Degradation Of Dye In Aqueous Solution Research Articles

The Role of Ascorbic Acid in the Process of Azo Dye Degradation in Aqueous Solution.

In this work, the role of ascorbic acid in the process of azo dye degradation was explained. For this purpose, the kinetics of azo dye degradation under different conditions was studied. Among them, the influence of daylight protection/exposition, different concentrations of ascorbic acid (0.567-0.014 mol/dm3), and temperature (20 °C and 50 °C) on the rate of the dyes' degradation was considered. For this process, the kinetic equation was proposed, which indicates that the process of azo dye degradation using ascorbic acid is first order. Moreover, the observed rate constants were determined, and the mechanism of azo dye degradation was proposed. Spectrophotometry results, together with FTIR, fluorescence spectroscopy, and DFT calculations, explain the origin of the decolorization of the azo dyes and highlight the role of ascorbic acid in this process. Detailed analysis of the obtained products indicates that the process itself goes through several stages in which equally or more toxic compounds are formed. Obtained results from LCMS studies indicate that during tropaeolin OO degradation, 1,2-Diphenylhydrazine (m/z 185.1073) is formed. Thus, the process of azo dye degradation should be carried out in protective conditions. The proposed mechanism suggests that ascorbic acid at high content levels can be used for azo dye degradation from aqueous solution and can be an alternative method for their removal/neutralization from waste solution but with caution during the process.

Gap type effect on photocatalytic degradation using newly hydrotalcite nanoposite precursor synthesized by hydrothermal method

<p>A novel technique involving hydrothermal synthesis was employed to prepare nanocomposite precursors of lamellar double hydroxide based basic mixed oxides. This method extended ongoing research on iron-impregnated hydrotalcite-supported nanomaterials. The iron-based Fe/MgAl-h nanocomposite was prepared via dry impregnation, introducing a known % by weight of Fe (NO3)3.9H2O metal salt into the hydrothermally synthesized MgAl-h structure. For comparative analysis, the photocatalytic performance of Fe/MgAl-h was compared with the coprecipitation-synthesized Fe/MgAl-c after calcination at 400°C, using various characterization techniques. Structural examination revealed a double-layered hydroxyl structure and the presence of iron oxide phase Fe2O3 in Fe/MgAl-h400. Optical assessments indicated an indirect band gap energy of 1.89 eV for solid Fe/MgAl-h400, which is suitable for visible light absorption. Photocatalytic experiments for methylene blue (MB) dye degradation in aqueous solution were performed under artificial irradiation with a tungsten lamp as the visible light source, mirroring the conditions of Fe/MgAl-c400. Using 50 mg/L MB concentration and 0.5 g/L catalyst quantity, increased MB removal efficiency with time was observed. A comparative study of hydrothermal and coprecipitation synthesis methods showed decreased photodegradation for the hydrothermally prepared solid. Fe/MgAl-h400 and Fe/MgAl-c400 exhibited reaction efficiencies of approximately 46% and 67%, respectively, possibly attributed to their distinct indirect and direct band gap characteristics. Moreover, a wider band gap in a semiconductor material offers several advantages for the degradation of dyes.</p>

Single step facile synthesis of Cu-SnO2/ZnO nanocomposite photocatalyst for methylene blue dye degradation in aqueous solution

A Cu-SnO2/ZnO nanocomposite was prepared using a single-step facile synthesis method, sol–gel, for photocatalyst application. The XRD of Cu-SnO2/ZnO nanocomposite shows SnO2 and ZnO have tetragonal rutile and hexagonal wurtzite, which is similar to HRTEM and SAED data. The crystallite sizes of SnO2, ZnO, Cu-SnO2, SnO2/ZnO, and Cu-SnO2/ZnO are 8.50 nm, 29.12 nm, 7.10 nm, 6.42 nm, and 3.50 nm, respectively. The calculated energy band gap of SnO2, ZnO, Cu-SnO2, and Cu-SnO2/ZnO from the DRS measurements is 3.60 eV, 3.20 eV, 3.34 eV, 3.48 eV, and 3.09 eV, respectively. The photoluminescence spectroscopy shows that Cu-SnO2/ZnO nanocomposite has a higher defect density than another sample. The Fourier Transform Infrared (FTIR) spectroscopy identifies the functional groups of the Cu-SnO2/ZnO powder samples. The EDS spectra of the synthesized Cu-SnO2/ZnO nanocomposite indicated the existence of the elements of Cu, Sn, Zn, and O, respectively. The photocatalyst activities of Cu-SnO2/ZnO have higher efficiency, ~78%, than other samples.

Enhanced photocatalytic activity of Cu and Ni-doped ZnO nanostructures: A comparative study of methyl orange dye degradation in aqueous solution

Heterogeneous photocatalysis has been considered one of the most effective and efficient techniques to remove organic contaminants from wastewater. The present work was designed to examine the photocatalytic performance of metal (Cu and Ni) doped ZnO nanocomposites in methyl orange (MO) dye degradation under UV light illumination. The wurtzite hexagonal structure was observed for both undoped/doped ZnO and a crystalline size ranging between 8.84 ± 0.71 to 12.91 ± 0.84 nm by X-ray diffraction (XRD) analysis. The scanning electron microscope (SEM) and energy dispersive X-ray (EDX) revealed the irregular spherical shape with particle diameter (34.43 ± 6.03 to 26.43 ± 4.14 nm) and ensured the purity of the individual elemental composition respectively. The chemical bonds (O–H group) and binding energy (1021.8 eV) were identified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results respectively. The bandgap energy was decreased from 3.44 to 3.16 eV when Ni dopant was added to the ZnO lattice. The comparative photocatalytic activity was observed in undoped and doped nanocomposites and found to be 76.31%, 81.95%, 89.30%, and 83.39% for ZnO, Cu/ZnO, Ni/ZnO, and Cu/Ni/ZnO photocatalysts, respectively, for a particular dose (0.210 g) and dye concentration (10 mg L−1) after 180 min illumination of UV light. The photocatalytic performance was increased up to 94.40% with the increase of pH (12.0) whereas reduced (35.12%) with an increase in initial dye concentration (40 mg L−1) using Ni/ZnO nanocomposite. The Ni/ZnO nanocomposite showed excellent reusability and was found 81% after four consecutive cycles. The best-fitted reaction kinetics was followed by pseudo-first-order and found reaction rate constant (0.0117 min−1) using Ni/ZnO nanocomposite. The enhanced photodegradation efficiency was observed due to decreases in bandgap energy and the crystalline size of the photocatalyst. Therefore, Ni/ZnO nanocomposite could be used as an emerging photocatalyst to degrade bio-persistent organic dye compounds from textile wastewater.

Comparative study using design experiment to assess an anionic dye degradation in aqueous solution through the application of different advanced oxidation processes

AbstractThis study aims to compare the anionic dye degradation (Titan yellow dye: DY9) in synthetic solution using three advanced oxidation processes, namely, Fenton process (FP) (H2O2/Fe2+), photo‐Fenton process (PhFP) (UV/H2O2/Fe2+), and photocatalytic process (PhCP) (TiO2/UV). To perform this study, design of experiments methodology was applied. A full factorial design was used to investigate the effect of operating parameters on the degradation yield. For each process, four parameters were considered, for “FP” and “PhFP,” the initial dye concentration ([DY9]0), the ratio R1 = [H2O2]/[Fe2+], the ratio R2 = [DY9] / [Fe2+], and the pH of solution and for “PhCP,” the initial dye concentration (([DY9]0), initial concentration of hydrogen peroxide [H2O2], dose of titanium oxide [TiO2], and the pH of solution. The averages of degradation yield obtained are 47.1%, 56.7%, and 68.5% for “FP,” “PhFP,” and “PhCP,” respectively. Main and interaction effects plots were constructed. An interaction index (In (%)) was defined, which allowed to quantify the impact of the interaction on the response. Three regression models were proposed and validated on basis of analysis of variance (ANOVA) and statistical criteria as corrected Akaike Information Criterion (AICc), Mallows Cp statistic, coefficient of determination (R2), and adjusted coefficient of determination (R2adj). These models showed that the “PhCP” model was the most statistically significant, including more interaction effect terms. Iso‐responses curves were plotted to predict the optimal conditions for each process. To achieve a full degradation of DY9, the predicting optimal conditions were expressed on intervals.

Charge separation effect in the nanocomposites of Co3O4-QDs: visible light photocatalytic dye degradation in aqueous solutions.

Photo-treatment of water is a promising environmentally friendly process that provides clean water and makes wastewater reusable in industry. Thus, efforts toward finding highly efficient photocatalysts have gained a huge attention to remove the organic contaminants in water. Quantum dots (QDs) are extensively utilized for photocatalytic remediation regarding their prominent optical, electrical, and chemical properties. Herein, we report the highly efficient and environmentally friendly synthesis of Co3O4-QDs-based graphene quantum dots (GQDs) and infinite coordination polymer comprising Zn nodes (Zn-ICP) nanocomposites as active and robust photocatalysts for photo-assisted water treatment. The pristine Co3O4-QDs, GQDs, and Zn-ICP showed lower activity under visible light. However, after functionalization of GQDs and Zn-ICP with Co3O4-QDs, the activity increased, and more photocatalytic efficiency was achieved. For instance, Zn-ICP, GQDs, Co3O4-QDs, Co3O4-QDs/Zn-ICP, and Co3O4-QDs/GQD degraded 21, 19, 52, 73, and 83% of rhodamine B (RhB) and 34, 46, 50, 73, and 76% of methylene blue (MB) after 60min. The high photocatalytic efficiency was ascribed to the conjugation of Co3O4-QDs with GQDs and Zn-ICP which causes efficient absorption of visible light. The existence of Co3O4-QDs was found to be essential not only for effective charge separation but also widening the region of light absorption followed by increase in photocatalytic performances. Charge separation in photocatalytic reactions, energy levels of nanocomposites, and mechanism of the photocatalytic process were investigated by photoluminescence spectra (PL), Mott-Schottky, electrochemical impedance (EIS), and diffuse reflectance UV-Vis spectroscopy (DRS).

An investigation of transition metal doped TiO2 photocatalysts for the enhanced photocatalytic decoloration of methylene blue dye under visible light irradiation

Photocatalytic decolouration of dyes/pollutants using semiconducting materials has grabbed great attention in recent days. The current study focuses on a sol-gel method for preparing semiconducting materials such as TiO2 (titanium oxide) and transition metal (Zn, Zr, Cu) doped TiO2, which were characterized by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), UV–visible Diffuse Reflectance Spectroscopy (DRS) and UV–visible spectrophotometer, respectively. The photocatalytic behaviour of samples was tested with Methylene blue (MB) dye by observing the decolouration of the MB dye in aqueous solutions under visible light irradiation. The UV-DRS spectra showed that Zn doped TiO2 demonstrated a better photocatalytic efficiency than TiO2 and Zr, Cu doped TiO2 catalysts. The effect of Zn doped TiO2 has a lesser band gap would probably lead to enhance the MB dye degradation in aqueous solutions under visible light irradiation compared to TiO2 and Zr, Cu doped TiO2 catalysts. UV–vis spectrum varied with the irradiation time between 10 and 60 min and the concentration of MB decreased with the increasing irradiation time. UV–vis study revealed that the Zn (0.01) doped TiO2 exhibited 99.64% MB decolouration as compared to 90.4% by pure TiO2. The absorbance spectrum of Zn doped TiO2 exhibited the lighter harvest in the visible light region, which facilitated more light energy for the utilization of the photocatalytic activity for the decoloration of MB. Zn doped TiO2 catalyst exhibited a greater photocatalytic activity than pure TiO2 and the other metal doped TiO2 catalysts.

Dye degradation in aqueous solution by dithionite/UV-C advanced reduction process (ARP): Kinetic study, dechlorination, degradation pathway and mechanism

In this study, the first attempt was carried out for the degradation of dye by an advanced reduction process (ARP). UV/dithionite process was used to explore the degradation of acid yellow 17 (AY17). The effects of operational parameters were investigated on AY17 removal. More than 90 % of AY17 was eliminated at only 5 min reaction time under conditions of 1.5 mM dithionite and pH = 9.0. The results of scavenging experiments confirmed that the hydrated electron (e−aq) was the dominant agent for the degradation of AY17. Although decolorization was fast by the UV/dithionite process, mineralization was not effective enough. Several intermediates were identified by LC/MS based on which the degradation pathways were proposed for AY17 for the first time. Electrical energy consumption was also considered which was significantly decreased with increase of dithionite concentration. Quantum yield was calculated for UV and UV/dithionite processes. Using dithionite, the quantum yield was increased by 75 times as compared to the UV process. This study showed that ARPs can be effective for the degradation of pollutants with large molecular structures. However, low mineralization of organic pollutants is still a limitation for the application of ARPs.

Designing a New Efficient Photocatalyst Based on Functionalization of Zn-Infinite Coordination Polymer with Ru(acac)3 Complex for Dye Degradation in Aqueous Solutions: Charge Separation Effect.

A new Zn-containing infinite coordination polymer, Zn-ICP, functionalized with Ru(acac)3 complex was designed and utilized as an efficient visible light photocatalyst for dye degradation in aqueous solutions. Incorporation of Ru(acac)3 not only extended the light absorption of the Zn-ICP to the visible region but also led to electron-hole separation. Upon visible light illumination, photoinduced electron transfer from excited state of Zn-ICP to Ru(acac)3 occurred, resulting in electron-hole separation as indicated by photoluminescence and electrochemical impedance spectroscopy. The obtained Ru-Zn-ICP revealed enhanced visible light photocatalytic activity in degradation of organic pollutants compared to pristine Zn-ICP owing to photoinduced electron transfer in the Ru-Zn-ICP system and efficient separation of photogenerated electron-hole pairs. The prepared Ru-Zn-ICP photocatalyst was readily recycled without major loss of activity in the successive cycles.

Mechanistic study of carmoisine dye degradation in aqueous solution by Fenton process

The carmoisine azo dye (AR14) solution 1 g/L was degraded by Fenton process under the following conditions: [Fe2+] = 3.57 mmol/L, [H2O2] = 194 mmol/L at pH = 3.0.The degradation pathway of AR14 by the Fenton process was investigated by means of IR, LC-MS-MS and Ion Chromatography analysis. Some aromatic anions such as 5,8-dihydroxy-2-nitronaphthalen-1-olate, benzoate, 5-hydroxy-4-nitro-2-sulfonatobenzoate and naphthalene-1-sulfonate were formed and identified. Moreover, a quantitative analysis of inorganic ions (sulfate and nitrate) produced during the degradation process helped to verify molar balance with regard to original sulfur and nitrogen elements. A feasible degradation pathway of AR14 was proposed and discussed.The reaction mechanisms proposed in this research should prove useful for future application of the technology to dyes decolorization.

Ultrafast degradation of Congo Red dye using a facile one-pot solvothermal synthesis of cuprous oxide/titanium dioxide and cuprous oxide/zinc oxide p-n heterojunction photocatalyst

The photodegradation of Congo red (CR) dye was studied with pure Cu2O, Cu2O/TiO2 (CT), and Cu2O/ZnO (CZ) heterojunctions photocatalysts. A facile one-pot solvothermal method with absolute ethanol as a solvent and reducing agent was used to prepare the photocatalysts. CT and CZ showed excellent adsorption properties and ultrafast photocatalytic activities on CR, especially CZ. The optimized CZ (1.5–1.5) resulted in an incredible photocatalytic activity by completely degrading 30 ppm CR within 10 min. The configuration of p-n heterojunction between Cu2O, TiO2, and ZnO successfully promoted the photogenerated electron-hole pairs separation for enhanced CR dye degradation in aqueous solution.

UV/Chlorine process for dye degradation in aqueous solution: Mechanism, affecting factors and toxicity evaluation for textile wastewater

Abstract In this study, UV/chlorine was used for the degradation of a food dye (Brilliant Blue FCF, BBF). The effect of pH, chlorine dosage and reaction time was studied on BBF degradation. More than 95 % of BBF was eliminated during 30 min reaction time at optimized conditions of pH = 3 and chlorine dosage = 0.6 mM. The scavenging assay showed that hydroxyl radicals had the highest contribution (66.9 %) while chlorine radicals (17 %) and dichlorine radicals (10.4 %) had minor role in degradation of the dye. Pseudo-first order model was well fitted for UV/chlorine process with the rate constant of 0.088 min−1. The effect of sulfate, chloride, nitrate and bicarbonate anions were studied in a way that bicarbonate ions showed high inhibitory effect on BBF degradation. The presence of iron and copper enhanced the degradation rate of BBF in UV/chlorine process. The application of solar irradiation instead of UV lamp was also tested. The results exhibited that solar irradiation can be considered for decolorization of BBF especially in the presence of transition metals. Mineralization of different processes were considered, the highest value obtained was around 37 % for UV/chlorine. The UV/chlorine was performed on a real wastewater. UV/chlorine process showed a high efficient process in terms of decolorization while the removal of organic compounds and detoxification (acute toxicity) was relatively poor. Finally, EE/O was calculated for BBF and COD removals from synthetic solution and real wastewater respectively.

Synthesis, crystal structure and photocatalytic properties of a Mn (II) metal-organic framework based on a thiophene-functionalized dicarboxylate ligand

A novel metal-organic framework formulated as [Mn(DMTDC)(DMF)] (1) was synthesized under solvothermal conditions by using a thiophene-functionalized dicarboxylate ligand, 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid (H2DMTDC), which displays a uninodal, 4-connected lvt net. After the removal of coordinated DMF, this framework displays permanent porosity and excellent photocatalytic activity for methylene blue (MB) dye degradation in aqueous solution under UV light.

Construction of Pillared-Layer MOF as Efficient Visible-Light Photocatalysts for Aqueous Cr(VI) Reduction and Dye Degradation

By using a controllable pillared-layer method, a novel visible-light responsive metal–organic framework (MOF) photocatalyst NNU-36 has been rationally constructed. The synthesized NNU-36 is of broad-range visible light absorption and good chemical stability which are beneficial to its application of photocatalysis. Photocatalytic experiments reveal that NNU-36 is highly efficient for Cr(VI) reduction and dye degradation in aqueous solution under visible light irradiation. Control experiments show that the pH value is vital for Cr(VI) reaction, and meanwhile, the use of hole scavenger of methanol promotes the photocatalytic reduction significantly. It has been also demonstrated that NNU-36 is efficient for dye degradation, in which the introduction of hydrogen peroxide (H2O2) significantly enhances the photocatalytic efficiency of dye degradation. This study illustrates that the introduction of hole scavengers or oxidants in the MOF-mediated photocatalytic reaction is a feasible approach to enhance the cat...

Bio inspired green synthesis of Ni/Fe3O4 magnetic nanoparticles using Moringa oleifera leaves extract: A magnetically recoverable catalyst for organic dye degradation in aqueous solution

In this work, we have developed a facile, low-cost and ecofriendly method for synthesis of nickel supported iron oxide magnetic nanoparticles (Ni/Fe3O4 MNPs) using Moringa oleifera (MO) leaves extract as reducing and capping agent. The as-synthesized Ni/Fe3O4 nanocomposite was characterized by various physicochemical characterization techniques such as FTIR, powder XRD, XPS, TEM and BET sorption methods. The results show that the Ni/Fe3O4 MNPs were exhibits spherical in shape with the size range of 16–20 nm. The room temperature magnetic measurements of composite clearly evince ferromagnetic natures with saturation magnetization (Ms) of 76.8 emu/g. The catalytic activity of Ni/Fe3O4 MNPs towards degradation of Malachite green (MG) dye was determined by UV–vis spectroscopy. The results show that as-synthesized Ni/Fe3O4 MNPs is an efficient catalyst for the degradation of Malachite green as compared to previous reports.

Multi‐Metal‐Substituted‐Goethite as an Effective Catalyst for Azo Dye Wastewater Oxidation

Different samples of goethite modified with cobalt, manganese, or aluminum were synthesized and characterized by means of X‐ray diffraction, chemical analysis, scanning electron microscopy, zeta potential measurements, and N2 adsorption–desorption isotherm analysis. The goethite oxides were tested as efficient catalysts for the degradation of methyl orange (MO, sodium 4‐[(4‐dimethylamino)phenylazo]benzenesulfonate), a sulfonated azo dye indicator, employing potassium persulfate (PS) in water, at pH 3. The Mn, Co, and Al substitution in goethite gave rise to active sites for PS activation. The most effective catalyst reached 93% of degradation at 120 min of reaction. The increase of temperature led to an expected conversion enhancement, and kinetic parameters were calculated for one of the evaluated catalysts. MO degradation curves best fitted to pseudo‐second order kinetics. The extent of mineralization, measured as total removed organic carbon (TOC), was also monitored. A significant degree of mineralization was achieved and confirmed by TOC analysis. A mechanism for MO oxidation with radicals was discarded and a pathway involving peroxymonosulfate species was proposed. The results indicate that the goethite‐substituted oxides are effective catalysts for the studied azo dye degradation in aqueous solution.

In-situ preparation of Fe2O3 hierarchical arrays on stainless steel substrate for high efficient catalysis

Hierarchical array catalysts with micro/nano structures on substrates not only possess high reactivity from large surface area and suitable interface, but intensify mass transfer through shortening the diffusion paths of both reactants and products for high catalytic efficiency. Herein, we first demonstrate fabrication of Fe2O3 hierarchical arrays grown on stainless-steel substrates via in-situ hydrothermal chemical oxidation followed by heat treatment in N2 atmosphere. As a Fenton-like catalyst, Fe2O3 hierarchical arrays exhibit excellent catalytic activity and life cycle performance for methylene blue (MB) dye degradation in aqueous solution in the presence of H2O2. The Fe2O3 catalyst with unique hierarchical structures and efficient transport channels, effectively activates H2O2 to generate large quantity of •OH radicals and highly promotes reaction kinetics between MB and •OH radicals. Immobilization of hierarchical array catalysts on stainless-steel can prevent particles agglomeration, facilitate the recovery and reuse of the catalysts, which is expected promising applications in wastewater remediation.

CoFe/SBA-15 catalyst coupled with peroxymonosulfate for heterogeneous catalytic degradation of rhodamine B in water

CoFe/SBA-15 catalysts were prepared by simultaneous incipient wetness impregnation using Co(NO3)2·6H2O and Fe(NO3)3·9H2O as the precursors and SBA-15 as the support. The catalysts were used to activate generation of sulfate radicals from peroxymonosulfate (PMS) for rhodamine B (RhB) dye degradation in aqueous solutions. The catalyst was characterized using X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. The effects of the Co and Fe loadings and calcination temperature on the catalytic performance, catalyst reusability, and kinetics and mechanism of catalytic oxidative degradation of RhB in the presence of CoFe/SBA-15 and PMS were investigated. The results show that the predominant Co-Fe oxide loaded on the support was the composite CoFe2O4, which provided the active catalytic sites, and was present in the SBA-15 matrix. The surface area, pore volume, and mean pore diameter of 10Co9.5Fe/SBA-15-700 were 506.1 m2/g, 0.669 cm3/g, and 7.4 nm, respectively, lower than those of SBA-15. 10Co9.5Fe/SBA-15-700 consisted of rod-like aggregates with diameters greater than 0.25 μm. It had a magnetic intensity of 8.3 emu/g; therefore, magnetic separation was feasible. 10Co9.5Fe/SBA-15-700 showed good catalytic activity and stability, with a RhB degradation rate higher than 96% and Co leaching lower than 32.4 μg/L. The catalytic oxidative degradation of RhB in the presence of FeCo/SBA-15 and PMS obeyed first-order kinetics, and the degradation rate increased with increasing CoFe/SBA-15 and PMS dosages and with decreasing initial reactant concentrations. Quenching tests showed that sulfate radicals played a dominant role in RhB catalysis. CoFe/SBA-15 maintained high catalytic activity and good stability during 10 recycling runs, with a RhB degradation rate greater than 84%, Co and Fe leaching for each run lower than 72.1 and 35 μg/L, respectively. CoFe/SBA-15 is an efficient catalyst for PMS oxidation, and has potential applications in the removal of refractory organics such as RhB in water.

Metastable microstructures containing zero valent iron for fast degradation of azo dyes

A novel iron powder obtained by ball milling ribbons of a rapidly solidified cast iron was tested for azo dye degradation in aqueous solution versus commercial Fe and a Fe-based metallic glass powders. The cast iron powders were at least as efficient in promoting the degradation reaction of ethyl-orange and direct blue-6 as the ball-milled metallic glass: dyes decomposition was complete in about an hour. The efficiency of alloy samples increases as a function of the decrease of particles size and does not appear to be strongly due to the structure of the phase containing Fe. The main reason for catalytic efficiency is the presence of metastable phases in the material. The zero valent iron that they contain is more prone to provide electrons for the degradation of N–N double bonds. The starting material is cheap and the sample preparation is straightforward. Therefore, it is believed these samples are suitable for fast degradation at room temperature of azo dyes compared with metallic glasses recently proposed in the literature.

PHOTOCATALYTIC ACTIVITY OF ZnAl2O4 SPINEL FOR PROCION RED DEGRADATION UNDER UV IRRADIATION

In this work, ZnAl2O4 spinel was used as photocatalyst for dye degradation in aqueous solutions under UV irradiation. This material was prepared by a route with chitosan as template. The effects of process variables, such as, initial dye concentration and photocatalyst concentration were investigated. Kinetic parameters were obtained and the reaction order was determined. The results revealed that both studied variables presented strong influence on the dye degradation efficiency, which attained 100% in some cases. It was found that the dye photocatalytic degradation under UV irradiation followed a first order kinetic behavior. The results indicated that ZnAl2O4 spinel can be used to treat dye containing effluents.