天然矿物负载Fe/Co催化H2O2氧化降解阳离子红3R

类Fenton反应关键是催化剂的活性,利用浸渍法负载铁、钴双金属对天然矿物材料进行改性,提高其催化活性,并运用扫描式电子显微镜(SEM)、X射线能谱仪(EDS)、X射线衍射(XRD)等表征手段对负载前后的材料进行表征分析.结果表明负载后材料中生成Fe2O3和Co Fe2O4两种新物质.将合成的催化剂用于催化H2O2氧化阳离子红3R染料废水,在催化剂投加量3 g·L-1,H2O2投加量0.3 m L·L-1,反应时间1 h条件下,100 mg·L-1阳离子红3R废水脱色率可达99.8%,TOC去除率可达58.4%,催化剂中活性组分主要为表面负载的Fe2O3和Co Fe2O4,电子自旋共振(ESR)分析表明催化氧化过程中产生羟基自由基,阳离子红3R发色基团在1 min已被完全破坏,光谱分析表明反应过程中有小分子物质生成.催化氧化效果受染料废水初始p H值影响小,适应p H范围广,解决了传统Fenton反应p H条件苛刻的问题.研究结果为印染废水处理提供了具有工程应用潜力的技术方法.     

处理水产养殖污水潜流湿地中的厌氧氨氧化菌群特征

厌氧氨氧化(anaerobic ammonium oxidation,ANAMMOX)是潜流湿地净化污水的重要功能,目前关于潜流湿地厌氧氨氧化特征还不清楚.为了解处理水产养殖污水潜流湿地中的厌氧氨氧化特点,采用16S rRNA基因克隆文库和实时荧光定量PCR技术以及多样性分析等方法,对处理水产养殖污水潜流湿地中ANAMMOX菌的结构、多样性和丰度进行了研究分析.结果表明,处理水产养殖污水潜流湿地中存在Candidatus brocadia和Candidatus kuenenia这2类已知的ANAMMOX菌和3类未知的ANAMMOX菌,其优势种群为Candidatus brocadia;在不同季节中,秋季潜流湿地中ANAMMOX菌的多样性最高(H',1.21),春季最低(H',0.64);在养殖周期内,潜流湿地中ANAMMOX菌的丰度(以鲜重计,下同)在8.0×104~9.4×106copies·g-1之间,总细菌丰度在7.3×109~9.1×1010copies·g-1之间;在潜流湿地不同层面以及不同季节中,ANAMMOX菌的丰度存在着明显的差异,总细菌丰度则差异不明显,ANAMMOX菌的丰度在不同层面上的差异没有随时间变化的规律性.根据潜流湿地中ANAMMOX菌的分布特征,改变养殖污水布水方式和调整湿地结构可以提高潜流湿地的反硝化效果.该研究为进一步优化潜流湿地结构,提高净化养殖污水效率提供了依据.     

The influence of oxygen concentration on the composition of gaseous products occurring during the self-heating of coal and wood sawdust

This article deals with an assessment of the influence of oxygen concentration on the composition and amount of combustion products generated in the course of heating coal particles and wood sawdust at 150 °C. This was done both with normal air and at 15% oxygen in the air in an isothermal furnace. The generated gases were analyzed by a Fourier Transform infrared spectrometer. Results show that under both conditions, the same substances are formed: water, carbon dioxide, carbon monoxide and aliphatic hydrocarbons. However, the quantities changed. At 21% oxygen, the concentrations of carbon monoxide and methane were higher than at 15% oxygen both in coal and wood. The oxygen concentration was also found to affect the rates of release of CO and CO₂. The rate of release of CO was higher at 21% oxygen, but that of CO₂ was higher at 15%, indicating two different mechanisms. In all cases, the concentrations of these gases were higher for coal than for wood. The results have implications for the specification of safe conditions of storage of coal and wood substances and the selection of safety measures.     

Reuse of nickel recovered from spent Ni–Cd batteries for the preparation of C/Ni and C/Ni/Pd layered electrodes for energy sources

Nickel recovered in the recycling process of Ni–Cd batteries was used as a main component of bath for electrodeposition of nickel onto carbon fabric in order to obtain C/Ni composite. A part of the obtained composite was additionally coated with a thin layer of palladium (C/Ni/Pd composite). All the materials were investigated to assess the possibility of their use in the processes of electrochemical storage (sorption/desorption) of hydrogen and electrochemical oxidation of methanol. The obtained results showed the composites to be active electrode materials in these processes. The electrodes exhibited high activity and cyclability, especially in the process of methanol oxidation due to electrocatalytic activity of both nickel deposited onto carbon fabric and the outer layer of porous palladium coating nickel substrate.     

Detoxification of hexavalent chromium in wastewater containing organic substances using simonkolleite-TiO2 photocatalyst

Innovative simple method for the preparation of simonkolleite-TiO₂ photocatalyst with different Zn contents was achieved. The prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, Raman and diffuse reflectance spectroscopy techniques. The photocatalytic activities of the materials were evaluated for the simultaneous detoxification of hexavalent chromium (Cr(VI)) and oxidation of organic compounds commonly present in wastewater under simulated solar light. The best photoreduction efficiency of Cr(VI) has been achieved at 1000 ppm simonkolleite-TiO₂ photocatalyst of 5% Zn/TiO₂ weight ratio, and pH value of 2.5 to enhance the adsorption onto catalyst surface. Photoreduction was significantly improved by using formic acid as holes scavenger owing to its chemical adsorption on the catalyst surface. Finally, 100% photoreduction of Cr(VI) could be achieved using formic/simonkolleite-TiO₂ systems under sunlight.     

Hydrogen peroxide (H2O2) requirement for the oxidation of crude oil in contaminated soils by a modified Fenton's reagent

The oxidation of soil organic matter (SOM) and total petroleum hydrocarbon were investigated in two soils at eight different hydrogen peroxide (H₂O₂) concentrations to determine the optimal H₂O₂ dosage for the efficient remediation of soils contaminated by crude oil with minimal SOM removal. In our study, H₂O₂ concentrations up to 1100 mM increased the SOM destruction up to 10%–15% in the two soils while no improvement of the crude oil removal efficiencies was observed. The results indicate that the destruction of SOM significantly limits the oxidation of crude oil because SOM might consume H₂O₂ more effectively than crude oil at H₂O₂ concentrations above 1100 mM. In addition, H₂O₂ concentrations higher than 1100 mM were not expected for both soils because of the extremely rapid H₂O₂ decomposition, and low H₂O₂ utilization, of both soils.     

Advanced treatment of biologically pretreated coal gasification wastewater by a novel heterogeneous Fenton oxidation process

Sewage sludge from a biological wastewater treatment plant was converted into sewage sludge based activated carbon(SBAC) with Zn Cl2 as activation agent, which was used as a support for ferric oxides to form a catalyst(Fe Ox/SBAC) by a simple impregnation method.The new material was then used to improve the performance of Fenton oxidation of real biologically pretreated coal gasification wastewater(CGW). The results indicated that the prepared Fe Ox/SBAC significantly enhanced the pollutant removal performance in the Fenton process, so that the treated wastewater was more biodegradable and less toxic. The best performance was obtained over a wide p H range from 2 to 7, temperature 30°C, 15 mg/L of H2O2 and 1 g/L of catalyst, and the treated effluent concentrations of COD, total phenols,BOD5 and TOC all met the discharge limits in China. Meanwhile, on the basis of significant inhibition by a radical scavenger in the heterogeneous Fenton process as well as the evolution of FT-IR spectra of pollutant-saturated Fe Ox/BAC with and without H2O2, it was deduced that the catalytic activity was responsible for generating hydroxyl radicals, and a possible reaction pathway and interface mechanism were proposed. Moreover, Fe Ox/SBAC showed superior stability over five successive oxidation runs. Thus, heterogeneous Fenton oxidation of biologically pretreated CGW by Fe Ox/SBAC, with the advantages of being economical, efficient and sustainable, holds promise for engineering application.     

Effects of different sludge disintegration methods on sludge moisture distribution and dewatering performance

A key step in sludge treatment is sludge dewatering. However, activated sludge is generally very difficult to be dewatered. Sludge dewatering performance is largely affected by the sludge moisture distribution. Sludge disintegration can destroy the sludge structure and cell wall, so as change the sludge floc structure and moisture distribution, thus affecting the dewatering performance of sludge. In this article, the disintegration methods were ultrasound treatment, K₂FeO₄ oxidation and KMnO₄ oxidation. The degree of disintegration (DD_COD), sludge moisture distribution and the final water content of sludge cake after centrifuging were measured. Results showed that three disintegration methods were all effective, and K₂FeO₄ oxidation was more efficient than KMnO₄ oxidation. The content of free water increased obviously with K₂FeO₄ and KMnO₄ oxidations, while it decreased with ultrasound treatment. The changes of free water and interstitial water were in the opposite trend. The content of bounding water decreased with K₂FeO₄ oxidation, and increased slightly with KMnO₄ oxidation, while it increased obviously with ultrasound treatment. The water content of sludge cake after centrifuging decreased with K₂FeO₄ oxidation, and did not changed with KMnO₄ oxidation, but increased obviously with ultrasound treatment. In summary, ultrasound treatment deteriorated the sludge dewaterability, while K₂FeO₄ and KMnO₄ oxidation improved the sludge dewaterability.