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Search Results (249)

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Keywords = Congo red (CR)

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22 pages, 17803 KB  
Article
Aminated Wood Aerogel via Tannic Acid/Polyethylenimine Co-Deposition for Enhanced Congo Red Removal
by Zhongjian Li, Luohui Wang, Xiaobo Xue, Man Yin, Lin Zhang, Xian Wang, Bing Zhou, Youming Dong, Xiangmeng Chen, Liuting Mo and Cheng Li
Gels 2026, 12(9), 846; https://doi.org/10.3390/gels12090846 - 16 Sep 2026
Abstract
Wood aerogel has emerged as a highly promising substrate for advanced adsorbents due to its green nature, low cost, high porosity, and unique three-dimensional (3D) interconnected network structure. Harnessing forest resources for developing high-performance aerogel materials is crucial for tackling organic dye pollution. [...] Read more.
Wood aerogel has emerged as a highly promising substrate for advanced adsorbents due to its green nature, low cost, high porosity, and unique three-dimensional (3D) interconnected network structure. Harnessing forest resources for developing high-performance aerogel materials is crucial for tackling organic dye pollution. This study presents a novel aminated wood-based aerogel engineered through the co-deposition of tannic acid (TA) and polyethylenimine (PEI) on a cellulose skeleton. The fabrication involved a top–down delignification process to create a porous wood aerogel framework, followed by the in situ loading of TA and the grafting of amino-rich PEI, resulting in the final TAPI-DW composite. Benefiting from the abundant active sites deposited on the aerogel’s hierarchically porous surface and the grafted –NH2 groups, TAPI-DW demonstrated an exceptional adsorption capacity for the anionic azo dye Congo red (CR). The adsorption equilibrium was achieved within approximately 6 h, with a lower pH environment promoting removal efficiency. Coexisting ion experiments indicated that the introduction of Ca2+ ions dramatically enhanced the CR adsorption capacity from 168.71 mg·g−1 to 301.14 mg·g−1. This superior capture performance is attributed to the synergistic interplay of the aerogel’s aligned microchannels (derived from the native wood structure) for rapid mass transfer and the intensive chemical interactions, including electrostatic attraction, hydrogen bonding, and π-π stacking between CR molecules and the functional groups (–NH2 and –OH) on the 3D skeleton. The Freundlich model fitting suggests a complex multilayer adsorption process on this heterogeneous wood aerogel surface. This work establishes a green and sustainable pathway for fabricating high-value biomass aerogel materials that show promise as candidates for the efficient remediation of dye-contaminated water. Further studies on reusability and long-term stability are needed to fully validate their potential for practical application. Full article
(This article belongs to the Section Gel Processing and Engineering)
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21 pages, 10857 KB  
Article
Investigating the Combined Effect of Ultrasound and an Iron Oxide Catalyst for the Degradation of Congo Red Dye
by Khursheed B. Ansari
Catalysts 2026, 16(9), 830; https://doi.org/10.3390/catal16090830 - 15 Sep 2026
Abstract
Industrial dyes remain a major source of water pollution and pose environmental and human health risks because of their carcinogenic and mutagenic properties. Of these, Congo Red dye shows high toxicity and stability in aquatic environments; therefore, removing it from water bodies is [...] Read more.
Industrial dyes remain a major source of water pollution and pose environmental and human health risks because of their carcinogenic and mutagenic properties. Of these, Congo Red dye shows high toxicity and stability in aquatic environments; therefore, removing it from water bodies is desirable. Among numerous methods, ultrasound-assisted catalysis for dye degradation remains promising. This work investigates the combined effect of ultrasound and an iron oxide (Fe2O3) catalyst for degrading Congo Red (CR) dye (a model industrial dye). The characterization of Fe2O3 particles was performed through SEM, XRD, and FTIR analyses. CR degradation was performed at 100–600 W ultrasound power, 0–120 min, and with 5–20% (w/v) Fe2O3. The ultrasound-driven CR degradation was compared with and without the Fe2O3 catalyst. Using ultrasound alone, maximum CR degradation reached 39.30%, while adding Fe2O3 (20% w/v) during ultrasonication enabled 93.20% CR degradation in 120 min. The optimized conditions for maximum CR degradation (93.21%) were 600 W, 30 °C, 120 min, and 20% w/v Fe2O3. The enhancement was attributed to acoustic cavitation, heterogeneous bubble nucleation on Fe2O3 surfaces, improved mass transfer, Fe3+/Fe2+ redox cycling, and reactive oxygen species generation. Further, the kinetic analysis indicated that the CR degradation followed a pseudo-second-order kinetic model, showing strong agreement with experimental data (R2 = 0.96). A detailed mechanism was proposed involving CR adsorption, azo-bond cleavage, aromatic ring hydroxylation, fragmentation, ring opening, and progressive oxidation into smaller intermediates. Overall, the present study demonstrates that ultrasound combined with Fe2O3 effectively enhanced Congo Red removal/decolorization under the investigated laboratory-scale conditions. Full article
(This article belongs to the Special Issue Design and Application of Combined Catalysis, 2nd Edition)
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18 pages, 7769 KB  
Article
Anisotropic Cotton-Stalk-Derived Hydrothermally Treated Cellulose–Chitosan Aerogels Toward Anionic Dye Adsorption and Water-in-Oil Emulsion Separation
by Shixue He, Chengbo Zhang, Daning Lang and Ronglan Wu
Gels 2026, 12(9), 814; https://doi.org/10.3390/gels12090814 - 5 Sep 2026
Viewed by 231
Abstract
Transforming agricultural residues into functional porous materials provides a sustainable strategy for wastewater remediation. Herein, cellulose was separated from cotton stalks via formic acid-assisted hemicellulose extraction and sodium chlorite delignification, and then sulfuric acid hydrolysis. Chitosan-assisted hydrothermally treated cellulose (CC) was prepared via [...] Read more.
Transforming agricultural residues into functional porous materials provides a sustainable strategy for wastewater remediation. Herein, cellulose was separated from cotton stalks via formic acid-assisted hemicellulose extraction and sodium chlorite delignification, and then sulfuric acid hydrolysis. Chitosan-assisted hydrothermally treated cellulose (CC) was prepared via hydrothermal treatment in the presence of chitosan. Anisotropic CC/chitosan composite aerogels were prepared via glutaraldehyde crosslinking and unidirectional freeze-drying. The hydrophilic CC/CS aerogel exhibited an oriented porous structure, a low density of 0.03 g cm−3, and a porosity of 85.33%. For Congo red (CR) adsorption, the equilibrium data were described well by the pseudo-second-order kinetic and Langmuir isotherm models, with a calculated maximum adsorption capacity of 483.09 mg g−1. Electrostatic attraction, hydrogen bonding, and pore-mediated retention jointly contributed to CR uptake. To realize oil–water separation, methyltrimethoxysilane (MTMS) vapor modification was applied to prepare hydrophobic aerogel (M-CC/CS). M-CC/CS presented an initial water contact angle (WCA) of around 134°, and the WCA remained above 115° after 600 s of water droplet exposure. The aerogel showed absorption capacities of 16.22–40.13 g g−1 toward various oils and organic solvents. Under gravity, M-CC/CS separated immiscible oil/water mixtures at a flux of 565.47 L m−2 h−1 and several water-in-oil (W/O) emulsions with efficiencies above 99.9% while maintaining high separation efficiency over 10 cycles. This work demonstrates a cotton-stalk-derived aerogel platform whose hydrophilic and hydrophobically modified forms can be used for dye adsorption and oily water treatment, respectively. Full article
(This article belongs to the Section Gel Applications)
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16 pages, 4355 KB  
Article
Biodegradation of Congo Red and Orange G by Bacillus cereus from the Saida Dumpsite: Experimental and In Silico Evidence
by Fatima Hamadeh, Shiraz Rawas, Rana El Hajj and Dalia El Badan
Bacteria 2026, 5(3), 53; https://doi.org/10.3390/bacteria5030053 - 1 Sep 2026
Viewed by 217
Abstract
Understanding the potential mechanisms of bacterial azo dye decolorization remains a challenge due to a limited understanding of the exact stereochemical forces guiding enzyme–substrate interactions. This study addresses these interactions by evaluating the in silico binding architectures of Orange G (OG) and Congo [...] Read more.
Understanding the potential mechanisms of bacterial azo dye decolorization remains a challenge due to a limited understanding of the exact stereochemical forces guiding enzyme–substrate interactions. This study addresses these interactions by evaluating the in silico binding architectures of Orange G (OG) and Congo Red (CR) against the Bacillus-derived azoreductase model AzrA (PDB ID: 3W77). Computational modeling predicted favorable thermodynamic properties within the calculated active site, yielding binding energy scores of −8.17 kcal/mol for CR and −6.63 kcal/mol for OG. These simulations identified hydrogen-bonding and aromatic π-π interactions within the predicted binding pocket. These predictions suggest potential enzyme–dye association but do not demonstrate catalytic activity or azo-bond cleavage. Independently, Bacillus cereus BC WW Saida achieved an 81% decolorization of OG within 144 h and a 70% reduction in CR within 96 h. High-performance liquid chromatography (HPLC) indicated chemical transformation, demonstrating a significant decrease in primary dye peaks alongside the emergence of novel intermediate peaks at 254 nm. Rather than definitively establishing a metabolic pathway, these outcomes deliver preliminary structural models of azoreductase-substrate affinities, offering a useful framework for the comparative evaluation of microbial catalysts for industrial effluent purification. Full article
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22 pages, 2552 KB  
Article
Ultrasound-Induced In Situ Self-Assembly of Bimodal Micro/Mesoporous UiO-66-NH2 Aerogels for High-Performance Congo Red Capture
by Tian Zhao, Shilin Peng, Yan Wu, Tianhang Wang, Xing Zhang, Zhuoheng Li, Xiangjiang Wu, Ying Chen and Yi Chen
Gels 2026, 12(9), 778; https://doi.org/10.3390/gels12090778 - 31 Aug 2026
Viewed by 215
Abstract
Metal–organic framework (MOF) powders possess remarkable adsorption capabilities, yet their practical application is severely hampered by poor processability, difficult recovery, and high mass-transfer resistance. Here, we report a green and rapid two-stage strategy for constructing UiO-66-NH2 self-assembled aerogels with a bimodal micro-/mesoporous [...] Read more.
Metal–organic framework (MOF) powders possess remarkable adsorption capabilities, yet their practical application is severely hampered by poor processability, difficult recovery, and high mass-transfer resistance. Here, we report a green and rapid two-stage strategy for constructing UiO-66-NH2 self-assembled aerogels with a bimodal micro-/mesoporous architecture. A brief thermal pretreatment (130 °C, 3 h) is used solely for precursor activation, after which the critical MOF crystallization and in situ self-assembly are driven under ambient conditions via ultrasonic cavitation (900 W, 15–60 min). This protocol simultaneously drives the nucleation, crystallization, and self-assembly of UiO-66-NH2 nanocrystals into a monolithic, self-supporting architecture, thereby replacing the conventional prolonged high-temperature solvothermal MOF crystallization with a rapid room-temperature process. The sonication time critically governs the structural evolution, transforming initially amorphous aggregates into well-defined regular octahedral nanocrystals that form an interconnected framework. The optimized aerogel (UNA-T60) exhibits an exceptional specific surface area (1196.9 m2 g−1) and a synergistic bimodal pore structure comprising intrinsic micropores and intercrystalline mesopores. This architecture enables rapid mass transfer and active-site accessibility, resulting in a maximum Congo Red (CR) adsorption capacity of 660.56 mg g−1, with kinetics conforming to the pseudo-second-order model (R2 > 0.999). The robust monolithic structure endows the material with outstanding reusability, retaining 90.8% of its initial adsorption capacity after four regeneration cycles. This work presents a paradigm-shifting approach for the sustainable fabrication of pure MOF aerogels, offering a promising solution for advanced dye wastewater treatment. Full article
(This article belongs to the Special Issue Advanced Functional Aerogels: Design and Innovation)
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24 pages, 16593 KB  
Article
Green Fabrication of Aspergillus terreus–Silver Oxide Bio-Nanocomposite for Sustainable Wastewater Treatments: Synthesis, Optimization, Toxicity Assessment, and Application
by Ghada Abd-Elmonsef Mahmoud, Ahmed Y. Abdel-Mallek and Rania Mahmoud Fouad
Sustainability 2026, 18(15), 7817; https://doi.org/10.3390/su18157817 - 2 Aug 2026
Viewed by 337
Abstract
The discharge of azo-dye-containing wastewater from textile and related industries represents a major environmental challenge because of the persistence, toxicity, and poor bio-degradability of synthetic dyes. Congo red dye (CR), one of the most widely used azo dyes, poses serious ecological and public [...] Read more.
The discharge of azo-dye-containing wastewater from textile and related industries represents a major environmental challenge because of the persistence, toxicity, and poor bio-degradability of synthetic dyes. Congo red dye (CR), one of the most widely used azo dyes, poses serious ecological and public health risks when released into aquatic ecosystems. Although numerous biological adsorbents have been investigated for dye removal, the development of sustainable fungal-based nanocomposites with high adsorption efficiency, optimized operational conditions, and verified environmental safety remains limited. Therefore, the present work describes the development and evaluation of a novel Aspergillus terreus–silver oxide nanoparticle (Ag2O NPs) myco-nanocomposite as a promising eco-friendly biosorbent for CR dye removal from aqueous solutions and real wastewater. Aspergillus terreus (GenBank accession PX920301) isolated from dye-contaminated wastewater, the adsorption efficiencies of dried mycelia, and the myco-nanocomposite were compared. Myco-nanocomposite was characterized using ultraviolet visible spectroscopic analysis (UV/Vis), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). A. terreus–Ag2O NPs myco-nanocomposite exhibited the highest ad-sorption efficiency 92.73%, adsorption capacity (qe) 118.7 mg/g and lowest CR dye residual by 3.81 mg/L, while A. terreus non-autoclaved dried mycelia recorded 78.28% CR removal, adsorption capacity (qe) 100.2 mg/g and CR dye residual by 11.39 mg/L. Adsorption parameters were optimized using a four-factor Box–Behnken experimental design, producing a highly significant quadratic model (R2 = 0.986). The highest optimized conditions were obtained at run 17 in which 100 mg L−1 CR dye, pH 8, 0.05 g adsorbent dosage, and 48 h contact time, with removal efficiency of 96.88%, followed by run 14 using 50 mg L−1 CR dye, pH 6, 0.05 g adsorbent dosage, and 48 h contact time, with removal efficiency of 95.79%. Phytotoxicity and microbial toxicity assays demonstrated that the treated wastewater was environmentally safer than untreated CR dye, exhibiting no inhibitory effects on representative bacteria, yeast, and filamentous fungi while improving wheat seedling growth. Furthermore, application of the myco-nanocomposite to real industrial wastewater achieved 94.92% decolorization. This study provides a sustainable myco-nanocomposite of A. terreus–Ag2O NPs which represents a promising green technology for the remediation of dye-contaminated industrial effluents and supports the development of environmentally sustainable wastewater management strategies and applicability of reusing treated wastewater. Full article
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19 pages, 6060 KB  
Article
Production of FeCl3-Treated Amine Functional Polymer Gel for Enhanced Removal of Methyl Orange and Congo Red Anionic Dyes
by Şeyda Getir, Atakan Toprak and Baki Hazer
Polymers 2026, 18(15), 1838; https://doi.org/10.3390/polym18151838 - 27 Jul 2026
Viewed by 389
Abstract
Synthetic dyes such as Methyl Orange (MO) and Congo Red (CR) are recalcitrant, toxic, mutagenic and resistant to conventional biodegradation, and their industrial discharge continues to contaminate aqueous ecosystems worldwide. This study reports the synthesis and characterization of a poly(MMA-co-2-AEMA) copolymer gel (Fe-Copolymergel-NH [...] Read more.
Synthetic dyes such as Methyl Orange (MO) and Congo Red (CR) are recalcitrant, toxic, mutagenic and resistant to conventional biodegradation, and their industrial discharge continues to contaminate aqueous ecosystems worldwide. This study reports the synthesis and characterization of a poly(MMA-co-2-AEMA) copolymer gel (Fe-Copolymergel-NH2) treated with FeCl3. It evaluates its adsorption performance from aqueous solution against the anionic azo dyes MO and CR. Extensive characterization using N2 adsorption–desorption at 77 K, FTIR-ATR, XPS, SEM, and TEM revealed that Fe modification significantly improved the material’s textural properties, increasing its specific surface area from 8.11 m2/g to 12.55 m2/g and creating a highly irregular, interconnected, sponge-like morphology. Adsorption experiments showed that Fe-Copolymergel-NH2 achieved competitive Langmuir maximum monolayer adsorption capacities of 3201.9 mg/g for CR and 1089.8 mg/g for MO. Kinetic modeling demonstrated that adsorption strictly followed the PSO model, primarily governed by chemisorption via electrostatic attractions and complexation within the internal structure at Fe3+ coordination centers. Thermodynamic analysis revealed that the dye removal process was spontaneous and exothermic. Consequently, the successful integration of Fe3+ coordination centers resolves the adsorption and structural limitations of pure polymer matrices, positioning Fe-Copolymergel-NH2 as a highly promising and efficient adsorbent for the remediation of dye-contaminated industrial wastewater. Full article
(This article belongs to the Special Issue Polymer Materials for Ecological and Environmental Applications)
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21 pages, 9727 KB  
Article
Efficient Binary Solution Adsorption Using Polyurethane Foam Composites Integrated with Zr-MOF and Milled Activated Carbon
by Supanicha Alapol, Thidarat Imyen, Khemmathin Lueangwattanapong, Nutchapon Chiarasumran, Maythee Saisriyoot, Anusith Thanapimmetha, Yi-Shen Huang, Chih-Feng Huang and Penjit Srinophakun
Polymers 2026, 18(13), 1669; https://doi.org/10.3390/polym18131669 - 6 Jul 2026
Viewed by 594
Abstract
Wastewater containing heavy metals and dyes poses serious environmental risks. This study developed a multifunctional composite by coating polyurethane foam (PUF) with milled activated carbon (mAC) and a zirconium-based metal–organic framework (Zr-MOF) for the simultaneous removal of hexavalent chromium (Cr(VI)) and Congo red [...] Read more.
Wastewater containing heavy metals and dyes poses serious environmental risks. This study developed a multifunctional composite by coating polyurethane foam (PUF) with milled activated carbon (mAC) and a zirconium-based metal–organic framework (Zr-MOF) for the simultaneous removal of hexavalent chromium (Cr(VI)) and Congo red (CR). The composite was synthesized using a hydrothermal method to grow Zr-MOF on the surface. The SEM analysis confirmed the successful incorporation of mAC and surface modification with Zr-MOF, which resulted in increased surface roughness and porous morphology. XRD and FTIR confirmed the presence of organic ligands connected to the metal structure and the functional groups of each component in composite materials. The optimum conditions for Zr-MOF/mAC/PUF adsorption (nearly 100% removal) in the binary Cr(VI)/CR solution (50 mg/L each) were 25 °C, pH 9, and 150 rpm for 24 h. The Zr-MOF/mAC/PUF was hydrophilic with a swelling ratio of 2.64 g/g. The thermodynamic investigation of Zr-MOF/mAC/PUF resulted in 141.6218 kJ/mol for Cr(VI) and 166.111 kJ/mol for CR of ΔH° (rapid adsorption), negative ΔG° (spontaneous adsorption), a high positive value of ΔS° (disorder structure) and low activation energy (approximately 2.5 to 2.8 kJ/mol). After analyzing the isotherm and reaction kinetics, the possible mechanism could be endothermic physicochemical adsorption and pseudo-second-order kinetic behavior, with electrostatic attraction and diffusion control. The study of 6-times-reused Zr-MOF/mAC/PUF adsorption identified as a decrease of 7.55 percentage point without changing notable morphology and functional groups, based on SEM and FTIR. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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29 pages, 23875 KB  
Article
Synthesis of Fe2O3/γ-Al2O3 via Sol-Gel Method for Congo Red Adsorption: Kinetic Analysis and DFT Insights
by Yiwang Tang, Hongxia Wang, Junchao Zhang, Yuning Ma, Xiyao Tian, Xintong Liu and Xiulan Xin
Nanomaterials 2026, 16(13), 814; https://doi.org/10.3390/nano16130814 - 1 Jul 2026
Viewed by 514
Abstract
With the growing emphasis on environmental sustainability, the proper treatment of industrial wastewater and the protection of groundwater resources have become pressing global concerns. Congo red (CR), a widely used azo dye, enters water bodies via wastewater discharge, posing persistent ecological risks to [...] Read more.
With the growing emphasis on environmental sustainability, the proper treatment of industrial wastewater and the protection of groundwater resources have become pressing global concerns. Congo red (CR), a widely used azo dye, enters water bodies via wastewater discharge, posing persistent ecological risks to surface and groundwater systems. Adsorption, as a direct and sustainable remediation approach, necessitates the development of high-performance adsorbents to inhibit CR migration into groundwater. In this study, a Fe2O3/γ-Al2O3 composite was synthesized via sol-gel method for efficient CR adsorption, thereby mitigating groundwater contamination risk. The composite exhibited a high specific surface area (246.22 m2/g) and a maximum adsorption capacity of 1027.72 mg/g. Adsorption behavior followed the pseudo-second-order kinetic and Langmuir isotherm models, consistent with chemisorption-driven monolayer adsorption. The Weber–Morris intraparticle diffusion model confirmed rapid initial surface adsorption, beneficial for practical groundwater remediation. pH-dependent adsorption efficiency further indicated the role of electrostatic interactions, informing process optimization under varying groundwater chemistries. DFT calculations demonstrated that Fe2O3/γ-Al2O3 possesses a higher adsorption affinity for CR than γ-Al2O3. Collectively, Fe2O3/γ-Al2O3 shows strong potential as a novel, efficient adsorbent for CR interception and groundwater quality protection. Full article
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27 pages, 10845 KB  
Article
Multifunctional Ag Nanoparticles and Ag/Jute Nanocomposites Derived from Erythroxylum coca Tea Waste for Antimicrobial Activity and Single/Multicomponent Catalytic Pollutant Degradation
by Yeshua Díaz Zamora, Mateo Burke Irazoque, Carla Calderón Toledo, Sergio Gutiérrez Cortez, Alien Blanco Flores, Delfino Reyes Contreras, Miguel A. Camacho López, Helen Paola Toledo Jaldin, Delia Monserrat Ávila Márquez and Alfredo Rafael Vilchis Néstor
J. Compos. Sci. 2026, 10(7), 342; https://doi.org/10.3390/jcs10070342 - 28 Jun 2026
Viewed by 773
Abstract
This work presents a sustainable strategy for the fabrication of multifunctional silver nanoparticles (Ag-NPs) and Ag/jute nanocomposites using Erythroxylum coca tea waste extract as a bioreducing and stabilizing agent, combined with picosecond pulsed laser irradiation. UV–Vis spectroscopy and transmission electron microscopy revealed the [...] Read more.
This work presents a sustainable strategy for the fabrication of multifunctional silver nanoparticles (Ag-NPs) and Ag/jute nanocomposites using Erythroxylum coca tea waste extract as a bioreducing and stabilizing agent, combined with picosecond pulsed laser irradiation. UV–Vis spectroscopy and transmission electron microscopy revealed the formation of Ag-NPs with diverse morphologies and broad size distributions, which became significantly more uniform after laser post-treatment without the need for additional chemical reagents. Following laser irradiation, the initially broad Ag surface plasmon resonance (SPR) peak transformed into a symmetric Gaussian-shaped band, centered at 407 ± 3 nm for all the Ag-NPs systems. The catalytic performance of unsupported Ag-NPs and Ag-NPs supported on jute fibers was comparatively evaluated by degrading Congo red (CR) dye, revealing that the supported nanocomposites exhibited enhanced catalytic stability, higher pollutant removal efficiency, and improved catalyst recovery. Furthermore, multicomponent catalytic reduction experiments involving CR and 4-nitrophenol (4-NP) in the presence of NaBH4 revealed simultaneous degradation and reduction pathways mediated by the Ag/jute nanocomposites, as evidenced by the emergence of new absorption bands during the reaction. In parallel, the synthesized Ag-NPs demonstrated pronounced antimicrobial activity against Escherichia coli, generating well-defined inhibition zones. Beyond conventional approaches centered on nanoparticle synthesis and morphology optimization, this study establishes a platform that combines agricultural waste valorization, laser-assisted nanoparticle engineering, and natural-fiber-supported nanocomposite fabrication, enabling efficient remediation of both single- and multicomponent pollutant systems while promoting catalyst reusability and environmental sustainability. These findings demonstrate the Ag/jute nanocomposites as sustainable and scalable catalytic materials for wastewater remediation and antimicrobial applications. Full article
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33 pages, 4258 KB  
Article
Congo Red–Functionalized Maize Stalk for Fe3+, Cr3+ and Mn2+ Adsorption: Multi-Analytical Characterization of Interaction Mechanisms
by Nicoleta Mirela Marin, Toma Galaon, Adriana Mariana Borș, Roxana Doina Trusca, Ludmila Motelica and Ovidiu Oprea
Polymers 2026, 18(13), 1600; https://doi.org/10.3390/polym18131600 - 27 Jun 2026
Cited by 1 | Viewed by 468
Abstract
This study examines the adsorption and interaction mechanisms of Congo red (CR) immobilized onto maize stalk (MS) to form MS-CR material, used for the removal of Fe3+, Cr3+, and Mn2+ (Mn+) from aqueous media. Initially, the [...] Read more.
This study examines the adsorption and interaction mechanisms of Congo red (CR) immobilized onto maize stalk (MS) to form MS-CR material, used for the removal of Fe3+, Cr3+, and Mn2+ (Mn+) from aqueous media. Initially, the MS was functionalized with CR, achieving adsorption capacities between 41.4 and 48.0 mg/g across pH 2–10, confirming the formation of hydrogen bonding and aromatic interactions, as indicated by the shift of the OH band from 3338.91 to 3335.54 cm−1 and the appearance of characteristic azo–aromatic peaks (1601–1506 cm−1) in the FTIR spectra. Stability tests showed that CR remains anchored to the lignocellulosic matrix even under 2 M HCl/NaOH. Subsequently, adsorption experiments revealed a strong pH dependence: at pH 10, removal efficiencies reached 93% for Mn2+, 89% for Fe3+, and 72% for Cr3+ at 2 mg/L, driven by surface deprotonation and enhanced electrostatic attraction. Increasing the initial metal concentration (1–10 mg/L) led to maximum adsorption capacities of 2.00 mg/g for Fe3+, 1.64 mg/g for Cr3+, and 1.46 mg/g for Mn2+. Desorption experiments identified 0.5 M HCl as the optimal regenerating agent, achieving 90–97% metal release. FTIR analysis of MS-CR–Mn2+ showed the disappearance of the 1243 cm−1 carboxyl band and the emergence of a metal–oxygen vibration at 559.37 cm−1, confirming adsorption via coordination to deprotonated carboxyl and phenolic groups. TG/DSC/DTG analysis demonstrated improved stability of MS-CR compared to native MS. SEM/EDX confirmed the presence of S, Na, and Mn+. The combined spectroscopic, microscopic, and thermal evidence demonstrates that MS-CR operates as a robust, multifunctional adsorbent capable of Mn+ retention, offering a sustainable solution for water treatment. Full article
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26 pages, 10337 KB  
Article
Advanced TiO2–SiO2–Biochar Thin-Film Nanocomposite Membranes for High-Performance Removal of Dyes and Heavy Metals from Wastewater
by Muhammad Shahid Sami, Fida Hussain, Ammarah Mushtaq, Jalal Shah, Sang-Eun Oh and Aneela Anwar
Water 2026, 18(12), 1480; https://doi.org/10.3390/w18121480 - 16 Jun 2026
Cited by 1 | Viewed by 690
Abstract
Next-generation wastewater treatment and recycling rely on membrane-based processes, but they face a trade-off among permeability, selectivity, and fouling resistance. In the present study, thin-film nanocomposite (TFN) membranes were fabricated by incorporating a ternary TiO2-SiO2-biochar nanofiller into a polysulfone [...] Read more.
Next-generation wastewater treatment and recycling rely on membrane-based processes, but they face a trade-off among permeability, selectivity, and fouling resistance. In the present study, thin-film nanocomposite (TFN) membranes were fabricated by incorporating a ternary TiO2-SiO2-biochar nanofiller into a polysulfone (PSf) support using nonsolvent-induced phase separation, after which m-phenylenediamine and trimesoyl chloride were used via interfacial polymerization to produce a selective polyamide layer. The membrane compositions were M1 (22 wt.% PSf), M2 (22 wt.% PSf/0.5 wt.% TiO2/0.5 wt.% SiO2/0.5 wt.% biochar), and M3 (polyamide-coated M2). FTIR, XRD, SEM, contact-angle, porosity, and mechanical analyses supported successful membrane formation and changes in morphology, wettability, and structural strength after nanofiller incorporation and TFC coating. The addition of a nanofiller increased the hydrophilicity of the membranes by decreasing the water contact angle from 98.6 ± 0.8° for pristine PSf to 35.6 ± 1.5° for the nanocomposite membrane. Consequently, the pure-water permeability increased from 21 to 37 L m−2 h−1 bar−1. After polyamide layer formation, the optimized TFN membrane maintained a contact angle of 55.4 ± 3.8° and achieved a high Congo red rejection of 98% with permeate flux of 7–9 L m−2 h−1 bar−1. The membrane also showed good antifouling performance, with flux recovery ratios exceeding 90%. For heavy-metal-containing solutions, the optimized membrane showed apparent removal efficiencies of 78–98% for multivalent heavy metals (Pb2+, Hg2+, Cd2+, Mn2+, Zn2+, Cu2+, Ni2+, Fe3+, As3+, and Cr6+). Static adsorption tests showed the order M2 > M3 > M1, confirming that exposed TiO2-SiO2-biochar sites contribute to pollutant uptake, while the superior filtration performance of M3 is attributed to the combined effect of the polyamide selective layer and adsorption-assisted interactions. Overall, the TiO2-SiO2-biochar-based TFN membrane provides a promising platform for dye removal and preliminary heavy-metal attenuation from contaminated water. Full article
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22 pages, 10412 KB  
Article
MgO Nanoparticles-Functionalized Palm Leaf Biochar for Efficient and Sustainable Congo Red Removal
by Basim Alfajri, Samah Daffalla, Hessah Alzouraiq, Salman Bin Maan, Ahmed Alfuzaya and Mohamed R. El-Aassar
J. Compos. Sci. 2026, 10(5), 270; https://doi.org/10.3390/jcs10050270 - 17 May 2026
Viewed by 768
Abstract
A major challenge in wastewater treatment lies in developing cost-effective and sustainable adsorbent materials for efficient dye removal. In this study, a novel biochar functionalized with MgO nanoparticles derived from palm leaf waste (MgO/PLB nanoparticles) was synthesized and evaluated for the removal of [...] Read more.
A major challenge in wastewater treatment lies in developing cost-effective and sustainable adsorbent materials for efficient dye removal. In this study, a novel biochar functionalized with MgO nanoparticles derived from palm leaf waste (MgO/PLB nanoparticles) was synthesized and evaluated for the removal of Congo red (CR) from aqueous solutions. FTIR, SEM, BET, and TGA investigations were used to thoroughly analyze the produced nanocomposite’s physicochemical properties. FTIR analysis verified the successful incorporation of MgO nanoparticles, as evidenced by the presence of characteristic Mg–O vibrations and noticeable changes in surface functional groups. SEM analysis revealed a transformation from a compact structure to a rough, particle-decorated morphology, indicating increased surface heterogeneity. BET analysis indicated the development of mesoporous structures, accompanied by a substantial increase in specific surface area from 2 to 178 m2/g. TGA results further confirmed enhanced thermal stability, indicating the formation of a structurally robust adsorbent. Batch adsorption tests showed that CR removal depends on pH, dosage, concentration, and contact time, with maximum efficiency (~99%) achieved at pH 4 using 0.03 g of adsorbent. The adsorption followed pseudo second order kinetics and was best described by the Langmuir isotherm, with a maximum capacity of 23.4 mg/g. The regenerated nanomaterial retained more than 89% of its adsorption capacity after four successive cycles, demonstrating good reusability and stability. The developed MgO/PLB nanoparticles exhibit efficient adsorption performance, combined with low-cost synthesis and the utilization of abundant agricultural waste, making it an affordable and long-lasting adsorbent for applications involving wastewater treatment. Full article
(This article belongs to the Section Nanocomposites)
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17 pages, 3534 KB  
Article
Antifouling Polysulfone/Multi-Walled Carbon Nanotube/Terbium Oxide Nanocomposite Nanofiltration Membrane for Dye Removal Applications
by Abeer M. Alosaimi
Polymers 2026, 18(10), 1165; https://doi.org/10.3390/polym18101165 - 9 May 2026
Viewed by 946
Abstract
Polysulfone (PSF) nanofiltration membranes incorporating oxidized multi-walled carbon nanotubes (o–MWCNTs) and terbium oxide (Tb2O3) nanoparticles were fabricated via the non-solvent-induced phase inversion technique. The effect of Tb2O3 loading (0, 1, 3, and 5% w/w [...] Read more.
Polysulfone (PSF) nanofiltration membranes incorporating oxidized multi-walled carbon nanotubes (o–MWCNTs) and terbium oxide (Tb2O3) nanoparticles were fabricated via the non-solvent-induced phase inversion technique. The effect of Tb2O3 loading (0, 1, 3, and 5% w/w) on membrane morphology, hydrophilicity, water permeability, dye rejection, and antibiofouling performance was systematically investigated. Membrane structure was characterized by FTIR spectroscopy, SEM, EDX, XRD, and water contact angle measurements. The results confirmed the successful incorporation of Tb2O3 within the membrane matrix, and morphological analysis revealed a relatively dense membrane structure without macrovoid formation. Filtration experiments conducted in a dead-end cell under pressures of 1–4 bar demonstrated a maximum water flux of 53 L m−2 h−1, with dye rejection exceeding 99.9% for both methylene blue (MB) and Congo red (CR) at 4 bar. Antibiofouling performance, evaluated by colony-forming unit analysis, revealed bacterial growth reductions of 59% against Gram-negative Escherichia coli and 89% against Gram-positive Candida albicans, attributed to the dark-active generation of reactive oxygen species by Tb2O3, eliminating the need for UV irradiation. These results demonstrate that the synergistic integration of o–MWCNTs and Tb2O3 effectively addresses the permeability-selectivity trade-off and mitigates biofouling limitations associated with pristine PSF membranes, thereby offering a promising multifunctional platform for sustainable industrial wastewater treatment. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials for Water Purification)
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25 pages, 7879 KB  
Article
Simultaneous Adsorptive Removal of Arsenic(V) and Congo Red by a MgZnFe LDH/Triazole Composite with Electrocatalytic Urea Oxidation Application
by Samar M. Mahgoub, Abdelghafar M. Abu-Elsaoud, Seham M. Hamed, Ahmed A. Allam, Saber A. A. Elsuccary, Mahmoud M. Ghuniem, Hend A. Mahmoud, Vehaan Subramanian and Rehab Mahmoud
Catalysts 2026, 16(5), 434; https://doi.org/10.3390/catal16050434 - 7 May 2026
Cited by 3 | Viewed by 1061
Abstract
Water contamination by arsenic(V) [As(V)] and Congo red (CR) dye poses concurrent threats to public health and aquatic ecosystems, particularly in regions where metallurgical and textile industries coexist. Developing a single adsorbent capable of simultaneously addressing these chemically distinct pollutants, while recovering value [...] Read more.
Water contamination by arsenic(V) [As(V)] and Congo red (CR) dye poses concurrent threats to public health and aquatic ecosystems, particularly in regions where metallurgical and textile industries coexist. Developing a single adsorbent capable of simultaneously addressing these chemically distinct pollutants, while recovering value from the spent material remains an open challenge in sustainable water treatment. This study reports the synthesis and evaluation of a novel ternary MgZnFe-LDH/1,2,4-triazole composite (TM-LDH/TZ), engineered for the concurrent adsorptive removal of As(V) and CR, and the subsequent repurposing of the pollutant-loaded material as an electrocatalyst for the urea oxidation reaction (UOR). The composite was prepared via co-precipitation and triazole surface grafting, then characterized by FTIR, XRD, BET, TGA, FESEM, and HRTEM. Batch adsorption experiments examined the influence of pH, adsorbent dose, initial concentration, and temperature, with equilibrium data modeled through Langmuir, Freundlich, Temkin, and the statistically grounded Advanced Monolayer Model (AMM); kinetics were assessed using pseudo-first/second-order and Elovich models. Maximum Langmuir adsorption capacities reached 204.75 mg g−1 for As(V) and 499.72 mg g−1 for CR simultaneously at pH 5 and 25 °C, surpassing the majority of previously reported single-pollutant adsorbents. Elovich and pseudo-second-order kinetics confirmed chemisorption as the governing pathway for As(V) and CR, respectively, while AMM thermodynamic analysis verified spontaneous adsorption across all experimental conditions. The spent composite delivered a UOR peak current density of 184.67 mA cm−2 that is nearly twice that of the fresh material, with a reduced charge-transfer resistance of 1.19 Ω, and removal efficiency remained above 85% through three successive regeneration cycles. The bifunctional design, coupling high-capacity dual-pollutant removal with catalytic valorization of waste, positions TM-LDH/TZ as a circular-economy-aligned platform for advanced water remediation. Full article
(This article belongs to the Section Catalysis for Sustainable Energy)
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