Organic Dyes In Water Research Articles

Green Synthesis of TEMPO@DFNS-Li2MnO3 Ceramic Nanostructures and Their Application as Photocatalysts Under Visible–UV Light for Removal of Organic Dyes in Water

Green Synthesis of TEMPO@DFNS-Li2MnO3 Ceramic Nanostructures and Their Application as Photocatalysts Under Visible–UV Light for Removal of Organic Dyes in Water

Reduced graphene oxide-TiO2/sodium alginate/polyacrylamide composite hydrogel for enhanced adsorption-photocatalytic degradation of methylene blue

The discharge of dye wastewater from various industries has emerged as a critical environmental concern, necessitating the implementation of effective methods such as photocatalytic technology to mitigate organic dyes in water. Nevertheless, the poor photocatalytic activityability and low reusability of most semiconductor photocatalysts have hindered their large-scale practical application. In this paper, the reduced graphene oxide-titanium dioxide composite (rGO-TiO2) was prepared via a hydrothermal method and subsequently immobilized onto a three-dimensional structure composed of sodium alginate (SA) and polyacrylamide (PAM) through sunlight-induced polymerization and ionic cross-linking techniques, resulting in the fabrication of a novel photocatalytic composite hydrogel (rGO-TiO2/SA/PAM). The composite hydrogel was found to exhibit good photocatalytic degradation efficiency for methylene blue(MB), achieving complete removal of MB under UV light irradiation for 100 min at pH 7 when using a rGO:TiO2 ratio of 3 wt%. Additionally, the synthesis of rGO-TiO2/SA/PAM effectively harnesses solar resources through simple synthetic steps, enabling easy recovery and separation from dye wastewater (with a recovery rate of approximately after first use). In contrast, nano-TiO2 and rGO-TiO2 exhibit lower recovery rates (∼80%). Furthermore the material demonstrates enhanced selective adsorption-photocatalytic degradation of MB in acid-base dye mixtures under UV light irradiation.

Adsorptive elimination of methylene blue dye from aqueous solution by chitosan‐nSiO2 nanocomposite: Adsorption and desorption study, scale‐up design, statistical, and genetic algorithm modeling

AbstractHeavy metals and organic dyes in water in concentrations exceeding the tolerable limit are unsafe for aquatic life and humans. Chitosan nanocomposites show a potential adsorption capacity to organic dyes. The present study encompasses the preparation of chitosan‐nSiO2 nanocomposites (CSNC) with different weight ratios of chitosan to nSiO2 and its application in the methylene blue (MB) dye adsorption. The nanocomposites were characterized with the help of SEM, BET, FTIR, XRD, and TGA. The adsorption experimentation was executed in batch mode under varying experimental conditions. Several isotherm and kinetic models were analyzed with the experimental data, and thermodynamic conditions required for adsorption were also determined. Maximum Langmuir adsorption capacities (qL) of the adsorbents for MB varied in the range of 21.32–31.34 mg g−1. The pseudo‐second‐order model was the best‐fitted kinetic model concerning all three adsorbents. The statistical modeling using multiple polynomial regression (MPR) for CWS CSNC1‐1 and CSNC2‐1 yielded the equations with R‐square ranging from 0.984 to 0.996. For GA modeling, it is more than 0.999. So, the efficient employment of statistical modeling, and genetic algorithms has also been achieved.

Nanofibers of chitosan-polycaprolactone blends as active support for photocatalytic nanoparticles: Outstanding role of chitosan in the degradation of an organic dye in water

Hybrid nanofibers of a chitosan-polycaprolactone blend containing titanium dioxide nanoparticles TiO2NPs, were prepared through electrospinning to study their adsorption and photocatalytic degradation capabilities of the model organic water pollutants, rhodamine B, RhB. To obtain uniform and bead-free nanofibers, an optimization of the electrospinning parameters was performed. The optimization was carried out by systematically adjusting the solution conditions (solvent, concentration, and polymer ratio) and instrumental parameters (voltage, needle tip-collector distance, and flow). The obtained materials were characterized by FT-IR, TGA, DSC, SEM, TEM, mechanical tensile test, and water contact angle. The photoactivity was investigated using a batch-type system by following UV–Vis absorbance and fluorescence of RhB.TiO2NPs were incorporated ex-situ into the polymer matrix, contributing to good mechanical properties and higher hydrophilicity of the material. The results showed that the presence of chitosan in the nanofibers significantly increased the adsorption of RhB and its photocatalytic degradation by TiO2NPs (5, 55 and 80 % of RhB degradation with NFs of PCL, TiO2/PCL and TiO2/CS-PCL, after 30 h of light irradiation, respectively), evidencing a synergistic effect between them. The results are attributed to an attraction of RhB by chitosan to the vicinity of TiO2NPs, favouring initial adsorption and degradation, phenomenon known as “bait-and-hook-and-destruct” effect.

Nata de coco as an abundant bacterial cellulose resource to prepare aerogels for the removal of organic dyes in water

A hydrogel-like product of the bacterial fermentation of coconut water is well-known as nata de coco which contains low-cost and high-quality bacterial cellulose. In this work, nata de coco was applied for the facile preparation of lightweight bacterial cellulose aerogels upon grinding and subsequent freeze-drying. The obtained aerogels possessed the three-dimensional network containing bacterial cellulose fibers with high crystallinity and porosity. The experimental results proved the high affinity of the bacterial cellulose network to the cationic dyes with adsorption capacities from 25 to 81 mg/g. By contrast, the aerogel was inefficient with most of the tested anionic dyes except for congo red which afforded a significant adsorption capacity of 145 mg/g. The promising results were obtained without any further chemical modification being applied to the bacterial cellulose aerogels and notably comparable to the previous performances of biomass-based sorbents. This biomaterial showed a great potential in environmentally-friendly treating organic dyes-polluted wastewater.

Bio-recovery of CuS nanoparticles from the treatment of acid mine drainage with potential photocatalytic and antibacterial applications

In the present work, CuS nanoparticles were biorecovered from a real acid mine drainage (AMD) and its photocatalytic and antibacterial activities were studied. CuS were formed by delivering biogenic H2S produced by a continuous sulfidogenic bioreactor to an off-line vessel containing the AMD. The main physico-chemical properties of CuS nanoparticles were analyzed by UV–vis spectroscopy, TEM, FE-SEM, XRD and XPS. Moreover, its photocatalytic activity on the photodegradation of organic dyes in water and its antibacterial activity against several bacterial strains were studied and compared with CuS nanoparticles synthetized from a CuSO4 aqueous solution based on the same synthesis method. CuS nanoparticles from the real AMD showed similar physico-chemical properties and photocatalytic and antibacterial activities in comparison to CuS nanoparticles formed with the copper solutions. These results open the way to recover valorous CuS nanoparticles from AMD with potential industrial applications using a metal bioremediation process based on sulfidogenic bioreactors.

Weak dehydration enhances the adsorption capacity of boehmite for anionic dyes

Various works have been conducted for enhancing anionic dye removal onto boehmite. However, the influence of the water content in boehmite on its adsorption performance has not been investigated to date. Therefore, we explored the impact of the level of dehydration of boehmite on its structural water content and anionic dye removal. Adsorbents were prepared via sol-gel method, followed by heat treatment under temperature range of 70–200 °C, covering weak and strong dehydration, and were tested for adsorption of methyl orange and Congo red. Surface properties of adsorbents including functional groups, crystallinity, surface area, porosity, and zeta potential were investigated. Strong dehydration yielded crystalline structures with high surface area (110–140 m2/g) and low water content, ineffective for anionic dye removal. Meanwhile, weakly dehydrated samples holding a low surface area (nonporous – 5.05 m2/g) and high water content exhibited excellent adsorption of the tested anionic dyes. The amorphous boehmite prepared at 100 °C showed the highest adsorption capacity of methyl orange (320 mg/m2, 900 mg/g), while the nonporous amorphous sample prepared at 200 °C demonstrated the highest adsorption capability for Congo red (527 mg/g). Through analyzing the adsorption results, chemical structure of the dyes, and surface characteristics of the adsorbents, we identified that the adsorption mechanism is influenced by electrostatic forces or hydrogen bonding. These findings present a promising application of weak dehydration and its resulting boehmite for effective adsorption of organic dyes in water.

ZnO/Graphene Oxide on Halloysite Nanotubes as a Superabsorbent Nanocomposite Photocatalyst for the Degradation of Organic Dyes

Using renewable photocatalysts for pollutant degradation represents a promising approach to addressing environmental water challenges by harnessing solar energy without additional energy consumption. However, for the practical use of photocatalysts, it is necessary to improve catalyst efficiency, considering cost and biocompatibility. In this study, we developed a new superabsorbent photocatalyst for the degradation of organic dyes in water. Our photocatalyst comprises halloysite nanotubes (HNTs) with a large outer diameter and Si-O and Al-O groups on the outer and inner surfaces, respectively; graphene oxide (GO) possessing numerous sp2 bonds and light-conductive properties; and ZnO, which can degrade organic molecules via a photon source. By exploiting the superabsorbent properties of GOs for organic dyes and stabilizing ZnO nanoparticles on HNTs to inhibit aggregation, our photocatalysts demonstrated significantly improved degradability compared to ZnO nanoparticles alone and combinations of ZnO with HNTs or GO. The structural characteristics of the nanocomposites were characterized using SEM, EDX, Raman spectroscopy, and XRD. Their enhanced photocatalytic activity was demonstrated by the degradation of rhodamine b in water, showing 95% photodegradation under UV illumination for 60 min, while the ZnO nanoparticles showed only 56% dye degradation under the same condition. Additionally, the degradation rate was enhanced by four times. Furthermore, the catalysts maintained their initial activity with no significant loss after four uses, showing their potential for practical implementation in the mass purification of wastewater.

Study on the synthesis of g-C<sub>3</sub>N<sub>4</sub>/TCPP porphyrin composite and its application as photocatalyst for treatmen of MB organic dye in water

The g-C3N4/TCPP porphyrin composite was successfully fabricated via self-assembly approach. The composite was characterized using UV-Vis spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and FT-IR techniques. The results showed good integration of the porphyrin nanofibers with diameter of less than 100 nm and the length of several micrometer on the g-C3N4’s surface. The prepared g-C3N4/TCPP porphyrin composite showed high photocatalytic efficiency for MB degradation under sunlight irradiation, with MB removal efficiency > 90% after 100 min of simulated sunlight irrdadiation. The g-C3N4/TCPP porphyrin composite could be used as a promising photocatalyst for the treatment of other organic dyes in water.

Synthesis of Calcium Peroxide Nanoparticles with Starch as a Stabilizer for the Degradation of Organic Dye in an Aqueous Solution

One of the most significant environmental problems in the world is the massive release of dye wastewater from the dyeing industry. Therefore, the treatment of dyes effluents has received significant attention from researchers in recent years. Calcium peroxide (CP) from the group of alkaline earth metal peroxides acts as an oxidizing agent for the degradation of organic dyes in water. It is known that the commercially available CP has a relatively large particle size, which makes the reaction rate for pollution degradation relatively slow. Therefore, in this study, starch, a non-toxic, biodegradable and biocompatible biopolymer, was used as a stabilizer for synthesizing calcium peroxide nanoparticles (Starch@CPnps). The Starch@CPnps were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET), dynamic light scattering (DLS), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). The degradation of organic dyes, methylene blue (MB), using Starch@CPnps as a novel oxidant was studied using three different parameters: initial pH of the MB solution, calcium peroxide initial dosage and contact time. The degradation of the MB dye was carried out via a Fenton reaction, and the degradation efficiency of Starch@CPnps was successfully achieved up to 99%. This study shows that the potential application of starch as a stabilizer can reduce the size of the nanoparticles as it prevents the agglomeration of the nanoparticles during synthesis.

Sulfidogenic Bioreactor-Mediated Formation of ZnS Nanoparticles with Antimicrobial and Photocatalytic Activity

The use of sulfidogenic bioreactors is a biotechnology trend to recover valuable metals such as copper and zinc as sulfide biominerals from mine-impacted waters. In the present work, ZnS nanoparticles were produced using "green" H2S gas generated by a sulfidogenic bioreactor. ZnS nanoparticles were physico-chemically characterized by UV-vis and fluorescence spectroscopy, TEM, XRD and XPS. The experimental results showed spherical-like shape nanoparticles with principal zinc-blende crystalline structure, a semiconductor character with an optical band gap around 3.73 eV, and fluorescence emission in the UV-visible range. In addition, the photocatalytic activity on the degradation of organic dyes in water, as well as bactericidal properties against several bacterial strains, were studied. ZnS nanoparticles were able to degrade methylene blue and rhodamine in water under UV radiation, and also showed high antibacterial activity against different bacterial strains including Escherichia coli and Staphylococcus aureus. The results open the way to obtain valorous ZnS nanoparticles from the use of dissimilatory reduction of sulfate using a sulfidogenic bioreactor.

Bifunctional Supertetrahedral Chalcogenolate Cluster-Based Assembly Materials Constructed by a Photoactive Ligand.

The assembly of supertetrahedral chalcogenolate clusters (SCCs) and multifunctional organic linkers could lead to the formation of tunable structures and synergistic properties. Two SCC-based assembled materials (SCCAM-1 and -2) constructed by a triangular chromophore ligand, tris(4-pyridylphenyl)amine, were successfully synthesized and characterized. The SCCAMs demonstrate unusually long-lived afterglow at low temperatures (83 K) and efficient activities for the photocatalytic degradation of organic dye in water.

In situ generation of H2O2 over Ce-doped BaTiO3 catalysts for enhanced piezo-photocatalytic degradation of pollutants in aqueous solution

Piezo-photocatalytic technique is a new-emerging strategy to promote the separation of electron-hole pairs and thus enhance catalytic performance. Here, a series of Ce-doped barium titanate (BTCe-x) composites were prepared by sol-gel/hydrothermal method, the applied in the removal of organic dyes in water under the piezo-photocatalytic effect. In this study, the BTCe-0.025 exhibit superior catalytic performance for different types of organic dyes (Acid Fuchsin (AF), Crystal Violet (CV), Congo Red (CR), Acid Chrome Blue K (ABK), Methylene Blue (MB), and Methyl Orange (MO)). For example, the degradation efficiency of AF, CR, and ABK is 99.1 %, 99.4 %, and 88.6 %, respectively, at a concentration of 10 mg/L for 10 min under visible light and ultrasonic vibration. This is attributed to the narrowing of the band gap and the negatively shifted conduction band under Ce doping, improving the utilization of visible light and enhancing the ability of O2 to reduce to ·O2–. Additionally, O2 in an aqueous solution generates H2O2 in situ and can react with Fe(II) to generate strongly oxidizing·OH radicals, which can greatly enhance the oxidation ability of organic pollutants. This work provides a new and efficient strategy for developing high-efficiency piezo-photocatalyst materials in removing pollutants from wastewater.

Synthesis of Nano CdZnS/SnS2/SnO2 Heterojunction for Photocatalytic Degradation of Rhodamine B

AbstractThe accumulation of organic dyes in water and their consequent detrimental effect to ecological environment have attracted worldwide extensive attention. It is urgent to develop rapid and efficient method to degrade organic dyes. In this paper, an efficient CdZnS/SnS2/SnO2 heterojunction is successfully prepared by sequential template approach and hydrothermal method. Comparison with CdZnS and SnS2/SnO2, the heterogeneous structure of CdZnS/SnS2/SnO2 greatly enhances the photocatalytic degradation ability of Rhodamine B (RhB). The apparent reaction rate of CdZnS/SnS2/SnO2 heterostructure is around 12.71 and 16.69 times higher than those of SnS2/SnO2 and CdZnS, respectively, reaching 0.0267 min−1. After CdZnS/SnS2/SnO2 photocatalysis of RhB solution, the BOD/COD ratio increases from 0.168 to 0.725, indicating that the biodegradability is greatly improved. It has been proved that ⋅OH, ⋅O2−, h+ and e− are the main active species involved in the degradation process. In addition, the CdZnS/SnS2/SnO2 exhibits good stability and reusability, with little change in the photocatalytic activity after five cycles. Its superior removal activity is mainly due to the formation of heterojunction improved light harvesting and enhanced separation efficiency. This work provides a new insight for photocatalytic degradation of organic dye wastewater by solar light.

A New 2D Metal-Organic Framework for Photocatalytic Degradation of Organic Dyes in Water

Two-dimensional (2D) metal-organic frameworks (MOFs) are fascinating photocatalytic materials because of their unique physical and catalytic properties. Herein, we report a new (E)-4-(3-carboxyacrylamido) benzoic acid [ABA–MA] ligand synthesized under facile conditions. This ABA–MA ligand is further utilized to synthesize a copper-based 2D MOF via the solvothermal process. The resulting 2D MOF is characterized for morphology and electronic structural analysis using advanced techniques, such as proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and scanning electron microscopy. Furthermore, 2D MOF is employed as a photocatalyst for degrading organic dyes, demonstrating the degradation/reduction of methylene blue (MeBl) dye with excellent catalytic/photodegradation activity in the absence of any photosensitizer or cocatalyst. The apparent rate constant (kap) values for the catalytic degradation/reduction of MeBl on the Cu(II)–[ABA-MA] MOF are reported to be 0.0093 min−1, 0.0187 min−1, and 0.2539 min−1 under different conditions of sunlight and NaBH4. The kinetics and stability evaluations reveal the noteworthy photocatalytic potential of the Cu(II)–[ABA–MA] MOF for wastewater treatment. This work offers new insights into the fabrication of new MOFs for highly versatile photocatalytic applications.

Synthesis of a novel ternary BiOBr/g-C3N4/Ti3C2Tx hybrid for effectively removing tetracycline hydrochloride and rhodamine B

The photodegradation of antibiotics and organic dyes in water in the current environment has attracted attention. However, its practical value in the river is poor because the efficient and recyclable photocatalysts are insufficient. Therefore, a novel ternary BiOBr/g-C3N4/Ti3C2Tx (BCT-x) hybrids were efficaciously prepared via the in-situ construction method for improving photodegradation of Tetracycline Hydrochloride (TC-HCl) and Rhodamine B (RhB) under Xenon lamp. The characterization results clarified that the combination of BiOBr and g-C3N4 could expand light absorption region. Meanwhile, the hybrids possessed accelerated carrier separation and migration ability due to the introduction of co-catalyst Ti3C2Tx with efficient electrical conductivity. The BCT-5 exhibited vintage photocatalytic activity for TC-HCl (97%, 60 min) and RhB (98%, 50 min). Photo-generated holes (h+) and superoxide radicals (•O2−) were the main active species. The Liquid Chromatography and Mass Spectrometry (LC-MS) analysis showed that TC-HCl could be photodegraded by BCT-5 into smaller molecular weight and non-toxic substances. A reasonable photocatalytic mechanism on BiOBr/g-C3N4/Ti3C2Tx was brought up. This study provides guidance for advancing the application of photocatalytic technology in water pollutant degradation.

Ultrasonic spray pyrolysis synthesis of TiO2/Al2O3 microspheres with enhanced removal efficiency towards toxic industrial dyes.

Developing low-cost and highly effective adsorbent materials to decolorate wastewater is still challenging in the industry. In this study, TiO2-modified Al2O3 microspheres with different TiO2 contents were produced by spray pyrolysis, which is rapid and easy to scale up. Results reveal that the modification of γ-Al2O3 with TiO2 reduced the crystallite size of Al2O3 and generated more active sites in the composite sample. The as-synthesized Al2O3-TiO2 microspheres were applied to remove anionic methyl orange (MO) and cationic rhodamine B (RB) dyes in an aqueous solution using batch and continuous flow column sorption processes. Results show that the Al2O3 microspheres modified with 15 wt% of TiO2 exhibited the maximum adsorbing capacity of ∼41.15 mg g-1 and ∼32.28 mg g-1 for MO and RB, respectively, exceeding the bare γ-Al2O3 and TiO2. The impact of environmental complexities on the material's reactivity for the organic pollutants was further delineated by adjusting the pH and adding coexisting ions. At pH ∼5.5, the TiO2/Al2O3 microspheres showed higher sorption selectivity towards MO. In the continuous flow column removal, the TiO2/Al2O3 microspheres achieved sorption capacities of ∼31 mg g-1 and ∼19 mg g-1 until the breakthrough point for MO and RB, respectively. The findings reveal that TiO2-modified Al2O3 microspheres were rapidly prepared by spray pyrolysis, and they effectively treated organic dyes in water in batch and continuous flow removal processes.

Photocatalytic Concrete Developed by Short Seedless Hydrothermal Method for Water Purification

Stormwater runoff management and treatment are significant topics for designing a sustainable city. Therefore, photocatalytic, permeable, and removable concrete is a promising solution to reduce pollution through leaching with permeable and scalable road. The objective of this work was to develop cost-effective and greener photocatalytic concretes that can be easily scaled-up, and to demonstrate their photocatalytic activities. To achieve this, seedless hydrothermal ZnO nanostructures (NSs) in 2 h were employed to functionalize a concrete surface by a soft functionalization process, avoiding overconsumption of energy and chemical products. In this work, two different concretes were studied and used for the degradation of organic dye in water. The results demonstrated the universality of the proposed functionalization process by showing similar gap values, ZnO NSs morphologies, and XRD pattern, compared to the concrete functionalized by the traditional two-step hydrothermal synthesis. The XRD results certified the presence of the ZnO Würtzite phase on the concrete surface. The synthesis feasibility was attributed to the basic pH and O− groups’ presence in concrete. Then, their photocatalytic efficiency was proved for organic dye removal in water. An almost total degradation was recorded after 5 h under artificial solar light, even after several uses, demonstrating a similar efficiency to the photocatalytic concrete functionalized by the traditional two-step synthesis.

Power‐Free Electrochemical Degradation of Tetracyclines Contributed by Flexible Magnetoelectric Flag Wind Generators

AbstractElectrochemical degradation is a commonly used strategy to remove organic contaminations in water. However, in some remote areas where electricity is insufficient, electrochemical degradation may become ineffective due to the absence of a power supply. Here, a unique self‐powered electrochemical system (SPES) is proposed to accomplish the power‐free degradation of tetracyclines (TCs) and organic dyes in water with the assistance of flexible magnetoelectric flag generators (MFGs). These MFGs convert wind energy into electricity. Under a wind speed of 6.3 m s−1, a 22 × 30 cm2 MFG yields a peak open‐circuit voltage of 3.5 V and an ultra‐high peak short‐circuit current of ≈13 mA. A suchlike MFG charges large capacitors of 5 F to 1 V in 184 min. Powered by a series of MFGs, 5 ppm of tetracycline hydrochloride (TCH) or organic dyes in water are totally degraded with SPES in only 10 min. Moreover, the MFG is fully foldable and portable, which is well‐suited for the migrating feature of the nomadic people in remote areas. The study opens up a new solution to the persistent problem of TCs contamination in natural waters in some remote regions where electricity is lacking.

Preparation of Z‐scheme spherical BiOI/Fe2O3/BiOBr for water pollution treatment

Tetracycline drugs play a very important role in medical production and animal husbandry, but their residues are difficult to be naturally degraded in water environment, which causes a certain threat to human health. In this paper, the BiOI/Fe2O3/BiOBr composite photocatalytic material was successfully prepared to degrade tetracycline. The morphology and structure of the material were characterized by XRD, SEM, TEM, EDX, FT‐IR, UV–vis DRS, PL, EIS, photocurrent response, BET, and TOC, and the effect of the material on the degradation of tetracycline under simulated sunlight was investigated. The results showed that when the mass of BiOI/Fe2O3 and BiOBr was 1:1, reacted at 160°C for 16 h, BiOI/Fe2O3/BiOBr has the best degradation effect on tetracycline. The degradation rate of tetracycline can reach 85% in 180 min, and its kinetic rate constant is 2.16 and 1.8 times that of single BiOI and BiOI/Fe2O3, respectively. Based on the capture experiment of active substances, a Z‐scheme catalytic mechanism is proposed to analyze the degradation process of tetracycline, and BiOI/Fe2O3/BiOBr also showed a certain photocatalytic activity to other antibiotics and organic dyes in water.