Azo Dye In Aqueous Solution Research Articles

Photocatalytic Degradation of Azo Dyes in Aqueous Solution Using TiO2 Doped with rGO/CdS under UV Irradiation

Photocatalytic Degradation of Azo Dyes in Aqueous Solution Using TiO2 Doped with rGO/CdS under UV Irradiation

Recycling and characterization of spent catalyst: Carmoisine dye removal from water and carbon monoxide conversion to carbon dioxide in air

This study describes the recycling of the spent Co-Mo-Al2O3 catalysts in hydro-treating diesel fuel and subsequent application in purifying wastewater and air from harmful contaminants. A sodium carbonate solution was used for the selective extraction of molybdenum with an extraction efficiency of at least 90 %. As a result, Mo-Al2O3 material was obtained. The material was characterized by EDX and low-temperature nitrogen adsorption. The materials showed high activity and stability as a Fenton-type catalyst in the oxidative degradation of the carmoisine azo dye in aqueous solution with 98 % removal in 30 min having 8.0 g/L catalyst at pH 2.0 and 60 °C temp. The carbon monoxide conversion to carbon dioxide was 100 % at 475 °C. The present work is very useful for the purification of water by removing carmoisine dye and air by converting carbon monoxide to carbon dioxide.

Fenton-Like Oxidation Systems for Destruction of Azo Dyes in Aqueous Solutions

The kinetic regularities of degradation of the azo dye methyl orange (MO) in photoinitiated oxidizing systems have been studied using a xenon lamp (UV–Vis) as a source of quasi-solar radiation. According to the efficiency and rate of dye destruction, the considered oxidizing systems can be arranged in the following series: {UV–Vis} {UV–Vis/S2O2-8} {S2O2-8/Fe0} {UV–Vis/S2O2-8/Fe0} {UV–Vis/S2O2-8/Fe2+}. It has been established that in photoinitiated Fenton-like oxidizing systems there is not only complete conversion of MO but also its deep mineralization in aqueous solution; a decrease in the content of total organic carbon reaches 60%. In this case, the specific catalytic activity of iron ions in the combined system {UV–Vis/S2O2-8/Fe0} is much higher than in {UV–Vis/S2O2-8/Fe2+}. Using inhibitors of radical reactions, it has been proved that in the combined system {UV–Vis/S2O2-8/Fe0} both hydroxyl and sulfate anion radicals take part in oxidative degradation. An inhibitory influence of anions (bicarbonates, chlorides, nitrates, and sulfates) and natural dissolved organic matter (Suwanee River 2R101N) on the process of mineralization of total organic carbon during oxidative destruction of MO in the combined system {UV–Vis/S2O/Fe0} has been found.

Fenton-Like Oxidation Systems for Destruction of Azo Dyes in Aqueous Solutions

Fenton-Like Oxidation Systems for Destruction of Azo Dyes in Aqueous Solutions

Enhanced photocatalytic performance of milkvetch-derived biochar via ZnO–Ce nanoparticle decoration for reactive blue 19 dye removal

In this research, the photocatalytic removal of reactive blue 19 (RB19) dye is investigated employing zinc oxide/cerium (ZnO@Ce) nanoparticles decorated with biochar under LED irradiation. Synthesis of ZnO@Ce nanoparticles decorated with biochar was performed utilizing the co-precipitation procedure and, then, the texture and morphology of the fabricated nanocomposite were analyzed using energy dispersive X-ray (EDX), field emission scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), and Fourier transform infrared (FTIR) spectroscopy techniques. Moreover, FE-SEM images demonstrate that ZnO–Ce nanoparticles were successfully decorated on the surface of biochar. The specific surface areas of biochar and biochar/ZnO–Ce were 519.75 and 636.52 m2/g, respectively. To achieve the maximum yield in the removal of RB19 dye, the effects of operating variables including dye concentration, LED lamp power, biochar@ZnO–Ce catalyst dose, pH and H2O2 dose were explored. Besides, the maximum percentage of RB19 dye removal was 96.47% under optimal conditions, i.e. catalyst dosage of 100 mg, H2O2 dosage of 1 mL, pH of 9, initial dye concentration of 5 ppm, LED power of 50 W, and reaction time of 140 min. Furthermore, the kinetic analysis reveals that the removal of RB19 dye follows the pseudo-first order kinetic model, with calculated values of a reaction rate constant of 0.045 min−1 and a correlation coefficient of R2 = 0.99, respectively. Moreover, the reusability and recyclability of biochar@ZnO/Ce nanocatalyst was promising over five runs, with only a 6.08% decrease in RB19 dye removal efficiency. Therefore, it can be concluded that the biochar @ZnO/Ce photocatalyst can be promisingly applied for the removal of azo dyes in aqueous solutions.

Fenton degradation of azo dyes

This review provides a general idea of Fenton oxidation of azo dyes. The effect of temperature or initial pH on the degradation process of some azo dyes in aqueous solution was investigated. From this study, it can be concluded that Fenton oxidation process is an effective method for azo dye removal.

Electrodeposited Fe on Cu foam as advanced fenton reagent for catalytic mineralization of methyl orange.

In many countries, the textile industry remains the major contributor to environmental pollution. Untreated textile dyes discharged into water negatively impact the performance of aquatic organisms and may cause a variety of serious problems to their predators. Effective wastewater treatment is a key to reducing environmental and human health risks. In this work, the Fe/Cu catalysts were used in heterogeneous Fenton’s reaction for the degradation of high concentrations of methyl orange (model azo dye) in aqueous solutions. For the first time, the catalysts were prepared onto commercial copper foams by potentiostatic electrodeposition of iron using an environmentally friendly electrolyte. The influence of electrodeposition conditions, H2O2 concentration, dye concentration and temperature on the model dye degradation was investigated. It was revealed that both the surface area and the catalyst loading play the major role in the effective dye degradation. The experimental results involving spectrophotometric measurements coupled with total carbon and nitrogen quantification suggest that a solution containing up to 100 mg/L of methyl orange can be successfully decolorized within 90 s at 50°C using porous Fe/Cu catalyst in the presence of hydrogen peroxide that largely surpasses the current state-of-the-art performance. Already within the first 10°min, ∼ 30% of total methyl orange concentration is fully mineralized. The described process represents a cost-efficient and environmentally friendly way to treat azo dyes in aqueous solutions.

Catalytic reduction of hazardous acid orange 10 dye by BiVO4/TiO2 nanocrystalline heterojunction and influence of aeration, FeSO4, H2O2 and FeCl3 on removal efficiency: A novel and environmentally friendly process

Bismuth vanadate in combination with titanium dioxide were synthesized by hydrothermal method and its photocatalytic activity was investigated under visible light irradiation for acid orange 10 (AO10) dye removal. The 10% BiVO4/TiO2 showed the highest catalytic activity in comparison with 20, 30, 40 and 50% BiVO4/TiO2 ratios. The removal of AO10 azo dye in aqueous solutions was studied in laboratory-scale experiments using 25 removal processes and their removal efficiencieswere evaluated, separately. The results showed that the amount of de-colorization for each oxidation process is completely different. The order of the investigated processes in removing the dye after 90 min is as follows: LED < TiO2 < BiVO4 < 10% BT/without LED < BiVO4/ LED < 50% BT < 40% BT < 30% BT < 20% BT < UV/H2O2 < 10% BT < 5a-10 %BT < 5F-10 %BT < 10a-10 %BT < 50F-10 %BT < 20a-10 %BT < 10F-10 %BT < 20F-10 %BT < 20H-10 %BT < 40H-10 %BT < 50H-10 %BT < 20a-20F-10 %BT < 20a-20F-50H-10 %BT. Among the above processes, 20a-20F-50H-10 %BT had the best removal performance and can be suggested for using in real conditions. Coagulation/precipitation process was done using 5 mg/L of FeCl3 as post-treatment reaching efficiency of 100% in the studied system.

Decolorization and Degradation of Methyl Orange Azo Dye in Aqueous Solution by the Electro Fenton Process: Application of Optimization

In a batch reactor, the EF advanced oxidation decolorization of aqueous solutions of methyl orange MO, a commercial azo reactive textile dye, was investigated in the presence of two different electrodes. The evaluation included various operational variables such as the IC current intensity (60 mA, 80 mA, and 100 mA), initial concentration of pollutant MO (20 mg/L, 40 mg/L, and 60 mg/L), initial pH of solution (3, 5, and 7), temperature of solution (20 °C, 30 °C, and 50 °C), and initial concentration of catalyst [Fe2+] (0.1 mM, 0.2 mM, and 0.3 mM) on the discoloration rate. A Box-Behnken Design of Experiment (BBD) was used to optimize the parameters that directly affect the Electro-Fenton (EF) process. Under the optimal experimental conditions such as [Fe2+] = 0.232 mM, pH = 3, IC = 80 mA, [MO] = 60 mg/L, and T = 30 ± 0.1 °C, the maximum discoloration rate achieved was 94.9%. The discoloration of the aqueous MO solution during the treatment time was confirmed by analysis of the UV-visible spectrum. After a review of the literature on organic pollutant degradation, the EF system provided here is shown to be one of the best in terms of discoloration rate when compared to other AOPs.

Catalytic non-thermal plasma process for the degradation of organic pollutants in aqueous solution

The aim of the present work was to optimize the performance of the Non-Thermal Plasma (NTP) technology coupled with a structured catalyst for the degradation of organic and recalcitrant pollutants in aqueous solution. Specifically, the catalyst consists of CeO2 supported onto ɣ-Al2O3 spheres, synthesized by the wet-impregnation method, and characterized through Raman spectroscopy, specific surface area (BET) by N2 adsorption at − 196 °C and Scanning Electron Microscopy (SEM). All experiments were carried out in a Dielectric Barrier Discharge (DBD) reactor. The first sets of tests were accomplished to optimize the degradation of Acid Orange 7 (AO7) azo dye in aqueous solution. The effect of catalyst formulation and oxygen flow rate in the reactor, as well as the reusability of the catalyst, were studied in detail. Moreover, the effect of radical scavengers was examined to suggest a plausible degradation mechanism, and an HPLC analysis was performed to understand to which extent degradation proceeds with the formation of intermediates. The best performance of the system in terms of total degradation and mineralization efficiencies is found for 15 min run time using 2.9 wt% CeO2/ɣ-Al2O3, with a voltage equal to 12 kV and 0.045 NL/min oxygen flow rate. The catalyst showed reusability properties after 5 runs and no intermediates were found by HPLC analysis, suggesting that AO7 degradation takes place with complete mineralization. Scavenger analysis showed that ozone is the most important reactive species responsible for degradation since its decomposition leads to the generation of effective secondary oxygen reactive species. Furthermore, given the semiconductor features of CeO2, it may also be excited by the plasma-generated UV radiation, suggesting that electron-hole pairs were also involved in the degradation mechanism. The remarkable efficiency of the proposed catalytic NTP treatment shows the potential of the system for the decontamination of aqueous solutions containing organic and recalcitrant pollutants. To confirm the potentiality of the system, the degradation of glyphosate (GLY) was also assessed under the optimal conditions set up for AO7 degradation, obtaining 84% degradation efficiency after 30 min run time.

Synthesis of visible spectrum-active TiO2 thin film induced by RF magnetron sputtering

TiO2 anatase phase has a key role in environmental and photocatalysis research. But, the TiO2 anatase phase is not able to give photocatalytic activity in the visible spectrum as it has a large bandgap, i.e., 3.2 eV which is the main drawback of it. Thus, if some method could decrease the bandgap of anatase, TiO2 - able to photocatalysis in the visible light irradiation. Hence, visible spectrum-active TiO2 (visi-TiO2) thin films on corning glass were deposited using RF magnetron sputtering in the present study. The visi- TiO2 was deposited at various RF powers (60, 120, 180, 200, and 300 W) and characterized using X-ray diffraction (XRD), UV–vis spectroscopy, and dye degradation under visible light. The XRD spectrum confirmed that an increase in RF power was generated phase transformation from rutile to anatase. The bandgap energy was calculated by the Tauc method, and the direct optical band gap of the visi- TiO2 film was observed to decrease from 3.15 to 2.87 eV as an increase in RF power. The visible light absorption edge in all Visi- TiO2 thin films is due to surface morphology. Photocatalytic activity of Visi-TiO2 film has been explored by degradation of direct blue 14 azo dye in aqueous solution as a contaminant of water in presence of visible spectrum irradiation. The photocatalytic degradation potential of Visi-TiO2 film was found to be 99% after 210 min. The newly discovered low bandgap anatase phase can be achieved by changing the sputtering parameters. The synthesis of a TiO2 anatase phase with a bandgap belongs to the visible and more chemical reactivity has implications for its use as a photocatalyst and artificial photosynthesis.

Photocatalytic degradation of azo dyes in aqueous solution by using highly ordered titania nanotube films

Photocatalytic degradation of azo dyes in aqueous solution by using highly ordered titania nanotube films

An evaluation into the biosorption and biodegradation of azo dyes by indigenous siderophores-producing bacteria immobilized in chitosan.

The biodegradation and biosorption efficiency of an indigenous siderophores-producing bacterial community on azo dyes with immobilization in chitosan beads was evaluated in this study. 13 bacterial strains were isolated from textile wastewater streams. The bacterial strains were tested for the production of siderophores as well as their ability to decolorize toxic azo dyes in aqueous solution. Both qualitatively and quantitatively, all of the strains displayed high siderophores productivity. Furthermore, they displayed remarkable decolorization efficiency for azo dyes (Acid Black 1 and Reactive Black 5) in both free and immobilized form. The immobilization process was found not only to enhance the decolorization but also the degradation of azo dyes by the bacterial isolates. In a SEM micrograph, bacterial strains were immobilized, and the pores in chitosan bead to be trapped and adsorbed for dyes from synthetic wastewater. The extent of dye compounds degradation were examined using UV-visible and FTIR spectrophotometers on treated water samples and dye absorbed beads. After 72h of incubation, the UV-visible analysis revealed that the bacterial community could significantly reduce both azo dyes in wastewater by 90% at 300 mgL-1 dyes initial concentration. FTIR study confirmed the bonds of these dyes were broken to form less toxic chemicals via the bacterial community immobilized in chitosan beads. The immobilized bacterial community thus demonstrated effective approach of azo dye biosorption and biodegradation.

Oxidative Degradation of Azo Dyes in Aqueous Solution by Water‐Soluble Iron Porphyrin Catalyst

AbstractTextile and food industries produce a significant volume of effluents containing azo dyes and other pollutants. These effluents are serious environmental threats, and new methods for their treatment and for the degradation of azo dyes are thus attracting much attention. The current study deals with the oxidative degradation of azo dyes by meso‐tetrakis(1‐methylpyridinium‐4‐yl)prophyrinatoiron(III), [FeIII(tmpyp)], and meta‐chloroperoxy benzoic acid (m‐CPBA) in aqueous solution at room temperature. The catalytic degradation of azo dyes was investigated by using rapid‐scan stopped‐flow spectrophotometry as a function of solution pH, [catalyst], [m‐CPBA], [dye] and [surfactants]. To obtain mechanistic insight, the reaction between [FeIII(tmpyp)] and m‐CPBA was also studied in aqueous solution in absence of azo dyes. Spectral analyses and kinetic data show that [FeIII(tmpyp)] is transformed into the transient intermediate [FeIV(O)(tmpyp)].+ (a compound I analog) within 20–30 ms followed by the formation of relatively stable [FeIV(O)(tmpyp)] (a compound II analog). Batch experiments reveal that the dye degradation rate is influenced by the solution pH and the concentrations of [FeIII(tmpyp)], m‐CPBA, dye, and surfactants. On the basis of the kinetic and spectroscopic data, a mechanistic scheme for the dye degradation reaction and a steady‐state rate equation are proposed. The products resulting from oxidative degradation of the azo dye amaranth have been analyzed by HPLC‐UV‐HRMS.

Degradation of anionic azo dyes in aqueous solution using a continuous flow photocatalytic packed-bed reactor: Influence of water matrix and toxicity evaluation

A continuous flow photocatalytic packed-bed reactor irradiated by UV-LEDs was employed for the degradation of two toxic anionic azo dyes: Eriochrome Black-T (EBT) and Methyl Orange (MeO). Commercial anatase TiO2 in pellets form was used as packing material for the photoreactor. The experimental tests were carried out using both distilled and tap water as aqueous matrix for the two selected dyes. The influence of the liquid flow rate on the performances of the photocatalytic packed-bed reactor was investigated in the range 0.5–2.1 mL/min. Photocatalytic results showed that, under UV light, the system allows to achieve steady-state dyes concentration values without deactivation phenomena in 510 min irradiation time. Using distilled water, the highest efficiency of the process (EBT and MeO decolorization of about 100 % and 90 %, respectively) was observed with a liquid flow rate of 0.5 mL/min (contact time =6.6 min). In the presence of tap water and using the same contact time, the EBT decolourization was still total whereas MeO degradation was lower and equal to 70 %. For this reason, the photocatalytic reactor was followed by an adsorption unit based on the use of activated carbon. With such configuration, the complete MeO decolourization was achieved.The total removal of toxicity for EBT was achieved with just one packed-bed reactor being the toxicity of potential by-products not relevant. In the case of MeO, the full toxicity removal was obtained only after powdered activated carbon filtration.

Removal of azo dyes in aqueous solutions using magnetized and chemically modified chitosan beads

Azo dyes in wastewater coming from textile industry are detrimental, toxic, and affect the human health; therefore efficient wastewater treatments are needed. To contribute to the solution to this problem, in this paper materials based on chitosan beads are studied. Magnetized chitosan beads (MC), MC coated with tetraethyl orthosilicate TEOS (TMC) and MC modified with TEOS and ethylenediamine (ETMC) were synthesized and tested as adsorbents for the removal of two azo dyes: Cibacron Brilliant Yellow 3G-P (CBY) and Cibacron Brilliant Red 3B-A (CBR) in aqueous solutions. The materials were characterized by FTIR, VSM, Raman, SEM, EDX, TGA and XRD. During the adsorption of CBY and CBR dyes in aqueous solutions using the MC, TMC and ETMC beads, it was found that the maximum adsorption capacity (Qm, mg.g−1) of the chitosan beads occurred at pH 2 for both azo dyes. The equilibrium experiments for adsorption of CBY fitted well with the Langmuir isotherm model, whereas the CBR adsorption fitted well with Freundlich isotherm model. The maximum adsorption capacity of the ETMC beads was 179.45 mg.g−1 for CBY, and 377.60 mg.g−1 for CBR. The adsorption kinetic data of CBY and CBR using the MC, TMC and ETMC beads were better adjusted by the pseudo-second-order kinetic model. The results of the competitive adsorption test for a binary mixture (ratio = 1:1 of CBY:CBR in the mixture) indicated that the ETMC beads recorded the best removal efficiency of the CBY dye (99.1%). Our results indicate, the ETMC material is a promising adsorbent for optimal removal of azo dyes in aqueous solutions.

Degradation of Acid Orange 7 Azo Dye in Aqueous Solution by a Catalytic-Assisted, Non-Thermal Plasma Process

The aim of this work was the optimization of the performance of the cold plasma technology coupled with a structured catalyst for the discoloration and mineralization of “acid orange 7” (AO7) azo dye. The structured catalyst consists of Fe2O3 immobilized on glass spheres, and it was prepared by the “dip coating” method and characterized by different chemico-physical techniques. The experiments were carried out in a dielectric barrier discharge (DBD) reactor. Thanks to the presence of the catalytic packed material, the complete discoloration and mineralization of the dye was achieved with voltage equal to 12 kV, lower than those generally used with this technology (approximately 20–40 kV). The best result in terms of discoloration and mineralization (80% after only 5 min both for discoloration and mineralization) was obtained with 0.25 wt% of Fe2O3 immobilized on the glass spheres, without formation of reaction by-products, as shown by the HPLC analysis. The optimized catalyst was reused for several reuse cycles without any substantial decrease of performances. Moreover, tests with radical scavengers evidenced that the most responsible oxidizing species for the degradation of AO7 dye was O2•−.

New application of Orchis mascula as a biocarrier for immobilization of mixed cells for biodegradation and detoxification of reactive azo dyes.

In this study, the application of novel biocarrier Orchis mascula plant for immobilization of non-adapted mixed cells biodegrade reactive azo dyes in aqueous solution was investigated via a sequential anaerobic-aerobic process. Three reactive azo dyes including red (RR2), blue (RB4), and yellow (RY15) were individually used as the target pollutants. Results revealed that the immobilized biocatalysts had a potential degrading efficiency, targeting the initial structure and the formed aromatic/aliphatic compounds, respectively. Complete decolorization (100%) of RR2, RB4, and RY15 was observed in the anaerobic phase with significant COD removal which has been enhanced during the subsequent aerobic phase. Results demonstrated that COD removals at 10, 20, and 40mg/L were 100± 0.13%, 95± 0.05%, and 90± 0.03% for RR2; 90± 0.11%, 85± 0.9%, and 81± 0.18% for RB4; and 100 ± 0.08%, 92 ± 0.16%, and 86 ± 0.06% for RY15, respectively. Immobilized cells exhibited better performance compared with free cells, particularly for high dye concentration up to 100mg/L.

Semiconducting polypyrrole@TiO2 pure anatase nanoparticles for photodegradation of reactive red 120 azo dye

In the recent years, the development of new and efficient materials for photocatalytic processes has been of growing interest for applications in wastewater treatment. In this sense, TiCl4 stabilized with H2SO4 was precipitated with ammonium hydroxide in the presence of sodium dodecyl sulfate and calcined to obtain thermally stable TiO2 nanoparticles, which were subsequently coated with semiconducting polypyrrole (PPy) by chemical oxidation resulting in a composite of TiO2@PPy. TiO2 and TiO2@PPy composite were characterized by SEM, Raman, XRD, UV/Vis–NIR, FTIR and TGA. It was observed that TiO2 consisted of spherical nanoparticles with number-average particle diameter of 19.2 nm and polydispersity index in sizes of 1.2, whereas TiO2@PPy composite consisted of agglomerated spherical PPy nanoparticles of number-average diameter of 182.4 nm coating TiO2 nanoparticles. The calculated optical bandgap of TiO2 was 3.07 eV, and it was demonstrated by the Rietveld refinement method of the XRD spectrum and from the Raman analysis that synthesized TiO2 corresponds to highly pure rhombic anatase crystal structure. TiO2@PPy composite was tested in the photodegradation of the reactive red 120 azo dye in aqueous solutions under visible light irradiation. It was observed that photodegradation rate increased with decreasing the initial dye concentration and increasing the composite load. Almost 100% of dye removal was achieved after 45 min of reaction for 20 mg L−1 of initial dye concentration and 1.0 g L−1 of composite load.

Enhanced azo dye removal in aqueous solution by H2O2 assisted non-thermal plasma technology

Abstract The focus of the present study is to assess the performances of H 2 O 2 assisted non-thermal plasma (NTP) technology for the degradation of the Acid Orange 7 textile azo dye in aqueous solution. The reactor configuration used during the experiments was the “dielectric barrier discharge” (DBD). The comparison between DBD (only non-thermal plasma) and H 2 O 2 /DBD system (in the presence of H 2 O 2 in the solution) was also performed. The experimental tests were carried out using 100 mL of aqueous solution with an initial Acid Orange 7 concentration equal to 10 mg/L, in the presence of oxygen as process gas in the DBD reactor operating with 20 kV of applied voltage. The results demonstrated that in presence of only oxygen in the DBD reactor, a discoloration and simultaneous mineralization of about 60% was obtained after only 2.5 min, while the addition of H 2 O 2 enhanced the dye degradation rate, obtaining in the same a discoloration and simultaneous mineralization of about 80%. The higher degradation rate achieved by adding H 2 O 2 could be attributed to the presence of higher amounts of hydroxyl radicals in DBD reactor. A deeply study on the influence of the main macroscopic parameters such as O 2 flow rate, H 2 O 2 and Acid Orange 7 initial concentration has been assessed in order to find the optimal operating conditions for the H 2 O 2 /DBD system. The kinetic evaluation and the energy yield study were performed under specific experimental condition. If compared with traditional AOPs, the results obtained with the H 2 O 2 /DBD system, showed that this technology is faster and extremely efficient and consequently very promising for the removal of Acid Orange 7 azo dye in aqueous solutions.