Partial degradation of five pesticides and an industrial pollutant by ozonation in a pilot-plant scale reactor

Aqueous solutions of a mixture of several pesticides (alachlor, atrazine, chlorfenvinphos, diuron and isoproturon), considered PS (priority substances) by the European Commission, and an intermediate product of the pharmaceutical industry (alpha-methylphenylglycine, MPG) chosen as a model industrial pollutant, have been degraded at pilot-plant scale using ozonation. This study is part of a large research project [CADOX Project, A Coupled Advanced Oxidation-Biological Process for Recycling of Industrial Wastewater Containing Persistent Organic Contaminants, Contract No.: EVK1-CT-2002-00122, European Commission, http://www.psa.es/webeng/projects/cadox/index.html] founded by the European Union that inquires into the potential coupling between chemical and biological oxidations for the removal of toxic or non-biodegradable contaminants from water. The evolution of pollutant concentration, TOC mineralization, generation of inorganic species and consumption of O3 have been followed in order to visualize the chemical treatment effectiveness. Although complete mineralization is hard to accomplish, and large amounts of the oxidant are required to lower the organic content of the solutions, the possibility of ozonation cannot be ruled out if partial degradation is the final goal wanted. In this sense, Zahn-Wellens biodegradability tests of the ozonated MPG solutions have been performed, and the possibility of a further coupling with a secondary biological treatment for complete organic removal is envisaged.     

Solar assisted photocatalytic and photochemical degradation of Reactive Black 5

The photocatalytic oxidative degradation of Reactive Black 5 (RB 5) has been investigated using TiO(2)-P25 as photocatalyst and sunlight as irradiation source in slurry form. The degradation was carried out at different experimental conditions to optimize the parameters such as amount of catalyst, concentration of dye and pH. A complete degradation of 3.85 x 10(-4) M dye solution under solar irradiation was observed in 3.5 h. The photochemical degradation using hydrogen peroxide results in the partial removal of the dye.     

Coupling solar photo-Fenton and biotreatment at industrial scale: main results of a demonstration plant

This paper reports on the combined solar photo-Fenton/biological treatment of an industrial effluent (initial total organic carbon, TOC, around 500mgL(-1)) containing a non-biodegradable organic substance (alpha-methylphenylglycine at 500mgL(-1)), focusing on pilot plant tests performed for design of an industrial plant, the design itself and the plant layout. Pilot plant tests have demonstrated that biodegradability enhancement is closely related to disappearance of the parent compound, for which a certain illumination time and hydrogen peroxide consumption are required, working at pH 2.8 and adding Fe(2+)=20mgL(-1). Based on pilot plant results, an industrial plant with 100m(2) of CPC collectors for a 250L/h treatment capacity has been designed. The solar system discharges the wastewater (WW) pre-treated by photo-Fenton into a biotreatment based on an immobilized biomass reactor. First, results of the industrial plant are also presented, demonstrating that it is able to treat up to 500Lh(-1) at an average solar ultraviolet radiation of 22.9Wm(-2), under the same conditions (pH, hydrogen peroxide consumption) tested in the pilot plant.     

T-ZnOw光催化降解甲基橙的动力学研究

研究了四针状氧化锌晶须在紫外光照射条件下对甲基橙的降解活性,考查了甲基橙溶液初始浓度、催化剂浓度及种类等对光催化降解的影响,并初步探讨了其反应动力学.实验结果显示,四针状氧化锌晶须光催化降解反应基本符合一级动力学规律,光催化效果随着甲基橙初始溶液浓度的增加而降低,最佳浓度为2g/L,是一种降解效果优异的光催化材料.     

TiO2/膨胀石墨复合材料的制备及其对亚甲基兰的光催化降解

采用快速升温法制备出以膨胀石墨为载体的TiO2/膨胀石墨光催化剂,用SEM及XRD对其表面形貌及结构进行表征,研究了该负载型光催化剂在紫外光照射下的催化能力,探讨了在催化剂中TiO2的负载量、亚甲基兰溶液的初始浓度及其pH值对光催化剂的降解能力的影响.结果发现,负载量为10%的光催化剂对40mg/L的亚甲基兰溶液5h的光降解率达到58.8%.     

Visible light-driven photocatalytic degradation and mineralization of the malachite green dye in a slurry photoreactor

The as-synthesized BiOCl nanoparticles were characterized by x-ray diffraction (XRD) and ultraviolet–visible (UV–Vis) techniques. The XRD pattern showed that a highly pure and crystalline phase has been obtained. The UV–vis diffuse reflectance spectroscopy (DRS) studies revealed the indirect band gap value of about 3.32 eV for the fabricated semiconductor. The disappearance of the dye, monitored spectrophotometrically, follows approximately pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Besides, the effect of some parameters such as the influence of the initial pH, catalyst weight, initial dye concentration, oxidant concentration, and salt concentration on the degradation of malachite green dye solution under visible light irradiation were investigated. The optimum conditions for the degradation of dye were 25 mg L^?1 dye concentration, pH of 8, and a catalyst amount of 0.7 g mL^?1. The addition of an optimal amount of hydrogen peroxide and potassium persulfate increases the degradation rate while NaCl and Na₂CO₃ decrease the rate. Complete mineralization has been confirmed by UV–Vis spectroscopy     

高效光催化降解气相苯纳米TiO2微球的制备EI北大核心CSCD

以四氯化钛为钛源,尿素为沉淀剂前驱物,硫酸钠为分散剂,利用水热法在水-醇体系中制备出纳米TiO2微球。运用X射线衍射、电子显微镜、N2吸附-脱附和紫外-可见光谱等手段表征样品的结构和性质,并考察了水热温度对纳米TiO2微球结构及光催化降解气相苯活性的影响。结果表明,此类微球由纳米颗粒组成,且比表面积大,介孔结构明显,光吸收出现明显的“蓝移”。光催化结果显示,微球具有很高的光催化活性,尤其是180℃下制备的微球仅用20min将苯完全去除,但生成CO2的量仍随时间有所增加,表明微球的强吸附性能促进其光催化降解过程,且矿化率高达5.5,是P25(2.7)的2倍。     

Solar photocatalytic degradation of isoproturon over TiO2/H-MOR composite systems

The photocatalytic degradation and mineralization of isoproturon herbicide was investigated in aqueous solution containing TiO₂ over H-mordenite (H-MOR) photocatalysts under solar light. The catalysts are characterized by X-ray diffraction (XRD), UV–Vis diffused reflectance spectra (UV–Vis DRS), Fourier transform-infra red spectra (FT-IR) and scanning electron microscopy (SEM) techniques. The effect of TiO₂, H-MOR support and different wt% of TiO₂ over the support on the photocatalytic degradation and influence of parameters such as TiO₂ loading, catalyst amount, pH and initial concentration of isoproturon on degradation are evaluated. 15 wt% TiO₂/H-MOR composite is found to be optimum. The degradation reaction follows pseudo-first order kinetics and is discussed in terms of Langmuir–Hinshelwood (L–H) kinetic model. The extent of isoproturon mineralization studied with chemical oxygen demand (COD) and total organic carbon (TOC) measurements and 80% mineralization occurred in 5 h. A plausible mechanism is proposed based on the intermediates identified by liquid chromatography–mass spectroscopy (LC–MS).     

碳量子点敏化二氧化钛复合光催化剂的制备与光催化降解苯酚

为了解决二氧化钛光催化剂存在的禁带宽度大和量子效率低的问题,利用具有优异光吸收性能和电子转移能力的碳量子点改性二氧化钛,可以大幅度提高二氧化钛的光催化性能。本文以富勒烯碳灰为原料,利用混酸回流法制备了一种发黄蓝光的碳量子点,然后采用一步水热法将碳量子点负载于二氧化钛制备了复合光催化剂。借助高分辨透射电子显微镜(HRTEM)、傅里叶变换红外光谱(FT-IR)、紫外可见光光谱(UV-vis)、荧光光谱、X射线衍射(XRD)、X射线光电子能谱分析(XPS)等表征手段对碳量子点和复合光催化剂进行表征,并以苯酚作为模拟废水进行光催化降解实验,结果表明,与纯二氧化钛相比,用碳量子点改性的二氧化钛对苯酚的去除率可提高60%,且其具有较好的稳定性与重复使用性,6次循环利用后仍可达到初次的97.8%。     

新型复合纳米材料用于光催化降解染料废水的研究进展EI北大核心CSCD

光催化技术是解决当今人类社会中环境问题和能源危机两大问题的有效途径,半导体材料在早期的研究中备受青睐。然而,单一半导体光催化剂存在可见光响应程度差、电子空穴对易复合等缺点,光催化技术在降解染料废水的应用中有效率较低,因此研究者对新型复合纳米材料作为光催化剂降解染料废水进行了深入的研究。本文介绍了石墨烯、金属有机骨架、碳量子点三种新型复合纳米材料用于光催化降解染料废水中污染物的研究进展和主要研究结果,按照复合纳米材料设计升级的思路,简述了部分新型复合纳米材料的制备方法,对目标污染物的降解率进行了分析。通过总结新型光催化材料降解水中污染物的性能,对未来发展趋势进行了展望,指出新型复合纳米材料在光催化方向今后的发展趋势和研究重点是有针对性的处理废水,并实现工业化。     

硫掺杂TiO2的制备及其光催化降解次甲基蓝研究

以TiCl4、(NH4)2SO4为原料,采用溶胶-凝胶法制备了硫掺杂纳米TiO2,利用XRD、TEM、FTIR等对样品进行了表征,并将其用于光催化降解次甲基蓝溶液.结果表明:制备的纳米TiO2为锐钛矿晶型,具有超强酸特征,平均粒径分布为10～30nm,S掺杂对TiO2的晶粒长大有抑制作用,经过硫掺杂的纳米TiO2光催化活性明显优于纯TiO2.     

Oxidation of pesticides by in situ electrogenerated hydrogen peroxide: study for the degradation of 2,4-dichlorophenoxyacetic acid

This paper reports an investigation on the performance of the H2O2 electrogeneration process on a rotating RVC cylinder cathode, and the optimization of the O2 reduction rate relative to cell potential. A study for the simultaneous oxidation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) by the in situ electrogenerated H2O2 is also reported. Experiments were performed in 0.3 M of K2SO4, pH of 10 and 3.5. Oxygen concentration in solution was kept in 25 mg L(-1). Maximum hydrogen peroxide generation rate was reached at -1.6 V versus SCE for both, acidic and alkaline solutions. Then, 100 mg L(-1) of 2,4-D was added to the solution. First order apparent rate constants for 2,4-D degradation ranged from 0.9 to 6.3x10(-5) m s(-1), depending on the catalyst used (UV or UV+Fe(II)). TOC reduction was favored in acidic medium where a decreasing of 69% of the initial concentration was observed in the process catalyzed by UV+Fe(II). This figure was an indication that some of the intermediates derived from 2,4-D decomposition remained in solution, mainly as lighter aliphatic compounds.     

纳米ZnO可见光催化活性的改善及其降解性能

由于半导体ZnO禁带宽度较宽,因而其可见光催化活性较差.本文分别采用N掺杂、碳包覆、贵金属修饰以及半导体复合等方式来改善纳米ZnO的可见光催化活性,并以罗丹明B为降解污染物,对比了不同材料可见光催化降解有机污染物的效率.研究结果显示以氨水为氮源,通过水热法制备的氮掺杂N-ZnO光催化剂,相比于纯ZnO,对可见光吸收增强...     

ZnAlTi型层状双氢氧化物光催化降解亚甲基蓝的性能研究

利用动态尿素水解法制备了3种不同比例的ZnAlTi型层状双氢氧化物,取部分样品分别在温度为500、600、700和900℃条件下煅烧4h,制得具有光催化性能的材料。研究催化剂不同摩尔比、催化剂用量、煅烧温度等不同因素对光催化降解亚甲基蓝过程的影响。结果表明,紫外光照射下,在反应温度为30℃、催化剂中Ti和Al的摩尔比为2、催化剂投加浓度为1.0g/L、亚甲基蓝初始浓度为10mg/L、煅烧温度为600℃的反应条件下,催化剂对亚甲基蓝的降解效果最好,光照反应12h后亚甲基蓝的降解率为94.4%。     

Construction of hierarchical FeIn2S4/BiOBr S-scheme heterojunction with enhanced visible-light photocatalytic performance for antibiotics degradation

Constructing heterojunction provides a promising tactic to improve the photocatalytic efficiency of catalysts. In this paper, hierarchical FeIn₂S₄/BiOBr heterostructure photocatalysts were prepared by facile two step methods and applied to effectively remove ciprofloxacin (CIP) and tetracycline (TC) under visible light. Compared to single catalyst, FeIn₂S₄/BiOBr hybrids display significantly improved photocatalytic activity. Among the series, 6 wt% FeIn₂S₄/BiOBr shows the optimal photocatalytic performance, where the degradation efficiencies of TC and CIP are 3.15 and 2.88 times greater than pure BiOBr, respectively. Such an improvement could arise from the S-scheme heterojunctions and unique hierarchical structures, which brings stronger light absorption, higher photoexcited charge separation efficiency and superior redox ability. Furthermore, 6 wt% FeIn₂S₄/BiOBr composite exhibits excellent stability and reusability. Radical capture experiments and EPR analyses uncover that O₂^–, h⁺ and OH are primarily reactive substances during photocatalytic removal of TC. The products of TC were detected by LC-MS analyses and possible decomposition paths are proposed. Eventually, a possible photodegradation mechanism over FeIn₂S₄/BiOBr S-scheme heterojunction is proposed. These findings supply new perspective for the simple synthesis of S-scheme photocatalysts with promising applications in environment remediation.     

Enhancing solar photocatalytic activity of Bi5O7I photocatalyst with activated carbon heterojunction

Passive solar photocatalysis is one of the most efficient ways for the treatment of dye industry wastewater. Some dyes such as methyl orange are recalcitrant to photolysis; therefore, photocatalysts are used to expedite their degradation. Photocatalysts are semiconductors, and their activity can be improved by creating heterojunctions. In the current work, an active photocatalyst, Bi₅O₇I_, was modified with activated carbon (AC), obtained by controlled carbonization of pistachio shells, to give xAC-Bi₅O₇I photocatalysts. AC loading improved the surface area of the catalyst and decreased its bandgap to 1.8 eV, making it suitable for use as a visible light photocatalyst. Activated carbon enhances adsorption, while Bi₅O₇I scavenges adsorbed molecules increasing the efficiency. 5AC-Bi₅O₇I catalyst containing 5% activated carbon displayed the optimum photocatalytic activity, which was 3.4-fold higher than that of pristine Bi₅O₇I. 5AC-Bi₅O₇I achieved 99.9 % reduction in the concentration of methyl orange in 80 min under sunlight irradiation. 5% AC-Bi₅O₇I is more efficient than commercial Degussa P25 photocatalyst as well. The methyl orange degradation efficiency of the catalysts studied was: 5AC-Bi₅O₇I > Bi₅O₇I > Degussa P25.     

Solar photocatalytic degradation of resorcinol a model endocrine disrupter in water using zinc oxide

Photocatalytic degradation (PCD) of resorcinol a potent endocrine disrupting chemical in aqueous medium was investigated by ZnO under sunlight irradiation in a batch photoreactor. The influence of various parameters such as photocatalyst amount, initial concentration of resorcinol and pH was examined for maximum PCD of resorcinol. A considerable influence of pH upon the chemical oxygen demand (COD) disappearance was observed. In general, neutral or basic pH is favorable for COD removal of resorcinol. PCD intermediates were identified using FTIR and GC/MS. Two of the initial oxidation intermediates detected were 1,2,4-trihydroxy-benzene and 1,2,3-trihydroxy-benzene. FTIR studies revealed 1,2,4-trihydroxy-benzene as the major PCD intermediate. A working photodegradation mechanism is also suggested for PCD of resorcinol. This work envisages the great potential that sunlight mediated photocatalysis has in the removal of resorcinol from waste water.     

ZnS在TiO2纳米管上的分散对其光催化降解染料废水的影响

水热法制备了TiO2纳米管,并采用简单加热回流的方法制备了ZnS/TiO2纳米复合材料。采用TEM、XRD分析手段对产物进行表征,并对其光催化降解酸性玫瑰红B(AR)染料废水进行了研究。考察了反应物供给速率、硫化锌复合量、催化剂稳定性、光照对光催化降解效果的影响。研究表明控制反应物供给速率和硫化锌的负载量可使硫化锌在二氧化钛纳米管表面均匀分散。当染料废水初始浓度为10mg/L,ZnS:TiO2=8:1时,ZnS/TiO2复合材料光催化活性最高。且催化剂稳定性较好。     

BiOBr and BiOCl decorated on TiO2 QDs: Impressively increased photocatalytic performance for the degradation of pollutants under visible light

BiOBr and BiOCl were decorated on TiO₂ QDs through n-p-p heterojunctions by a simple strategy and they were applied for degradation of three organic dyes upon visible illumination. The obtained photocatalysts were analyzed via XRD, FESEM, EDX, UV–vis DRS, PL, BET, TEM, HRTEM, FT-IR, EIS, XPS, and transient photocurrent measurements. The TiO₂ QDs/BiOBr/BiOCl nanocomposite with 20% wt. of BiOBr and 30% wt. of BiOCl displayed superior photoability in the degradation of methylene blue, rhodamine B, and fuchsine, which was almost 34.5, 176, and 78.7-times larger than TiO₂ and 27.8, 13.5, and 51.5-folds greater than TiO₂ QDs, respectively. The results show that the construction of intimate n-p-p heterojunctions between BiOBr, TiO₂ QDs, and BiOCl counterparts leads to enhanced visible-light harvesting and improved charge separation, resulted efficiently increased photocatalytic activity. The trapping results proved that h⁺, ^•O₂⁻, and OH^• species have considerable effects on the degradation reaction. We think that the improved efficiency of the ternary TiO₂ QDS/BiOBr/BiOCl photocatalyst is a splendid alternative for the removal of toxic contaminants from wastewater.