Adsorption and Photodegradation of Methylene Blue by Using PAni/TiO2 Nanocomposite

In this study, polyaniline-titanium dioxide (PAni-TiO₂) nanocomposite has been prepared and was utilized as an effective catalyst for photodegradation of methylene blue (MB) dyes from aqueous solution. Adsorption characteristic on the PAni-TiO₂ surface and the aqueous solubility of the dyes also play an important role in the photodegradation of dye. Adsorption and photodegradation process occurs simultaneously on the surface of the catalyst at first adsorption occurs (21.5%) on the outer surface of the catalyst and then photodegrade the material up to (66.5%). In reaction mechanism OH^· makes the vital role to the degradation of methylene blue and its intermediates. To know the surface and stability of the photocatalyst, it was characterized by FTIR, TEM, TGA–DTA, XRD, UV-vis spectrophotometer, and SEM analysis. Kinetic data indicate that up to 20 minutes photodegradation rates usually follows the pseudo-first-order reaction. After 20 minutes, it follows the Langmuir-Hinshelwood (LH) kinetics. Photo reactivity of PAni-TiO₂ was studied with pH of solution, dosage of photocatalyst and concentration of dye. The reaction rate constant (r) and equilibrium binding constant (K) values were incredibly significant than other catalyst.     

Simple and low temperature preparation and characterization of CdS nanoparticles as a highly efficient photocatalyst in presence of a low-cost ionic liquid

A simple and low temperature method is proposed for preparation of CdS nanoparticles in presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [EtSO₄], a room-temperature ionic liquid (RTIL). The powder X-ray diffraction (XRD) studies display that the products are excellently crystallized in the form of cubic structure and size of the nanparticles prepared in presence of the RTIL is smaller than that prepared in water. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are very pure and nearly stoichiometric. The results obtained by scanning electron microscopy (SEM) demonstrate that the CdS nanoparticles prepared in presence of the RTIL have lower tendency for aggregation relative to the prepared sample in water. Diffuse reflectance spectra (DRS) of the product prepared in the neat RTIL, shows 1.52 eV blue shift relative to bulk CdS, which can be attributed to quantum confinement effect of the CdS nanoparticles. A possible formation mechanism for CdS nanoparticles in presence of the RTIL is presented. Photocatalytic activity of the CdS nanoparticles towards photodegradation of methylene blue (MB) using UV and visible lights was performed. The results demonstrate that observed firstorder rate constant for photodegradation of MB on CdS nanoparticles prepared in the neat RTIL are about 20 and 6 times greater than the prepared sample in water using visible and UV lights, respectively.     

Sulfate-reducing bacteria detection based on the photocatalytic property of microbial synthesized ZnS nanoparticles

This work presented a novel method for specific detection of sulfate-reducing bacteria (SRB) based on the photocatalytic property of ZnS nanoparticles. ZnS semiconductor nanoparticles were synthesized by taking advantage of the characteristic bacterial metabolite, sulfide, and then ZnS nanomaterials were used as photocatalyst for methylene blue (MB) photodegradation. As the amount of ZnS photocatalyst synthesized from microbe metabolized sulfide was affected by initial bacterial concentration before cultivation, the photodegradation ratio of MB was highly related with initial SRB concentration. Under the optimized conditions, a linear relationship between the MB photodegradation ratio and the logarithm of SRB concentration was observed in the range of 1.0 × 10³–1.0 × 10⁸ cfu mL⁻¹. Besides, this proposed method showed excellent specificity for SRB detection. To the best of our knowledge, this is the first example of using the photocatalytic property of microbial synthesized ZnS for bacterial detection.     

Ag@AgBr光催化剂的制备及其可见光催化降解亚甲基蓝反应性能

采用沉积-沉淀及光还原法制备了Ag@AgBr等离子体光催化剂,利用X射线衍射、扫描电镜和紫外-可见漫反射光谱对其进行了表征,并考察了该等离子体光催化剂在可见光(λ420nm)下的催化性能,探讨了催化剂用量、pH值、亚甲基蓝初始浓度、H2O2添加量、循环使用及捕获剂对Ag@AgBr催化性能的影响.结果表明,当亚甲基蓝的初始浓度为10mg/L,催化剂用量为1g/L,pH=9.8时,光照12min后,亚甲基蓝的降解率高达96%,且样品经5次循环使用后活性基本保持不变;而少量H2O2的添加对光催化活性影响不大,过量的H2O2会降低光催化活性;乙二胺四乙酸捕获空穴后比异丙醇捕获·OH后的光催化活性降得更低.同时,对Ag@AgBr等离子体光催化剂可见光降解亚甲基蓝的催化机理进行了分析.     

The Role of the Relative Dye/Photocatalyst Concentration in TiO2 Assisted Photodegradation Process

Despite photocatalytic degradation is studied generally focusing the catalyst, its interaction with the contaminant molecule plays a fundamental role in the efficiency of that process. Then, we proposed a comparative study about the photodegradation of two well‐known dyes, with different acidity/basicity – Methylene Blue (MB) and Rhodamine B (RhB), catalyzed by TiO₂ nanoparticles, varying both dye and photocatalyst concentrations. The results showed that the amphoteric character of MB molecules, even in a range of concentration of 5.0–10.0 mg L^?1, did not imply in pH variation in solution. Therefore, it did not affect the colloidal behavior of TiO₂ nanoparticles, independent of the relative dye/catalyst concentration. The acid–base character of RhB influenced the resultant pH of the solution, implicating in different colloidal behavior of the nanoparticles and consequently, in different degradation conditions according to dye concentration. As the isoelectric point of TiO₂ is between the pH range of the RhB solutions used in this study, from 1.0 to 7.5 mg L^?1, the resultant pH was the key factor for degradation conditions, from a well dispersed to an agglomerated suspension.     

Study of catalytic reduction and photodegradation of methylene blue by heterogeneous catalyst

The photocatalytic degradation of methylene blue is investigated in aqueous solution containing CoS/nanoAl-MCM-41 photocatalyst under visible light. The catalyst is characterized by X-ray diffraction (XRD), UV-vis diffused reflectance spectra (UV-vis DRS) and transmission electron microscopy (TEM) techniques. The effect of CoS, nanoAl-MCM-41 support and different wt% of CoS over the support on the photocatalytic degradation and influence of parameters such as CoS loading, catalyst amount, pH and initial concentration of methylene blue on degradation are evaluated. Hypsochromic effects (i.e. blue shifts of spectral bands) resulting from N-demethylation of the dimethylamino group in methylene blue occurs in presence of CoS/nanoAl-MCM-41 under ambient condition. Meanwhile, the bleaching of methylene blue MB, by sulfide ion, in an aqueous solution is studied in the presence nanoAl-MCM-41 catalyst. In the presence of sulfide ions, MB is bleached to its colorless leuco (LMB) and MBH(2)(+) forms. In an acidified solution (pH<2) the bleaching process generates LMB and by changing pH between 2.0 and 7.0 bleaching of MB dye to MBH(2)(+) form is observed. Using nanoAl-MCM-41 with encapsulated CoS nanoparticles only causes demethylation of MB in aqueous solution.     

Fe3O4@SiO2@TiO2-Co/rGO磁性光催化剂的合成及其光催化活性研究

采用溶胶-凝胶法和水热法（HTM）合成了Fe₃O₄@SiO₂@TiO₂-Co/rGO复合纳米粒子（磁性光催化剂）,通过X射线衍射、扫描电子显微镜及其能量分散光谱和UV-vis漫反射光谱对产物进行了表征分析.研究了Co掺杂量、溶液pH值、亚甲基蓝（MB）溶液初始浓度以及干扰离子（例如Cl^-、SO₄^2-、CO₃^2-）等因素对MB降解的影响,并对磁性光催化剂的可重复使用性进行了分析.正常实验条件下（pH=7,[MB]=10 mg/L,磁性光催化剂用量=0.1 g/50 mL）,150 min内MB最大去除率达到98.24%.干扰离子影响MB降解次序为CO₃^2- < Cl^- < SO₄^2-,磁性光催化剂重复使用7次MB光降解率仅下降7.07%,新型磁性光催化剂具有良好的MB降解性能和较高的重复使用性能.     

Photocatalytic degradation of methylene blue and phenol on Fe-doped sulfated titania

Fe-doped sulfated titania (FST) photocatalysts with high photocatalytic activity were prepared from industrial titanyl sulfate solution and characterized using X-ray diffraction (XRD), thermogravimetry analysis?Cdifferential scanning calorimeter (TGA-DSC), Fourier transform infrared spectroscopy (FT-IR), and nitrogen adsorption?Cdesorption techniques. The photocatalytic activity of the FST photocatalyst was evaluated using the photodegradation of methylene blue (MB) and the photooxidation of phenol in aqueous solutions in the presence of UV irradiation, respectively. The effect of various parameters, such as calcining temperature, calcination time, initial concentration of substrate, amount of catalyst and pH value on the photocatalytic activity of FST photocatalyst was investigated. Among the parameters studied, calcining temperature, initial concentration of substrate, and amount of catalyst have a very similar effect on the activity of FST photocatalyst for both the photodegradation of MB and the photooxidation of phenol, while the others have distinct differences. The optimal calcination conditions were 500?°C, 1.5?h and 650?°C, 2.5?h; the optimal catalyst concentration were 1.0 and 1.2?g?L^?1; the optimal pH values were 8 and 4 for the photodegradation of MB and the photooxidation of phenol, respectively. In addition, the mechanism for the high photocatalytic efficiency of FST photocatalyst has also been put forward.     

花状ZnO/ZnS异质结构的简易合成、结构表征及光催化活性

采用简便的两步溶液相化学方法,在较低温度下(80℃),制备出了花状的ZnO/ZnS异质结构。分别利用X射线衍射、X射线光电子能谱仪、扫描电子显微镜、透射电子显微镜、紫外-可见光谱仪等测试手段对所制备的样品进行表征,结果表明ZnO/ZnS异质结构是由花状ZnO纳米结构和ZnS纳米粒子组成。在光降解罗丹明B(RhB)的测试中,ZnO/ZnS异质结构样品体现出了比ZnO前驱物和商业P25光催化剂更高的光催化效率,这主要可归因于异质结构更有利于电子-空穴的有效分离。ZnO/ZnS光催化剂体现出良好的循环稳定性。     

Hydrothermal low-temperature preparation and characterization of ZnO nanoparticles supported on natural zeolite as a highly efficient photocatalyst

Abstract  

Nanoparticles of zinc oxide were supported on natural zeolite using a hydrothermal method. The catalyst was characterized by X-ray diffraction, UV–vis diffuse reflectance spectra, scanning electron microscopy, and energy-dispersive X-ray techniques. The maximum rate constant for photodegradation of methylene blue (MB) was observed at 80 wt.% ZnO. The influence of various parameters such as catalyst composition, initial concentration of MB, calcination temperature, pH, and catalyst weight on the photodegradation reaction was studied. It was found that photodegradation of MB followed pseudo-first-order kinetics. The rate constant of the reaction for 80 wt.% ZnO at optimized conditions was approximately 3.8 times higher than that for bare ZnO. The photocatalyst had good reusability after four runs. The higher activity of the supported catalyst is due to greater adsorption of MB on the catalyst and its capability to delocalize the conduction-band electrons of excited ZnO.     

Electrospinning preparation of NiO/ZnO composite nanofibers for photodegradation of binary mixture of rhodamine B and methylene blue in aqueous solution: Central composite optimization

One‐dimensional nanofiber of p‐type NiO/n‐type ZnO heterojunctions with various molar ratios of Ni to Zn at different calcination temperatures were successfully synthesized using the electrospinning method, and they were fully characterized. The photocatalysts thus obtained were applied in aqueous solutions for rhodamine B (RDB) and methylene blue (MB) degradation. The p–n heterojunctions built among the cubic structure NiO and hexagonal structure ZnO in the composite nanofiber are responsible for generation of electrons and holes and subsequently superoxide and hydroxyl radical production by carriers which lead to degradation of the dyes in solution. The composite nanofibers (ZnNi1) calcined at 550 °C for 3 h showed the highest photocatalytic activity for degradation of the dyes in aqueous solution. The optimum values were found to be 180 min, 7.0, 1 g l^?1 and 3.0 and 3.0 mg l^?1 for irradiation time, pH, photocatalyst dosage and initial concentration of RDB and MB, respectively. For these optimum conditions, the photocatalytic degradation of RDB and MB was found to be 99.37 and 98.44%, respectively. The maximum photodegradation of RDB and MB using ZnNi1 was 59.41 and 65.43%, respectively. First‐order kinetics based on the Langmuir–Hinshelwood model successfully fitted the experimental data.     

Photo-oxidation of phenol over titania pillared zirconium phosphate and titanium phosphate

The photodegradation of phenol was studied in the aqueous solutions over titania pillared zirconium phosphate and titanium phosphate under solar radiation and compared with that of the UV-radiation (6 W low pressure Hg vapor lamp). This reaction was studied by varying different parameters such as catalyst dose, initial phenol concentration, pH of solution and irradiation time. The degradation rate of phenol was favourable under neutral pH condition. The degradation process approximately obeyed first-order kinetics with apparent rate of degradation constant increasing with decreasing the initial phenol concentration.     

Spectroscopic investigations on the photodegradation of toluidine blue dye using cadmium sulphide nanoparticles prepared by a novel method

A novel method to prepare cadmium sulphide nanoparticles (CdS NPs) possessing nearly uniform size was adopted using eggshell membrane (ESM), under different pH conditions. Significant yield of CdS NPs with smallest possible size was obtained by increasing the pH of the reaction medium from acidic to alkaline. The above prepared CdS NPs have been characterized by UV-vis absorption as well as emission spectra, powder X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The efficiency of the above prepared CdS NPs as a catalyst for the photodegradation of toluidine blue (TB) dye, as a function of pH as well as the ratio between the catalyst and the substrate was studied after irradiation with UV light. The results showed that an efficient interaction took place between the catalyst and the substrate to cause degradation of the selected dye. A maximum degradation of toluidine blue dye (90%) was observed at pH 8 which is higher than that of the efficiencies at pH 4 and pH 6.     

Enhancement of cyanide photocatalytic degradation using sol–gel ZnO sensitized with cobalt phthalocyanine

In this work, the photodegradation of cyanide in aqueous suspension was used to determine the photocatalytic activity of sol–gel prepared ZnO which was impregnated with the Co (II) phthalocyanine (CoPc), as sensitizer. The prepared catalyst was characterized by Scanning Electron Microscopy (SEM) with Energy Dispersed Spectroscopy (EDS) detector, X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FT-IR) and Diffuse UV–Vis Reflectance spectroscopy. Specific surface area was calculated from nitrogen adsorption isotherm using BET method. Compared with commercial ZnO and TiO₂ Degussa P25 photocatalysts, the sol–gel prepared ZnO catalyst sensitized with cobalt phthalocyanine showed the highest activities for degradation of cyanide in aqueous solution under visible light irradiation.     

Green synthesis of activated carbon doped tungsten trioxide photocatalysts using leaf of basil (Ocimum basilicum) for photocatalytic degradation of methylene blue under sunlight

Tungsten oxide (WO₃) nanoparticles were prepared hydrothermally by basil leaves extract, and Activated Carbon (AC) was prepared by the carbonization of date pits. Moreover, 1, 2 and 3% of AC doped WO₃ nanoparticles have been fabricated under hydrothermal conditions. The obtained samples have been characterized by using different techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), simultaneous thermogravimetric analysis (TG-DTGA), fourier transform infrared (FT-IR), BET surface area, and Ultra-Violet spectroscopy (UV–Vis). It was observed that band-gap energy of the fabricated materials decreases by increasing AC amount. Similarly, BET surface area and porosity results showed increasing the content of AC, surface area, pore size and pore volume were decreased. The functional groups, determined by FT-IR, played a significant role in the photocatalytic performance. The photocatalytic performance of fabricated samples was used for the degradation of methylene blue (MB) at neutral pH under visible light radiations, and it is observed that WO₃/3%AC photocatalyst showed the highest degradation of MB. Both, capped phytochemicals of basil extract and the nanocomposites, were improved the photocatalytic performance, about 94% photodegradation was observed within 25 min under the reaction conditions. The photocatalyst was stable and about 85% and 81% photodegradation of MB were found under the two times of reusability tests.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.