微波均相沉淀法制备纳米ZnO及其光催化性能

以硫酸锌和尿素为原料,采用微波均相沉淀法制备出了纳米ZnO. 探讨了反应物配比、反应物浓度、反应时间、反应温度等条件对产物的影响. 并用TEM, IR, TGA, XRD, UV-Vis等测试手段对其进行了表征. 利用紫外-可见分光光度计测试了光吸收特性,发现纳米ZnO对200~380 nm波长范围的光有很强的吸收性,在可见光范围内也有较强的吸收. 研究了纳米ZnO光催化降解甲基橙的动力学行为,在紫外光直接照射下,光催化降解甲基橙,以分光光度法测量甲基橙的即时浓度,从而得出了不同条件下甲基橙降解的脱色速率,以比较不同的降解效果.     

陶瓷粉体催化臭氧化降解水中苯酚

将陶瓷粉末应用于降解苯酚废水用臭氧化催化剂,表征了陶瓷的化学组成、0电荷pH和表面羟基密度,并考察了反应条件的影响.结果表明,陶瓷粉末对于臭氧化降解质量浓度为100mg·L-1的模拟苯酚废水具有较为显著的催化效果.不同温度的影响试验表明,在278～308 K时,苯酚的降解速率随温度升高而加快,然而(与单独臭氧化比较)在较低温度下陶瓷的催化效果更加显著.结合羟基自由基清除剂的影响试验,推断在催化臭氧化过程中臭氧分子和羟基自由基共同氧化污染物,陶瓷粉末的表面羟基促进了臭氧分子到羟基自由基的转变,因而加快了臭氧化过程.     

超声、臭氧、光催化及其组合工艺处理苯酚废水

研究了在一定条件下,超声、臭氧、光催化等高级氧化技术的不同组合方法对苯酚的降解效果。结果表明,对于质量浓度为100 mg/L的苯酚溶液,反应时间为1 h时,超声、臭氧氧化、光催化三者单独降解率分别为8%、36%、35%。紫外光光催化分别与超声波或臭氧组合对苯酚降解有一定的协同作用,降解率分别为50%、78%;而声光催化技术与臭氧三者组合降解苯酚的效果尤佳,降解率达到85%。这归功于超声波的机械作用对臭氧扩散引起的积极作用以及声光催化协同产生的H2O2,从而生成的羟基自由基。     

Nd/ZnO制备及其光催化性能研究

以六水合硝酸锌、六水合硝酸钕和氨水为原料,采用直接沉淀法制备了纯净的氧化锌、掺杂钕的Nd/ZnO光催化剂,分别以甲基橙、亚甲基蓝、苯酚为光催化反应的模型化合物,考察了ZnO、Nd/ZnO光催化剂的紫外光催化活性。结果表明,当Nd在ZnO中掺杂质量百分数为0.5%时,三种模型化合物光催化降解率最大(甲基橙光催化降解率为85.9%,苯酚光催化降解率为27.8%,亚甲基蓝光催化降解率为71.2%);在相同条件下,三种模型化合物光催化降解率大小顺序为:甲基橙!亚甲基蓝!苯酚。     

ACF催化臭氧化降解苯酚的反应参数影响

研究了活性碳纤维(ACF)催化臭氧化降解苯酚过程中各种参数的影响。结果表明,ACF能够显著提高臭氧化效率,当ACF为1g,反应10min时苯酚的去除率为96.8%,而同样条件下活性炭仅为68%;臭氧化效率在酸性下几乎相同并高于碱性下,而且在碱性下随pH值升高而降低;臭氧化空气流量从0.04m3/h增加到0.16m3/h,反应10min时的效率提高为17%;苯酚初始浓度升高到500mg/L仅使臭氧化效率下降不到10%。重复实验表明臭氧化过程中ACF的催化性能可以得到原位再生。     

γ-Al_2O_3负载氧化锰催化臭氧化苯酚的研究

采用纳米级γ-Al_2O_3作为催化剂基体,制备γ-Al_2O_3负载氧化锰纳米催化剂来催化臭氧化降解水中的苯酚。采用浸渍法制备负载型的金属氧化物催化剂,以间歇反应的方式对不同浸渍浓度下催化剂的效能,不同催化剂投加量及苯酚溶液初始pH值等影响因素进行了深入研究。研究表明,4%Mn/γ-Al_2O_3催化剂显著提高了臭氧化降解水中苯酚的效果。催化剂投加量试验研究表明4%Mn/γ-Al_2O_3催化剂具有更多的活性位点。基于此,提出了催化臭氧化苯酚的反应机理。     

水力空化强化臭氧降解水中苯酚影响因素研究

研究了在水力空化强化臭氧降解苯酚时臭氧通入量、多孔板的参数、多孔板的入口压力对苯酚降解的影响。研究表明:三者对苯酚的降解均有较大影响。增加臭氧通入量、提高入口压力都有利于苯酚的降解。研究水力空化强化臭氧氧化作用的动力学,结果表明,苯酚在单独水力空化、臭氧氧化以及它们的联合工艺下的降解均符合表观一级动力学;且在水力空化强化臭氧氧化的工艺中苯酚的去除率比在单独水力空化、臭氧氧化时有显著的提高,表明水力空化强化臭氧氧化的工艺中存在协同作用。     

ZnO/氧化石墨烯复合材料的制备及其可见光催化性能?

以均匀沉淀法制备纳米ZnO,并将其负载在氧化石墨烯(GO)上制得了ZnO/GO复合材料。XRD、TEM、UV、PL等证实在GO表面分散着颗粒均匀的ZnO纳米颗粒,GO与ZnO纳米颗粒之间存在电子转移效应,抑制ZnO中光生电子空穴对的复合,提高了ZnO的可见光催化性能;考察了复合材料在模拟太阳光条件下降解亚甲基蓝的光催化性能,当GO添加量为10%时,模拟太阳光照射90 min后,对亚甲基蓝的降解率达到97.2%,经过10次循环使用后降解率没有明显降低,复合材料的可见光催化活性明显优于纯的纳米ZnO,同时ZnO/GO复合材料对部分工业染料也有很好的降解活性。     

碱性矿物水镁石催化臭氧化—机理与应用

文章系统综述了碱性矿物水镁石及其煅烧产物在臭氧化净水中的应用及其机理。以活性艳红染料、硝基苯、苯胺、苯酚为例,分别研究了水镁石煅烧前后对不同类型的有机污染物的催化臭氧化降解效果。文章在前文实验的基础上,提出了水镁石煅烧前后的不同催化机理,进一步发展了臭氧化催化理论,为碱性矿物水镁石及其煅烧产物的利用提供了理论上的指导。     

ZnO/氧化石墨烯复合材料的制备及其可见光催化性能

以均匀沉淀法制备纳米ZnO,并将其负载在氧化石墨烯(GO)上制得了ZnO/GO复合材料。XRD、TEM、UV、PL等证实在GO表面分散着颗粒均匀的ZnO纳米颗粒,GO与ZnO纳米颗粒之间存在电子转移效应,抑制ZnO中光生电子空穴对的复合,提高了ZnO的可见光催化性能;考察了复合材料在模拟太阳光条件下降解亚甲基蓝的光催化性能,当GO添加量为10%时,模拟太阳光照射90 min后,对亚甲基蓝的降解率达到97.2%,经过10次循环使用后降解率没有明显降低,复合材料的可见光催化活性明显优于纯的纳米ZnO,同时ZnO/GO复合材料对部分工业染料也有很好的降解活性。     

活性炭负载Fe~(3+)催化臭氧氧化水中双酚A

采用浸渍法在活性炭上负载铁制备催化剂Fe/AC,用于催化臭氧氧化水中内分泌干扰物双酚A(BPA),研究了Fe/AC/O3体系的协同效应,探讨了Fe/AC投加浓度、臭氧浓度和BPA初始浓度等工艺参数的作用规律,并分析了Fe/AC/O3体系在不同pH值下的催化反应机制。结果表明,在Fe/AC/O3体系下,反应60 min后,BPA和COD的去除率分别为97.44%和69.47%,效果明显优于臭氧体系的70.15%、30.89%和活性炭体系的14.69%、7.53%之和,具有明显的协同作用;Fe/AC/O3体系降解BPA符合一级反应动力学,当Fe/AC的投加浓度为5.0 g/L,臭氧浓度为15.0 mg/L,BPA初始浓度为50.0 mg/L时,Fe/AC/O3体系降解BPA的反应速率常数为0.05972 min-1;其反应机制受溶液pH值的影响,在酸性条件下是吸附和臭氧直接氧化共同作用,而在碱性条件下以·OH间接氧化为主,活性炭上负载的Fe3+促进了·OH的生成,大大提高了BPA的反应效率和矿化率。     

超声波臭氧技术联用处理对硝基苯胺废水研究

分别采用臭氧、单频超声协同臭氧处理、双频超声强化臭氧氧化处理对硝基苯胺废水,考察了废水初始pH、臭氧通入量、超声波频率及功率等因素对处理效果的影响。结果表明,超声与臭氧协同作用可以有效地降解对硝基苯胺废水,且以双频超声强化臭氧氧化效果最佳,其优化处理条件:pH为11,臭氧的产生速率为30 mg.min-1,双频功率搭配为110 W-50 W,反应时间为50 min。此时COD、对硝基苯胺和硝基苯的去除率分别为96.4%、99.8%和98.8%,经处理后的水质能达到GB 8978-1996的一级排放标准。     

Treatment of Water Contaminated with Chlorinated Organic Herbicide 2,4-D by an Ozone/Gamma Process

Radiation-induced degradation of 50 ppm 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated in different ozonation times. Co-60 gamma-source was used as a gamma-source with a dose rate of 0.07 kGy/h. Ozonized samples were irradiated for the 0.2 kGy dose. It is observed that irradiation enhances the degradation of 2,4-D with ozone. The amount of passed ozone from samples is between 0.0695 g/L and 8.33 g/L with a flow rate of ozone at 0.078 L/min (10 g/h), from 10 s to 1200 s with the ozone generator. Aliphatic acids and chloride were determined with ion chromatography. Formaldehyde, dissolved oxygen, pH and total acidity were also measured. Both species and amounts of radiolytic intermediates were determined. 2,4-dichloro phenol (2,4-DCP) is one of the toxic intermediates of 2,4-D observed with GC/MS and it decomposes at further ozonation times. It is observed that combination of ozone/gamma irradiation is more effective for degradation of 2,4-D and its intermediate 2,4-DCP. Chloride ions are observed as completely released with combined processes at lower ozonation times although nearly 98% are released with 20 min' ozonation. Intermediate 2,4-DCP decomposes at earlier ozonation times than 2,4-D.     

苯酚的O_3/H_2O_2化学氧化反应动力学研究

应用 Stopped- flow光谱仪研究苯酚在 2 88～ 30 8K和 p H=3.2～ 9.8的 O3 / H2 O2 氧化反应动力学。通过实验及分析认为 :在不同酸度的实验条件下苯酚 O3 / H2 O2 氧化降解的途径及动力学不同。在酸性及弱酸性(p H=6 .5 )下苯酚 O3 / H2 O2 氧化反应机理是苯酚直接为 O3 氧化 ,在碱性 (p H=9.8)时为自由基机理     

Influence parameters in the ozonation of phenol wastewater treatment using bubble column reactor under continuous circulation

The ozonation of phenol wastewater treatment system has been investigated with effective mass transfer between gas and liquid phase in a bubble column reactor. The designed bubble column reactor was investigated for increasing the rate of mass transfer of ozone, the rate of oxidation of phenol in the solution, the solubility and decomposition rate of ozone in the distilled water were also studied at different flow rates. The decomposition rate constants were calculated based on pseudo first order kinetics. The oxidation of phenol was investigated in order to provide the overall reaction rate constant for the reaction between ozone and phenol at 25 °C. The influence of the operating parameters like initial phenol concentration, ozone flow rate and pH for the destruction of phenol by ozonation were studied. The pseudo first order rate constant was depending on the initial concentration of phenol solution. A comparison of TOC removal percentage between bubble column reactor and bubble diffuser using ozonation were reported.     

Kinetics of the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation

In this study, high-gravity intensified heterogeneous catalytic ozonation is utilized for treatment of phenol-containing wastewater, and the kinetics of the direct reaction between ozone and phenol in the presence of excess tertiary butanol (TBA) is investigated. It is revealed that the direct reaction between ozone and phenol in the rotating packed bed (RPB) follows the pseudo-first-order kinetics with a reaction rate constant higher than that in the conventional bubbling reactor (BR). Under different conditions of temperature, initial pH, high-gravity factor, and gaseous ozone concentration, the apparent reaction rate constant varies in the range of 0.0160–0.115 min^-1. An empirical power-exponential model is established to characterize the effects of these parameters on the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation.     

苯酚液相臭氧化动力学特性的研究

应用Stopped-flow光谱仪对苯酚在288－313K温度和pH=3.2-9.3的液相臭氧化反应动力学特性进行了实验研究。通过实验及分析认为：苯酚的O3氧化降解反应，O3与苯酚的计量比为3；在不同酸度的实验条件下，苯酚的液相O3氧化降解的途径及动力学不同。     

Ozonation of Phenol-Containing Wastewater Using O3/Ca(OH)2 System in a Micro Bubble Gas-Liquid Reactor

The degradation of phenol in aqueous solution was investigated in an integrated process consisting of O₃/Ca(OH)₂ system and a newly developed micro bubble gas-liquid reactor. The effects of operating parameters such as Ca(OH)₂ dosage, reactor pressure, liquid phase temperature, initial phenol concentration and inlet ozone concentration on degradation and mineralization (TOC removal) were studied in order to know the ozonation performance of this new integrated process. It is demonstrated that the degradation and TOC removal efficiency increased with increasing inlet ozone concentration and increasing Ca(OH)₂ dosage before 2 g/L, as well as decreasing initial phenol concentration. The optimum Ca(OH)₂ dosage should exceed Ca(OH)₂ solubility in liquid phase. The reactor pressure and liquid phase temperature have little effects on the removal and TOC removal efficiency. When Ca(OH)₂ dosage exceeded 3 g/L, the degradation and TOC removal of phenol almost reached 100% at 30 and 55 min, respectively. The intensification mechanism of Ca(OH)₂ assisted ozonation was explored through analysis of the precipitated substances. The mechanism for Ca(OH)₂ intensified mineralization of phenol solution is the simultaneous removal of CO₃^2- ions, as hydroxyl radical scavengers, due to the presence of Ca²⁺ ions. Results indicated that the proposed new integrated process is a highly efficient ozonation process for persistent organic wastewater treatment.     

Studies on cerium oxidation in catalytic ozonation process: A novel approach for organic mineralization

A novel regenerative catalytic system has been developed using cerium and ozone in nitric acid medium. It was found that cerium(III) was oxidized to cerium(IV) by ozone in nitric acid medium with good conversion yields. The conversion rate of Ce(III) was measured under various parameters viz. ozone–air flow rate, initial concentration of Ce(III), and concentration of nitric acid at 25 °C. It was found that the conversion of Ce(III) increased with increasing ozone flow rate and concentration of nitric acid while decreased with increasing Ce(III) concentration. The pseudo first order kinetic constants were evaluated for Ce(III) oxidation. The efficiency of this hybrid system comprising of ozone and cerium redox pair towards organic mineralization was evaluated taking phenol as the model organic pollutant and compared with Ce(III) catalyzed and uncatalyzed ozonation processes. The presence of Ce(III) catalyst increased the destruction efficiency of phenol compared to uncatalyzed ozonation whereas a synergetic effect was observed between the cerium redox pair (Ce(III) and Ce(IV)) and ozone towards phenol mineralization and a maximum TOC removal was obtained in the latter case. Kinetic interpretations have been made with some simplifying assumptions owing to the much complex nature of ozone and metal ion interactions. This hybrid catalytic ozonation process may find its suitability for continuous organic destruction at room temperature.     

Mineralization improvement of phenol aqueous solutions through heterogeneous catalytic ozonation

To assess the mineralization level achieved, aqueous solutions of phenol have been treated with ozone in the presence of different solid catalysts. Activated carbon was the principal catalyst investigated, although some additional experiments were carried out by utilizing metal oxide‐based catalysts (ie Ti, Co and Fe) supported onto alumina. Usage of Co/Al₂O₃ led to the highest values of phenol byproduct mineralization, nevertheless some metal leaching was experienced in the process. The operating variables studied when using activated carbon as the catalyst were ozone gas concentration, amount of catalyst added and temperature. Regardless of the catalyst type used, two different ozonation kinetic regimes were observed: (I) an initial period, corresponding to the presence of phenol in solution, characterized by small amounts of dissolved ozone and no improvement of the mineralization degree if comparing catalytic and non‐catalytic runs; (II) a second period, free of phenol, in which dissolved ozone accumulated in water and the beneficial effects of catalysts on mineralization were noticed. Experimental data also demonstrated the improvement in oxalic acid elimination in the presence of heterogeneous catalysts. Finally, consumption of ozone per mass of carbon removed, reaction factors and Hatta numbers were also calculated. Copyright © 2003 Society of Chemical Industry