Oxidation Of Dye Research Articles

Correction to: Efficient electrochemical oxidation of reactive dye using a novel Ti/nanoZnO–CuO anode: electrode characterization, modeling, and operational parameters optimization

In the current study, electrochemical removal of reactive orange 7 (RO7) dye in aqueous solution was examined over a novel Ti/nanoZnO–CuO electrode prepared through electrophoretic deposition technique. Surface morphology, crystal structure, and elemental investigation of the prepared electrode were done by Field emission scanning electron microscopy, X-ray energy dispersive spectrometry, and X-ray diffraction analysis, which confirmed the presence of CuO nanoparticles along with ZnO nanoparticles in uniform coated layer. Besides, some electrochemical properties of the Ti/nanoZnO–CuO electrode were evaluated applying linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy analysis. Based on these analyses, the Ti/nanoZnO–CuO electrode behaves as a non-active electrode as well as it possessed smaller charge-transfer resistance and higher current density than Ti and Ti/nanoZnO electrodes. Further, chrono-amperometry along with chrono-potentiometry tests were conducted to assess the novel electrode stability and service lifetime. Obtained results indicated the presence of CuO nanoparticles conducive to the enhancement of stability and conductivity properties. To evaluate the prepared electrode performance and optimize the removal process, four independent variables of pH, electrolyte concentration, current, and reaction time as inputs along with RO7 removal efficiency as response function in central composite design were investigated. Under optimal conditions, the RO7 removal efficiency and chemical oxygen demand of 99.16% and 66.66% were obtained after 60 min for Ti/nanoZnO–CuO electrode. According to the obtained results, Ti/nanoZnO–CuO electrode can be used in the electrochemical treatment of organic pollutants as a promising electrode.

Cu(II)-metalated Silica-based Inorganic-Organic Hybrid: Synthesis, Characterization and Its Evaluation for Dye Degradation and Oxidation of Organic Substrates

Cu(II)-metalated Silica-based Inorganic-Organic Hybrid: Synthesis, Characterization and Its Evaluation for Dye Degradation and Oxidation of Organic Substrates

Nanostructured spinel-type M(M = Mg, Co, Zn)Cr2O4 oxides: novel adsorbents for aqueous Congo red removal

Nanostructured spinel-type M(M = Mg, Co, Zn)Cr2O4 oxides with novel adsorbents for aqueous Congo red removal were synthesized by a polyacrylamide gel method and studied for their phase structure, microstructure, adsorption performance, and multiferroic behavior. The phase structure and purity analysis revealed that the nanostructured spinel-type M(M = Mg, Co, Zn)Cr2O4 oxides presented a spinel-type cubic structure, and the formation of a secondary phase such as Cr2O3, MgO, ZnO, or Co3O4 was not observed. The microstructure characterization confirmed that the spinel-type MCr2O4 oxides grew from fine spherical particles to large rhomboid particles. Adsorption experiments of spinel-type MCr2O4 oxides for adsorption of Congo red dye were fitted well with the pseudo-second-order kinetics. The adsorption capacity of the ZnCr2O4 oxide (44.038 mg/g, pH 7, temperature 28 °C, initial dye concentration 30 mg/L) was found to be higher than that of MgCr2O4 oxide (43.592 mg/g, pH 7, temperature 28 °C) and CoCr2O4 oxide (28.718 mg/g, pH 7, temperature 28 °C). The effects of initial adsorbent concentration, initial dye concentration, pH, and temperature between the ZnCr2O4 oxide and Congo red dye at which optimal removal occurs, were performed. The thermodynamic studies confirmed that a high temperature favors the adsorption of Congo red dye onto ZnCr2O4 oxide studied. The nanostructured spinel-type M(M = Mg, Co, Zn)Cr2O4 oxides that exhibited high adsorption performance for adsorption of Congo red dye can be ascribed to the synergistic effect of electrostatic interaction, pore filling, and ion exchange. The present work suggested that the nanostructured spinel-type M(M = Mg, Co, Zn)Cr2O4 oxides have excellent adsorption performance and multiferroic behavior, which shows potential applications for removal of the Congo red dye from wastewater, magnetic memory recording media, magnetic sensor, energy collection and conversion device, and read/write memory.

Efficient electrochemical oxidation of reactive dye using a novel Ti/nanoZnO–CuO anode: electrode characterization, modeling, and operational parameters optimization

Efficient electrochemical oxidation of reactive dye using a novel Ti/nanoZnO–CuO anode: electrode characterization, modeling, and operational parameters optimization

Optical and dielectric properties of polyaniline-ZnO nanoparticles for enhancing photodegradation of organic pollutants

Over the last decade, there is a growing interest in developing visible light active polymer conductors. Herein, the visible-light-driven photocatalytic activity of Pani-ZnO nanoparticles were fabricated by in situ polymerization. The adsorption and photo-electrochemical properties were evaluated for the photodegradation of two dyes namely Orange G (OG) and methyl Orange (MO) at different pHs. The synthetized polymers were characterized by scanning electron microcrospy (SEM) and diffuse reflectance. To provide further insights into the synergistic effect, the optical and dielectric constants allow to calculate the refractive index, optical conductivity, extinction coefficient (k), dissipation factor (tan δ) and relaxation time (τ). These properties were exploited to study the charge transfer and electronic properties of Pani-ZnO nanoparticles. The as-fabricated samples showed improved photoactivity compared to Pani alone. The optimal ZnONPs ratio (30 wt%. Pani-ZnO 30%) gives the higher degradation under sunlight, and the hetero-system exhibits high stability and recyclability for the dye oxidation. The current research offers a new understanding of designing high performance of Pani based photocatalysts for the water treatment.

Synthesis and Characterization of Co/Al-PILCs for the Oxidation of an Azo Dye Using the Bicarbonate-Activated Hydrogen Peroxide System

Synthesis and Characterization of Co/Al-PILCs for the Oxidation of an Azo Dye Using the Bicarbonate-Activated Hydrogen Peroxide System

Cryptomelane nanorods coated with Ni ion doped Birnessite polymorphs as bifunctional efficient catalyst for the oxygen evolution reaction and degradation of organic contaminants

AbstractThe intelligent design or development of dual‐functional catalysts using non‐precious metals especially for the oxygen evolution reaction (OER) in sustainable energy systems and degradation of organic pollutants is still a difficult and a significant challenge. Furthermore, the development of these catalysts is of great importance in terms of energy security and solution of the environmental problems. To meet these requirements, herein, we describe the synthesis of a Ni‐ion doped Birnessite@Cryptomelane (Ni2+/B@Cr) hybrid structure as a bifunctional efficient catalyst for the OER in neutral media and degradation of dye pollutants. The Ni2+/B@Cr catalyst exhibited a sharp onset potential at 390 mV (vs. RHE) and achieved a current density of 1 mA cm−2 at a low ƞ of 430 mV with a Tafel slope of ~96 mV dec−1. The results of electrochemical impedance spectroscopy (EIS) studies indicated that Ni intercalation into birnessite layer and heterostructure of the hybrid electrocatalyst Ni2+/B@Cr increased the conductivity by lowering the resistance of charge transfer (Rct = 4.82 Ω) and oxygen evolution processes (ROER = 4.13 Ω). The durability assay identified Ni2+/B@Cr as stable electrocatalyst with 10% loss of activity after long‐term stability tests (10 h, under 500‐mV overpotential). In addition, the Ni2+/B@Cr achieved high (86.67 s−1 g−1) and rapid (173 s) catalytic performance for the reduction of methylene blue (MB). Overall, this paper presents a low‐cost production strategy for the design of highly efficient bifunctional catalysts, offering boosted electrocatalytic and degradation performance for water oxidation and organic dye contamination, respectively.

A simple and cost-effective new synthesis method of copper molybdate CuMoO4 nanoparticles and their catalytic performance

Nanopowders of copper molybdate, α-CuMoO 4 , were prepared through calcination of an oxalate complex in static air at 550 °C. The oxalate complex was investigated by Fourier transform infrared spectroscopy and thermal gravimetric analysis. The as-prepared copper molybdate was characterized by X-ray powder diffraction and the Brunauer–Emmett–Teller technique. Its catalytic effectiveness was verified by the oxidation reaction of methylene blue (MB) with hydrogen peroxide (H 2 O 2 ) and by the reduction reaction of para-, meta-, and ortho-nitrophenol. The prepared copper molybdate exhibited exceptionally high catalytic performance of the oxidation of methylene blue dye and of the reduction reaction of the three isomers of nitrophenol to the three corresponding aminophenol isomers. The evolution of the catalytic activity was controlled by utilizing UV-Vis absorption spectroscopy. • Copper molybdate, CuMoO 4 , nanoparticles were prepared successfully via a new and simple process, without resorting to any solvent at relatively low temperature. • CuMoO 4 nanocatalyst exhibits high efficiency for the reduction reaction of the three isomers of nitrophenol to the three corresponding aminophenol isomers. • The copper molybdate exhibits exceptionally high catalytic performance of the oxidation of methylene blue dye.

Enhancement in photostability of betalain dye from basella Alba fruits using zinc oxide nanoparticles

Recently environmental pollution due to industrial effluents is a major concern for researchers, so the development of natural dyes is widely accepted due to their low cost, biodegradability, low toxicity, and non -carcinogenic nature and also replaces existing hazardous chemicals in industries. Many plants and fruit extracts can be used as natural dyes, but their efficiency depends on photostability and photo degradation activity. Herein reported extraction of natural dye fromBasella Alba fruit using different solvents and photo stability was investigated under UV and visible light. To enhance the stability of extracted pure dye, zinc oxide nanoparticles were added and it acts as an excellent photostabilizer that shows better performance over betalain dye. UV visible spectrum of pure dye shows an absorbance peak of 480 nm and functional groups of both dye and zinc oxide were identified by FTIR spectrum. The structure and surface morphology of the synthesized nanoparticle was confirmed by UV–Visible, XRD, SEM-EDAX and TEM analysis. The crystalline structure of zinc oxide was confirmed by XRD and composition was analyzed by EDAX studies. The wurtzite type structure of zinc nanoparticle was confirmed by XRD. The external morphology of prepared zinc oxide nanoparticles is captured using FESEM. The HRTEM and SAED images are confirmed the crystalline structure of the synthesized material. The photostability and photodegradation studies were performed under UV light and at various temperatures like 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C. These results clearly show a piece of evidence for the usage of nanoparticles for enhancing photostability of natural dyes.

Graphene/fluorescein dye-based sensor for detecting As(III) in drinking water

A complex of reduced graphene oxide (rGO) and fluorescein (FL) dye nanoparticles of size between 50 and 100 nm has been prepared and its sensing performance for detection of As(III) in drinking water has been reported. When As(III) binds to the rGO–FL nanoparticles the relative quenching of fluorescence was increased with increase in As(III) concentration thus provide two linear calibration ranges (0–4.0 mmol L−1 and 4.0–10 mmol L−1). The fluorescence quenching mechanism was investigated by using time-resolved fluorescence spectroscopy and molecular modeling. The detection limit of this sensor has been determined as equal to 0.96 µg L−1 which is about 10 times lower than the WHO stipulated standard for As(III) in drinking water (10 µg L−1). The analytical performance and potential application of the nanosensor was compared to commercial field kits used in arsenic monitoring. The sensor proposed in this study is fast, sensitive and accurate for detection of As(III) in drinking water and environmental samples.

Identification of a pathway for electron uptake in Shewanella oneidensis

Extracellular electron transfer (EET) could enable electron uptake into microbial metabolism for the synthesis of complex, energy dense organic molecules from CO2 and renewable electricity1–6. Theoretically EET could do this with an efficiency comparable to H2-oxidation7,8 but without the need for a volatile intermediate and the problems it causes for scale up9. However, significant gaps remain in understanding the mechanism and genetics of electron uptake. For example, studies of electron uptake in electroactive microbes have shown a role for the Mtr EET complex in the electroactive microbe Shewanella oneidensis MR-110–14, though there is substantial variation in the magnitude of effect deletion of these genes has depending on the terminal electron acceptor used. This speaks to the potential for previously uncharacterized and/or differentially utilized genes involved in electron uptake. To address this, we screened gene disruption mutants for 3667 genes, representing ≈99% of all nonessential genes, from the S. oneidensis whole genome knockout collection using a redox dye oxidation assay. Confirmation of electron uptake using electrochemical testing allowed us to identify five genes from S. oneidensis that are indispensable for electron uptake from a cathode. Knockout of each gene eliminates extracellular electron uptake, yet in four of the five cases produces no significant defect in electron donation to an anode. This result highlights both distinct electron uptake components and an electronic connection between aerobic and anaerobic electron transport chains that allow electrons from the reversible EET machinery to be coupled to different respiratory processes in S. oneidensis. Homologs to these genes across many different genera suggesting that electron uptake by EET coupled to respiration could be widespread. These gene discoveries provide a foundation for: studying this phenotype in exotic metal-oxidizing microbes, genetic optimization of electron uptake in S. oneidensis; and genetically engineering electron uptake into a highly tractable host like E. coli to complement recent advances in synthetic CO2 fixation15.

Electrochemical and photocatalytic studies of Ta3N5-TaON-PEDOT-PANI nanohybrids

The present study deals with the synthesis, characterization, and testing of tantalum nitride- tantalum oxynitride (Ta3N5-TaON) coupled organic polymers (poly (3,4-ethylene dioxythiophene)-polyaniline; PEDOT-PANI) for the electrochemical oxidation and dye degradation applications. The ammonolysis followed by chemical oxidation was employed for the formation of Ta3N5-TaON-PEDOT-PANI nanohybrids, and instrumental techniques such as powder XRD, XPS, FESEM, HR TEM, and UV–Vis analysis were used for the investigation of physicochemical properties. Further, the efficiency of formed nanohybrids was evaluated by taking the active electrocatalytic behavior towards mebendazole (MBZ) oxidation and photocatalytic dye (methylene blue and methyl red) degradations under UV–Visible light illumination. From the analysis of the results, the Ta3N5-TaON-PEDOT-PANI nanohybrids showed excellent activity and stability towards MBZ oxidation and photocatalytic dye degradation, i.e., the highest dye degradation efficiency of > 97% was obtained. Also, the MBZ degradation efficiency was continued for>500 min even after the test. Further from the photocatalytic results, a plausible dye degradation mechanism was proposed based on UV–Vis spectra and thereby confirming the potential catalytic oxidation and degradation behavior of Ta3N5-TaON-PEDOT-PANI nanohybrids.

Hard-NaCl template-regulated LiCoO2 catalyst with enhanced activity for aqueous and gaseous organics elimination

Developing new and effective catalytic materials is of significant importance to the catalytic oxidation of multiphase organic pollutants. In the present work, lithium cobalt oxide (LiCoO2) was synthesized and modified via hard-NaCl template regulation for the oxidative elimination of organic dye, e.g. rhodamine B (RhB), and VOCs, e.g. benzene. Compared with the pristine sample, a medium-level NaCl addition offered a much more advanced reactivity towards RhB oxidation, with the elimination percentage rising from 31% to 60% after 20-min reaction for 50 mL 5 mg/L RhB and 4 g/L catalyst. As to benzene oxidation, the above NaCl-assisted catalyst manifested a giant step forward from the inertness of the unmodified sample, with 82%-86% of the ∼460 ppm inlet benzene being removed by the NaCl-LiCoO2 catalyst at 350 °C and 120 L/g/h in contrast to the 5% removal efficiency of the pristine sample. Characterization studies confirmed the fully developed mesoporous structure after NaCl removal, which facilitated the reactant diffusion as well as the accessibility of the catalytical sites, and the strengthened oxidativity of the NaCl-modified sample was ensured by its large number of surface adsorbed oxygen species. Besides, the C6H6-TPSR measurements gave a direct experimental evidence to the high activity of the oxygen species induced by NaCl modification. These favorable factors were all conducive to dye and VOCs oxidation.

Kinetic Evaluation of Bismarck Brown Y Azo Dye Oxidation by Fenton Processes in the Presence of Aromatic Mediators

Kinetic Evaluation of Bismarck Brown Y Azo Dye Oxidation by Fenton Processes in the Presence of Aromatic Mediators

Facile synthesis of recoverable superparamagnetic AgFeO2@Polypyrrole/SiO2 nanocomposite as an excellent catalyst for reduction and oxidation of different dyes in wastewater

AbstractFabrication of a triple‐component nanocomposite system having a unique design and unusual property combinations offers a special chance to take advantage of all components and overcome the limitations of mono nanoparticles (NPs). Novel superparamagnetic AgFeO2@polypyrrole/SiO2 (AgFeO2@PPy/SiO2) triple‐component nanocomposite was synthesized in facile three‐step method using (i) coprecipitation, (ii) in situ chemical oxidative polymerization, and (iii) Stöber process. The structure and morphology of the nanocomposite were characterized by Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The triple nanocomposite has a drastic catalytic effect as compared with AgFeO2@PPy core–shell NPs and AgFeO2 NPs. The rate constant of chromotrope 2R reduction followed the order: AgFeO2@PPy/SiO2 (0.9209 min−1) > AgFeO2@PPy (0.2274 min−1) > AgFeO2 (0.1365 min−1). AgFeO2@PPy/SiO2 exhibited high catalytic recyclable performance towards the degradation of different kinds of dyes either by reduction (chromotrope 2R, tartrazine, and methylene blue) or by oxidation (methylene blue, aniline blue, and methyl violet 2B) from aqueous solution. The degradation percentage for the reduced dyes was 99.38%, 98.64%, and 98.17% and for the oxidized dyes was 75.84%, 99.34%, and 91.79%, respectively. Batch mode catalytic study was conducted with the nanocomposite to determine the maximum removal of tartrazine and aniline blue under different operational parameters was 99.5% and 99.34%, respectively. The recovery and reusability of the AgFeO2@PPy/SiO2 nanocomposite were studied using the reduction of tartrazine and the oxidation of aniline blue. Thirteen consecutive recovery reaction cycles were performed for the reduction process and nine cycles for the oxidation reaction. All the reactions revealed high stability and constant efficiency of the catalyst. The maximum percentages were 99.5% for the reduction and 99.34% for the oxidation of dyes. These values decreased through the cycles to 76.35% and 79.70% for reduction and oxidation, respectively. Based on the experimental results obtained, the synthesized materials proved to have a high potential for the removal of all investigated dyes from an aqueous solution.

Metalloenzyme-Inspired Ce-MOF Catalyst for Oxidative Halogenation Reactions.

The structure of UiO-66(Ce) is formed by CeO2–x defective nanoclusters connected by terephthalate ligands. The initial presence of accessible Ce3+ sites in the as-synthesized UiO-66(Ce) has been determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR)-CO analyses. Moreover, linear scan voltammetric measurements reveal a reversible Ce4+/Ce3+ interconversion within the UiO-66(Ce) material, while nanocrystalline ceria shows an irreversible voltammetric response. This suggests that terephthalic acid ligands facilitate charge transfer between subnanometric metallic nodes, explaining the higher oxidase-like activity of UiO-66(Ce) compared to nanoceria for the mild oxidation of organic dyes under aerobic conditions. Based on these results, we propose the use of Ce-based metal–organic frameworks (MOFs) as efficient catalysts for the halogenation of activated arenes, as 1,3,5-trimethoxybenzene (TMB), using oxygen as a green oxidant. Kinetic studies demonstrate that UiO-66(Ce) is at least three times more active than nanoceria under the same reaction conditions. In addition, the UiO-66(Ce) catalyst shows an excellent stability and can be reused after proper washing treatments. Finally, a general mechanism for the oxidative halogenation reaction is proposed when using Ce-MOF as a catalyst, which mimics the mechanistic pathway described for metalloenzymes. The superb control in the generation of subnanometric CeO2–x defective clusters connected by adequate organic ligands in MOFs offers exciting opportunities in the design of Ce-based redox catalysts.

Bioinspired Synthesis of Ce1-x O2:x%Cu2+ Nanobelts for CO Oxidation and Organic Dye Degradation.

Ce1–xO2:x%Cu2+ nanobelts were bioinspired, designed, and fabricated using commercial filter papers as scaffolds by adding Cu(NO3)2 in the original sol solution of CeO2 nanobelts, which display excellent catalyst properties for CO oxidation and photocatalytic activity for organic dyes. Compared with pure CeO2, CuO belts were synthesized using the same method and the corresponding Ce0.5O2:50%Cu2+ bulk materials were synthesized without filter paper as scaffolds; the synthesized Ce1–xO2:x%Cu2+ nanobelts, especially Ce0.5O2:50%Cu2+ nanobelts, can decrease the reaction temperature of CO to CO2 at 100 °C with the conversion rate of 100%, much lower than the formerly reported kinds of Ce1–xO2:x%Cu2+ catalysts. Meanwhile, the synthesized Ce1–xO2:x%Cu2+ nanobelts also display better photocatalytic activity for organic dyes. All of these results provide useful information for the potential applications of the synthesized Ce1–xO2:x%Cu2+ nanobelts in catalyst fields.

Synthesis, characterization and photo-Fenton catalytic activity of magnetic CuFe2O4/Fe2O3 materials

In this work, we proposed to immobilize Fe2O3 nanoparticles on the surface of magnetic CuFe2O4 particles by a facile impregnation – annealing method at different annealing temperatures (200, 300, 400 and 500°C) in order to create new heterogeneous photo-Fenton catalysts with enhanced catalytic performance for the oxidation of organic dyes. The influences of annealing temperatures used in the synthesis procedure on the phase composition, the morphology, the particle size and the surface functional groups of our catalysts were investigated by XRD, FE-SEM and FTIR techniques, respectively. The photo-Fenton catalytic performance was evaluated by the degradation of methylene blue under both UVA and visible light illumination in the presence of H2C2O4 as radical-producing source. According to the experimental results, Fe2O3 nanoparticles were successfully coated on CuFe2O4 surface, which successfully formed the α-Fe2O3 phase in the phase composition and also increased the Fe3+ content on the surface. As a consequence, the rate constant of photo-Fenton catalytic degradation of methylene blue over these samples were clearly improved. More especially, owing to the good magnetic property of CuFe2O4 component, our CuFe2O4/Fe2O3 samples were easy to be separated from the solution by a magnet, making them more feasible in practical applications of environmental treatment. Among our catalytic samples, the CuFe2O4/Fe2O3 sample annealed at 300°C showed the best performance with the highest rate constants under both UVA light and visible light. Its catalytic activities was found to be 6.8 times higher than CuFe2O4 under UVA light and 2.1 times higher than CuFe2O4 under visible light. However, when the annealing temperature was up to 500°C, the catalytic activity was reduced, which can be explained by the growth of particles and the stabilization of surface Fe-O bonds.

The photo-electrochemical properties of nano-sized ZnO. Application for the oxidation of dyes under sunlight

The photo-electrochemical properties of nano-sized ZnO. Application for the oxidation of dyes under sunlight

Photocatalytic oxidation of cationic dyes in single and binary solutions in presence of Zn-Cd oxides obtained from calcined LDH.

In the present paper, zinc and cadmium layered double hydroxides (ZnCd-LDH) have been prepared through co-precipitation route then calcined at different temperatures. Their photocatalytic activity was determined by photodegradation of industriel toxic dyes (rhodamine B (RB) and crystal violet (CV)) in single and binary solutions illuminated with UVA or sunlight irradiation. It was found that the highest photodiscoloration efficiency was obtained for the nanomaterial heated at 700 °C (ZnCd-700). The physicochemical properties of ZnCd-LDH and ZnCd-700 were determined by PXRD, FTIR, DSC, TG/DTG, and DRS-UV-Vis. By heating the ZnCd-LDH material, some demixtion to ZnO and CdO phases occurred, corresponding to a band gap energy value of 2.93 eV for the formed zinc oxide nanoparticles. The results revealed that with 1 g·L-1 of ZnCd-700 dose, the photodiscoloration of dyes was enhanced significantly where in single solution, it was > 83.9% and ≥ 98.0% in 90 min of UVA ilumination and sunlight, respectively. Whereas, the removal of CV and RB was > 89.7% and ≥ 98.7% in binary solution under UVA and solar irradiations, respectively. The superoxide anion radical (O2•-) was identified as the most influential reactive species for dyes degradation. In binary solution, the CV dye was photodiscolored faster than RB while in single solution, the result was the opposite. The re-use study of ZnCd-700 as photocatalyst showed a slight decrease of dyes discoloration varying between 1.4 and 7.1% from the second to the fourth use.