TiO_2光催化处理水中苯酚的环境风险研究

利用薄膜水循环TiO2光催化反应器(TiO2-WFCPR)处理水中苯酚的实验数据,分析了不同处理条件下苯酚光催化降解过程中间产物的降解规律和出水的环境风险。研究结果表明,即使苯酚已达《污水综合排放标准》(GB8978—1996)一级排放标准,但出水中还不同程度地存在有害的中间产物,排放时会对环境造成危害,因此应以残留苯酚及其中间产物的浓度及影响确定该工艺最终的反应时间。足够的反应时间和偏碱性条件是降低苯酚及其中间产物环境风险的关键因素。苯酚初始浓度及进水pH越高,苯酚达标的反应时间会越长,处理的经济性就越差。所以,从环境风险与经济性综合考虑,该工艺适用于处理苯酚初始质量浓度≤60.00mg/L的水,适宜的pH为6.0～8.0。

光催化技术在处理废水中的规模化应用

光催化技术是环境污染治理较具代表性的先进氧化技术,并在空气净化、污水处理等方面展示出较好的应用前景.该文侧重于分析国内外光催化水处理设备研发情况及应用发展现状,并对作者及其团队在光催化规模化处理褐煤气化生化废水和高速公路服务区生活废水方面的工作进行了总结.

基于光伏-光催化混合水处理系统的实验研究

提出并建立具有光伏发电和污水处理双重功能的光伏-光催化混合水处理(SOLWAT)系统,实验考察太阳辐照度约950 W/m^2、环境温度约33℃及风速约3 m/s条件下温度和模拟废水的光谱吸收对光伏组件发电效率的影响,研究该系统对3种模拟机污染物:亚甲基蓝(MB)、酸性红26(AR26)和对氯苯酚(4-Cp)的降解性能。结果表明:SOLWAT系统的电池组件工作温度低于仅具有单一光伏发电功能的参比系统,但其发电效率因模拟废水的光谱吸收作用而低于参比系统。SOLWAT系统对上述3种模拟有机污染物的降解率均达99%,模拟污染物光催化降解反应动力学的反应级数均为一级,矿化率达80%以上。

光触媒水处理器对集中空调水处理系统中军团菌及自然菌去除效果的实验观察

目的:研究光催化水处理器对集中空调水处理器中军团菌及自然菌消毒效果。方法:依据《公共场所集中空调通风系统卫生规范》(2006年)进行试验。结果:光催化水处理器运行至24h、48h和72h时对冷却循环水中自然菌的去除率分别为99.98%、99.99%和99.99%,均达到消毒效果;运行24h后水样中军团菌由阳性变为未检出,达到消毒效果。表明光催化水处理器中复合光催化泡沫金属网的杀灭成分无逸出或逸出物对水中细菌没有明显抑制作用。结论:采用试验用光触媒的水处理器可以去除军团菌,对自然菌去除效果明显,在集中空调系统水处理系统中应用前景广泛。这种采用纳米光触媒法的水处理系统尚需要观察长期连续运转后细菌去除效果。

Accelerated separation of photogenerated charge carriers and enhanced photocatalytic performance of g-C3N4 by Bi2S3 nanoparticles

Employing photothermal conversion to improve the photocatalytic activity of g-C3N4 is rarely reported previously. Herein, different ratios of g-C3N4/Bi2S3 heterojunction materials are synthesized by a facile ultrasonic method. Advanced characterizations such as X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy are employed to analyze the morphology and structure of the prepared materials. Compared with sole counterparts, the heterojunction materials CN-Bi S-2 exhibit significantly enhanced photocatalytic performance, which is 2.05-fold as g-C3N4 and 4.42-fold as Bi2S3. A possible degradation pathway of methylene blue(MB) was proposed. Based on the photoproduced high-energy electrons and photothermal effect of Bi2S3, the transfer and separation of electron-hole pairs are greatly enhanced and more active species are produced. In addition, the relatively high utilization efficiency of solar energy has synergistic effect for the better photocatalytic performance.

Facile preparation of sepiolite@LDH composites for the visible-light degradation of organic dyes

Sepiolite@LDH(Sep@LDH)composites were designed and prepared based on the assembly of layered double hydroxides(LDH)on acidified sepiolites(Sep)for the simultaneous photocatalytic degradation of methyl orange(MO)and methylene blue(MB).The structure,morphology,texture,optical properties,and photocatalytic performance of the prepared Sep@LDH were studied in detail.Among the Sep@LDH composites,Sep4@LDH(4.0 g Sep)exhibited the highest photocatalytic activity under visible‐light irradiation,which could be attributed to its large surface area,high crystallinity,and plentiful active sites on its surface.The photodegradation of the dyes followed a pseudo first‐order kinetic model(Langmuir‐Hinshelwood model),indicating that the copious and homogeneous active sites on the surface of the composites contributed to the high photocatalytic activity.The photodegradation mechanism was studied by examining the active species(^-OH,h+,and·O2^-anions)using appropriate scavengers.It was found that·OH radicals played a critical role in the photocatalytic process of MO and MB,where the generation of·OH radicals occurred on the electron/hole(e^-/h+)pairs on the surface of the Sep@LDH composites.

THE INVESTIGATION ON PHOTOCATALYTIC TREATMENT OF WASTE WATER CONTAINING PHENOL OVER ZnO

This paper adopts a medium pressure mercury lamp as light source and ZnO powder as catalyst to investigate the effect of radioactive wave length, component of phenol ZnO suspension and stirring method on phenol decomposition rate. The optimized conditions for the phenol decomposition are: (1) Radioactive wave length: 360～420 nm; (2)Phenol concentration in the suspension is less than 200 mg/l; (3)ZnO concentration is 3～8 g/l; (4)pH value is 5～7; (5)Reaction temperature is 25℃～40℃; (6)Agitation at atmosphere. Phenol can decompose in two ways: (1)Reacting with photogenerated cavity; (2)Reacting with ·OH radical.

A Novel Multi-Tube Photoreactor with UV Light and Immobilized TiO_2 Thin Film for Water Treatment

A novel multi-tube photoreactor with 0.0188m3 valid reaction volume was constructed in pilot-scale. This rectangular reactor consisted of 13 regularly distributed silica glass tubes coating with TiO2 thin film photo-catalyst. Total active area of TiO2 thin film is 0.3916m2. The ratio of surface area to volume achieves 20.8m-1. Photocatalytic experiment of phenol red demonstrates that the apparent reaction rate constant (k) is 0.074 65 h-1 and 0.16502h-1 for reaction system with and without micro-bubbles mixing. The corresponding apparent quantum efficiency (a) is 8.1771 X 10-7g.J-1 and 4.9036 x 10-7g-J-1, respectively. COD value of reactant could decrease to 17mg.L-1 and high performance liquid chromatography (HPLC) only shows two absorption peaks in 24 h pho-tocatalytic process time, so this photoreactor has good photomineralization effect. Experimental results reveal that photocatalytic destruction of organics is possible by using the multi-tube photoreactor.

Preparation and photocatalytic activity of Gd-doped TiO_2 nanofibre

In order to realize the photocatalysis of TiO2 in the sunlight and directly apply it to waste water treatment, the Gd-doped TiO2 nanofibre was synthesized using two-step synthesis method as follows: Firstly, potassium carbonate, titanium dioxide and proper gadolinium oxide （dopant） were calcined in the muffle at high temperature and the doped gadolinium K2Ti4O9 fibres were obtained; secondly, the fibre was heated using glycerol as solvent until Gd-doped TiO2 nanofibres were obtained. The synthesized samples were characterized using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that Gd-doped TiO2 nanofibre heat-treated by glycerol solvent can inhibit the agglomeration, so the grain diameter of the fibre is smaller than that without heat-treated with glycerol. Meanwhile, the diameter of the fibre decreases with the increase of the heating temperature and time. 97% 98% of Gd-doped TiO2 nanofibre is anatase. The photocatalysis results showed that the photocatalysis activity of Gd-doped TiO2 nanofibre is just a little lower than that of TiO2 powder.

Preparation of TiO_2-activated carbon complex membranes and their photoelectrocatalytic activity

The experimental process of preparing TiO 2 activated carbon complex membranes with activated carbon powder as main carrier, PTFE as binder and wire netting as matrix is described in detail, and both photo catalysis and photo electro catalysis are measured to study the properties of complex membranes. Experimental results show that the photo catalytic activity of the membranes is high and stable in the process of treating Rhodamine B; the application of an electric field accelerates the speed of photo catalysis, and the efficiency of photo catalysis is increased 2.5 times when the applied voltage is 0.8 V; and the degradation of Rhodamine B follows the dynamics of first order reaction. It is concluded from the discussion of experimental results that the preparation process of TiO 2 activated carbon complex membranes is a simple low cost process suitable for large scale application.

Photocatalytic degradation of sulfamethazine by graphitic carbon nitride-modified zinc molybdate:Effects of synthesis method on performance, degradation kinetics,and mechanism

In the present study,zinc molybdate(β‐ZnMoO4)and graphitic carbon nitride(g‐C3N4)‐modifiedβ‐ZnMoO4(β‐ZnMoO4/g‐C3N4)were prepared to decontaminate aqueous solutions from the antibiotic sulfamethazine(SMZ).Our results revealed that the hydrothermal synthesis method greatly influenced the photocatalytic activity of the resultant catalysts.The pristineβ‐ZnMoO4samples obtained under more intensive synthesis conditions(24h at280°C)showed higher photocatalytic activity than that prepared for12h at180°C(denotedβ‐ZnMoO4‐180).In the case of in situ hydrothermal synthesis ofβ‐ZnMoO4/g‐C3N4,a surface‐modified sample was only obtained under the reaction conditions of180°C for12h.Compared with the sheet‐likeβ‐ZnMoO4‐180sample,theβ‐ZnMoO4‐180/g‐C3N4composite showed enhanced photocatalytic activity for the degradation of SMZ.By contrast,the hydrothermal reaction at280°C caused the gradual decomposition of g‐C3N4.It is believed that the structural incorporation of g‐C3N4intoβ‐ZnMoO4at280°C might disrupt the crystal growth,thereby deteriorating the performance of the composite catalysts formed at this temperature.For the composite catalysts prepared by the ultrasonic method,a remarkable increase in the degradation rate of SMZ was only observed at a high g‐C3N4content of8mol%.The photocatalytic degradation of SMZ byβ‐ZnMoO4‐180/g‐C3N4composite catalysts followed pseudo‐first‐order kinetics.Further study of the photocatalytic mechanism revealed that holes and superoxide radicals were the dominant oxidative species in the photodegradation process.The enhanced photocatalytic performance of the composites was attributed to the higher separation efficiency of the photogenerated electron‐hole pairs at heterogeneous junctions.The degradation intermediates of SMZ were detected by liquid chromatography‐mass spectrometry,from which plausible reaction pathways for the photodegradation of SMZ were proposed.Our results indicated that the synthesis method for g‐C3N4composites should be carefully selected to achieve superior photocatalytic performance.

In-situ route for the graphitized carbon/TiO composite photocatalysts with enhanced removal efficiency to emerging phenolic pollutants

TiO2 is the most photoactive material because of its superstrong photooxidizing ability,and TiO2 photocatalysis has been widely applied in sustainable water treatment and environmental remediation.However,poor sunlight or visible-light harvesting efficiency and fast recombination rate of the photogenerated charge carriers severely limit the practical applications of TiO2.To overcome these problems,the present work demonstrates a facile in-situ co-condensation method combined with hydrothermal treatment to prepare a series of graphitized carbon/TiO2 composite photocatalysts,and anatase TiO2 phase andp-p-conjugated polycyclic aromatic carbon structure are created simultaneously.As-prepared TiO2/C composites exhibit remarkably high visible-light photocatalytic activity in the degradation of aqueous emerging phenolic pollutants,acetaminophen(APAP)and methylparaben(MPB),and apparent rate constant of the TiO2/C composite with carbon doping level of 10.3%for APAP and MPB removal is 7.6 and 2.8 times higher than that of bare TiO2,and 6.2 and 2.6 times higher than that of Degussa P25 TiO2.Based on the results of photoelectrochemical experiments,indirect chemical probe measurements,and ESR spectroscopy,it is verified that doping TiO2 with graphitized carbon is responsible for this enhanced photocatalytic activity,which renders the improved visible-light harvesting ability,the accelerated separation of the photogenerated charge carriers,and enlarged BET surface areas.Through analyzing the intermediates yielded in the photodegradation process,the pathway of visible-light photocatalytic degradation of APAP and MPB over the TiO2/C composite is proposed.

Synthesis of TiO2 supported on activated carbon by MOCVD： operation parameters study

A novel metallo-organic chemical vapor deposition (MOCVD) technique has been applied to the preparation of the photocatalytic titanium dioxide supported on activated carbon. The effects of various condition parameters such as carrier gas flow rate, source temperature and deposition temperature on the deposition rate were investigated. The maximum deposition rate of 8.2 mg/(g.h) was obtained under conditions of carrier gas flow rate of 400 ml/min, source temperature of 423 K and deposition temperature of 913 K. The deposition rate followed Arrhenius behavior at temperature of 753 K to 913 K, corresponding to activation energy Ea of 51.09 kJ/mol. TiO2 existed only in anatase phase when the deposition temperature was 773 K to 973 K. With increase of deposition temperature from 1073 K to 1273 K, the rutile content sharply increased from 7% to 70%. It was found that a deposition temperature of 773 K and a higher source temperature of 448 K resulted in finely dispersed TiO2 particles, which were mainly in the range of 10-20 nm.