Removal Efficiency Of Acid Orange 7 Research Articles

Vitamin C promoted refractory organic contaminant elimination in the zero-valent iron/peracetic acid system: Efficiency, mechanism and effects of various parameters

The conventional zero-valent iron/peracetic acid (ZVI/PAA) system is severely limited owing to the passivation of ZVI and the low recovery of Fe2+. In this study, a reducing agent, vitamin C (H2A), was used for the first time to enhance the ZVI/PAA system as a way to improve its degradation performance. Under optimal conditions, the removal efficiency of the H2A/ZVI/PAA system was 82.9%, while that of the H2A/PAA and ZVI/PAA systems were only 19.0% and 25.6%. Free radical quenching and electron paramagnetic experiments (EPR) confirmed that CH3C(O)O•, •OH and CH3C(O)OO• were the major active species for acid orange 7 (AO7) degradation with contributions of 9.7%, 75% and 14.4%, respectively. The degradation mechanism was proposed through UV–vis full-wavelength scanning and chemical oxygen demand (COD) experiments. The removal of AO7 was not affected in the presence of Cl−, SO42− and HCO3−, while inhibition occurred with humic acid. ZVI exhibited excellent catalytic properties and stability, and the removal efficiency of AO7 exceeded 70% after three cycles. Additionally, the H2A/ZVI/PAA system showed good ability to remove AO7 in well water, lake water, river water and reservoir water, and the elimination efficiency of MO, DCF and ACE also exceeded 70%. Overall, this study contributes new cognition for enhancing the ZVI/PAA system to degrade contaminants, which is expected to achieve a cleaner water environment.

Visible-light-driven removal of AO7 by peroxymonosulfate-assisted Z-scheme AgBr/LaFeO3 heterojunction vis accelerated electronic transfer

In this work, AgBr/LaFeO3 (ALFO) Z-scheme heterojunction photocatalyst was successfully synthesized by simple in-situ precipitation method, and photocatalysis was coupled with peroxymonosulfate (PMS) to remove acid orange 7 (AO7) by enhanced electron transfer. The Z-scheme heterojunction between AgBr and LaFeO3 provides the driving force for charge transfer and improves the charge separation rate. At the same time, PMS can act as an electron acceptor to promote photogenerated charge separation and maximize the generation of reactive oxygen species. The obtained results showed that the prepared ALFO photocatalyst has excellent reusability and excellent AO7 removal efficiency. This work successfully demonstrated the synergistic effect of ALFO photocatalyst, promoted light utilization and PMS activation, and provided a potential application prospect for effectively reducing environmental pollution by using solar energy.

Using a promising biomass-based biochar in photocatalytic degradation: highly impressive performance of RHB/SnO2/Fe3O4 for elimination of AO7.

The release of industrial dyes into the environment has recently increased, resulting in harmful effects on people and ecosystems. In recent years, the use of adsorbents in photocatalytic nanocomposites has attracted significant interest due to their low cost, efficiency, and eco-friendly physical and chemical characteristics. Herein, Acid Orange 7 (AO7) removal was investigated by photocatalytic degradation using Rice Rusk Biochar (RHB), Tin (IV) Oxide (SnO2), and Iron Oxide (Fe3O4) as heterogeneous nanocomposite. After the preparation of RHB, the nanocomposite was synthesized and characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET), and Fourier-Transform Infrared Spectroscopy (FT-IR). To optimize the elimination of AO7 by the One-Factor-At-a-Time (OFAT) method, effective parameters including mixing ratio (RHB:SnO2:Fe3O4), dye concentration, solution pH, and nanocomposite dose were studied. The results showed that the removal efficiency of AO7 after 120min under the optimal mixing ratio of 1:1.5:0.6, dye concentration of 75mg/l, solution pH of 4, and nanocomposite dose of 0.7g/l was 92.37%. Moreover, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal rates were obtained at 82.22 and 72.22%, respectively. The Average Oxidation State (AOS) and Carbon Oxidation State (COS) of the AO7 solution were increased after the process, indicating biodegradability improvement. Various scavenger effects were studied under optimal conditions, and the results revealed that O2- and H+ reactive species play a crucial role in the photocatalytic degradation of AO7. The reusability and stability of nanocomposite were tested in several consecutive experiments, and the degradation efficiency was reduced from 92 to 79% after five consecutive cycles. It is expected that this research contributes significantly to the utilization of agricultural waste in photocatalytic nanocomposites for the degradation of environmental pollutants.

Low salinity enhances azo dyes degradation in aerobic granular sludge systems: Performance and mechanism analysis

The biodegradation performance of azo dyes can be enhanced under low salinity conditions, but the internal biodegradation mechanism is still unclear. Aerobic granular sludge (AGS), a salt-tolerant biological wastewater treatment technology, was used in this study to explore the enhancement mechanism of acid orange 7 (AO7) degradation at low salinity level (1.0 %). Results indicated that the AGS structure and reactor performance were almost unaffected by different AO7 concentrations (5–10 mg/L). Compared with salt-free conditions, the AO7 removal efficiency was elevated by 9.9 %–19.0 % at 1.0 % salinity level, owing to the enrichment of AO7 decolorizing bacteria (e.g. Acinetobacter) and functional enzymes (e.g. FMN-dependent azoreductase). The up-regulated genes involving in the key metabolic functions (e.g. carbon metabolism and oxidative phosphorylation) promoted the electron and energy production, thereby facilitating the AO7 decolorization and degradation. These results aid understanding of the enhancement mechanism of AO7 biodegradation under low salinity conditions from macroscopic and microscopic perspectives.

Constructing Z-scheme AuAg@δ-Bi2O3/BiOBr multi-heterojunction for efficient photocatalytic removal of dye, antibiotic and heavy metal ions: Performance and mechanism investigation

The AuAg alloy nanoparticles were decorated on the δ-Bi2O3 surface to obtain AuAg@δ-Bi2O3, then AuAg@δ-Bi2O3 were hydrothermally combined with BiOBr plate to form Z-scheme AuAg@δ-Bi2O3/BiOBr. The photocatalytic activity of samples were evaluated by the removal of dyes (rhodamine B (RhB) and acid orange 7 (AO7)), tetracycline (TC) and reduction of Cr(VI) under simulated sunlight irradiation. With the decoration of δ-Bi2O3, the δ-Bi2O3/BiOBr composites exhibit higher photocatalytic activity than bare BiOBr. The optimal catalytic efficiency is achieved by 10%δ-Bi2O3/BiOBr sample, which leads to ∼75.7% of AO7, 84.9% of RhB and 67.5% of Cr(VI) removed after 25 min irradiation. After the introduction of AuAg nanoparticles, the photocataltyic activity of 10%δ-Bi2O3/BiOBr can be further enhanced. The removal efficiency of AO7, RhB and Cr(VI) can reach ∼97.9%, ∼97.3% and ∼84.5% after 25 min irradiation, respectively. The AuAg alloy nanoparticles located at the interface of Z-scheme δ-Bi2O3/BiOBr can accelerate the photogenerated charges separation over the way of a Z-scheme charge migration mechanism. In addition, AuAg alloy nanoparticles located at δ-Bi2O3 surface compensates the consumption of photogenerated charges in the direct Z-scheme δ-Bi2O3/BiOBr heterojunction due to their SPR effect, and even further promotes the separation of photogenerated charges in the composite.

Non-noble-metal TiC-nanoparticle-promoted charge separation and photocatalytic degradation performance on Bi2O3 microrods: degradation pathway and mechanism investigation.

In the present work, a promising binary TiC/Bi2O3 photocatalyst was obtained via a simple hydrothermal route. In the photodegradation experiment of acid orange 7 (AO7) and tetracycline (TC) irradiated by simulated sunlight, the attachment of TiC nanoparticles on the Bi2O3 microrods leads to an obvious improvement in the photocatalytic removal properties of the Bi2O3 microrods. The optimal removal efficiency of AO7 was achieved by the 7.5%TiC/Bi2O3 sample, which results in about 91.5% dye removal within 75 min of reaction. Meanwhile, the 7.5%TiC/Bi2O3 sample also exhibits favorable photodegradation performance for the degradation of TC, leading to about ∼76.9% TC being degraded after 75 min of irradiation. More importantly, the degradation pathways of AO7 and toxicity analysis of the intermediate products were performed based on liquid chromatography-mass spectrometry detection and theoretical simulation. The superior photocatalytic behavior of the TiC/Bi2O3 composite is attributed to the effective separation and migration of photoexcited electrons and holes in the heterojunction, where the TiC nanoparticles act as an acceptor of photoexcited electrons.

Modeling and optimization of Acid Orange 7 adsorption process using magnetite/carbon nanocomposite

The efficiency of a new magnetite/carbon nanocomposite (MCN), applied as adsorbent for the removal of Acid orange 7 (AO7) dye from aqueous solutions was investigated. The MCN was synthesized by combustion, and characterized using modern and relevant techniques. A full factorial design experiment was conducted to identify the optimum conditions for adsorption. The main effect of four process parameters: pH, dye concentration, adsorbent dose and temperature, and their interactions on the removal efficiency were established. A highly significant (p < 0.001) second-order polynomial model (R2 and R2adj of 0.99) provided great removal rates using: pH of 6–7, adsorbent dose of 1–1.5 g/L and initial dye concentration of 50–100 mg/L. The significance of the independent variables as well as their interactions was tested by ANOVA which revealed that the regression is statistically significant at 95% confidence level. Predicted data obtained for the removal efficiency were in good agreement with the experimental determinations (98%). The adsorption isotherms study demonstrated that the Sips model had the best fit with the experimental data (R2 0.9810) and a maximum adsorption capacity of 180.04 mg/g was obtained. The negative values obtained for Gibbs free energy and for enthalpy indicate that the adsorption process is spontaneous and has an exothermic character. After four consecutive cycles of adsorption/desorption, the removal efficiency of AO7 using MCN was yet 83.60%. The results demonstrated that MCN is a promising adsorbent, and response surface optimization could be successfully used to optimize the adsorption process parameters.

Hydrogen peroxide enhanced sonophotocatalytic degradation of acid orange 7 in aqueous solution: optimization by Box–Behnken design

AbstractBACKGROUNDSonophotocatalysis has gained great attention for research into practical applications to treat refractory organic dye from wastewater. However, its degradation efficiency needs to be improved further. To further enhance the sonophotocatalytic performance, here we report a novel hydrogen peroxide (H2O2)‐assisted titania (TiO2)‐based sonophotocatalyic system (H2O2‐US‐UV/TiO2) for degradation of acid orange 7 (AO7).RESULTSEffects of operating parameters including catalyst dosage, concentration of the oxidative agents and initial pH were analyzed through a response surface method coupled with Box–Behnken experimental design (RSM‐BBD) and experiments. Introducing H2O2 into the US‐UV/TiO2 system can significantly enhance AO7 removal. A quadratic model was proposed for predicting AO7 degradation using the RSM‐BBD method, and the statistical significance of the model was confirmed by ANOVA. The real AO7 removal efficiency (95.8%) under experimental conditions of 0.5 g L−1 TiO2, 4 mmol L–1 H2O2, and initial pH 3 was comparable with the predicated value (98.6%) obtained from this model. Quenching tests revealed that the hydroxyl radical (˙OH) was the key reactive species in the sonophotocatalytic system. Degradation products including 2‐naphthol, 4‐carboxylphenylglycine, cinnamic acid and 1,10‐Decanediol were identified.CONCLUSIONAdding H2O2 improved the degradation performance of AO7 in the US‐UV/TiO2 system; H2O2 concentration was a more significant experimental factor than initial pH and TiO2 dosage. A degradation pathway of AO7 removal was suggested according to results of liquid chromatography‐mass spectrometry. The novel hybrid H2O2‐US‐UV/TiO2 system can be utilized as an efficient process for recalcitrant dye wastewater treatment. © 2021 Society of Chemical Industry (SCI).

Synthesized Cr/TiO2 immobilized on pumice powder for photochemical degradation of acid orange-7 dye under UV/visible light: influential operating factors, optimization, and modeling.

The current study aimed to investigate the removal efficiency of acid orange-7 (AO7) using synthesized Cr/TiO2 immobilized on pumice powder under visible light and UV irradiation. The characterization of synthesized nanocatalyst examined by scanning electron microscope, X-ray diffraction, and Fourier transforms infrared. The optimum of experimental parameters including catalyst dosage, dye concentration, time and pH, D-optimal Design (DOD) along with response surface methodology obtained by R software. The initial and outlet concentration was measured using a spectrophotometer. Besides, Analysis of variance results for the quadratic model showed simple linear regression with high significance and provided as a predicting model. The differences less than 0.2 between multiple and adjusted R2 in two models indicate that two examined models fitted suitably. The highest removal efficiency of AO7 was 95 and 74% under visible and UV irradiation, respectively. Therefore, the higher removal efficiency in visible light reduces the costs and energy, moreover, offers an environmentally friendly method. The results showed that the removal efficiency of AO7 increased considerably with rising catalyst dosage and time, as well as minimizing dye concentration, and pH.

Efficient removal of acid orange 7 using a porous adsorbent-supported zero-valent iron as a synergistic catalyst in advanced oxidation process.

This study focuses on the synthesis of granular red mud reinforced by zero-valent iron (Fe@GRM) and its application for the removal acid orange 7 (AO7) from aqueous solution. Then ZVI is employed as a catalyst for the activation of persulfate (PS) to produce sulfate radicals (SO4•-) that are produced at 900°C in an anoxic atmosphere using the direct reduction of iron oxide in the red mud with maize straw as the reductant. Furthermore, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used to illustrate the morphology and porous structure of the Fe@GRM. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that Fe@GRM was loaded with zero-valent iron. This characterization confirmed that the Fe@GRM was a porous structure material that contained zero-valent iron. The influence of conditions for AO7 elimination, including initial pH, Fe@GRM dosage, initial AO7 concentrations, and temperature, is also investigated. The removal efficiency of AO7 was 90.78% using Fe@GRM/PS, while only 18.15% was removed when Fe@GRM was used alone. The degradation kinetics were well fitted to a pseudo-first-order kinetic model, and the rate of removal increased with temperature, demonstrating an endothermic elimination process. The Arrhenius activation energy of the process was 20.77kJ/mol, which indicated that the reduction of AO7 was a diffusion-mediated reaction. Fe@GRM is a low-cost material that demonstrated outstanding performance with great potential for wastewater treatment.

Electrochemical/Fe3+/peroxymonosulfate system for the degradation of Acid Orange 7 adsorbed on activated carbon fiber cathode.

Acid Orange 7 (AO7), as a most common and widely used synthetic dyes in the printing and dyeing industry, was hardly degradable by traditional wastewater treatment methods. Here, activated carbon fiber (ACF) as an in-situ regenerated cathodic adsorbent in the electrochemical/Fe3+/peroxymonosulfate process (EC/ACF/Fe3+/PMS) was firstly investigated for AO7 removal and compared with several different processes. The results indicated that the effective adsorption of AO7 on ACF can be enhanced under electrolytic conditions, while the adsorbed AO7 on ACF can be completely degraded and mineralized in EC/ACF/Fe3+/PMS process resulting in the in-situ regeneration of ACF. Besides, the electrical energy per order values were investigated, which showed an apparent reduction of electrical energy consumption from 0.42831 to 0.09779 kWh m-3 when ACF-cathode replaced Pt-cathode. Further study revealed that higher conversion rate of Fe2+ from Fe3+ was observed with ACF-cathode. It deserved to be mentioned that the removal efficiency of AO7 was satisfactory and stable even after reusing ACF cathode for 10 times. Furthermore, structure and elements of ACF surface were investigated, which indicated the structure of ACF was intact in EC/ACF/Fe3+/PMS due to inhibition of ACF corrosion by electron migration at cathode. In addition, the total iron content of the effluent in EC/ACF/Fe3+/PMS was lower than that of EC/Fe3+/PMS due to the deposition of iron on ACF-cathode surface. Therefore, advantages of EC/ACF/Fe3+/PMS for AO7 degradation were not only a much higher oxidation efficiency and in-situ regenerated cathodic adsorbent, but also a lower electrical energy consumption and lesser iron ions contents in the effluent.

TiO2-SiO2/GAC particles for enhanced electrocatalytic removal of acid orange 7 (AO7) dyeing wastewater in a three-dimensional electrochemical reactor

Abstract In this work, granular activated carbon (GAC) supported TiO2-SiO2 oxide (TiO2-SiO2/GAC) was prepared and packed in a three-dimensional electrochemical reactor (3DER) for the removal of acid orange 7 (AO7) dyeing wastewater. The characteristics and the electrocatalytic performance of the prepared TiO2-SiO2/GAC were investigated to verify the feasibility of TiO2-SiO2/GAC application as particle electrodes. Results show that the TiO2-SiO2/GAC could significantly improve the AO7 removal efficiency, extend service life of particle electrodes, and enhance the stability of 3DER system. Orthogonal array was designed to optimize the operation parameters of 3DER, which was determined as electric field intensity 1 V/cm, filling amount of TiO2-SiO2/GAC particles 200 g/L, electrolytic concentration (Na2SO4) 0.07 mol/L, pH 3, treatment time 120 min. Under the optimal condition, the AO7 decolorization rate and COD removal efficiency are 83.20% and 48.95% respectively. The possible intermediates generated in 3DER during AO7 decomposition were identified and the biodegradability of the effluent was also estimated. Results suggest that the 3DER with TiO2-SiO2/GAC particle electrodes could be an alternative for the pretreatment of dyeing wastewater before biological treatment.

Oxidation of organic contaminant in a self-driven electro/natural maghemite/peroxydisulfate system: Efficiency and mechanism

Electro-assisted iron-mediated persulfate (PS) activation process has been successfully employed to oxidize organic contaminant. However, a majority of iron-based catalysts used for PS activation was synthesized through complicated or demanding procedures and may have potential risks on environment during the preparation process. Herein, natural maghemite (NM) which is abundant on the earth was employed to activate peroxydisulfate (PDS) in an electrolytic cell. The voltage was provided by microbial fuel cell (MFC) instead of external power as reported in the previous studies, so as to establish a self-driven electro/natural maghemite/PDS system (MFC/NM/PDS) for the oxidation of acid orange 7 (AO7). The results showed that above 90% removal efficiency of AO7 was achieved in a wide range of pH (3.0–9.0) after 100min reaction. Singlet oxygen was identified for the first time during PDS activation and surface bound sulfate radicals served as the dominant active species responsible for AO7 oxidation. The underlying mechanism of AO7 elimination in the MFC/NM/PDS system was elucidated through quenching tests, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) techniques. The variation of TOC and cytotoxicity to Escherichia coli was explored. The intermediate products formed were identified using LC-TOF-MS technique and a possible pathway of AO7 degradation was proposed.

Study of C.I. Acid Orange 7 removal in contaminated water by photo oxidation processes

C.I. Acid Orange 7 (AO7) commonly used as a textile dye and could be degraded by UV/ZnO, UV/H2O2 and UV/H2O2/Fe (III) (photofenton) processes. In the photocatalytic degradation of dye by UV/ZnO process, effect of some parameters such as UV irradiation time, presence of ZnO and UV irradiation, pH, concentrations of ZnO, dye, H2O2 and ethanol was examined and first order reaction rate constant was calculated equal to 2.39×10-2 min-1 at experimental condition. The semi-log plot of dye concentration versus time was linear, suggesting first order reaction. Efficiency of photodegradation process in the absence of ZnO photocatalyst and UV light was small. Increasing the UV irradiation time increased AO7 removal. Ethanol had inhibitory effect on this process. Maximum AO7 removal was seen at neutral pH area. In the UV/H2O2 process, effect of some parameters such as presence of H2O2 and UV irradiation, amount of H2O2, effect of pH and addition of bicarbonate on the efficiency of dye removal were examined. Absence of each of UV irradiation or H2O2 decreased AO7 removal efficiency near to zero. Increasing H2O2 concentration increased dye removal to some extent but at higher H2O2 concentrations, dye removal efficiency did not increase. Increasing pH to value about 9 increased the AO7 removal efficiency and increasing bicarbonate anion concentration decreased it. Rate constant of AO7 removal by this process was calculated to be equal to 4.221×10-1 min-1 at experimental condition. Also, the order of UV/ H2O2/Fe (III) &gt; UV/ H2O2 &gt; UV/Fe (III) &gt; H2O2/Fe (III), was seen for AO7 removal efficiency of these processes. Increasing Fe (III) and oxalate concentration increased dye removal efficiency.

Simultaneous synthesis-immobilization of nano ZnO on perlite for photocatalytic degradation of an azo dye in semi batch packed bed photoreactor

Abstract A novel, simple and simultaneous synthesis-immobilization of nano ZnO on perlite (nZnO-P) as a photocatalyst for photocatalytic degradation of Acid orange 7 (AO7) in aqueous solution was investigated. The effect of operational parameters such as initial dye concentration, initial pH, flow rate, photocatalyst granule size, temperature and the kinetic of the removal of AO7 in terms of the Langmuir-Hinshelwood model in a designed semi batch packed bed photoreactor connected to an on-line sampling UV-Vis spectrophotometer was studied. The results showed that AO7 removal efficiency increased with nZnO-P using the designed setup and the proposed photocatalyst was more efficient than TiO2 as a standard catalyst. Our results confirmed the pseudo-first-order kinetics model. The values of the adsorption equilibrium constant, KAO7, the kinetic rate constant of surface reaction, kc, and the activation energy (Ea) were found to be 0.57 (mg.l−1)−1, 0.41 mg.l−1.min−1 and 11.44 kJ/mol, respectively.

Simultaneous removal of color, organic compounds and nutrients in azo dye-containing wastewater using up-flow constructed wetland

Combination of aerobic and anaerobic processes in constructed wetlands can enhance the treatment performance in textile wastewater. This study assessed the treatment of azo dye Acid Orange 7 (AO7) and nutrients using five laboratory-scale up-flow constructed wetlands (UFCW) with and without supplementary aeration, and with different emergent plants. Supplementary aeration controlled the size of aerobic and anaerobic zones in the UFCW reactors as evidenced by the oxidation–reduction potential (ORP) and dissolved oxygen (DO) profile of the UFCW. The AO7 removal efficiency was above 95% in all UFCW reactors and most of the color was extensively removed in the anaerobic region of the UFCW beds. The intermediates produced through the breakage of azo bond were significantly reduced in the UFCW reactors with supplementary aeration. The results indicated the applicability of the UFCW reactors to the treatment of azo dye-containing wastewater. The removals of T-N and T-P were in the range of 60–67% and 26–37%, respectively, among the UFCW reactors. The COD and NH 4-N removals in the aerated reactors were about 86 and 96%, respectively. On the other hand, the COD and NH 4-N removals were in the range of 78–82% and 41–48%, respectively, in the non-aerated reactors. The supplementary aeration enhanced the removal efficiencies in organic matter, NH 4-N and aromatic amines in the UFCW reactors.

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.

Effects of gap size and UV dosage on decolorization of C.I. Acid Orange 7 by UV/H 2O 2 process

Wastewater from textile processing plants can be highly colored and difficult to decolorize. During the past few years attention has been drawn to chemical techniques that could be used to textile wastewater decolorization. A crucial feature in designing such systems is the optimization of operating conditions. In the present study, advanced oxidation treatment, the UV/H 2O 2 process has been applied to decolorization of the azo dye C.I. Acid Orange 7 (AO7) in aqueous solution in a batch photo reactor. The effects of the reactor gap size and UV dosage on decolorization of dye have been investigated. The method of study involved monitoring the rate of dye solution decolorization during irradiation by a low-pressure mercury lamp and varying gap size and volume of the reactor. The rate of color removal was studied by measuring of the absorbance at characteristic wavelength. The gap size of the reactor was adjusted by different depths of the reactor. The results of this study showed that the removal efficiency of AO7 is optimal with 0.3 cm gap size and 83.33 W l −1 of UV dosage.

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.

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.