Initial Acid Orange 7 Concentration Research Articles

Efficient photocatalytic degradation of acid orange 7 over N-doped ordered mesoporous titania on carbon fibers under visible-light irradiation based on three synergistic effects

N-Doped ordered mesoporous titania on carbon fibers (NOMT/CFs) has been prepared by a liquid-crystal template (LCT) method with the aid of supercritical deposition. The NOMT/CFs product has been characterized by X-ray diffraction analysis, scanning electron and transmission electron microscopies, X-ray photoelectron spectroscopy, N2 sorption, UV/Vis diffuse reflectance spectrophotometry, and photoluminescence. The photoactivity of the obtained product in the degradation of acid orange 7 (AO7) solution under visible-light irradiation has been evaluated. A photocatalytic mechanism involving three synergistic effects of NOMT/CFs is proposed, whereby the titania acts as an electron/hole generator with its ordered mesostructure facilitating electron–hole separation, N-doping enhances visible-light adsorption, and the CFs serve to concentrate the pollutant around the active sites, favor electron transfer, and facilitate convenient recycling. Gas chromatography and mass spectrometry have been used to analyze the intermediates generated in the conversion of AO7, allowing a tentative decomposition pathway to be proposed. The effects of catalyst amount, pH, and initial AO7 concentration have been examined as operational parameters. The photocatalytic reactions follow pseudo-first-order kinetics and are discussed in terms of a modified Langmuir–Hinshelwood model.

Efficiency of a Photoreactor Packed with Immobilized Titanium Dioxide Nanoparticles in the Removal of Acid Orange 7.

In this paper, the removal efficiency of Color Index Acid Orange 7 (AO7) as a model contaminant was investigated in a batch-recirculated photoreactor packed with immobilized titanium dioxide type P25 nanoparticles on glass beads. The effects of different operational parameters such as the initial concentration of AO7, the volume of solution, the volumetric flowrate, and the light source power in the photoreactor were investigated. The results indicate that the removal percent increased with the rise in volumetric flowrate and power of the light source, but decreased with the rise of the initial concentration of AO7 and the volume of solution. The AO7 degradation was followed through total organic carbon, gas chromatography/mass spectroscopy (GC/MS), and mineralization products analysis. The ammonium and sulfate ions were analyzed as mineralization products of nitrogen and sulfur heteroatoms, respectively. The results of GC/MS revealed the production of 1-indanone, 1-phthalanone, and 2-naphthalenol as intermediate products for the removal of AO7 in this process.

Electrochemical Abatement of Organic Pollutants in Continuous‐Reaction Systems through the Assembly of Microfluidic Cells in Series

AbstractThe electrochemical treatment of wastewater contaminated by organic pollutants was performed under a continuous mode by using, for the first time, various micro‐electrochemical cells in series. A synthetic solution of acid orange 7 (AO7), a largely used azoic dye, was chosen as model wastewater. Both the electro‐Fenton (EF) method with a cheap compact graphite cathode and electrochemical oxidation (EO) at a boron‐doped diamond (BDD) anode were used. EO gave higher abatement of total organic carbon (TOC), but drastically higher energetic consumptions than EF. It is worth mentioning that very different operating conditions were set for EF and EO to optimize their performances. The utilization of three cells in series, all working with EO, allowed an increase in the abatement, but gave rise to quite high energetic consumptions. Conversely, in the case of EF, the utilization of three reactors in series gave rise to a slight increase in the abatement of the TOC, because of the formation of products that are resistant to EF. The utilization of two reactors in series, devoted respectively to EF and EO, each working at optimized operating conditions, gave very good figures of merit in terms of the abatement of TOC and energetic consumption. In particular, high abatement of TOC coupled with drastically lower energetic consumptions than that achieved by the sole EO process were obtained. The effects of current density, flow rate, and initial concentration of AO7 on the process were investigated.

A highly efficient single chambered up-flow membrane-less microbial fuel cell for treatment of azo dye Acid Orange 7-containing wastewater

Single chambered up-flow membrane-less microbial fuel cell (UFML MFC) was developed to study the feasibility of the bioreactor for decolorization of Acid Orange 7 (AO7) and electricity generation simultaneously. The performance of UFML MFC was evaluated in terms of voltage output, chemical oxygen demand (COD) and color removal efficiency by varying the concentration of AO7 in synthetic wastewater. The results shown the voltage generation and COD removal efficiency decreased as the initial AO7 concentration increased; this indicates there is electron competition between anode and azo dye. Furthermore, there was a phenomenon of further decolorization at cathode region which indicates the oxygen and azo dye are both compete as electron acceptor. Based on the UV–visible spectra analysis, the breakdown of the azo bond and naphthalene compound in AO7 were confirmed. These findings show the capability of integrated UFML MFC in azo dye wastewater treatment and simultaneous electricity generation.

Synthesis of rod-like α-FeOOH nanoparticles and its photocatalytic activity in degradation of an azo dye: Empirical kinetic model development

Goethite (α-FeOOH) nanostructures were synthesized using a well-known one-step facile hydrothermal method. The X-ray diffraction pattern confirmed the formation of the α-FeOOH with orthorhombic structure. The field emission scanning electron microscopy revealed that the synthesized α-FeOOH had rod-like morphology. The photocatalytic activity performance of synthesized α-FeOOH was evaluated in the degradation of C.I. Acid Orange 7 (AO7), as a model organic pollutant. The degradation of AO7 in mere photolysis without α-FeOOH and adsorption with α-FeOOH is negligible. The degradation of AO7 with α-FeOOH under UVA irradiation was considerable which confirmed the photocatalytic activity of synthesized α-FeOOH. The band gap of synthesized nanoparticles was obtained by Tauc-Mott plot and determined around 2.5ev. The photocatalytic degradation kinetic characteristics were studied by investigation effect of different operational parameters including α-FeOOH dosage, pH and initial AO7 concentration as the effective operational parameters. Using the non-linear regression, an empirical kinetic model was developed for predicting the photocatalytic degradation efficiency by taking account into the apparent first order kinetic and operational parameters. The predictive capability of developed model was evaluated by comparing the experimental photocatalytic degradation efficiency and calculated ones by model. It was found that the developed model fit well with experimental data.

Removal of noxious dye—Acid Orange 7 from aqueous solution using natural pumice and Fe-coated pumice stone

Rapid removal of the Acid Orange 7 (AO7) from aqueous solutions using natural pumice (NP) and Fe-coated pumice (Fe-CP) as low-cost adsorbents was well investigated and elucidated. The impact of several influential parameters such as initial pH, initial AO7 concentration and contact time on the adsorption of AO7 removal was studied and optimized. The good agreement of adsorption equilibrium data and analysis of isotherms with the Freundlich isotherm proved that it is the best fitted adsorption isotherm model for the depicting the AO7 adsorption on both the developed adsorbents, which clearly indicates the heterogeneity of the adsorbent surface. The maximum adsorption capacities for the NP and Fe-CP were found to be 15.56 and 27.68mg/g, respectively. The rate of adsorption followed the pseudo-second-order kinetic model.

Easy simultaneous synthesis–immobilization of nanosized CuO–ZnO on perlite as a photocatalyst for degradation of acid orange 7 from aqueous solution in the presence of visible light

In order to improve the photocatalytic activity, the researchers have loaded some metals or metal oxides on semiconductors such as TiO2 and ZnO surface. This study investigated the degradation of acid orange 7 (AO7) from aqueous solution by prepared nanosized CuO–ZnO immobilized on expanded perlite (nCuO-ZnO-P) as a photocatalyst in the presence of visible light. First, nCuO-ZnO-P was simultaneously synthesized–immobilized by pyrolysis of previously adsorbed Cu2+ and Zn2+ on perlite at 723.15 K in oven. The results showed that, unlike ZnO, the prepared nanosized photocatalyst has an effective photocatalytic activity in the presence of visible light. The effective parameters on AO7 degradation which were evaluated in the designed batch photoreactor included initial concentration of AO7 (C0), pH, the granule size of used perlite for immobilization (D), and temperature (T). It was found that the content of degradation was followed by increasing order: C0 = 15 > 25 > 35 > 45 > 55 mg l−1, pH 7 > 8 > 9 > 6 > 5, D = 0.50 > 0.75 > 1.00 > 1.25 > 1.50 mm, and T = 318.15 > 308.15 > 298.15 > 288.15 > 278.15 K.

Preparation of natural pyrite nanoparticles by high energy planetary ball milling as a nanocatalyst for heterogeneous Fenton process

In the present study pyrite nanoparticles were prepared by high energy mechanical ball milling utilizing a planetary ball mill. Various pyrite samples were produced by changing the milling time from 2h to 6h, in the constant milling speed of 320rpm. X-ray diffraction (XRD), scanning electron microscopy (SEM) linked with energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis and Brunauer–Emmett–Teller (BET) were performed to explain the characteristics of primary (unmilled) and milled pyrite samples. The average particle size distribution of the produced pyrite during 6h milling was found to be between 20nm and 100nm. The catalytic performance of the different pyrite samples was examined in the heterogeneous Fenton process for degradation of C.I. Acid Orange 7 (AO7) solution. Results showed that the decolorization efficiency of AO7 in the presence of 6h-milled pyrite sample was the highest. The impact of key parameters on the degradation efficiency of AO7 by pyrite nanoparticles catalyzed Fenton process was modeled using central composite design (CCD). Accordingly, the maximum removal efficiency of 96.30% was achieved at initial AO7 concentration of 16mg/L, H2O2 concentration of 5mmol/L, catalyst amount of 0.5g/L and reaction time of 25min.

Removal of Acid Orange 7 Dye from Water Via Plasma-Polymerized Allylamine-Coated Quartz Particles

A novel method of acid orange 7 (AO7) removal has been developed via the deposition of plasma-polymerized allylamine (ppAA) films on quartz particles. ppAA films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization time of 5 to 60 min. Polymerization time had a significant effect on surface chemistry where the XPS nitrogen concentration, XPS C-O, C-N concentration, isoelectric point and the number of positively charged groups per nm2 all increased with increasing polymerization time. Increasing polymerization time increased AO7 adsorption due to greater concentrations of positively charged amine groups on the surface. The pH and initial AO7 concentration were varied to investigate their effect on AO7 adsorption. Increasing the initial AO7 concentration increased adsorption for all polymerization times. pH had a significant effect on AO7 adsorption with maximum adsorption at pH 3 and significantly less at pH values of 5–9. Regeneration of ppAA-coated quartz particles for up to 4 cycles using pH 12 Milli-Q water resulted in only slight losses in adsorption capacities. ppAA-coated particles have shown to successfully remove AO7 dye from solution and therefore demonstrate potential for use in the treatment of industrial dye wastestreams.

Reductive transformation and enhancement in biodegradability of mono-azo dye by high carbon iron filings (HCIF)

In the present study, reductive degradation of commercially used mono-azo dye, C.I. Acid Orange 7 (AO7), has been investigated using high carbon iron filings (HCIF) in batch reactors. Extent of dye degradation was monitored on the basis of removal efficiencies of various parameters like color and chemical oxygen demand (COD). Enhancement in biodegradability of AO7 dye was evaluated on the basis of an increase in BOD5 and BOD5/COD ratio. The effect of different operating conditions, namely, initial pH, HCIF dosage, and initial dye concentration, were evaluated at mixing intensity of 30 rpm for 120 min. More than 90% decolorization was achieved at all experimental conditions studied. Optimum decolorization efficiency of 99.55% was achieved at pH 3 using HCIF dosage of 28.56 g/l and 100 mg/l initial AO7 concentration. In the adsorption experiments carried out at different initial dye concentrations, a significant amount of unreduced dye remained adsorbed onto the HCIF even after 120 min of reaction time, thus, decreasing the actual reduction efficiency. Under the optimal reaction conditions, COD removal efficiency of 64.71% was observed. The biological oxygen demand (BOD) for 100 mg/l AO7 dye solution increased from 2.32 mg/l of the untreated dye solution to 27.84 mg/l after 120 min. Biodegradability measured as BOD5/COD ratio was increased significantly from 0.0136 of the original solution to 0.464 after 120 min. First-order dye degradation kinetics was evaluated at different operating conditions. In experiments conducted at different pH, highest degradation constant (kobs) of 1.40 min−1 was recorded at pH 3. kobs increased linearly with increase in HCIF dosage whereas highest surface area normalized rate constant (kSA) of 0.0495 l/m/ min was achieved at 28.56 g/l HCIF dosage. The kobs decreased as the initial AO7 concentration increased, suggesting saturation of ZVI surface reactive sites. The results suggest that HCIF can be used as a promising pre-treatment method, for recalcitrant azo dyes during conventional treatment methods.

Determination of optimum conditions for removal of Acid Orange 7 in batch-recirculated photoreactor with immobilized TiO2-P25 nanoparticles by Taguchi method

This study investigated the optimum conditions in the removal of model contaminant C.I. Acid Orange 7 (AO7) in batch-recirculated photoreactor with immobilized TiO2-P25 nanoparticles. The effect of different operational parameters such as initial concentration of AO7, volume of solution, volumetric flow rate, time of the reaction, and power of light source were studied and optimized by Taguchi method. Sixteen experiments were performed to examine the effect of the parameters on the removal of AO7. To reduce the error, each experiment was repeated three times and the signal/noise (S/N) was calculated. Results indicated that the power of light source was the most effective parameter in comparison to others. Based on the S/N ratio, the optimized conditions for the removal of AO7 in batch-recirculated photoreactor were initial concentration of AO7 (20 mg L−1), volume of solution (500 mL), volumetric flow rate (140 mL min−1), time of reaction (60 min), and power of light source (13 W).

Degradation of Acid Orange 7 in aqueous solution by zero-valent aluminum under ultrasonic irradiation

Degradation of azo dye Acid Orange 7 (AO7) by zero-valent aluminum (ZVAl) in combination with ultrasonic irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with sole ultrasonic, sole ZVAl/air system, ultrasonication + ZVAl/air system (US-ZVAl). In ZVAl/air system, the degradation of AO7 could almost not be observed within 30min. The degradation of AO7 by ZVAl/air system was obviously enhanced under ultrasound irradiation, and the enhancement is mainly attributed to that the production of hydroxyl radicals in ultrasound-ZVAl process was much higher than that in sole ultrasonic or in sole ZVAl/air system. The variables considered for the effect of degradation were the power of ultrasound, the initial concentration of AO7, as well as the initial pH value and the dosage of zero-valent aluminum. The results showed that the decolorization rate increased with the increase of power density and the dosage of ZVAl, but decreased with the increase of initial pH value and initial concentration of AO7. More than 96% of AO7 removal was achieved within 30min under optimum operational conditions (AO7: 20mg/L, ZVAl: 2g/L, pH: 2.5, ultrasound: 20kHz, 300W). This study demonstrates that ultrasound-ZVAl process can effectively decolorize the azo dye AO7 in wastewater.

Hydrophilic composite membranes for simultaneous separation and photocatalytic degradation of organic pollutants

TiO2/Al2O3 composite membranes were prepared using a sol–gel technique. After membrane characterization, six layers as optimal number of coatings was chosen (0.2μm homogenous thin film). Filtration and photodegradation were coupled by using TiO2/Al2O3 membranes in a photocatalytic membrane reactor under UV light. Experimental results clearly showed that TiO2 thin film under UV irradiation enhanced the wettability of the ceramic membrane, were higher and more stable water flux were reached rapidly. Acid Orange 7 (AO7) were used as model pollutant. Dye was not completely degraded, 25% of degradation was obtained for only one pass corresponding to a contact time of several milliseconds. Photonic efficiency equal to 0.29 was reached. Evolution of the kinetic degradation versus the initial concentration of AO7 were consistent with the Langmuir Hinselwood model. The photodegradation allows to increase significantly composite membrane flux and to strongly prevent flux decrease when AO7 solutions were filtrated. Membrane cleaning was performed without chemicals by irradiating membrane surface under static conditions.

Enhanced bio-decolourisation of acid orange 7 by Shewanella oneidensis through co-metabolism in a microbial fuel cell

The decolourisation of acid orange 7 (AO7) (C.I.15510) through co-metabolism in a microbial fuel cell by Shewanella oneidensis strain 14063 was investigated with respect to the kinetics of decolourisation, extent of degradation and toxicity of biotransformation products.Rapid decolourisation of AO7 (>98% within 30 h) was achieved at all tested dye concentrations with concomitant power production. The aromatic amine degradation products were recalcitrant under tested conditions. The first-order kinetic constant of decolourisation (k) decreased from 0.709 ± 0.05 h−1 to 0.05 ± 0.01 h−1 (co-substrate – pyruvate) when the dye concentration was raised from 35 mg l−1 to 350 mg l−1. The use of unrefined co-substrates such as rapeseed cake, corn-steep liquor and molasses also indicated comparable or better AO7 decolourisation kinetic constant values. The fully decolourised solutions indicated increased toxicity as the initial AO7 concentration was increased.This work highlights the possibility of using microbial fuel cells to achieve high kinetic rates of AO7 decolourisation through co-metabolism with concomitant electricity production and could potentially be utilised as the initial step of a two stage anaerobic/aerobic process for azo dye biotreatment.

Design equation with mathematical kinetic modeling for photooxidative degradation of C.I. Acid Orange 7 in an annular continuous-flow photoreactor

The decolorization of C.I. Acid Orange 7 (AO7), an anionic monoazo dye of acid class was investigated using UV/H(2)O(2) process in an annular continuous-flow photoreactor (ACFP) as a function of oxidant, dye concentrations, reactor length and volumetric flow rate. The removal efficiency of AO7 was a function of operational parameters and increased with increasing initial concentration of H(2)O(2) but it was low at high flow rate and initial concentration of AO7. Results indicated that the decolorization rate was pseudo-first order kinetic with respect to the dye concentration. A rate equation for decolorization of AO7 was obtained by kinetic modeling. Design equation for ACFP reactor was obtained with combination of kinetic model and rearranged tubular reactor design equation. Design equation was used for predicting concentration of AO7 and also electrical energy per order (E(EO)) at different conditions. The calculated results obtained from design equation and kinetic model were in good agreement with experimental data.

Effect of dye auxiliaries on the kinetics of advanced oxidation UV/H2O2 of Acid Orange 7 (AO7)

AbstractBACKGROUND: The effect of four dye‐auxiliary chemicals, typically employed in acid dyeing, on the performance of UV/H2O2 decolouration of the model non‐biodegradable dye C.I. Acid Orange 7 (AO7) was investigated. The initial concentration of AO7 was 0.150 g L−1, while the concentration of the auxiliary compounds (NaCl, Na2SO4, Na2CO3 and CH3COOH) was varied in the range 1–10 g L−1.RESULTS: The negative influence of the presence of the dye‐auxiliary compounds studied on the decolouration rate of AO7 decreased in the following order: CH3COOH > Na2SO4 > NaCl > Na2CO3. Results were quantified in terms of the observed kinetic rate constant, kobs (s−1), of AO7 decolouration as a function of dye auxiliary chemical concentration. The decolouration rate of AO7 decreased as the concentration of dye‐auxiliary compound increased in the range 1–5 g L−1, while higher concentrations had a minor effect. Upon addition of 5 g L−1 of CH3COOH, NaCl and Na2SO4, the kinetic rate constant decreased by 39%, 30% and 12%, respectively.CONCLUSIONS: It was concluded that the presence of NaCl, Na2SO4 and above all of CH3COOH should be considered in the design of the treatment of real dye‐bath effluents by UV/H2O2. Copyright © 2008 Society of Chemical Industry

Granular activated carbon-biofilm configured sequencing batch reactor treatment of C.I. Acid Orange 7

The aim of this study is to investigate the mineralization of C.I. Acid Orange 7 (AO7) by biological process in oxygen limited condition under GAC-biofilm configured sequencing batch reactor (SBCR) operation. The granular activated carbon (GAC) used was immobilized with azo dye-degrading microbes through attachment by immersing the GAC into anaerobic bioreactor treating dye-containing wastewater for more than 200 days. The SBCR system was fed with 2 l of AO7-containing wastewater and was operated in FILL, REACT, DRAW and IDLE periods in a time ratio of 3:20:0.45:0.15 for a cycle time of 24 h. Nearly complete mineralization of AO7 was achieved with the biological system working at initial AO7 concentration of 625 mg/l, dissolved oxygen (DO) below 0.25 mg/l and without the presence of external carbon sources. Reductive environment was well developed in the phases with the addition of external carbon sources, and this had improved the decolorization rate but deteriorated chemical oxygen demand (COD) removal efficiency.

Kinetic modeling on photooxidative degradation of C.I. Acid Orange 7 in a tubular continuous-flow photoreactor

The decolorization of C.I. Acid Orange 7 (AO7), an anionic monoazo dye of acid class, was investigated using UV radiation in the presence of H 2O 2 in a tubular continuous-flow photoreactor as a function of oxidant and dye concentrations, reactor length and volumetric flow rate. The removal efficiency of AO7 depends on the operational parameters and increases as the initial concentration of H 2O 2 is increased but it decreases when the flow rate and initial concentration of AO7 are increased. The decolorization rate follows pseudo-first order kinetic with respect to the dye concentration. A rate equation for decolorization of AO7 was achieved by kinetic modeling. This model allows predicting concentration of AO7 in different photoreactor lengths for different volumetric flow rates and initial concentrations of H 2O 2 and AO7. The calculated results obtained from kinetic model were in good agreement with experimental data.

Decolorization of orange II by catalytic oxidation using iron (III) phthalocyanine-tetrasulfonic acid

Orange II, C.I. Acid Orange 7 (AO7), is oxidatively decolorized via catalytic oxidation by iron(III) phthalocyanine-tetrasulfonic acid (Fe(III)-PcTS) as a biomimetic catalyst and KHSO 5 as an oxygen donor. The nature of the decolorization of AO7 was investigated in the catalyst concentration range of 10–50 μM, in which the initial concentration of AO7 was 417 mg l −1. A 99.6% decolorization was observed at [KHSO 5] = 2.5 mM and [Fe(III)-PcTS] = 20 μM after a 3-h reaction period. However, the fact that only 4.9% of the TOC was removed indicated that the conversion to CO 2 was incomplete. The results of a total organic nitrogen analysis of the reaction mixture showed that the nitrogen in the azo chain was mainly converted to N 2 gas. In addition, 38.6% of the AO7 was converted to 1,2-dihydroxynaphthalene, and 21.4% to p-phenolsulfonic acid. These results indicate that the degradation via this catalytic system involves the conversion of AO7 to phenolic compounds, followed by N 2 production. In addition, a Microtox test showed that toxicity of the solution increased as a result of AO7 oxidation using this catalytic system.

Photodestruction of Acid Orange 7 (AO7) in aqueous solutions by UV/H 2O 2: influence of operational parameters

The photodestruction of Acid Orange 7 (AO7), an anionic acidic dye, was studied in the UV/H 2O 2 process. H 2O 2 and UV light have a negligible effect when they were used on their own. Removal efficiency of AO7 was sensitive to the operational parameters such as initial H 2O 2 concentration, initial AO7 concentration, pH and different light sources. The photodestruction of AO7 was inhibited by addition of EtOH as an electron scavenger. The semi-logarithmic graphs of the concentration of AO7 versus time (t<30 min) were linear, suggesting pseudo-first order reactions (k optimum =0.105 min −1) . A simple kinetic model is proposed which is in agreement with experimental results.