Preparation of stone-shaped CuBi2O4 by solid phase method and H2O2 assisted visible light degradation for orange II

CuBi₂O₄ is widely used in photocatalytic degradation for pollutants in water due to its strong visible light response characteristics, excellent chemical stability, non-toxic, and low cost. Here, stone-shaped CuBi₂O₄ was prepared with CuO and Bi₂O₃ as raw materials by high temperature solid phase. The effect of calcined temperature and time on the product was discussed. This material was analyzed and discussed by XRD, SEM, XPS, and DRS, and the visible light activity of degradation for Orange II was explored. The results showed that the absorption edge of prepared CuBi₂O₄ expands to the visible region, and the band gap was about 1.77 eV. The photocatalytic degradation rate of Orange II was 42.6% under the optimal conditions. After H₂O₂ assisted, the degradation rate was more than 2 times, and repeated experiments verified that the prepared catalysts had high stability. Finally, a reasonable mechanism of H₂O₂ assisted degradation enhancement is proposed. This work gives new ideas for the preparation of new and efficient catalytic materials.

     

Remedy of dye manufacturing process effluent by UV/H2O2 process

The effluent from dye manufacturing industry is more difficult to be treated than laboratory synthesized wastewater according to high variability of composition and color intensity. Thus, this study aimed to propose the method for remedying industrial effluent by UV/H2O2 process in a recirculated batch reactor system while considering the effects on hydrogen peroxide dosage, UV power and wastewater intensity for the removal of color and COD. From the experimental results, it was feasibly treated that the distinguished removal of color and COD by increasing the hydrogen peroxide dosage and UV power, but not by the strong intensity of industrial effluent. Therefore, UV/H2O2 process of the developed reactor was a positively superior treatment or pre-treatment for dye manufacturing plant effluent to comply the regulated requirements.     

Decolorization and mineralization of a phthalocyanine dye C.I. Direct Blue 199 using UV/H2O2 process

In this study, the successful decolorization and mineralization of phthalocyanine dye (C.I. Direct Blue 199, DB 199) by an advanced oxidation process (AOP), UV/H2O2, were observed while the experimental variables such as hydrogen peroxide dosage, UV dosage, initial dye concentration and pH were evaluated. The operating conditions for 90% decolorization of C.I. DB 199 and 74% removal of total organic carbon (TOC) were obtained for initial dye concentration of 20 mgl(-1), hydrogen peroxide dosage of 116.32 mM, UV dosage of 560 W and pH of 8.9 in 30 min. The pseudo-first order rate constant is a linear function of reverse of initial dye concentration. They linearly increased by incrementing UV dosage, yet were non-linear enhancement by increasing the hydrogen peroxide concentration. A higher pseudo-first order rate constant about 0.15 min(-1) was observed while hydrogen peroxide concentration within 5.82-116.32 mM. Moreover, the decolorization of C.I. DB 199 was observed to be more difficult than that of an azo dye, C.I. Acid Black 1, under the same operating conditions.     

Sonochemical assisted impregnation of Bi2WO6 on TiO2 nanorod to form Z-scheme heterojunction for enhanced photocatalytic H2 production

In this work, Bi₂WO₆/TiO₂ nanorod heterojunction was prepared by sonochemical assisted impregnation method. After loading 2 wt% Bi₂WO₆ on TiO₂ nanorods, the photocatalytic hydrogen production rate of 2026 µmol/h/g was achieved. Compared to commercial P25 and TiO₂ nanorods, ∼13 and ∼3 folds enhanced activity was observed. The excellent photocatalytic performance of Bi₂WO₆/TiO₂ nanorod photocatalyst was mainly attributed to i) reduction of bandgap due to heterojunction formation, ii) quick transport of photogenerated charge carriers, and iii) efficient charge carrier separation supported by UV-DRS, photocurrent measurement, Impedance study, and photoluminescence spectra analysis. The Z-scheme band alignment for Bi₂WO₆/TiO₂ nanorod heterojunction was proposed based on the Mott-Schottky measurement. This result demonstrated the effective utilization of Z-scheme heterojunction of Bi₂WO₆/TiO₂ for photocatalytic reduction application.     

Photochemical degradation of diethyl phthalate with UV/H2O2

The decomposition of diethyl phthalate (DEP) in water using UV-H2O2 process was investigated in this paper. DEP cannot be effectively removed by UV radiation and H2O2 oxidation alone, while UV-H2O2 combination process proved to be effective and could degrade this compound completely. With initial concentration about 1.0mg/L, more than 98.6% of DEP can be removed at time of 60 min under intensity of UV radiation of 133.9 microW/cm2 and H2O2 dosage of 20mg/L. The effects of applied H2O2 dose, UV radiation intensity, water temperature and initial concentration of DEP on the degradation of DEP have been examined in this study. Degradation mechanisms of DEP with hydroxyl radicals oxidation also have been discussed. Removal rate of DEP was sensitive to the operational parameters. A simple kinetic model is proposed which confirms to pseudo-first order reaction. There is a linear relationship between rate constant k and UV intensity and H2O2 concentration.     

Synthesis and characterization of novel magnetically separable NiFe2O4@AlMCM-41-Cu2O core-shell and its performance in removal of dye

The synthesis of magnetic NiFe₂O₄@AlMCM-41-Cu₂O core-shell as a new class of visible light driven photocatalyst was suggested. The magnetic NiFe₂O₄ core was prepared by solvothermal method. The intermediate AlMCM-41 shell was prepared by the method of liquid crystal templating mechanism and subsequently cuprous oxide (Cu₂O) nanoparticles (NPs) were synthesized in NiFe₂O₄@AlMCM-41core-shell via colloidal chemistry approach. The properties of prepared magnetic core-shell were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption–desorption measurement and vibration sample magnetometer (VSM). Based on EDX results, the weight percentage (wt%) of NiFe₂O₄ core, MCM-41 shell and Cu₂O NPs were calculated to be 68.89, 30.55 and 0.56%, respectively. It consisted of mesoporous structure with a surface area of 687.00 m² g^?1, an average pore size of 2.95 nm and possessed excellent magnetic properties of 4.74 emu g^?1. The TEM results indicated that the NiFe₂O₄ as core were regular spheres with diameter of 68 nm, and the average thickness of AlMCM-41 shells was ～35 nm. The particles size of Cu₂O incorporated in core-shell was less than 5 nm. The photocatalytic activity was evaluated under visible light irradiation using the removal of methylene blue (MB) dye as a model reaction. The removal rate of MB achieved up to 90% after 60 min under visible light irradiation, and the NiFe₂O₄@AlMCM-41-Cu₂O can be recycled and reused.     

TiO2-Cu2O复合膜的制备及其可见光催化降解染料性能研究

采用电化学方法制备了TiO2-Cu2O纳米复合材料,并用喷涂法在玻璃表面制成TiO2-Cu2O复合膜.通过X射线衍射(XRD)、扫描电镜(SEM)等手段对TiO2-Cu2O复合材料进行了表征,用正交设计法研究了TiO2-Cu2O复合膜与Fe2 EDTA构成的Fenton试剂在可见光照射下催化降解亚甲基兰的性能,并用实验证实了H2O2存在.结果显示,TiO2-Cu2O复合膜光催化降解性能明显优于TiO2膜和Cu2O膜.与传统Fenton试剂相比,TiO2-Cu2O复合膜与Fe2 EDTA构成的Fenton试剂体系有效作用时间更长,并可重复使用.     

Decolorization of azo dye acid black 1 by the UV/H2O2 process and optimization of operating parameters

An advanced oxidation process, UV/H2O2, was applied for decolorization of a di-azo dye (acid black 1). The effects of operating parameters such as hydrogen peroxide dosage, UV dosage and initial dye concentration, on decolorization have been evaluated. The acid black 1 solution was completely decolorized under optimal hydrogen peroxide dosage of 21.24 mmol/l and UV dosage of 1400 W/l in less than 1.2 min. The decolorization rate followed pseudo-first order kinetics with respect to the dye concentration. The rate increased linearly with volumetric UV dosage and nonlinearly with increasing initial hydrogen peroxide concentration. It has been found that the degradation rate increased until an optimum of hydrogen peroxide dosage, beyond which the reagent exerted an inhibitory effect. For real case application, an operation parameter plot of rate constant was developed. To evaluate the electric power and hydrogen peroxide consumption by UV/H2O2 reactor, 90% color removal was set as criteria to find the balance between both factors.     

Pilot scale annular plug flow photoreactor by UV/H2O2 for the decolorization of azo dye wastewater

A pilot scale annular plug flow photoreactor with thin gap size, which combines with UV irradiation and hydrogen peroxide, was employed to deal with colored dyeing wastewater treatment. In the experiment, a mono-azo dye acid orange 10 was the target compound. The experimental parameters such as flow rate, hydrogen peroxide dosage, UV input power, pH and dye initial concentrations in a pilot scale photoreactor with flow rate of 9.32 m3day(-1) were investigated. Ultimately, the degradation rates were calculated and compared with a 100-l batch reactor. In our plug flow photoreactor design, the degradation rate of acid orange 10 was 233 times higher than that of 100-l annular batch reactor with same UV light source. The residence time needed for 99% decolorizing of 100 l of 20 mgl(-1) acid orange 10 wastewater was 26.9 min for the thin gap plug flow reactor and was far shorter than that of batch reactor needed.     

Microstructural Evolution of Fe2O3 and ZnFe2O4 during Sonochemical Synthesis of Zinc Ferrite

The microstructural evolution of Fe₂O₃ and ZnFe₂O₄ during high-temperature (600–800°C) sonochemical synthesis of zinc ferrite is studied by x-ray diffraction analysis. The results are used to develop a qualitative model for ultrasonically activated solid-state reactions A _s +B _s C _s.     

Degradation of dyehouse effluent containing C.I. Direct Blue 199 by processes of ozonation, UV/H2O2 and in sequence of ozonation with UV/H2O2

The decolorization and mineralization of cotton dyeing effluent containing C.I. Direct Blue 199 (DB 199) by advanced oxidation processes (AOPs) such as ozonation, UV/H(2)O(2), and in sequence of ozonation with UV/H(2)O(2) processes were evaluated in this study. By ozonation alone, the color removal was almost 100% for DB 199 and greater than 80% for dye bath effluent rapidly within 5 and 15 min, respectively. Meanwhile, the reduction of total organic carbon (TOC) was about 60% for DB 199 and almost no change for dye bath effluent, respectively due to incomplete mineralization. On the other hand, by UV/H(2)O(2) alone, the color removing not only took longer time but obtained lower removal efficiencies for DB 199 and dye bath effluent about 80% and 95% in 30 and 120 min, respectively. Nevertheless, it was more effective than ozonation for TOC removal while about 75% and 80% in 30 and 120 min, respectively. As a result, this study conducted the combination with the above two processes in order to shorten time demand as well as the higher removal efficiencies of both color and TOC simultaneously. Thus, the sequence process was designed to begin with ozonation to rapidly remove color proficiently, following by UV/H(2)O(2) in order to promptly remove remaining TOC efficiently. The successful process design by sequence of ozonation with UV/H(2)O(2) has proved the significant improvement for the removal of both color and TOC in dye bath effluent shortly. Besides, the lab prepared dye solution was substantially much easier to be decolorized than field dye bath effluent so that the lab results were utilized to design the further applications of pilot or full scale.     

MWNTs-TiO2和AC-TiO2复合材料制备及其在染料吸附降解中的应用

采用溶胶-凝胶法,以钛酸四丁酯为原料,分别以多壁碳纳米管和活性炭为载体,并分别在载体表面上负载纳米TiO2颗粒,制备出碳纳米管-TiO2(MWNTs-TiO2)和活性炭-TiO2(AC-TiO2)两种复合材料。采用X射线粉末衍射(XRD)和透射电子显微镜(TEM)对样品进行表征,结果显示,经500℃热处理后,TiO2主要以锐钛矿形式存在,纳米TiO2颗粒均匀的负载于载体的表面。吸附降解的实验结果表明,MWNTs-TiO2和AC-TiO2两种复合材料对活性染料甲基橙吸附降解效果均好于纯纳米TiO2颗粒,而MWNTs-TiO2复合材料的吸附降解效果更好,更适合作为纳米TiO2光催化载体。     

超声波化学法制备纳米铁酸锌粉末的影响因素

超声辐射Fe(NO3)3·9H2O、不同锌盐和脲的混合水溶液得到前驱体,再经过高温焙烧得到纳米ZnFe2O4粉末.得到的纳米ZnFe2O4粉末用X射线衍射(XRD),傅立叶转换红外光谱(FT-IR)表征得到确认.系统研究了超声波化学法制备纳米铁酸锌粉末工艺中不同锌盐、超声波辐射时间、焙烧温度和焙烧时间等影响因素,结果表明:Fe(NO3)3·9H2O与Zn(NO3)2·6H2O为原料,超声波辐射为4h,焙烧温度为950q℃,焙烧时间为14h可制备结晶良好、分散性好、粒度小于100nm的尖晶石型铁酸锌粉末.     

Sepiolite/Cu2O/Cu photocatalyst: Preparation and high performance for degradation of organic dye

A novel ternary sepiolite/Cu₂O/Cu (SCC) nanocomposite was successfully synthesized by a facile one-pot method. The Cu₂O/Cu nanoparticles in the SCC nanocomposite are well dispersed on the sepiolite surface. It exhibited enhanced photocatalytic performance in the degradation of congo red (CR), remarkably superior to that of Cu₂O or Cu₂O/Cu nanoparticles. Elemental copper in the SCC serves as a good electron acceptor to promote the transfer of photo-generated electrons in Cu2O and suppress the recombination of the photo-generated electrons and holes of the composite. The enhanced photocatalytic efficiency is attributed to the synergistic effect of sepiolite and Cu₂O/Cu. This type of SCC nanocomposites is a promising candidate as photocatalytic material for environmental protection.     

Decolourisation of dye solutions by oxidation with H(2)O(2) in the presence of modified activated carbons

The decolourisation of dye solutions by oxidation with H(2)O(2), using activated carbon as catalyst, is studied. For this purpose, three different samples, mainly differing in the respective surface chemistries, were prepared and characterized. Moreover, this work involved three pH levels, corresponding to acid, neutral and alkaline solutions, and six dyes belonging to several classes. The catalytic decolourisation tests were performed in a laboratorial batch reactor. Adsorption on activated carbon and non-catalytic peroxidation kinetic experiments were also carried out in the same reactor, in order to compare the efficiencies of the three processes. The non-catalytic reaction is usually inefficient and, typically, adsorption presents a low level of decolourisation. In these cases, the combination of activated carbon with hydrogen peroxide may significantly enhance the process, since the activated carbon catalyses the decomposition of H(2)O(2) into hydroxyl radicals, which are very reactive. Based on the experiments with the different activated carbon samples, which have similar physical properties, it is proved that the surface chemistry of the catalyst plays a key role, being the basic sample the most active. This is discussed considering the involvement of the free electrons on the graphene basal planes of activated carbon as active centres for the catalytic reaction. Additionally, it is shown that the decolourisation is enhanced at high pH values, and a possible explanation for this observation, based on the proposed mechanism, is given.     

Oxidative degradation of dimethyl phthalate (DMP) by UV/H(2)O(2) process

The photochemical degradation of dimethyl phthalate (DMP) in UV/H(2)O(2) advanced oxidation process was studied and a kinetic model based on the elementary reactions involved was developed in this paper. Relatively slow DMP degradation was observed during UV radiation, while DMP was not oxidized by H(2)O(2) alone. In contrast, the combined UV/H(2)O(2) process could effectively degraded DMP, which is attributed to the strong oxidation strength of hydroxyl radical produced. Results show that DMP degradation rate was affected by H(2)O(2) concentration, intensity of UV radiation, initial DMP concentration, and solution pH. A kinetic model without the pseudo-steady state assumption was established according to the generally accepted elementary reactions in UV/H(2)O(2) advanced oxidation process. The rate constant for the reaction between DMP and hydroxyl radical was found to be 4.0 x 10(9) M(-1)s(-1) through fitting the experimental data to this model. The kinetic model could adequately describe the influence of key factors on DMP degradation rate in UV/H(2)O(2) advanced oxidation process, and could serve as a guide in designing treatment systems for DMP removal.     

Gallic acid degradation in aqueous solutions by UV/H2O2 treatment, Fenton's reagent and the photo-Fenton system

Gallic acid (3,4,5-trihydroxybenzoic acid) is a major pollutant present in the wastewater generated in the boiling cork process, as well as in other wastewaters from food manufacturing industries. Its decay in aqueous solutions has been studied by the action of several oxidation systems: monochromatic UV radiation alone and combined with hydrogen peroxide, Fenton's reagent and the combination Fenton's reagent with UV radiation (photo-Fenton system). The influence of the pH is discussed and the quantum yields are determined in the UV radiation system. Also, the influence of operating variables (initial concentrations of H2O2 and Fe(II), and pH) is established in the Fenton's reaction. The apparent pseudo-first-order rate constants are evaluated in all the experiments conducted in order to compare the efficiency of each one of the processes. Increases in the degradation levels of gallic acid are obtained in the combined processes in relation to the single UV radiation system, due to reactions of the very reactive OH*. These improvements are determined in every process by calculating the partial contribution to the overall decomposition rate of the radical pathways. For the oxidant concentrations applied, the most effective process in removing gallic acid was found to be the photo-Fenton system. The rate constant for the reaction of gallic acid with OH was also determined by means of a competition kinetics model, being its value 11.0+/-0.1 x 10(9)l mol(-1)s(-1).     

H(2)O(2)/UV degradation kinetics of isoprene in aqueous solution

Hydrogen peroxide and UV radiation have been used in the photochemical degradation of isoprene in aqueous solutions. A kinetic study is carried out taking into account the contribution of the UV radiation reaction and the combined reaction with hydrogen peroxide. An empirical reaction rate expression, which considers the two reactions taking place in parallel, is suggested. Pseudo-first order rate constants are obtained from batch reactor data. As the molar ratio of H(2)O(2):isoprene increases, the rate of reaction increases linearly while the concentration of H(2)O(2) is observed to be nearly constant throughout the reaction; suggesting that the H(2)O(2) acts as a pseudo-catalyst. Nearly complete oxidation of isoprene is achieved. These results indicate that the H(2)O(2)/UV process appears to be a competitive alternative destructive treatment for removing isoprene from water present at low levels.     

Photocatalytic degradation of methyl orange: influence of H2O2 in the TiO2-based system

The purpose of this study was to investigate the photocatalytic oxidation of a reactive azo dye. The photocatalytic activity of the TiO2 was studied using a reactor equipped with UV-A sources, with maximum emission at 365 nm. The photocatalytic activity of the TiO2 powder (99.9% anatase) and thin films has been measured through the decomposition of methyl orange solutions. The thin film was prepared by doctor blade and spray pyrolysis deposition (SPD). The TiO2 suspensions were prepared at 1 g/L concentration, and the initial methyl orange concentration was fixed at 7.8125 mg/L. The influence of the TiO2 (powder or thin films) and/or O2 and H2O2 on the photobleaching rate, was tested under different experiments, at pH = 5. Thin films (doctor blade) of TiO2 formed of mezo-sized aggregates formed of nanosized anatase crystallites show better photobleaching efficiency than thin film (SPD) due to their large internal surface. The rate is even higher in H2O2 compared to oxygen environment.