Electrochemical degradation of Acid Red I dye and its treatment by UV light

Degradation of Acid Red I (ARI) dye by electrochemical treatment and UV light irradiation was studied in this work. The effect of the current density and the concentration of NaCl and dye on the decoloration and degradation efficiency were studied and optimized. The UV irradiation was monitored by UV-Vis spectrophotometry and chemical oxygen demand. The kinetic constants for decoloration and degradation were calculated. Degradation of 86% was achieved in 160?min and the first-order kinetic constant was 0.013?min^?1. Degradation products were identified by gas chromatography/mass spectrometry. The mechanism for the degradation of ARI was proposed.     

Photocatalytic degradation of methyl orange using ZnO nanorods

Nanosized ZnO rods were synthesized using a microwave-assisted aqueous method. High molecular weight polyvinyl alcohol was used as a stabilizing agent. Size, surface morphology, and structure were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). SEM and TEM images show that ZnO nanorods have diameters of about 50?nm and lengths of a few micrometers. The XRD pattern reveals that ZnO nanorods are of hexagonal wurtzite structure. The average crystallite size calculated from Scherrer's relation was found to be 40?nm. The effects of catalyst loading, pH value, and initial concentration of methyl orange on the photocatalytic degradation efficiency using ZnO nanorods as photocatalyst were discussed. The results revealed that ZnO nanorods with a diameter of 50?nm showed the highest photocatalytic activity at a surface density of 0.2?g?dm^?3.     

Photocatalytic degradation of methyl orange using ZnO/TiO composites

ZnO/TiO₂ composites were synthesized by using the solvothermal method and ultrasonic precipitation followed by heat treatment in order to investigate their photocatalytic degradation of methyl orange (MO) in aqueous suspension under UV irradiation. The composition and surface structure of the catalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscopy (TEM). The degradation efficiencies of MO at various pH values were obtained. The highest degradation efficiencies were obtained before 30min and after 60min at pH 11.0 and pH 2.0, respectively. A sample analysis was conducted using liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry. Six intermediates were found during the photocatalytic degradation process of quinonoid MO. The degradation pathway of quinonoid MO was also proposed.     

Carbon nanotubes-incorporated MIL-88B-Fe as highly efficient Fenton-like catalyst for degradation of organic pollutants

CNTs were incorporated into MIL-88B-Fe to get a new Fenton-like catalyst (C@M). Fe(II) was introduced in C@M to get a fast initiation of Fenton-like reaction. Fe(II) content in C@M was related with oxygen-containing functional groups on CNTs. C@M shows efficient catalytic degradation of pollutants over a wide pH range. Iron-based metal organic frameworks have been verified to be efficient heterogeneous Fenton catalysts due to their open pore channels and highly uniform distribution of metallic centers. In these catalysts, however, the iron element is mainly in the form of Fe(III), which results in a process required to reduce Fe(III) to Fe(II) to initiate Fenton reaction. To address this problem, carbon nanotubes (CNTs) with electron-rich oxygen-functional groups on the surface were incorporated into the metal organic frameworks (MIL-88B-Fe) to improve Fe(II) content for an enhanced Fenton-like performance. The prepared CNT@MIL-88B-Fe (C@M) showed much stronger catalytic ability toward H₂O₂ than MIL-88B-Fe. The pseudo-first-order kinetic constant for phenol degradation by C@M (0.32 min^–1) was about 7 times that of MIL-88B-Fe, and even higher than or comparable to the values of reported heterogeneous Fenton-like catalysts. Moreover, the Fenton-like system could effectively degrade various kinds of refractory organic pollutants and exhibited excellent catalytic activity over a wide pH range (4–9). XPS analysis confirmed that Fe(II) content of the catalyst gradually increased with CNT loadings. Electron spin resonance analysis showed that the signal intensity (•OH) of C@M was much higher than MIL-88B-Fe, which was consistent with the degradation efficiency of pollutants. Furthermore, the Fe(II) content of the catalyst gradually increased along with the oxygen-functional group content of CNTs. The result demonstrated that oxygen-containing functional groups of CNTs have a significant impact on the enhanced catalytic performance of C@M. This study provides a new insight to enhance Fenton reaction by using nanocarbon materials.     

Photocatalytic degradation of methyl orange using ZnO/TiO2 composites

ZnO/TiO₂ composites were synthesized by using the solvothermal method and ultrasonic precipitation followed by heat treatment in order to investigate their photocatalytic degradation of methyl orange (MO) in aqueous suspension under UV irradiation. The composition and surface structure of the catalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscopy (TEM). The degradation efficiencies of MO at various pH values were obtained. The highest degradation efficiencies were obtained before 30 min and after 60 min at pH 11.0 and pH 2.0, respectively. A sample analysis was conducted using liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry. Six intermediates were found during the photocatalytic degradation process of quinonoid MO. The degradation pathway of quinonoid MO was also proposed.     

Anaerobic degradation kinetics of reactive dye with different carbon sources

This study aims to investigate the anaerobic degradation kinetics of reactive dye, C.I. Reactive Red 141 (Evercion Red H-E7B) by partially granulated anaerobic mixed culture using three carbon sources, namely modified starch (MS), polyvinyl alcohol (PVA) and acrylic size (AS) during batch incubation. There is a first-order kinetics reaction in the decolorization processes using MS and PVA as carbon sources, while a zero-order kinetics relationship describes the decolorization process for the AS carbon source. The k values and color removal rate of decolorization with MS carbon source was higher than those of PVA and AS carbon sources. This is because the MS carbon source was well degraded in comparison to AS and PVA, respectively This study also found dye reduction could be enhanced through the addition of MS as a carbon source. The decolorization rates increased with decrease in dye concentrations of RR 141. In contrast, the decolorization rates increased with increase in COD concentration.     

赤泥基零价铁类芬顿降解罗丹明B和磺胺嘧啶的催化性能

为了有效去除废水中的有机污染物和实现赤泥(RM)的再利用,利用废弃活性炭(WAC)作为碳源,通过还原焙烧-磁选二步法制备了赤泥基零价铁(ZVI/RM)材料作为类芬顿催化剂催化氧化废水中常见的有机污染物罗丹明B (RhB)和磺胺嘧啶(SD).材料表征结果表明,零价铁均匀分布在材料上,且材料具有明显的介孔结构.当初始pH为...     

制备钙钛矿催化剂LaNiO3用于染料废水的降解脱色

为改善普通石墨电极的电催化性能,将以溶胶-凝胶法合成的钙钛矿氧化物LaNiO3混合其它原料做成气体扩散电极,用于电化学降解活性艳红X-3B,以脱色率来考核催化剂的氧还原活性.采用星点设计-效应面曲线法对催化剂制备工艺进行了优化,得出最佳工艺参数为:柠檬酸含量为金属离子物质的量的1.54倍,pH值为9.94,焙烧温度为824.39℃.采用X射线衍射(XRD)、动电位扫描等检测分析方法对所制备的催化剂进行表征和分析.结果表明,制备的催化剂晶相纯净、晶型完整、衍射峰强度较高,是较完整的钙钛矿结构;相比于普通石墨电极,掺杂催化剂的气体扩散电极极化阻力高,氧还原性能良好,有利于有机物的降解.     

Enhanced heterogeneous Fenton-like activity by Cu-doped BiFeO<Subscript>3</Subscript> perovskite for degradation of organic pollutants

Heterogeneous Fenton-like reaction has been extensively investigated to eliminate refractory organic contaminants in wastewater, but it usually shows low catalytic performance due to difficulty in reduction from Fe(III) to Fe(II). In this study, enhanced catalytic efficiency was obtained by employing Cu-doped BiFeO₃ as heterogeneous Fenton-like catalysts, which exhibited higher catalytic performance toward the activation of H₂O₂ for phenol degradation than un-doped BiFeO₃. BiFe_0.8Cu_0.2O₃ displayed the best performance, which yielded 91% removal of phenol (10 mg L^–1) in 120 min. The pseudo first-order kinetic rate constant of phenol degradation in BiFe_0.8Cu_0.2O₃ catalyzed heterogeneous Fenton-like reaction was 5 times higher than those of traditional heterogeneous Fenton-like catalysts, such as Fe₃O₄ and goethite. The phenol degradation efficiency could still reach 83% after 4 cycles, which implied the good stability of BiFe_0.8Cu_0.2O₃. The high catalytic activity of BiFe_0.8Cu_0.2O₃ was attributed to the fact that the doping Cu into BiFeO₃ could promote the generation of Fe(II) in the catalyst and then facilitate the activation of H₂O₂ to degrade the organic pollutants.

Open image in new window

     

Electrochemical degradation of the dye indigo carmine at boron-doped diamond anode for wastewaters remediation

Here we demonstrate that anodic oxidation with a boron-doped diamond (BDD) electrode can be applied to the remediation of wastewaters containing indigo carmine. This environmentally friendly method decontaminates completely acid and alkaline aqueous solutions of this dye. The degradation rate increases with increasing current and dye concentration. Indigo carmine is more rapidly removed in alkaline than in acid medium, but its kinetics does not follow a defined reaction order. Isatin 5-sulfonic acid is the main aromatic product formed. Oxalic and oxamic acids are generated as ultimate carboxylic acids. The nitrogen of the dye is converted into NH₄ ⁺ and NO₃ ⁻.     

One-step synthesis of bentonite-supported nanoscale Fe/Ni bimetals for rapid degradation of methyl orange in water

Although nanoscale zero-valent iron (nano-Fe⁰) is used to remediate pollutants, this reagent still presents stability and reactivity issues. To solve those issues, we synthesized bentonite-supported nanoscale iron bimetals B-Fe/Ni and B-Fe/Pd. We then used those reagents to degrade the methyl orange dye in water. Results of scanning electron microscopy and X-ray diffraction showed that the presence of bentonite and bimetal decreased nanoscale iron aggregation and increased methyl orange removal efficiency. More than 90 % of methyl orange at 100 mg/L was degraded by B-Fe/Ni (0.15 g/L) in 10 min. By comparison, only 62 % of methyl orange was degraded by B-Fe, and 35 % of methyl orange was degraded by nano-Fe⁰. The degradation rate decreased with the increase of the initial concentration of methyl orange. Lower pH allowed fast removal of methyl orange. Overall our findings show that a nanoscale Fe/Ni on bentonite-supported material is more efficient than nano-Fe⁰. One-step synthesis is more convenient than current two-step-synthesized nanoscale bimetals. Bentonite-supported nanoscale bimetals could therefore be an economic competitive candidate for contaminated water remediation.     

The usability of oxidative stress and detoxification biomarkers in Gammarus pulex for ecological risk assessment of textile dye methyl orange

The present study was undertaken to determine the toxicity of the methyl orange by using the changes of some antioxidant and detoxification enzyme activities in Gammarus pulex. Lethal Concentration (LC) value of Methyl Orange (MO) was determined. Three sublethal doses of MO (1/4; 1/8 and 1/16 of LC value) were exposed to G. pulex for 24 and 96?h. Superoxide dismutase (SOD), Catalase (CAT), Glutathione peroxidase (GSH-P_X), Cytochrome p450 (CYP1A1), Glutathione S-transferase (GST) activities as well as Glutathione (GSH) and Malondialdehyde (MDA) levels were determined by using The enzyme-linked immunosorbent assay (ELISA) kit. The CAT and CYP1A1 activities were decreased in all the groups exposed to different doses of MO. GST activity and GSH, MDA levels were increased all the groups exposed to different doses of MO. The GSH-P_X activities were changed in all the groups. MO affected SOD activity at different levels and in different concentrations. In our study, it has been found that exposure duration didn’t significantly affect the biochemical biomarkers except for GST and GSH. In conclusion, alterations in antioxidant and detoxification enzymes and lipid peroxidation may potentially be used as sensitive biomarkers for risk assessment of dyes in the environment and may contribute to the establishment of discharge regulations.     

响应面法优化一株链霉菌对偶氮染料AR30的降解脱色条件

以一株对偶氮染料红30(AR30)具有较强降解脱色作用的菌株Streptomyces sp.FX649为研究对象,在单因素实验基础上,选择染料初始浓度、培养时间、pH与培养温度为主要因素,采用Box-Benhnken组合实验和响应面分析法对降解条件进行了精确优化.经实验修正,获得了最佳降解脱色条件,即在染料浓度110 mg.L-1、培养时间36 h、pH 7.3与培养温度31.3℃时该菌对染料AR30的降解脱色率为95.1%.     

Treatment of azo dye Orange II in a sequential anaerobic and aerobic-sequencing batch ractor system

We studied the biodegradation of Orange II in a sequential anaerobic and aerobic-sequencing batch reactor system. Granular activated carbon was used either packed into a column or added directly into the anaerobic reactor to investigate the treatment performance between the two operation conditions. We found that the circulation of mixed liquor between the anaerobic reactor and the carbon-packed column enhanced the chemical oxygen demand from 28 to 52% and Orange II removal efficiencies from 88 to 96%, under simultaneous adsorption and biodegradation process. The morphology of microbes was observed under an electron-scanning microscope.     

Rapid photocatalytic degradation of the recalcitrant dye amaranth by highly active N-WO<Subscript>3</Subscript>

Dye wastewater is a major source of toxic aromatic amines released into the environment. Semiconductor photocatalysis is a clean, solar-driven process for the treatment of dye wastewater. To enhance applicability of semiconductor photocatalysis, the catalyst used should be visible light active. Here we report a facile synthesis of a highly visible-light-active nitrogen-doped tungsten oxide, N-WO₃, by thermal decomposition of peroxotungstic acid–urea complex. The structure and properties of N-WO₃ are characterized by X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy. The photodegradation of amaranth catalyzed by N-WO₃ is evaluated in a batch system under visible and ultraviolet A (UVA) light. Our results show successful doping of N in both interstitial and substitutional sites and the presence of N₂-like species. The N doping surprisingly expands the usable portion of the solar spectrum up to the near-infrared region and enhances the photocatalytic activity. At typical experimental conditions such as 25 mg/L of amaranth, 1 g/L of N-WO₃, and pH 7, 100 % degradation of amaranth is achieved within 2 h under both visible and UVA light. The photocatalytic activity of N-WO₃ is maintained in repeated cycles, indicating its exceptional photostability. To the best of our knowledge, this is the first time that a reusable, highly visible-light-active N-WO₃ can be obtained through thermal decomposition of peroxotungstic acid–urea complex.     

Accelerated degradation of orange G over a wide pH range in the presence of FeVO<Subscript>4</Subscript>

In this study, FeVO₄ was prepared and used as Fenton-like catalyst to degrade orange G (OG) dye. The removal of OG in an aqueous solution containing 0.5 g·L^–1 FeVO₄ and 15 mmol·L^–1 hydrogen peroxide at pH 7.0 reached 93.2%. Similar rates were achieved at pH 5.7 (k = 0.0471 min^–1), pH 7.0 (k = 0.0438 min^–1), and pH 7.7 (k = 0.0434 min^–1). The FeVO₄ catalyst successfully overcomes the problem faced in the heterogeneous Fenton process, i.e., the narrow working pH range. The data for the removal of OG in FeVO₄ systems containing H₂O₂ conform to the Langmuir–Hinshelwood model (R² = 0.9988), indicating that adsorption and surface reaction are the two basic mechanisms for OG removal in the FeVO₄–H₂O₂ system. Furthermore, the irradiation of FeVO₄ by visible light significantly increases the degradation rate of OG, which is attributed to the enhanced rates of the iron cycles and vanadium cycles.

Open image in new window

     

Biological treatment of the dye Reactive Blue 19 by cattails and anaerobic bacterial consortia

This study demonstrates the bioremediation potential of anaerobic sludge and cattail (Typha angustifolia) for the treatment of the dye Reactive Blue 19 (RB19). The anaerobic sludge and cattails used in this study were not previously exposed to dyes or other xenobiotics. Different anaerobic sludge concentrations (30%, 50%, and 70%) were used along fixed dye concentrations at pH 8.0 and 25 °C. Subsequently, 50% sludge was selected to treat RB19 at various concentrations. The discoloration of non-hydrolyzed dye was between 70% and 85% using 50% biomass. For the hydrolyzed form of RB19, the range of decoloration was 70%–90%. Dye treatment efficiencies between 50% and 75% were observed for the two forms of the dye when treated with T. angustifolia. Overall, the anaerobic biomass at pH 8.0 showed better potential than cattails to treat RB19. The observation that non-enriched anaerobic sludge can decolorize RB19 is important because it opens up the prospects of developing anaerobic treatment systems, which can easily decolorize dyes in industrial wastewaters and also possesses potential advantages over systems using defined bacterial cultures.     

Enhanced degradation of Orange II using a novel UV/persulfate/sulfite system

Environmental Chemistry Letters - UV-activated persulfate (PS) systems have been widely employed to remove organic contaminants. However, the heavy use of persulfate&nbsp;may lead to secondary...     

Size and shape effects of MnFe2O4 nanoparticles as catalysts for reductive degradation of dye pollutants

• Size and shape-dependent MnFe₂O₄ NPs were prepared via a facile method. • Ligand-exchange chemistry was used to prepare the hydrophilic MnFe₂O₄ NPs. • The catalytic properties of MnFe₂O₄ NPs toward dye degradation were fully studied. • The catalytic activities of MnFe₂O₄ NPs followed Michaelis–Menten behavior. • All the MnFe₂O₄ NPs exhibit selective degradation to different dyes. The magnetic nanoparticles that are easy to recycle have tremendous potential as a suitable catalyst for environmental toxic dye pollutant degradation. Rationally engineering shapes and tailoring the size of nanocatalysts are regarded as an effective manner for enhancing performances. Herein, we successfully synthesized three kinds of MnFe₂O₄ NPs with distinctive sizes and shapes as catalysts for reductive degradation of methylene blue, rhodamine 6G, rhodamine B, and methylene orange. It was found that the catalytic activities were dependent on the size and shape of the MnFe₂O₄ NPs and highly related to the surface-to-volume ratio and atom arrangements. Besides, all these nanocatalysts exhibit selectivity to different organic dyes, which is beneficial for their practical application in dye pollutant treatment. Furthermore, the MnFe₂O₄ NPs could be readily recovered by a magnet and reused more than ten times without appreciable loss of activity. The size and shape effects of MnFe₂O₄ nanoparticles demonstrated in this work not only accelerate further understanding the nature of nanocatalysts but also contribute to the precise design of nanoparticles catalyst for pollutant degradation.