Decolorization Of Acid Orange Research Articles

Synergetic degradation of Acid Orange 7 by fly ash under ultrasonic irradiation

The present work aimed to investigate the feasibility of fly ash, a by-product of coal combustion, for enhanced degradation of an azo dye Acid Orange 7 (AO7) under ultrasonic irradiation. X-ray diffraction and energy dispersive X-ray analysis indicated that ultrasonic irradiation did not change the crystal structure of fly ash. The decolorization efficiency of AO7 by the combined process could reach 76.7%, while ultrasonic process alone only removed 3.8% of AO7 within 60 min. A synergetic effect between fly ash and ultrasonic irradiation was firstly observed. The decolorization of AO7 fitted the first-order rate kinetics, and the K1 was 0.0246 min−1 for the combined process. Radical quenching experiment by iso-propanol (ISP) indicated that 24.8% of AO7 decolorization was contributed to hydroxyl radicals, indicating that the contribution of hydroxyl radicals was not as significant as expected. Theoretic analysis revealed that the sizes of fly ash cover the estimated resonance size of cavitation bubbles generated in this experiment. As such, fly ash particles could act as nucleus to generate more cavitation bubbles and enhance the ultrasonic degradation efficiency. Fly ash combined with ultrasonic irradiation has the great potential for practical treatment of wastewater containing organic pollutants.

Monopersulfate oxidation of Acid Orange 7 with an iron(III)-tetrakis(N-methylpyridinium-4-yl)porphyrin intercalated into the layers of montmorillonite and pillared clay

A biomimetic catalyst, iron(III)-tetrakis(N-methylpyridinium-4-yl)porphyrin (FeTMPyP), was loaded into montmorillonite (Mt) and pillared clay (Pi). The catalytic activities of the prepared catalysts for the decolorization of Acid Orange 7 (AO7) in the absence and presence of humic acid (HA), a major component of waste water, were compared. Turnover frequencies (TOFs) for the FeTMPyP-loaded Pi (6.7–9.4h−1) were larger than those for the FeTMPyP-loaded Mt (2.9–3.3h−1), while decolorization for the FeTMPyP-loaded Mt was inhibited in the presence of HA (TOFs of 1.3–2.1h−1). These results can be attributed to the fact that the large expansion in basal spacing for the Mt permitted the catalyst to be eluted and HA to be inserted into the Mt layer. However, the levels of catalyst elution and the inhibition of AO7 decolorization by HA were significantly suppressed in the case of the FeTMPyP-loaded Pi catalyst, which was prepared using smaller OH/Al and Al/Mt ratios. These results indicate that the Pi is more suitable support for the FeTMPyP catalyst than the Mt.

RSM modeling and optimization of glucose oxidase immobilization on TiO2/polyurethane: Feasibility study of AO7 decolorization

In this paper, simultaneous photocatalytic (TiO2/polyurethane) and enzymatic (glucose oxidase) process was investigated in re-circulating open channel photo-bioreactor for decolorization of Acid Orange 7 (AO7). Response surface methodology (RSM) was employed to determine effects of three main independent parameters (incubation temperature, pH value of the enzyme solution, and incubation time) on immobilization of glucose oxidase (GOx) on TiO2/PU. Analysis of variance showed high coefficient of determination value (R2=99.74%, adjusted-R2=99.51%). The optimum value of the incubation temperature, pH, and incubation time for immobilization process were found to be 37°C, 6.15, and 1h, respectively. Results demonstrated that the pseudo-first order constant of AO7 decolorization using GOx/TiO2/PU and TiO2/PU under UV light with feed flow rate of 10mL/min were 0.307min−1 and 0.0297min−1, respectively.

Ultrasound enhanced heterogeneous activation of peroxydisulfate by bimetallic Fe-Co/GAC catalyst for the degradation of Acid Orange 7 in water

Bimetallic Fe-Co/GAC (granular activated carbon) was prepared and used as heterogeneous catalyst in the ultrasound enhanced heterogeneous activation of peroxydisulfate (PS, S2O2−8) process. The effect of initial pH, PS concentration, catalyst addition and stirring rate on the decolorization of Acid Orange 7 (AO7) was investigated. The results showed that the decolorization efficiency increased with an increase in PS concentration from 0.3 to 0.5 g/L and an increase in catalyst amount from 0.5 to 0.8 g/L. But further increase in PS concentration and catalyst addition would result in an unpronounced increase in decolorization efficiency. In the range of 300 to 900 r/min, stirring rate had little effect on AO7 decolorization. The catalyst stability was evaluated by measuring decolorization efficiency for four successive cycles.

A novel photochemical system of ferrous sulfite complex: Kinetics and mechanisms of rapid decolorization of Acid Orange 7 in aqueous solutions

We previously reported the decolorization of the azo dye Acid Orange 7 (AO7) by sulfate radical (SO4−) in the presence of iron(II) sulfite complex and oxygen under UV–vis irradiation (photo-iron(II) sulfite system). This system, however, achieves very limited mineralization of AO7 (in terms of total organic carbon (TOC) removal), which is not in accordance with literature reports on the oxidation of organic contaminants by SO4−. In the present work, kinetics and products under irradiation of xenon lamp (350 W) were analyzed to reveal the reaction pathway of decolorization of AO7. Steady-state approximation (SSA) of SO4− radicals and apparent kinetics of AO7 were examined. The reaction between AO7 and SO4− was found to proceed in two steps, namely, electron transfer and SO4− addition. The second-order rate constant for the reaction between AO7 and SO4− was found to be 8.07 ± 1.07 × 109 M−1 s−1 by SSA and 6.80 ± 0.68 × 109 M−1 s−1 by competition kinetics method. The apparent kinetics of the decolorization of AO7 under irradiation closely fits the mechanism of radical chain reactions of various reactive sulfur species. By liquid chromatography coupled with mass spectrometry, we identified the sulfate adduct AO7–SO4 and confirmed the two-step reaction between AO7 and SO4−. This stable sulfate adduct provides a good explanation of the poor TOC removal during decolorization of AO7 by the photo-iron(II) sulfite system.

Performance study of open channel reactor on AO7 decolorization using glucose oxidase/TiO2/polyurethane under UV–vis LED

An open channel photo-bioreactor irradiated with visible and UVA light-emitting diode (UVA–vis LED) was evaluated in a recirculated mode. The novel process was composed of TiO2nanoparticles/polyurethane (PU) and glucose oxidase (GOx)/TiO2/PU. The ability of LEDs as a light source in decolorization of acid orange 7 (AO7) was investigated using the mentioned simultaneous method. Furthermore, decolorization of AO7 was studied under various conditions including different feed flow rates and glucose concentrations in the photo-bioreactor. The results demonstrated that application of GOx/TiO2/PU photo-biocatalyst under UVA-LED and Blue-LED was technically feasible due to high percentage (>99%) of decolorization in 45 and 90min with recycling rate of 10mL/min, respectively.

Evaluation of macrocomposite based sequencing batch biofilm reactor (MC-SBBR) for decolorization and biodegradation of azo dye Acid Orange 7

The present study deals with the decolorization of azo dye Acid Orange 7 (AO7) using a macrocomposite based sequencing batch biofilm reactor (MC-SBBR). The effect of biofilm thickness towards the decolorization as well as the biodegradation of aromatic amines formed through AO7 treatment process was investigated. The results obtained indicate that the biofilm thickness reached its steady state at development period of 7 days with average biofilm thickness of about 115 μm. Almost complete decolorization of AO7 within 3 h of treatment time and more than 80% of the COD removal were achieved by the applied biofilm system. Decolorization of AO7 in this study nicely followed first order kinetic with a k value of 3.36 h−1. Fourier transform infrared (FTIR) and UV–Vis spectral analysis further confirmed the decolorization of AO7. Monitoring the dye metabolites through HPLC suggested that more than 90% of facultative anaerobically formed aromatic amines i.e. p-benzoquinone and 1,2-naphtolquinone were successfully removed by the MC-SBBR system. Phytotoxicity study also showed that AO7 metabolites produced by MC-SBBR system were less phytotoxic than the parent compound.

Reduction of Cr(VI) in aqueous solution with DC diaphragm glow discharge

This paper investigated the reduction of Cr(VI) in aqueous solution with direct current diaphragm glow discharge (DGD). The glow discharge sustained around the hole on a quartz tube which divided the electrolyte cell into two parts. The reduction efficiencies of Cr(VI) under different applied voltages, initial conductivities, hole diameters, hole numbers, initial pH values and initial concentrations were systematically studied. The results showed that the reduction efficiency of Cr(VI) increased with the increase of applied voltage, initial conductivity, hole diameter and hole number. The different initial pH values showed less effects on the reduction of Cr(VI). The reduction efficiency decreased with the increasing initial concentration. In addition, the simultaneous reduction of Cr(VI) and decolorization of acid orange (AO) with DGD were also fulfilled. Furthermore, the energy efficiency for Cr(VI) reduction with DGD was calculated and compared with those in photocatalysis and other glow discharge reactor.

Decolorization of Acid Orange 7 with peroxymonosulfate oxidation catalyzed by granular activated carbon

In this study, granular activated carbon (GAC) was used as a catalyst to activate peroxymonosulfate (PMS) to degrade azo dye Acid Orange 7 (AO7) in aqueous solution. A remarkable synergistic effect was found in the GAC/PMS combined system. The dye decolorization was much faster in the combined system than that in only GAC adsorption or PMS oxidation system. For the GAC/PMS system, the decolorization efficiency increased as the PMS concentration, the GAC dosage and the reaction temperature increased. The reaction followed a pseudo-first-order kinetic and a much lower activation energy was determined to be 25.13kJmol−1. The recovery performance of GAC was also studied through the GAC-reuse experiment. It was found that GAC had no obvious deactivation after four times reusing, which implied that the catalysis ability of GAC can be regenerated by the GAC/PMS combined system. Although GAC has almost lost its adsorption capacity, the GAC/PMS combined system could still significantly degrade AO7 as before. The initial reaction mechanisms were also discussed in detail.

Photocatalytic activity of La3+-doped TiO2 synthesized via sol-gel method

La3+-doped TiO2 samples were synthesized via sol-gel method using titanium tetraisopropoxide as inorganic precursor. The X-ray diffraction, scanning electron microscopy, X-ray phototoelectron spectroscopy (XPS) and nitrogen adsorption measurements were used to characterize the samples. Doping with La3+ inhibited the transformation of anatase phase to rutile during calcination treatment and the growth of crystallite size. XPS analysis confirmed the presence of La3+in the form of La2O3 on the surface of TiO2. The photocatalytic activity of La3+-doped TiO2 samples was investigated in terms of decolorization and degradation efficiencies of Acid Orange 7 (AO7) dye. It was found that doping with La3+ enhanced the photocatalytic activity of TiO2. The performance of doped samples was also evaluated using synthetic dye-bath effluent of AO7. Solar-driven La3+-doped TiO2 photocatalysis was found significantly efficient for the decolorization and degradation of AO7.

Biosorption and biodegradation of Acid Orange 7 by Enterococcus faecalis strain ZL: optimization by response surface methodological approach

Reactive dyes account for one of the major sources of dye wastes in textile effluent. In this study, decolorization of the monoazo dye, Acid Orange 7 (AO7) by the Enterococcus faecalis strain ZL that isolated from a palm oil mill effluent treatment plant has been investigated. Decolorization efficiency of azo dye is greatly affected by the types of nutrients and the size of inoculum used. In this work, one-factor-at-a-time (method and response surface methodology (RSM) was applied to optimize these operational factors and also to study the combined interaction between them. Analysis of AO7 decolorization was done using Fourier transform infrared (FTIR) spectroscopy, desorption study, UV-Vis spectral analysis, field emission scanning electron microscopy (FESEM), and high performance liquid chromatography (HPLC). The optimum condition via RSM for the color removal of AO7 was found to be as follows: yeast extract, 0.1% w/v, glycerol concentration of 0.1% v/v, and inoculum density of 2.5% v/v at initial dye concentration of 100 mg/L at 37 °C. Decolorization efficiency of 98% was achieved in only 5 h. The kinetic of AO7 decolorization was found to be first order with respect to dye concentration with a k value of 0.87/h. FTIR, desorption study, UV-Vis spectral analysis, FESEM, and HPLC findings indicated that the decolorization of AO7 was mainly due to the biosorption as well as biodegradation of the bacterial cells. In addition, HPLC analyses also showed the formation of sulfanilic acid as a possible degradation product of AO7 under facultative anaerobic condition. This study explored the ability of E. faecalis strain ZL in decolorizing AO7 by biosorption as well as biodegradation process.

Degradation of Acid Orange 7 in aqueous solution by a novel electro/Fe2+/peroxydisulfate process

A novel process in which electrochemistry (EC) was coupled with ferrous ion activation of peroxydisulfate (Fe2+/S2O82−) was proposed for the decolorization of Acid Orange 7. In this process, the reaction between peroxydisulfate and externally added ferrous ion results in the production of sulfate free radical as well as ferric ion, and at the same time ferrous ion could be electro-regenerated at the cathode by the reduction of ferric ion. Color removal by the Fe2+/S2O82− process was significantly enhanced in the presence of applied current. The effects of some important reaction parameters such as initial pH, current density, S2O82− concentration and Fe2+ concentration on the decolorization of Acid Orange 7 by EC/Fe2+/S2O82− process were investigated. The results showed that the decolorization efficiency was not significantly affected by the initial pH value, and the decolorization efficiency increased with the increase of S2O82− concentration and Fe2+ concentration. The current densities had little effect on the decolorization of Acid Orange 7 at the beginning of the reaction, while it improved the decolorization efficiency after 60min reaction. The GC–MS analysis was employed to identify the intermediate products and a plausible degradation pathway is proposed. The chemical oxygen demand (COD) removal efficiency was 57.6% after 60min reaction and it reached 90.2% when the reaction time was extended to 600min. Toxicity test with Daphnia magna showed that the acute toxicity of the solution increased during the first stage of the reaction, and then gradually decreased with the progress of the oxidation.

Involvements of chloride ion in decolorization of Acid Orange 7 by activated peroxydisulfate or peroxymonosulfate oxidation

The effects of chloride anion (Cl −) (up to 1.0 mol/L) on the decolorization of a model compound, azo dye Acid Orange 7 (AO7), by sulfate radical (SO 4 −·) based-peroxydisulfate (PS) or peroxymonosulfate (PMS) oxidation under various activated conditions (UV 254nm/PS, Thermal (70°C/PS, UV 254nm/PMS, Co 2+/PMS) were investigated. Methanol and NH 4 + were used as quenching reagents to determine the contributions of active chlorine species (dichloride radical (Cl 2 −·) and hypochlorous acid (HCIO)). The results indicated that the effects of Cl − on the reaction mechanism were different under various activated conditions. For UV/PS and Thermal/PS, the inhibition tendency became more clear as the Cl − concentration increased, probably due to the reaction between Cl − and SO 4 −· and the generation of Cl 2 −· or HCIO. For UV/PMS, Cl − did not exhibit inhibition when the concentration was below 0.1 mol/L. As Cl − concentration reached to 1.0 mol/L, the decolorization rate of AO7 was, however, accelerated, possibly because PMS directly reacts with Cl − to form HCIO. For Co 2+/PMS, Cl − exhibited a significant inhibiting effect even at low concentration (≤ 0.01 mol/L). When Cl − concentration exceeded 0.1 mol/L, the activation of PMS by Co 2+ was almost completely inhibited. Under this condition, HCIO maybe played a major role in decolorization of AO7. The results implicated that chloride ion is an important factor in SO 4 −·-based degradation of organic contamination in chloride-containing water.

A New Integrated Photoreactor for Microwave Assisted Decolorization of Acid Orange 7 (AO7) in Aqueous Solutions

A new integrated photoreactor was assembled using a newly designed source, emitting both microwave power and UV radiation inside the reacting medium. The method is highly flexible and cheap, eliminating the need for the multimode and monomode microwave applicators, which are currently used for the excitation of a microwave electrodeless lamp. The characteristics of the source and the results from the decolorization of Acid Orange AO7 in an aqueous solution with hydrogen peroxide are presented. The decolorization process was carried out in batch condition and as continuous treatment and the effective reaction constant of the processes are reported. The experiments show that the photoreactor could be suitable for industrial application.

Statistical analysis for enzymatic decolorization of acid orange 7 by Coprinus cinereus peroxidase

Enzymatic decolorization of the monoazo dye, acid orange 7 (AO7) by the fungal peroxidase from Coprinus cinereus NBRC 30628 is a complex system, which is greatly affected by temperature, pH, enzyme activity and the concentrations of H 2O 2 and dye concentration. The study of these factors and investigating the combined interactions between them by applying one-factor-at-a-time (OFAT) method and two other statistical methods including 2-factorial method and response surface methodology (RSM) were aimed in this work. Through OFAT analysis the optimized conditions were a temperature of 25 °C, pH 9.0 with H 2O 2 concentration of about 3.9 mM and AO7 concentration of 40 mg/l. A complete decolorization attained under such conditions in only 1 min. For statistical optimization, 2-factorial design method was applied first, and three factors of temperature, pH and initial dye concentration were recognized as significant factors. Then, response surface analysis was conducted through central composite design and a second-order polynomial model ( R 2 = 0.9718) was generated. ANOVA analysis of this model indicated that the temperature, pH and their interaction were the most significant in decolorization of AO7. The optimum condition through RSM was found to be the temperature of 25 °C, pH value of 9.0 and 50 mg/l of AO7 initial concentration, for the maximum decolorization of 100%.

Oxidative Decolorization of Acid Azo Dyes by a Mn Oxide Containing Waste

A Mn oxide containing mine tailings, generated in the Kalahari Mn fields, has been shown to oxidatively breakdown acid azo dyes acid orange (AO) 7, acid red 88, acid red 151 and acid yellow 36 but not acid yellow 9. The total reducible Mn content of the tailings is 33%, of which 3% is hydroquinone extractable and thus easily reducible. The net oxidation state of the Mn within the tailings is 3+. Decolorization of AO 7 by the Mn tailings increases with decreasing pH. The decolorization mechanism is initiated on the hydroxyl group of AO 7 and proceeds via successive electron transfers from the dye molecule to the oxide surface resulting in the asymmetric cleavage of the azo bond. The reaction products have been identified as 1,2-naphthoquinone, 4-hydroxybenzenesulfonate, and coupling products involving 1,2-naphthoquinone and benzenesulfonate radicals. The AO 7: Mn(III) reaction stoichiometry has been tentatively calculated to be 1:3. The reaction shows longevity with 95% decolorization still observed after 60 days of dye replenishment. Further breakdown of 1,2-naphthoquinone and 4-hydroxybenzenesulfonate was not observed, thus these compounds are considered to be the terminal reaction products of the AO 7- Mn tailings reaction.

Descoloração de alguns azocorantes por processos de fotólise direta e H2O2 /UV.

A descoloração dos azocorantes acid orange 7 (AO7), direct orange 34 (DO34), direct red 23 (DR23) e direct yellow 86 (DY86) foi investigada por fotólise direta e fotodegradação assistida por peróxido de hidrogênio respectivamente em reator fechado e aberto à atmosfera sob irradiação UV em seus pHs naturais a 30 ºC. A descoloração dos quatro azocorantes (1,5x10-4 mol L-1) não foi significativa, quando se utilizou H2O2 em reator fechado em 3 h de irradiação, enquanto que em reator aberto, a descoloração foi respectivamente de 96, 82, 32 e 45% para AO7, DO34, DR23 e DY86. A descoloração por fotólise direta em reator aberto foi significativamente maior em comparação ao fechado.

Decolorization of Azo Dyes in Bioelectrochemical Systems

Azo dyes are ubiquitously used in the textile industry. These dyes need to be removed from the effluent prior to discharge to sewage due to their intense color and toxicity. In this study we investigated the use of a bioelectrochemical system (BES) to abioticlly cathodic decolorization of a model azo dye, Acid Orange 7 (AO7), where the process was driven by microbial oxidation of acetate atthe anode. Effective decolorization of AO7 at rates up to 264 +/- 0.03 mol m(-3) NCC d(-1) (net cathodic compartment, NCC) was achieved at the cathode, with concomitant energy recovery. The AO7 decolorization rate was significantly enhanced when the BES was supplied with power, reaching 13.18 +/- 0.05 mol m(-3) NCC d(-1) at an energy consumption 0.012 +/- 0.001 kWh mol(-1) AO7 (at a controlled cathode potential of -400 mV vs SHE). Compared with conventional anaerobic biological methods, the required dosage of organic cosubstrate was significantly reduced in the BES. A possible cathodic reaction mechanism for the decolorization of AO7 is suggested based on the decolorization products identified: the azo bond of AO7 was cleaved at the cathode, resulting in the formation of the colorless sulfanilic acid and 1-amino-2-naphthol.

A novel advanced oxidation process to degrade organic pollutants in wastewater: Microwave-activated persulfate oxidation

This article, for the first time, provides a novel advanced oxidation process based on sulfate radical (SO4*-) to degrade organic pollutants in wastewater: microwave (MW)-activated persulfate oxidation (APO) with or without active carbon (AC). Azo dye acid Orange 7 (AO7) is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 (up to 1000 mg/L) is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion (up to 0.50 mol/L), the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 (500 mg/L) is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 (484 nm), during MW-APO, two bands in the ultraviolet region (228 nm and 310 nm) are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO4*- is identified with quenching studies using specific alcohols. Both SO4*- and *OH could degrade AO7, but SO4*- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.

Efeitos de agentes oxidantes e oxigênio dissolvido na descoloração do azo corante acid orange 7 por fotólise e fotocatálise

The decolorization of acid orange 7 azo dye by photolysis and photocatalysis by ZnO was investigated in the presence of oxidants such as NaClO3, NaBrO3, NaIO4, and K2S2O8 in an open reactor at 30 oC. The decolorization was relatively fast at lower oxidants concentrations and slow rate at larger concentrations, except for persulfate in the photocatalysis. Concerning photolysis the rate constant enhanced gradually, except for chlorate, outreaching the obtained values by photocatalysis, at higher concentrations. The air saturation decreased the rate constant in both processes and indicated that the azo dye can be decolorized without dissolved oxygen in persulfate medium.