Decolorization Efficiency Of Acid Orange 7 Research Articles

Decolorization of acid orange 7 in moving bed biofilm reactor packed with polyhydroxyalkanoate/activated carbon

Moving bed biofilm reactor (MBBR) using various carrier medium has been widely employed in wastewater treatment. This study aimed to investigate the feasibility of polyhydroxyalkanoate (PHA) and activated carbon (AC) composite (PHA/AC) as biofilm carrier to enhance MBBR treatment of azo dye acid orange 7 (AO7). Each PHA/AC carrier had a height of 0.40 cm and a cylindrical diameter of 1.25 cm. The biofilm on PHA/AC carrier was characterized using microscopic and chemical analysis. AO7 decolorization efficiency and kinetics were evaluated. The incorporation of AC in PHA was found to promote biofilm growth. Mature biofilm of 2075 ± 79.30 μm was successfully formed on PHA/AC carrier. Compared to a control reactor, the MBBR with 5 % (v/v) PHA/AC exhibited improved decolorization, with decolorization efficiency and first-order rate constant, kAO7, increasing from 78.2 % and 9.90 × 10−4 min−1 to 95.0 % and 1.70 × 10−3 min−1, respectively. The enhancement of decolorization in MBBR was attributed to the presence of anoxic zone within the biofilm that favored the azo bond cleavage. Batch studies on the effects of suspended activated sludge (AS) and biofilm amounts showed an additive effect on decolorization efficiency when combined. The combined suspended AS and biofilm also resulted a 3–4 folds increase in kAO7 value compared to AS alone. The results indicate that PHA/AC was an effective carrier and its biofilm exhibited high decolorizing ability for AO7. The enhancement provided by the PHA/AC biofilm makes it advantageous for developing efficient and environmentally-friendly wastewater treatment systems with compact design and minimal sludge production.

Activation of peroxymonosulfate by pyrophosphate for the degradation of AO7 at neutral pH.

In the present study, pyrophosphate (PP) was used to activate peroxymonosulfate (PMS) for acid orange 7 (AO7) removal under neutral pH conditions. The removal rate of AO7 (20 mg/L) was 84% within the reaction time with a rate constant value of 0.0165 min-1 under optimum conditions. Additionally, the effects of the concentrations of PMS and PP in solutions with various pH values and the coexisting inorganic anions on AO7 removal were measured. In addition, the performance of phosphate (P(V)) on PMS activation was compared with that of phosphite (P(III)) species. In contrast to P(III), the concentration of P(V) showed a positive correlation with the efficiency of AO7 decolorization. PMS activation in different types of buffer solutions was also examined, and the results indicated that the decolorization efficiency of AO7 induced by PP addition, and the buffer solution also contributed to PMS self-decomposition. Singlet oxygen (1O2) might be the primary reactive oxygen species (ROS) in the PP/PMS system in which AO7 is decolorized at an initial pH of 7.06, as indicated by quenching experiments and electron spin resonance (ESR) tests. Therefore, PP/PMS systems may be promising technologies for removing organic contaminants, particularly for PP-rich electroplating wastewater.

Performance of Meyerozyma caribbica as a novel manganese peroxidase-producing yeast inhabiting wood-feeding termite gut symbionts for azo dye decolorization and detoxification

For hazardous toxic pollutants such as textile wastewater and azo dyes, microbial-based and peroxidase-assisted remediation represents a highly promising and environmentally friendly alternative. Under this scope, gut symbionts of the wood-feeding termites Coptotermes formosanus and Reticulitermes chinenesis were used for the screening of manganese peroxidase (MnP) producing yeasts intended for decolorization and detoxification of textile azo dyes, such as Acid Orange 7 (AO7). To this end, nine out of 38 yeast isolates exhibited high levels of extracellular MnP activity ranging from 23 to 27 U/mL. The isolate PPY-27, which had the highest MnP activity, was able to decolorize various azo dyes with an efficiency ranging from 87.2 to 98.8%. This isolate, which represents the molecularly identified species Meyerozyma caribbica, was successfully characterized in terms of morphological and physiological traits, as well as enzymatic activities. Almost complete decolorization was achieved by the MnP-producing M. caribbica strain SSA1654 after 6 h of incubation with 50 mg/L of the sulfonated azo dye AO7 at 28 °C with an agitation speed of 150 rpm. The maximum decolorization efficiency of AO7 reached 93.8% at 400 mg/L. The decolorization of AO7 was confirmed by Fourier transform infrared (FTIR) and UV–Vis spectral analysis. High performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC–MS) were used to identify AO7 decomposition intermediates. Based on UV–Vis spectra, FTIR, HPLC, and GC–MS analyses, a plausible AO7 biodegradation mechanism pathway was explored, showing azo bond (-N=N-) cleavage and toxic aromatic amines mineralization CO2 and H2O. Microtox® and phytotoxicity assays confirmed that the AO7 metabolites produced by the strain SSA1654 were almost non-toxic compared to the original sulfonated azo dye.

Activation of peroxymonosulfate by phosphite: Kinetics and mechanism for the removal of organic pollutants

In this study, phosphite (HPO32−) was used as a novel activator to activate peroxymonosulfate (PMS) for acid orange 7 (AO7) removal. Under the optimized conditions, the decolorization efficiency of AO7 was 82.1% within 60 min with rate constant values (kobs) of 0.0301 min−1. Besides, effects of the solution pH and the co-existing inorganic anions including Cl−, HCO3−, HPO42− and SO42− on AO7 removal were also investigated. Except for SO42−, other examined co-existing inorganic anions displayed favorable effects on the removal of AO7. Furthermore, the mechanism for PMS activation by the HPO32− was deeply elucidated by radical scavenger including ethanol (EtOH), tert-butanol (TBA), l-histidine and tiron, and electron spin resonance (ESR) studies. It was proposed that singlet oxygen (1O2) would be the dominant reactive oxygen species (ROS) in the HPO32−/PMS system for contamination degradation at neutral pH condition. The findings of this study provided useful information for the application of the substances in industrial wastewaters to activate PMS for organic contaminants degradation and in particular for HPO32--rich electroplating wastewater treatment.

Biochar-activated persulfate for organic contaminants removal: Efficiency, mechanisms and influencing factors.

Turning biomass into biochar as a multifunctional carbon-based material for water remediation has attracted much research attention. Sawdust and rice husk were selected as feedstock for biochar (BC) production, aiming to explore their performance as a catalyst to activate persulfate (PS) for degrading acid orange 7 (AO7). There was an excellent synergistic effect in the combined BC/PS system. Sawdust biochar (MX) showed a faster and more efficient performance for the AO7 degradation due to its abundant oxygen functional groups, compared to rice husk biochar (DK). In the BC/PS system, AO7 was well decolorized and mineralized. Based on the two-dimensional correlation analysis method, the azo conjugation structure and naphthalene ring of AO7 molecule changed first then benzene ring changed during the reaction. Moreover, AO7 decolorization efficiency increased with the increase of PS concentration and biochar dosage, and the deacrease of pH. Biochar deactivated after used twice. When the biochar reached its adsorption equilibrium of AO7, the AO7 could not be degraded in the BC/PS system. SO4- and OH participated in the reaction together and OH played the main role in activating PS to AO7 decolorization based on the radical scavengers experiment. All of results indicate using biochar to activate PS for degradation of AO7 contaminated water is a promising method.

Synthesis of microsize Fe/Cu bimetallic particles using in situ acid‐mediated coating: Application on decolorization of azo dye acid orange 7

Iron‐based bimetallic particle has become an attractive material in environmental remediation, particularly for wastewater treatment. However, it is yet to be applied in large scale processes, mainly due to the requirement of multistep syntheses for the desired materials, as well as the rigorous control of the conditions for its synthesis. This study introduces a facile methodology to synthesize micro‐size iron/copper bimetallic particles (mFe/Cu‐BPs) by in situ coating of Cu on the surface of Fe in an acidic media for the removal of azo dye Acid Orange 7 (AO7) in aqueous media. Morphological analyses showed that Cu planted on the surface of the particles exhibit a dense leaf‐like structure with great connectivity and electron movement between Fe0 core and Cu shell. In addition, the effects on the decolorization of AO7 via key parameters such as theoretical Cu mass loading (TMLCu), initial pH, dosage, and initial AO7 concentration were assessed. Experimental results revealed that the decolorization efficiency of AO7 was highly dependent on the operational conditions. Under optimal conditions (TMLCu of 0.6 g Cu/g Fe, initial pH of 3.0, mFe/Cu‐BP dosage of 45 g/L, and initial AO7 concentration of 1000 mg/L), decolorization of AO7 as a function of reaction time was investigated via UV‐vis spectrometry, which confirmed that the azo bond of AO7 successfully cleaved by mFe/Cu‐BPs. The maximum decolorization, COD, and TOC removal efficiencies were found to be 99.55, 83.91, and 73.81% after 30 min of reaction time, respectively. Lastly, the potential mechanism for the decolorization of AO7 is proposed. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1901–1907, 2018

Biodegradation of Acid Orange 7 in a combined anaerobic-aerobic up-flow membrane-less microbial fuel cell: Mechanism of biodegradation and electron transfer

A distinctive combination of anaerobic-aerobic in a single chambered up-flow membrane-less microbial fuel cell (UFML MFC) was developed to explore the interrelation and mechanism between Acid Orange 7 (AO7) biodegradation and bioelectricity generation. The performance of AO7 biodegradation in UFML MFC was evaluated by various operating configurations. This study demonstrated that the UFML MFC capable to sustain high decolorization efficiency throughout a long term operation. Besides, the obtained results illustrated that the AO7 decolorization would compete with exoelectrogens and other anaerobic microbial activities for electrons that released from the substrate. The decolorization efficiency of AO7 was ranging from 89% to 96% during operated in various configurations. However, the voltage output was highly affected as the AO7 dosage was increased. Therefore, these results indicated that most of the available electrons were more prone to be used by AO7 decolorization rather than voltage output. Moreover, the results suggested that the high AO7 dosage and continuous 24-h flow pattern could inhibit the other anaerobic microbial activities, and consequently more electrons can be used for AO7 decolorization and electricity generation. Furthermore, AO7 decomposition intermediates were further identified by using high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC–MS). The results demonstrated that the residual aromatic compounds from decomposition of AO7 were recalcitrant to be biodegraded in anaerobic region. However, the aromatic compounds can be further biodegraded in aerobic region. Therefore, the proposed biodegradation pathway showed the AO7 can be completely mineralized by using a combination of anaerobic-aerobic UFML MFC.

Carbonate-activated hydrogen peroxide oxidation process for azo dye decolorization: Process, kinetics, and mechanisms

Advanced oxidation processes offer effective solutions in treating wastewater from various industries. This study is the first time to investigate the potential of carbonate-activated hydrogen peroxide (CAP) oxidation process for the removal of organic pollutant from highly alkaline wastewaters. Azo dye acid orange 7 (AO7) was selected as a model pollutant. The influences of various parameters on AO7 decolorization by the CAP oxidation were evaluated. Furthermore, the active species involved in AO7 degradation were explored using scavenger experiments and electron spin resonance analysis. Additionally, AO7 degradation products by the CAP oxidation were identified to elucidate possible transformation pathways. Results showed that the CAP oxidation had better AO7 decolorization performance compared to bicarbonate-activated hydrogen peroxide method. The AO7 decolorization efficiency augmented from 3.70 ± 0.76% to 54.27 ± 2.65% when carbonate concentration was increased from 0 to 50 mM at pH 13.0, and then changed slightly with further increasing carbonate concentration to 70 mM. It increased almost linearly from 5.95 ± 0.32% to 94.03 ± 0.39% as H2O2 concentration was increased from 5 to 50 mM. Moreover, trace amount of Co(II) could facilitate AO7 decolorization by the CAP reaction. Superoxide and carbonate radicals might be the main reactive oxygen species involved in the CAP process. Finally, a possible degradation pathway of AO7 by the CAP oxidation was proposed based on the identified products.

Effect of Persulfate on the Degradation of Acid Orange 7 (AO7) by Dielectric Barrier Discharge Plasma

A novel process for decolorization of Acid Orange 7 (AO7) dye wastewater by dielectric barrier discharge plasma coupled with persulfate (PS) was investigated, and the enhancing performance of PS on the AO7 decolorization efficiency and energy efficiency were examined under different molar ratio of AO7 to PS (MR), gas discharge gap, initial concentration of AO7 and gas discharge atmosphere. The experimental results indicate that the decolorization efficiency (ƞ) and the energy efficiency (γ) increased with the addition dosage of PS until the MR of 1:100, and an increment in the decolorization efficiency and energy efficiency reached 60.5% and 0.33 g/(kW h) respectively at an MR of 1:100. An increase in the gas discharge gap and in the initial concentration of AO7 greatly decreased the decolorization efficiency of AO7, but the increment in energy efficiency due to PS addition increased with the AO7 initial concentration and discharge gap except for the discharge gap of 8 mm, and the highest increment in energy efficiency of 0.75 g/(kW h) was obtained at a gas discharge gap of 6 mm and an initial concentration of 30 mg/L. Moreover, higher AO7 decolorization efficiency was achieved in air than in Ar atmosphere, while the increment in decolorization efficiency and energy efficiency due to PS addition was not influenced by the gas discharge atmosphere. The experimental results imply that PS was activated into stronger radical species such as sulfate radical and hydroxyl radical, which contributed to a higher decolorization performance. The possible motivator of PS was tentatively concluded as UV irradiation, Joule heating effect, etc.

Synergetic degradation of Acid Orange 7 (AO7) dye by DBD plasma and persulfate

The synergetic degradation performance of Acid Orange 7 (AO7) by dielectric barrier discharge plasma (DBDP) and persulfate (PS) was examined. Addition of PS in AO7 solution hardly degraded any AO7 in 50min, but when DBDP was initiated over the solution surface, PS greatly enhanced the decolorization efficiency of AO7, and the improvement efficacy depended on the addition dosage of PS, the applied voltage, the air discharge gap and the gas discharge atmosphere. An increase in AO7 decolorization efficiency of 60% was obtained for AO7 solution of 5mg/L at a PS addition dosage of 100:1 (molar ratio of PS to AO7) and a discharge power of 3.6W, correspondingly, the decolorization rate of AO7 was accelerated by 6.7 times. The improvement on AO7 degradation mainly attributes to the enhanced production of sulfate radical (SO4−) and hydroxyl radicals (OH) which are produced from the activated PS by DBD plasma. The activators of PS were tentatively speculated as the UV irradiation and heat released in discharge channels, and hydrated electrons may also play a role in the activation process of PS. The intermediates identified by GC–MS and the TOC measurement show that addition of PS into AO7 solution had little effect on the degradation pathways of AO7, but greatly improved the mineralization of AO7, which was mainly due to the increased production of SO4− and OH.

Bioelectrochemical reduction of an azo dye by a Shewanella oneidensis MR-1 formed biocathode

Presently there is great interest to develop pure culture cathodes in bioelectrochemical systems (BES) for achieving decolorization/reduction of azo dyes. In this study, we investigated the decolorization of a model azo dye, acid orange 7 (AO7) in a biocathode inoculated with a model electrogenic microorganism Shewanella oneidensis MR-1 (MR-1). The decolorization efficiency of AO7 reached 95.8 ± 4.6%, 86.4 ± 2.0%, and 77.8 ± 1.0% in 46 h in the biocathode fed with lactate, in the biocathode without lactate, and in the abiotic cathode respectively. Thus, enhanced decolorization of AO7 occurred in the biocathode, compared to the abiotic cathode, regardless of the presence of lactate. To further investigate the AO7 reduction mechanism and electron transfer between the electrode and S. oneidensis, the cathode potential was controlled such that hydrogen was not produced. In the absence of lactate, the AO7 decolorization efficiency (78.5 ± 0.8%) and sulfanilic acid (SA) production efficiency (70.9 ± 1.5%) in the biocathode were higher than the AO7 decolorization efficiency (63.7 ± 3.6%) and the SA production (56.1 ± 1.9%) efficiency in the abiotic cathode. This suggests that the reduction of AO7, with electrode as the sole electron donor, was enhanced by electron transfer between the cathode and the S. oneidensis formed biofilm on the cathode surface. This study demonstrated that S. oneidensis enhanced the capture of electrons from the cathode electrode for the reduction of the organic pollutant AO7.

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.

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.