Photooxidation of azo dye reactive black 5 using a novel supported iron oxide: heterogeneous and homogeneous approach.

Photooxidation of azo dye Reactive Black 5 (RB5) by H202 was performed with a novel supported iron oxide in a batch reactor in the range of pH 2.5-6.0. The iron oxide was prepared through a fluidized-bed reactor (FBR) and much cheaper than the Nafion-based catalysts. Experimental results indicate that the iron oxide can significantly accelerate the degradation of RB5 under the irradiation of UVA light (wavelength = 365 nm). An advantage of the catalyst is its long-term stability, which was confirmed through using the catalyst for multiple runs in the degradation of RB5. In addition, this study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in the batch reactor. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of RB5 during pH 4.5-6.0, the homogeneous catalysis is of increasing importance below pH 4.0 because of the Fe ions leaching from the catalyst to solution.     

Noble metal modified titania catalysts in the degradation of reactive black 5: a kinetic approach

The photocatalytic degradation of Reactive Black 5 (RB 5), a di-azo dye was investigated over M/TiO2 (M = Ag, Au and Pt) photocatalysts irradiated with UV and visible light. TiO2 was prepared by sol-gel technique (Syn-TiO2). Photodeposition of metal salt precursors over Syn-TiO2 was carried out so as to obtain 1 wt% of M/TiO2 catalysts. The photodecolourization and photodegradation reactions were also compared with commercial TiO2 (Degussa P25) catalyst. Kinetic studies for the decolourization of RB 5 showed that it followed pseudo first order. Recycling of catalysts was performed to check the economic feasibility of the photocatalytic process. In order to check the applicability of M/TiO2 catalyst in the treatment of industrial effluent, real textile effluent was collected from an industry and subjected to photodegradation and the results are presented. Enhanced activity of M/TiO2 catalyst under visible light irradiation highlights its importance in the field of photocatalysis.     

草酸铁络合物／H2O2／UV体系对靛红染料废水脱色的研究

以草酸铁络合物/H2O2作光氧化剂,利用紫外光对水溶性染料靛红进行了光氧化降解试验研究。结果表明,在pH值为3,[Fe(Ⅲ)]/[C2O42-]=1/3,H2O2为100 mg/L条件下,光照30 min后,质量浓度为30 mg/L的染料溶液其脱色率达到98.5%,COD去除率为54.4%。与UV/Fe3+、UV/H2O2、UV/草酸等光氧化体系相比,脱色效果较为明显。     

载锰污泥活性炭催化臭氧氧化草酸废水的研究

为研究在催化臭氧化过程中,载锰污泥活性炭对草酸废水降解的催化效果,以及为污泥的资源化探索一条新途径,本实验采用连续流臭氧氧化实验,通过单因素实验方法考察了载锰污泥活性炭催化臭氧化反应的主要影响因素及最佳反应条件,同时对催化臭氧化反应机理进行了探讨。结果表明:在臭氧浓度为5.0 mg/L,载锰污泥活性炭投加量为100 mg/L,pH值为3.5的最佳反应条件下,60 min内草酸的去除率最高达91.2%。叔丁醇对草酸降解具有抑制作用,催化臭氧化反应符合羟基自由基的反应机制。该方法的处理效果较为明显,对评价催化臭氧法的效果具有较明显的参考价值。     

Ti/MCM-22/MCM-41微介孔复合材料光催化降解酸性红B模拟废水的研究

采用纳米自组装法制备了具有吸附性和光催化性的Ti/MCM-22/MCM-41微介孔复合材料,利用X射线衍射、N2吸附、扫描电镜等方法对其进行表征。将复合材料用于光催化降解酸性红B的实验,考察了催化剂用量、光照时间、pH值和染料初始浓度对光催化降解率的影响,并对光降解产物进行了紫外光谱分析。结果表明:当染料的初始浓度为50 mg/L,废水pH在6左右,催化剂投加量为0.1 g/L,光照时间120 min,酸性红B的去除率可达98%以上,光催化降解反应遵循一级反应动力学方程。降解产物的紫外光谱图表明,降解后酸性红B的两个特征吸收带消失,结构的共轭系被打破,颜色消失,说明该复合材料去除水中的酸性红B主要是通过光催化作用。     

Degradation of 4-chlorophenol by the anodic-cathodic cooperative effect with a Pd/MWNT gas-diffusion electrode

Pd/multi-walled carbon nanotubes (MWNTs) catalyst used for the gas-diffusion electrode was prepared by ethylene glycol (EG) reduction and characterized by the X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicated that Pd particles with an average size of 8.0 nm were highly dispersed in the MWNTs with amorphous structure. In a diaphragm electrolysis system with a Ti/RuO(2)/IrO(2) anode and the Pd/MWNT gas diffusion cathode, the degradation of 4-chlorophenol was performed by a combination of electrochemical reduction and oxidation. The combined process was in favor of improving 4-chlorophenol degradation efficiency. The optimum reaction conditions were as following: initial pH 7, aeration with hydrogen and air. Under the optimized electrolysis conditions the removal of 4-chlorophenol in the anodic and cathodic compartments were 98.5 and 90.5%, respectively. Additionally, based on the analysis of electrolysis intermediates using high performance liquid chromatography (HPLC) and ion chromatography (IC), the electrolysis degradation of 4-chlorophenol was proposed containing the intermediates, such as phenol, hydroquinone, benzoquinone, maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid, acetic acid and formic acid.     

Photodegradation of aqueous reactive dye using TiO(2)/zeolite admixtures in a continuous flow reactor

The photocatalytic degradation of an organic dye, i.e. reactive blue 19 (RB19), was studied by employing different TiO(2)/zeolite (TZ) photocatalysts, which have TiO(2)/(TiO(2) + zeolite) weight ratios ranging from 20 to 80%, in a continuous flow system. Three light sources including two UV lights (i.e. λ(max,254 nm) and λ(max,365 nm)) and natural sunlight were used. The results showed that the decoloring rate of RB19 increased as the amount of TiO(2) in the TZ catalyst increased. The photodegradation of RB19 exhibited pseudo-first-order kinetics with respect to the concentration of RB19. Almost 100% of initial RB19 was mineralized under the controlled conditions in this study. And the activities of the prepared photocatalysts were retained after long-term durability experiments. Compared with UV lights (i.e. λ(max,254 nm) and λ(max,365 nm)), the decoloring efficiency of RB19 was significantly increased under natural sunlight illumination, which is likely due to the long-wavelength incident light that photoexcited RB19 and accelerated the degradation rate of RB19 radicals by the UV fraction of sunlight.     

Efficient degradation of dye pollutants in wastewater via photocatalysis using a magnetic zinc oxide/graphene/iron oxide-based catalyst

In this paper, we present a proof-of-concept study of the enhancement of photocatalytic activity via a combined strategy of fabricating a visiblelight responsive ternary heterostructure and improving overall photostability by incorporating magnetic zinc oxide/graphene/iron oxide (ZGF). A solvothermal approach was used to synthesize the catalyst. X-ray diffraction (XRD), scanning electron microscopic, energy dispersive X-ray, transmission electron microscopic, vibrating sample magnetometric, and ultravioletevisible diffuse reflectance spectroscopic techniques were used to characterize the synthesized samples. The obtained optimal Zn(NO₃)₂ concentration, temperature, and heating duration were 0.10 mol/L, 600 C, and 1 h, respectively. The XRD pattern revealed the presence of peaks corresponding to zinc oxide, graphene, and iron oxide, indicating that the ZGF catalyst was effectively synthesized. Furthermore, when the developed ZGF was used for methylene blue dye degradation, the optimum irradiation time, dye concentration, catalyst dosage, irradiation intensity, and solution pH were 90 min, 10 mg/L, 0.03 g/L, 100 W, and 8.0, respectively. Therefore, the synthesized ZGF system could be used as a catalyst to degrade dyes in wastewater samples. This hybrid nanocomposite consisting of zinc oxide, graphene, and iron oxide could also be used as an effective photocatalytic degrader for various dye pollutants.     

Fe-O/CeO_2催化剂的制备、表征及其对垃圾渗滤液微波催化氧化活性的研究

以浸渍法制备用于常温常压微波催化氧化工艺的负载型Fe-O/CeO_2催化剂并通过XRD和SEM手段进行表征;利用优化制备后的催化剂进行微波催化氧化垃圾渗滤液的研究.结果表明:Fe-O/CeO_2催化剂中活性组分Fe以α-Fe_2O_3和CeFe_2的形式存在.在渗滤液初始COD_(Cr)5 736 mg/L、氨氮1 840 mg/L、色度500倍和pH 8.69的条件下,在Fe-O/CeO_2投加量10 g/L、H_2O_2(30%)投加量22.5 mL/L、微波功率800 W、微波辐射时间10 min和水样初始浓度C_(水样)/C_(原水)为100%的最佳运行条件下,微波催化氧化工艺对COD_(Cr)、氨氮和色度的去除率分别为73%、78%和85%;在反应的第4～8 min和第2～8 min,COD_(Cr)和氨氮去除率分别与反应时间呈近似直线的关系.     

Photocatalytic reduction of Cr(VI) in a fully illuminated fluidized bed reactor

The potential of a fluidized bed reactor for the UV-A photocatalytic reduction of Cr(VI), a priority water pollutant, by utilizing a TiO(2)/quartz sand composite, was explored. The effects of oxalic acid (OA) as a sacrificial agent in the heterogeneous system was also investigated and compared with the homogeneous photoreduction by the same dicarboxylic acid under both oxygenated or anoxic conditions of the reacting media. The performance of the 'preconditioned' photocatalyst, either by pretreating it with the OA solution (at dark or under UV-A illumination) or by letting the catalyst stand wet with the OA solution, during designated time intervals (1-5 weeks) prior to its reuse, was assessed. Then, up to 95% reduction of Cr(VI) to Cr(III) was achieved in less than 100 min.     

新型微介孔复合材料La/13X/MCM-41光催化降解壬基酚的研究

以碱处理后的13X分子筛、硅酸钠为原料,加入模板剂,同时引入La2O3,在水热条件下晶化生成具有良好的吸附性能和光催化性能的新型微孔-介孔复合材料La/13X/MCM-41,并将其应用于壬基酚(NP)的光催化降解.通过XRD、TEM、FT-IR、N2吸附-脱附等技术对复合材料的微观结构进行了表征分析.考察了催化剂用量、NP初始浓度、初始pH、光照时间等对NP光催化降解效率的影响.结果表明:在催化剂用量为0.1 g/L、初始浓度为1 mg/L、初始pH为6、光照时间为210 min的最佳条件下,NP的光催化降解效率可达93％以上,反应符合一级动力学方程,复合材料La/13X/MCM-41具有较高的催化活性.     

一株长江优势菌的降解特性研究

从长江水体中分离到一株最优功能菌株JD1,经初步鉴定该菌株为琼氏不动杆菌属(acinetobacter junii)。该菌株最高可耐受质量浓度600 mg/L的乐果,降解乐果的最适温度为32℃,在30~37℃的广泛温度下仍生长良好,最适pH值为7.2左右,具有广泛的pH值生长范围(pH=5.5~9.0)。研究发现,装液量、接种量对菌株的降解有明显影响。装液量由3/10调整为1/5时,JD1对质量浓度100 mg/L的乐果降解率从21%提高到51.54%。试验表明,该菌株可以在质量浓度高达2 400 mg/L的苯酚中生长良好。     

The catalytic and photocatalytic oxidation of organic substances using heterogeneous Fenton-type catalysts.

This paper deals with catalytic and photocatalytic oxidation of organic substances using H202 over heterogeneous Fenton-type catalysts. In the study a series of Fe-containing catalysts was experienced. A zeolite named as FeZSM-5 was selected as the most active heterogeneous Fenton-type catalyst. The FeZSM-5 reported was prepared by hydrothermal crystallization in the presence of iron salt. In contrast to the homogeneous Fenton system the catalyst prepared had minimal, if any, leaching of iron ions, was stable during 30 catalytic runs and didn't lose its activity in the presence of complexing agents, e.g. P2O7(4-). The catalyst was active in oxidation of organic substances at pH from 1.5 to 8, maximum activity was observed at pH = 3. The FeZSM-5 effectively oxidized a simulant of the warfare agent, diethylnitrophenil phosphate, which is hardly detoxified by other methods. It appeared that the rate of oxidation of formic acid, ethanol and benzene over FeZSM-5 increased under the action of visible light (lambda > 436 nm), quantum efficiency being 0.06-0.14.     

Heterogeneous catalytic oxidation of hypophosphite by H2O2: pH effect.

Phosphorus chemicals control key aspects of eutrophication and other environmental process. Hypophosphite (HP) originating from manmade and natural sources was evidenced as present in the environment and was investigated rarely. Recently, iron oxide has been used as a catalyst for oxidising organic contaminants with hydrogen peroxide (i.e. heterogeneous Fenton-like reaction). This study focused mainly on the oxidation of 1.0 mM HP by hydrogen peroxide in the presence of a novel iron oxide catalyst (B1 catalyst) which was prepared through a fluidised-bed Fenton reactor (FBR-Fenton). The background experiments including the oxidation experiment of HP by air only, by H2O2 only and adsorption of HP by B1 catalyst were first elucidated. It was found that HP could not be oxidised at all by air and H2O2 at pH 2.5-12 in 24 hours. On the other hand, it could be adsorbed by B1 catalyst with 89.8% removal at pH 2.5 in 5 hours and complete desorption at pH 11.0. Then, we investigated the effects of pH and Fe leaching from the catalyst on the oxidative efficiency of HP. We found that although the removal rate of HP at pH 2.5 is faster than that at pH 4.0, B1 catalyst has a higher HP oxidation efficiency at pH 4.0 than that at pH 2.5. We conclude that it is a major heterogeneous catalytic oxidation by our novel iron oxide catalyst to oxidise HP at pH 4.0. Also, B1 could be a useful and potential catalyst for the treatment of HP wastewater.     

Photodegradation of reactive blue 19 dye using magnetic nanophotocatalyst α-Fe_2O_3/WO_3:A comparison study of α-Fe_2O_3/WO_3 and WO_3/NaOH

The photocatalytic degradation of reactive blue 19(RB19) dye was investigated in a slurry system using ultraviolet(UV) and light-emitting diode(LED) lamps as light sources and using magnetic tungsten trioxide nanophotocatalysts(α-Fe_2O_3/WO_3 and WO_3/NaOH) as photocatalysts.The effects of different parameters including irradiation time,initial concentration of RB19,nanophotocatalyst dosage,and pH were examined.The magnetic nanophotocatalysts were also characterized with different methods including scanning electron microscopy(SEM),energydispersive X-ray spectroscopy(EDS),transmission electron microscopy(TEM),X-ray diffraction(XRD),photoluminescence(PL),differential reflectance spectroscopy(DRS),Fourier transform infrared spectroscopy(FTIR),and vibrating sample magnetometry(VSM).The XRD and FTIR analyses confirmed the presence of tungsten trioxide on the iron oxide nanoparticles.The VSM analysis confirmed the magnetic ability of the new synthesized nanophotocatalyst Ω-Fe_2O_3/WO_3 with 39.6 emu/g of saturation magnetization.The reactor performance showed considerable improvement in the α-Fe_2O_3-modified nanophotocatalyst.The impact of visible light was specifically investigated,and it was compared with UV-C light under the same experimental conditions.The reusability of the magnetic nanophotocatalyst α-Fe_2O_3/WO_3 was tested during six cycles,and the magnetic materials showed an excellent removal efficiency after six cycles,with just a 7% decline.     

Decolorization of anthraquinone dye Reactive Blue 19 by the combination of persulfate and zero-valent iron

Decolorization of anthraquinone dye Reactive Blue 19 (RB19) with sulfate radicals generated in situ from persulfate and zero-valent iron (ZVI) was investigated. The effects of initial solution pH, initial concentration of RB19, ZVI and persulfate, reaction temperature and common dissolved anions were studied. 100% color removal efficiency and 54% TOC removal efficiency were achieved in 45 min with an initial RB19 concentration of 0.1 mM under typical conditions (pH 7.0, 0.8 g L(-1) ZVI, 10 mM persulfate and 30 C). The decolorization efficiency of RB19 increased with higher iron dosage, higher initial persulfate concentration, and higher reaction temperature. It is also an acid driven process. The decolorization process followed pseudo-first order kinetics and the activation energy was 98.1 kJ mol-1. RB19 decolorization was inhibited by common dissolved anions such as CL-, NO3-, H2PO4- and HCO3- since they reacted with sulfate radicals that retarded the oxidation process. The experiment demonstrated that the combination of persulfate and ZVI was a promising technology for the decolorization of dye wastewater.     

Photocatalytic degradation of di(2-ethylhexyl)phthalate adsorbed by chitin A.

Di(2-ethylhexyl)phthalate (DEHP) is a ubiquitous environmental contaminant due to its extensive use as a plasticiser and its persistence. Currently, there is no cost-effective treatment method for its removal from industrial wastewater. In a previous study, DEHP was effectively adsorbed from aqueous solution by biosorption onto chitinous materials. Biosorption can pre-concentrate DEHP from the aqueous phase for further treatment. As biosorption cannot degrade DEHP, in this study the degradation (and detoxification) of DEHP adsorbed onto chitinous material by photocatalytic oxidation (PCO) is attempted. PCO relies on hydroxyl radical (.OH), which is a strong oxidising agent, for the oxidative degradation of pollutants. It is a non-selective process which can degrade DEHP adsorbed onto chitinous material. The first part of this study is the optimisation of the degradation of adsorbed DEHP by PCO. Adsorption was carried out in the physicochemical conditions optimised in the previous study, with 500 mg/L chitin A and 40 mg/L DEHP at initial pH 2, 22+/-2 degrees C and 150 rpm agitation for 5 min. After optimisation of PCO, a 61% removal efficiency of 10 mg/L of DEHP was achieved within 45 min under 0.65 mW/cm2 of UV-A with 100 mg/L TiO2, and 10 mM of H2O2 at initial pH 12. The optimisation study showed that UV-A and TiO(2) are essential for the degradation of DEHP by PCO. The degradation intermediates/products were identified by GC-MS analysis. GC-MS results showed that the di(2-ethylhexyl) side chain was first degraded, producing phthalates with shorter side chains. Further reaction produced phathalic anhydride and aliphatic compounds such as alkanol and ester. The toxicities of parental and degradation intermediates in the solution phase and on chitinous materials were followed by the Microtox test. Results indicated that toxicity can be removed after 4 h treatment by PCO. Thus the decontamination of DEHP by integrating biosorption and PCO is feasible.     

Application of cuprous oxide synthesized from copper-containing waste liquid to treat aqueous reactive dye

Cuprous oxide that was prepared from Cu-containing waste liquid from a printed circuit board manufacturer was used to carry out Fenton-like and photo-Fenton-like oxidation reactions to decolorize a reactive dye (RB19). A microwave hydrothermal method was applied in the synthesis. The highest recovery rate of Cu from wastewater was 87% and was obtained when the synthesis was performed at a power of 200 W for 15 min. An RB19 decolorization efficiency of 99.9% was achieved when the Fenton-like reaction was conducted with 50 mmol/L H(2)O(2) and 0.9 g/L of Cu(2)O. The decolorization of RB19 was more effective when the system was irradiated with visible light than with UV light. Under irradiation, the decolorization rate was the highest when the decolorization was performed in the RB19 solution that contained 50 mmol/L H(2)O(2) and 0.9 g/L CuO(2) in the Fenton-like and the 365 nm-irradiated photo-Fenton-like reactions. In the case of irradiation under 410 nm visible light, the system was operated with lower H(2)O(2) (30 mmol/L) and Cu(2)O (0.5 g/L) to achieve a decolorization rate higher than 365 nm-irradiated photo-Fenton-like reactions.     

Photocatalytic degradation of p-nitrophenol by zinc oxide particles

The degradation of p-nitrophenol (PNP) by ZnO particles has been studied. With increasing PNP loading the degradation rate decreased. The mineralization of PNP was rather slow compared with the degradation. With a decrease in particle diameter or an increase in surface area, the degradation rate significantly increased. The degradation capability with solar irradiation was found to be superior to UV light irradiation. It was found that 30 mg L(-1) of PNP was completely degraded by solar light with the accumulated UV light of around 23 kJ L(-1) at ZnO dosage of 5 g L(-1). The degradation PNP by ZnO with UV light or solar light was faster than that by TiO(2).     

Photodegradation of hydrophobic disperse dyes and dye-bath effluents by silicadodecatungstate (SiW12O40(4-/5-)) nanoparticles.

Polyoxometalate (POM) silicadodecatungstic acid has been applied as a photochemical catalyst for the degradation of SETAPERS Black WNSP, a disperse dyestuff preparation widely used to dye polyester and polyamide fabrics. It could be demonstrated that the disperse dyestuff was photo-reduced by SiW12O40(5-), the one-electron reduced form of POM, as evidenced by Heteropolyblue (HPB) formation. For completion of the photochemical redox cycle, isopropanol (IsOH) was required. Acetone (Ac) served solely as an effective solute and photosensitizer; however this effect was suppressed in the presence of POM. Threshold (0.087 mM) and optimum (0.375 mM) POM concentrations existed and decolorization kinetics were inhibited upon the addition of dye auxiliary chemicals. Increasing the dyestuff concentration from 50 mg/L to 150 mg/L did not affect initial decolorization kinetics revealing that not the formation of the excited [POM-Substrate]* complex, but its reduction to HPB was the rate limiting step. POM-mediated, IsOH-assisted UV-photodegradation of disperse dyes and dye-baths is by far more effective than applying other, more well known chemical oxidation methods (O3, H202/UV, Power Ultrasound). Key to the action of POM redox catalysts is the feature that particularly heteropoly tungstates undergo facile re-oxidation to their original state, thus allowing regeneration of the photocatalyst, a feature that may become critical for real-scale application.