kinetic and Isotherm Analysis. International Journal of Biological Macromolecules, 319; 145538.
Siddiqui, S. I., E. S. Allehyani, S. A. Al-Harbi, Z. Hasan, M. A. Abomuti, H. K. Rajor, and S. Oh (2023). Investigation of Congo Red Toxicity Towards Different Living Organisms: A Review. Processes, 11(3); 807.
Siregar, P. M. S. B. N., N. R. Palapa, A. Wijaya, E. S. Fitri, and A. Lesbani (2021). Structural Stability of Ni/Al Layered Double Hydroxide Supported on Graphite and Biochar Toward Adsorption of Congo Red. Science and Technology Indonesia, 6(2); 85–95.
Su, Y., Y. Wang, L. Ding, Y. Chen, and D. Song (2025). An Innovative and Efficient Strategy for Removing Congo Red Using Magnetic Hollow Zn/Co Zeolitic Imidazolate Framework Composite. Environmental Research, 264; 120399.
Suebphanpho, J., S. Chanchit, S. Phimphakan, and J. Boonmak (2025). Metallogel Synthesis from Cu(II) Complex with Benzotriazole-5-Carboxylic Acid for Enhanced Congo Red Dye Adsorption and Anion Exchange. ACS Omega.
Tcheka, C., M. M. Conradie, V. A. Assinale, and J. Conradie (2024). Mesoporous Biochar Derived from Egyptian Doum Palm (Hyphaene Thebaica) Shells as Low-Cost and Biodegradable Adsorbent for the Removal of Methyl Orange Dye: Characterization, Kinetic and Adsorption Mechanism. Chemical Physics Impact, 8; 100446.
Tolkou, A. K., A. Giannoulaki, P. Chalkidi, E. Arvaniti, S. Fykari, S. Kritaki, and G. Z. Kyzas (2025). Removal of Anionic and Cationic Dyes from Wastewater by Tetravalent Tin-Based Novel Coagulants. Processes, 13(7); 2103.
Wan, H., X. Zhu, J. Wang, F. Cao, Y. Zhang, Z. Yao, S. Wang, D. Bhattacharyya, and K. Tang (2025). Adsorptive Nanofibrous Membranes for Bidirectional Removal of Cationic and Anionic Dyes. Separation and Purification Technology, 361; 131515.
Wei, Q., Y. Zhang, K. Zhang, J. I. Mwasiagi, X. Zhao, C. W. K. Chow, and R. Tang (2022). Removal of Direct Dyes by Coagulation: Adaptability and Mechanism Related to the Molecular Structure. Korean Journal of Chemical Engineering, 39(7); 1850–1862.
Wibiyan, S., I. Royani, and A. Lesbani (2024). Synthesis and Performance of ZnAl@Layered Double Hydroxide Composites with Eucheuma cottonii Adsorption and Regeneration of Congo Red Dye. Indonesian Journal of Environmental Management and Sustainability, 8(3); 126–134.
Wijaya, A. and N. Yuliasari (2023). Biochar Derived from Rice Husk as Effective Adsorbent for the Removal Congo Red and Procion Red MX-5B Dyes. Indonesian Journal of Material Research, 1(1); 1–7.
Wu, C., Z. Zhao, J. Zhong, Y. Lv, X. Yan, Y. Wu, and H. Zhang (2024). Adsorption of Dye Through Hydrochar Derived From Co-Hydrothermal Carbonization of Garden Waste and Sewage Sludge: The Adsorption Enhancement Mechanism of Lignin Component. Journal of Water Process Engineering, 67; 106233.
Xu, Z. X., X. Q. Ma, J. Zhou, P. G. Duan, W. Y. Zhou, A. Ahmad, and R. Luque (2022). The Influence of Key Reactions During Hydrothermal Carbonization of Sewage Sludge on Aqueous Phase Properties: A Review. Journal of Analytical and Applied Pyrolysis, 167; 105678.
Yang, H., G. Zhang, X. Chen, and W. Zhang (2025). Quaternized Fenugreek Gum Grafted Poly(Acrylamide-Co-Methacryloxyethyltrimethyl Ammonium Chloride) Novel Composite Hydrogel for Efficient Removal of Congo Red Dye. International Journal of Biological Macromolecules, 320; 146090.
You, H., B. Huang, C. Cao, X. Liu, X. Sun, L. Xiao, J. Qiu, Y. Luo, Q. Qian, and Q. Chen (2021). Adsorption–Desorption Behavior of Methylene Blue Onto Aged Polyethylene Microplastics in Aqueous Environments. Marine Pollution Bulletin, 167; 112287.
Yu, S., B. Peng, P. Wu, J. Li, Q. Liu, S. Li, Y. Gu, Y. Liu, Z. Lu, J. Wang, and J. Xing (2025). Deposition of Polydopamine Onto Magnetic Chitosan Microspheres for Efficient Adsorption of Congo Red and Easy Recycling. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 722; 137313.
Zauška, L., P. Pillárová, D. Volavka, E. Kinnertová, J. Bedna?ík, J. Brus, V. Hornebecq, and M. Almáši (2025). Kinetic Adsorption Mechanism of Cobalt(II) Ions and Congo Red on Pristine and Schiff Base-Surface-Modified MIL-101(Fe)-NH?. Microporous and Mesoporous Materials, 386; 113493.
Zhang, F., C. Liu, S. Wang, and Y. Zhang (2025). Fabricating Efficient SnO?/Hydrochar Heterojunction Visible Light Photocatalyst for Cr(VI) Reduction. Journal of Molecular Structure, 1336; 142084.
Zhao, P., S. Yu, Y. S. Zhang, H. Cheng, X. Yang, Q. Li, Y. Zhang, and H. Zhou (2025). Ni Transformation and Hydrochar Properties During Hydrothermal Carbonization of Cellulose. Fuel, 382; 133772.
Zhou, F., K. Li, F. Hang, Z. Zhang, P. Chen, L. Wei, and C. Xie (2022). Efficient Removal of Methylene Blue by Activated Hydrochar Prepared by Hydrothermal Carbonization and NaOH Activation of Sugarcane Bagasse and Phosphoric Acid. RSC Advances, 12(3); 1885–1896.