Application of TiO2/perlite photocatalysis for degradation of ammonia in wastewater

The purpose of this study was removal of ammonia by a new photocatalytic process from synthetic wastewater under UV irradiation. TiO₂ was used as the photocatalyst and immobilized on perlite granules as a supporter. The prepared catalysts were characterized by SEM and FTIR analysis showed that TiO₂/perlite catalyst has mesoporous structures and uniform coating of TiO₂ on support. Also, the optimum efficiency of photocatalytical degradation of ammonia was obtained at pH 11 for UV intensity irradiation with 125 W lamp. About 68% degradation of ammonia in wastewater was achieved after 180 min of irradiation by using the optimized reaction conditions.     

悬浮态TiO_2光催化降解腐殖酸的影响因素研究

在悬浮态TiO2光催化体系中,探讨了光催化氧化降解腐殖酸的规律,考察了催化剂投加量、腐殖酸溶液初始浓度、初始pH值、光强、反应时间等因素对腐殖酸去除效果的影响。结果表明,光催化氧化法降解腐殖酸的效率比直接光解法有显著提高,腐殖酸的去除率从34.73%增加到65.61%(反应时间为3 h);TOC的去除率也大幅度提高,直接光解反应对TOC几乎无去除作用,而光催化氧化对TOC的去除率达37.5%;腐殖酸的初始浓度增加,初始pH值降低,光强增大,光照时间延长均能提高腐殖酸的降解率,其中pH值和光强的影响较为显著。另外,催化剂的投加量存在一个最佳值。     

High Performance Photocatalysts Based on N-doped Graphene-P25 for Photocatalytic Reduction of Carbon Tetrachloride

Carbon tetrachloride (CCl₄) is a kind of toxic and persistent groundwater contaminant. Considering keeping drinking water safe, a novel kind of N-doped graphene (NGS)-P25 TiO₂ photocatalyst was prepared by a facile one-step hydrothermal method for the removal of CCl₄ from contaminated water. Simultaneously, nitrogen-doping and the reduction of graphene oxide, and loading of P25 were finished during the same process. The photocatalytic efficiency of resulted NGS-P25 nanoparticles was studied for the degradation of CCl₄. The results indicated that NGS-P25 exhibited the highest photocatalytic activity under UV light irradiation, outperforming graphene-P25, bare P25 or NGS. The effects of NGS-P25 dosage, irradiation time, CCl₄ concentration and pH on CCl₄ photocatalytic degradation efficiency were discussed in detail. Accordingly, the optimum experimental conditions were obtained. Moreover, the high performance photocatalyst of NGS-P25 can be extended to environmental pollution control and remediation towards various pollutants.     

Electrochemical-assisted photocatalytic degradation of textile washwater

Photocatalytic methods with TiO₂ catalyst were successfully applied to the decomposition of many organic contaminants. In this paper the performance of an electrochemical-assisted photocatalytic degradation of textile washwater containing procion blue dye was investigated. Several operational parameters to achieve optimum efficiency of this electrochemical-assisted photocatalytic degradation system have been done. The main objective was to determine the chemical oxygen demand (COD) and colour removal of the organic pollutant. The effects of pH, current density, supporting electrolyte, the irradiation time and photocatalyst on treatment efficiency were studied. The results showed that electrochemical-assisted photocatalytic process was used efficiently with 90% COD removal and complete colour removal after 7 h treatment.     

Effect of dissolved oxygen concentration and light intensity on photocatalytic degradation of phenol

Catalyst loading is an important parameter that needs to be optimized in the operation of photocatalytic slurry reactors. In this study on photocatalytic degradation of phenol, the optimum catalyst loading was found to depend mainly on the dissolved oxygen (DO) concentration in the aqueous solution, especially at higher irradiation intensities. The estimated Langmuir-Hinshelwood (L-H) kinetics constants were found to vary with light intensity and dissolved oxygen concentration. The intermediate products of photocatalytic oxidation were identified.     

稀土元素Ce掺杂TiO_2光催化剂制备及微波强化光催化活性

在[Bmim]PF6离子液体介质中微波辅助制备稀土元素Ce掺杂改性的TiO_2光催化剂TiO_2-Ce,以甲基橙溶液和苯酚溶液为模拟污染物,在紫外光照和微波辐射-紫外光照降解条件下考察TiO_2-Ce催化剂的光催化活性。利用荧光技术以对苯二甲酸作为荧光探针检测TiO_2-Ce催化剂表面产生的羟基自由基,并对光催化降解反应进行动力学分析,以了解光催化降解反应机理。结果表明,通过优化反应条件制得的TiO_2-Ce催化剂具有较高光催化降解活性和热稳定性,在紫外光照和微波辐射-紫外光照条件下降解60 min后,甲基橙降解率分别为98.6%和99.3%,苯酚降解率分别为96.6%和97.2%。荧光光谱分析表明,TiO_2-Ce在微波辐射-紫外光照条件下产生的羟基自由基比紫外光照多,因而微波辐射-紫外光照具有强化TiO_2-Ce降解模拟污染物作用的效果。反应动力学数据表明,TiO_2-Ce光催化降解甲基橙溶液反应呈一级反应动力学规律,其表观速率常数k最大值为0.056 2 min-1。     

Fe(NO3)3-太阳光催化降解双酚A的研究

采用Fe(NO3)3为催化剂,在自然光照射下对双酚A的降解过程进行了研究。考察了Fe(NO3)3用量、体系的pH值、双酚A初始浓度、光照时间等因素对双酚A降解效率的影响,并测定了双酚A的CODCr去除率。结果表明,当Fe(NO3)3和双酚 A 摩尔比为0.8：1、体系pH为3、双酚A初始浓度为10 mg/L时,经太阳光照射降解三天,双酚A 的降解率可达到99.4%,其COD去除率可达到66.8%。     

水溶液中纳米二氧化钛光催化降解甲基橙的影响因素

用沸腾回流直接水解法制备了粒径为25～35 nm纯锐钛矿型纳米二氧化钛(TiO2).用X射线衍射和透射电镜表征材料的结构与形貌.用该催化剂催化降解甲基橙,研究了催化剂用量、甲基橙的起始浓度、溶液pH值、光强度、溶液中添加金属离子的影响.结果表明:在较强紫外光照射下,当甲基橙的起始浓度为0.02 g/L,TiO2用量为1.0g/L,光催化效率最高.酸性条件有利于光催化降解甲基橙.掺加Fe3 或Zn2 的光催化效率显著增加.掺加Mn2 或Ca2对光催化活性没有影响.在紫外光区域(366 nm),样品对催化降解水溶液中甲基橙的活性较高.     

Synthesis of multiwalled carbon nanotubes supported manganese and cobalt zinc oxides nanoparticles for the photodegradation of malachite green

Multiwalled carbon nanotubes (MWNTs) supported and unsupported bimetallic zinc and manganese oxides nanoparticles (Zn–Mn NPs) were synthesized by wet chemical precipitation method. Zn–Mn and MWNTs/Zn–Mn oxides NPs were used as photocatalysts for the photodegradation of malachite green in aqueous medium under UV irradiation. The photodegradation study of malachite green was carried out by UV/vis spectrophotometer. The Mn–Zn and MWNTs/Mn–Zn oxides NPs degraded about 93% and 96% of dye, respectively, within 2 h of irradiation time. Effect of several parameters like time, pH, catalyst dosage and concentration of dye on the photocatalytic degradation was studied. The optimum conditions were obtained at pH 9 (93% dye degraded in 1.5 h), at 0.0435 g of catalyst (76.04% of dye degraded in 1 h), at 12.5 ppm dye concentration (88.41% dye degraded in 45 min). The activity of recovered catalyst was also examined.     

Statistical optimization of process conditions for photocatalytic degradation of phenol with immobilization of nano TiO<Subscript>2</Subscript> on perlite granules

Response surface methodology (RSM) using D-optimal design was applied to optimization of photocatalytic degradation of phenol by new composite nano-catalyst (TiO₂/Perlite). Effects of seven factors (initial pH, initial phenol concentration, reaction temperature, UV irradiation time, UV light intensity, catalyst calcination temperature, and dosage of TiO₂/perlite) on phenol conversion efficiency were studied and optimized by using the statistical software MODDE 8.02. On statistical analysis of the results from the experimental studies, the optimum process conditions were as follows: initial pH, 10.7; initial phenol concentration, 0.5 mM; reaction temperature, 27 °C; UV irradiation time, 6.5 h; UV light intensity, 250 W; catalyst calcination temperature, 600 °C; and TiO₂/perlite dosage, 6 g/L. Analysis of variance (ANOVA) showed a high coefficient of determination (R²) of 91.8%.     

Preparation of TiO2 Nanoparticles Coated Cotton Fibers at Low Temperature and Their Photocatalytic Activity

TiO_2 nanoparticles coated cotton fiber composite was successfully prepared by using a sol-gel method at low temperature(about 100℃) using tetrabutyl-titanate [Ti(OBu)_4] as raw material.The preparation of the TiO_2 colloid and the composite were described.The properties of resulting materials were characterized by SEM and XRD,the photocatalytic degradation performance was tested using methylene blue(MB) as the target pollutant in aqueous solution.The results showed that the amorphous TiO_2 nanoparticles were distributed evenly on the outer surfaces of cotton fibers,which shows efficient photocatalytic properties when exposed to UV light,the degradation rate of MB reached 95.35% under the conditions of catalyst dosage 2.5 g/L,MB concentration 50 mg/L,irradiation time 120 min,and pH 10,and the photocatalytic activity of TiO_2/cotton fibers remained above 90% of its activity as-prepared after being used four times,the degradation rate of MB could reach 88.78% when irradiation time was 120 min.The photocatalytic degradation of MB could be properly described by the first-order kinetic law.By comparison of the removal rates of MB with and without UV light,it could be affirmed that the disappearance of MB was due to photodegradation rather than adsorption on cotton fibers.     

The degradation of an azo dye in a batch slurry photocatalytic reactor

The photocatalytic degradation of a commercial azo-reactive textile dye, Remazol Red F-3B, has been investigated in a batch slurry reactor using semiconductor catalysts like, ZnO and TiO₂, and two UV sources emitting mainly at 254 and 365 nm. Non-irradiated catalysts and non-catalyzed UV irradiation have negligible effect on the dye degradation. Initial pH, dye concentration, light power and catalyst loading as well as the catalyst type and UV wavelength are considered as process variables. The results showed that decolorization and TOC removal efficiencies of ZnO are higher under 365 nm UV. On the other hand, when two photocatalysts are compared, the decolorization performance of ZnO is higher than TiO₂ under 365 nm UV_, while TiO₂ performs better under 254 nm UV. Furthermore, from the TOC removal point, TiO₂ performs better than ZnO irrespective of the UV wavelength. TiO₂ irradiated under 254 nm UV degrades successfully both benzene and naphthalene derivatives.     

Hydroxyapatite photocatalytic degradation of calmagite (an azo dye) in aqueous suspension

The hydroxyapatite (HAP) is prepared by precipitation method and examined for the photocatalytic degradation of calmagite, a toxic and non-biodegradable azo-dye compound. The physicochemical properties of hydroxyapatite material were characterized using BET surface area, XRD, FT-IR, and SEM analysis. The FT-IR analysis of the hydroxyapatite revealed that the peak intensity due to absorbance of surface PO₄³⁻ group centered at wave number 1030 cm⁻¹ is drastically decreased upon exposure to UV for 1 h. The study includes dark adsorption experiments at different pH conditions, influence of the amount of catalyst, and effect of pH on photocatalytic degradation of dye, chemical oxygen demand (COD) removal, biological oxygen demand (BOD₅) increase and SO₄²⁻ and NO₃⁻ ions evolution during the degradation. At optimum photocatalytic experimental conditions the same is compared with commercial degussa P-25 TiO₂. The photocatalytic treatment significantly reduced the COD (92% removal) and increased the BOD₅/COD ratio to 0.78. Considerable evolution of SO₄²⁻ (8.5 mg L⁻¹) and NO₃⁻ (12.2 mg L⁻¹) ions are achieved during the degradation process, thus reflecting the usefulness of the hydroxyapatite photocatalytic treatment in calmagite removal in wastewater.     

CNTs负载TiO2对茜素红溶液的降解研究

以钛酸四丁酯为前驱体,冰醋酸为水解抑制剂,采用溶胶-凝胶法制备纳米TiO₂/CNTs复合催化剂。测定复合催化剂对不同浓度茜素红溶液的光降解活性,并对光催化降解动力学进行研究。结果表明,在CNTs负载质量分数7.5%、焙烧温度450 ℃和焙烧时间3.5 h条件下制备的TiO₂/CNTs复合催化剂光催化活性得到提升。相同条件下,TiO₂/CNTs对150 mg·L^-1茜素红溶液的最终降解率达67%,而TiO₂的最终降解率只有56%。复合催化剂光催化活性提升的原因是CNTs负载后光催化粒子在紫外光照射下生成更多的氢氧根活性自由基。光催化降解动力学符合Langmuir-Hinshelwood方程,催化剂对污染物的表观吸附是整个反应的“瓶颈”。随着反应浓度的增大,光催化降解反应的反应级数由一级反应逐渐下降为零级反应。     

Photocatalytic degradation of 4-nitroaniline using solar and artificial UV radiation

The photocatalytic degradation (PCD) of 4-nitroaniline was studied in the presence of TiO₂ suspensions in a batch and continuous annular reactor. Artificial and solar radiation was employed as sources of UV radiation. The effect of catalyst loading, pH, presence of anions and initial concentration on the rate of photocatalytic degradation was investigated. p-Aminophenol, p-benzoquinone and hydroquinone were identified as the intermediates during the degradation process. A kinetic expression for PCD of 4-NA is provided.     

Photodegradation of cellulose under UV light catalysed by TiO2

BACKGROUND: Since natural cellulose is an insoluble, crystalline microfibril, which is difficult to react with other compounds, most reactions related with cellulose are heterogeneous. The methods of cellulose degradation include acid hydrolysis, thermal degradation, alkaline degradation and catalytic degradation. Photocatalysis is a very powerful process. RESULTS: With 10 g cellulose dissolved in 100 mL ZnCl₂ solution (66%), the 5‐hydroxymethyl furfural yield in the corrugated plate photocatalytic reactor reached 3.87 g L^?1 under the following experimental conditions: 2 h irradiation under ultraviolet (UV) lamp (power—21 W), nine TiO₂ coating cycles, and 42° corrugated plate angle. CONCLUSION: Owing to the enhancement of catalyst surface area illuminated by UV light and the large number of photons captured on the catalyst surface, the energy efficiency per mass (EE/M) of the corrugated plate photocatalytic reactor for photocatalytic degradation of cellulose was 10.9 kWh kg^?1. This is therefore an effective technology for 5‐HMF preparation from cellulose. Copyright © 2011 Society of Chemical Industry     

The photocatalysis of BiFeO3 disks under visible light irradiation

The photocatalytic process of BiFeO₃ disks under visible light irradiation can be termed as photo-Fenton-like reaction. The active hydroxyl radicals (•OH) generated during the photocatalytic process were quantified using a terephthalic acid (TA) fluorescence probing technique, which were proved to be greatly influenced by the loading of H₂O₂ and catalyst dosage. Our results showed that the photocatalytic efficiency was enhanced with the increasing •OH concentration. There is an optimal loading of H₂O₂ (80 mM) and catalyst dosage (2.0 g/L), at which the photocatalytic degradation rate of MO was enhanced to 97% under visible light irradiation for 3 h.     

1,3-二乙酸咪唑磷钨酸盐的制备及其对甲基红的光催化降解性能

采用元素分析和红外光谱对所制磷钨酸1,3-二乙酸咪唑盐催化剂进行表征,考察了光照时间、催化剂用量对光催化降解有机染料甲基红效率的影响. 结果表明,无光催化剂时甲基红可直接光解,完全光解所需时间为220 min;催化剂用量为0.02?0.10 g时,对甲基红光降解效率随催化剂用量增加显著提高;加入0.08 g催化剂后,紫外光照射60 min可使甲基红溶液降解完全,降解效率为未加入催化剂时的3倍.     

Residence time distribution analysis and optimization of photocatalysis of phenazopyridine using immobilized TiO2 nanoparticles in a rectangular photoreactor

Optimization of photocatalytic degradation of phenazopyridine (PhP) under UV light irradiation using immobilized TiO₂ nanoparticles was studied. The effect of operational parameters was investigated using response surface methodology (RSM). Maximum removal efficiency was achieved at the optimum conditions: initial drug concentration of 10 mg/L, UV light intensity of 47 W/m², flow rate of 200 mL/min, and reaction time of 150 min. The residence time distribution (RTD) analysis was studied to find the effect of flow rate on the drug removal efficiency. The tracer (PhP) pulse injection response was studied with UV–vis measurements and was used to prepare RTD curves.