Fenton's oxidation of MTBE with zero-valent iron

Methyl tert-butyl ether (MTBE) has become a contaminant of increasing concern in the U.S. Traditional remediation technologies are successful in removing MTBE from contaminated water, but usually transfer the contaminant from the aqueous to another phase. Fenton's oxidation of MTBE provides a promising alternative to traditional remediation techniques in that it may mineralize the contaminant rather than just phase transfer. This bench-scale study investigated the feasibility of Fenton's oxidation of MTBE using zero-valent iron as the source of catalytic ferrous iron. The oxidation reactions were able to degrade over 99% of the MTBE within 10 min, and showed significant generation, and subsequent degradation, of the MTBE oxidation byproduct acetone. Second-order rate constants for MTBE degradation were 1.9 x 10(8) M(-1) s(-1) at pH 7.0 and 4.4 x 10(8) M(-1) s(-1) at pH 4.0. The total organic carbon was reduced by over 86% when a H2O2:MTBE ratio of 220:1 or greater was used.     

Continuous combined Fenton's oxidation and biodegradation for the treatment of pentachlorophenol-contaminated water

Pentachlorophenol (PCP) was studied as a model recalcitrant compound for a sequential chemical oxidation and biodegradation treatment, in a continuous laboratory-scale system that combined a Fenton’s chemical reactor and a packed-bed bioreactor.PCP degradation and dechlorination were observed in the Fenton’s reactor at a residence time of 1.5 h, although no reduction of total organic carbon (TOC) was observed. Both PCP degradation and dechlorination were strongly dependent on the H₂O₂ dose to the chemical reactor. The PCP degradation intermediates tetrachlorohydroquinone and dichloromaleic acid were identified in this reactor. Further treatment of the Fenton’s reactor effluent with a packed-bed bioreactor (operating at a residence time of 5.5 h) resulted in partial biodegradation of PCP degradation intermediates and reduction in TOC, although no further reduction of PCP or dechlorination was achieved in the bioreactor. Increased residence time in the bioreactor had no significant impact on degradation of TOC. Recycle of the effluent from the bioreactor to the chemical reactor increased the TOC degradation, but not the extent of the PCP degradation or dechlorination.A mathematical model of the combined Fenton’s oxidation and biodegradation system supported the experimental results. While the model over-predicted the PCP and TOC degradation in the combined system, it adequately predicted the sensitivity of these parameters to different H₂O₂ doses and recycle rates. The model indicated that high recycle rates would improve TOC degradation.     

矿物绝缘电缆与非标矿物绝缘电缆的比较

从矿物绝缘电缆产品的标准、结构、载流量、使用寿命等方面与非标矿物绝缘电缆进行综合比较,结合矿物绝缘电缆在实际工程中消防设施、重要场所的应用情况,提出民用建筑消防设施中采用矿物绝缘电缆的必要性。     

盐池微溶结晶矿物盐对混凝土的影响研究

经研究发现,盐池底盐池微溶结晶矿物盐对混凝土强度等综合影响甚微,改变了人们传统观念,为盐池中工程的顺利实施提供了有力的依据,该研究对整个沿海盐田上的工程建设具有较好的参考作用。     

Degradation of 2,4-dichlorophenol by immobilized iron catalysts

The degradation of 2,4-Dichlorophenol (from now on 2,4-DCP) has been carried out on Nafion-Fe (1.78%) in the presence of H2O2 under visible light irradiation. A solution containing 2,4-DCP (TOC 72 mg C/L)) is seen to be mineralized in approximately 1 h in the presence of H2O2 (10 mM) under solar simulated visible light (80 mW cm-2) at pH values between 2.8 and 11. Homogeneous photo-assisted Fenton reactions were capable of mediating 2,4-DCP degradation only up to pH 5.4. The degradation kinetics of 2,4-DCP on Nafion-Fe membranes was more favorable than the one observed during Fenton photo-assisted processes at pH 2.8. The degradation of 2,4-DCP was investigated as a function of the substrate, oxidant concentration and applied light intensity. The Nafion-Fe was seen to be effective over many cycles during the photo-catalytic degradation of 2,4-DCP showing an efficient and stable performance during 2,4-DCP degradation without leaching out Fe(3+)-ions into the solution. Evidence is presented that the degradation at the surface of the Nafion-Fe membrane seems to be controlled by mass transfer and not by chemical reaction of the species in solution. The approach used to degrade 2,4-DCP is shown to be valid for other chloro-carbons like 4-chlorophenol, 2,3-chlorophenol and 2,4,5-trichlorophenol.     

Effect of surfactants on the determination of soluble iron in waters

The effects of pure cationic, anionic and non-ionic detergents, industrially prepared detergents, sodium tripolyphosphate, sodium pyrophosphate, soap and NTA, in quantities up to 1000 mg l^?1, on the analysis of soluble iron in water using the phenanthroline, tripyridine and biquinoline methods were investigated. The tripyridine method is superior to the other two methods for the determination of iron in the presence of up to 1000 mg l^?1 of various surfactants but not for up to 100 mg l^?1 of non-ionic detergents. The phenanthroline method can be used to determine iron in the presence of up to 1000 mg l^?1 of cationic, anionic and non-ionic detergents, but sodium tripolyphosphate interfered above 2 mg l^?1. The biquinoline method can be used for the determination of iron in the presence of up to 1000 mg l^?1 of cationic, 100 mg l^?1 of anionic and 70 mg l^?1 of non-ionic detergents, and 50 mg l^?1 of sodium tripolyphosphate.     

Displacement of five metals sorbed on kaolinite during treatment with modified Fenton's reagent

The displacement of sorbed metals during the treatment of soils and groundwater with modified Fenton's reagent was investigated using five common metal contaminants (cadmium, copper, lead, nickel, and zinc) and kaolinite as a model sorbent. Modified Fenton's conditions included three H(2)O(2) concentrations (0.9, 1.8, 2.7 M) and two catalysts: soluble iron (III) at pH 3 and iron (III)-NTA chelate at pH 6. Iron (III)-catalyzed Fenton's reactions released significant amounts of zinc, cadmium, and copper. Modified Fenton's reactions catalyzed by iron (III)-NTA released zinc, cadmium, copper, and lead, and resulted in greater amounts of metals release than the iron (III)-catalyzed reactions. Metals release may have been mediated by transient oxygen species, such as superoxide, generated by propagation reactions, which become dominant at the relatively high hydrogen peroxide concentrations used. Metals release from kaolinite was undetectable when sufficiently low hydrogen peroxide concentrations were maintained to minimize propagation reactions. These results indicate that using dilute concentrations of hydrogen peroxide for Fenton's ISCO may minimize potential metals mobility when treating contaminated soils and groundwater containing a mixture of organic and metal contaminants.     

钢铁厂冶炼渣分类及矿物组成分析

现代炼钢工艺流程中有高炉炼铁、铁水脱硫预处理、转炉复合吹炼、电弧炉冶炼和二次精炼等冶炼工序,分别产生高炉渣、铁水脱硫渣、转炉钢渣、电弧炉钢渣和精炼渣等冶炼渣。本文介绍了各类冶炼渣的产生、化学成分及矿物组成。     

Effects of iron surface pretreatment on sorption and reduction kinetics of trichloroethylene in a closed batch system

The decline of trichloroethylene (TCE) in a metallic iron-water system results from the combination of reduction reaction and sorption onto iron surfaces. Sorption, particularly by highly impure iron, accelerates the removal of TCE from the aqueous phase, but delays the prevalence of steady-state conditions. In this case, an overly high value of reaction rate constant in the design of a treatment system would be used. In this work, the effects of an iron surface with 8.0% C, 6.1% O and 0.8% Si separately following HCl-washing and H2-reducing pretreatment on sorption and reduction rates were examined. The amounts of both aqueous and sorbed TCE were measured using a modified solvent-extraction method. TCE sorption onto an iron surface, as quantified by the Langmuir sorption maximum, followed the trend H2-reduced Fe0 > HCl-washed Fe0 > untreated Fe0 (0.887, 0.365 and 0.311 mg/g, respectively). Measurements of the concentration of sorbed TCE revealed that about 34-37% of the initial mass of TCE in the aqueous phase was removed by sorption by H2-reduced Fe0, 16-19% was removed by HCl-washed Fe0 and 13-16% was removed by untreated Fe0. A combination of new and previously reported data on cast iron's capacity to sorb TCE revealed a linear relationship between this capacity and the C fraction in the surface of the iron, with the coefficient of determination (r2) exceeding 0.99. The first-order observed rate constants (k(obs)) of the reduction of TCE in contact with Fe0 were obtained from the slope of a plot of total TCE loss rate (-dC(T)/dt) versus the amount of TCE in the aqueous phase (C(w)) using linear least-squares analysis. The k(obs) values were 0.080, 0.148 and 0.191 h(-1) for untreated, HCl-washed and H2-reduced Fe0, respectively. Normalized to iron surface area concentration, the specific rate constants (k(SA)) were 2.3 7x 10(-3) , 2.31 x 10(-3) and 5.62 x 10(-3) h(-1) m(-2) L, respectively. The results indicated that HCl-washing approximately doubled k(obs), primarily because of the increase in the surface area of the iron, and it slightly decreased k(SA) due to rapid corrosion during the rinsing process. Both the number of reactive sites and the sorption capacity per unit iron surface area through the H2-reducing pretreatment were increased due to the reduction of iron oxide layer and the carbonization of carbon-containing subjects on the iron's surface. Hence, the H2 reduction of cast iron promotes the removal of TCE from contaminated water by the concurrent sorption and reduction.     

Controlling soluble iron and manganese in a water-supply reservoir using hypolimnetic oxygenation

Soluble metals such as iron (Fe) and manganese (Mn) often reach problematic levels in water-supply reservoirs during summer stratification following the onset of hypolimnetic hypoxia. The behavior of soluble and particulate Fe and Mn was studied following the installation of a hypolimnetic oxygenation system in Carvins Cove Reservoir, a water-supply impoundment managed by the Western Virginia Water Authority. During oxygenation, manganese concentrations were very low in the bulk hypolimnion (<0.05 mg l⁻¹), but high concentrations (>2.0 mg l⁻¹) were still observed in the benthic region close to the sediment, despite near-sediment dissolved oxygen concentrations in excess of 5.0 mg l⁻¹. Oxygenation appears to affect the location of the oxic/anoxic boundary sufficiently to restrict substantial transport of soluble Mn to the bulk water of the hypolimnion. However, the position of the oxic/anoxic boundary was not uniformly affected along the reservoir bottom, allowing horizontal transport of soluble Mn from higher elevations in contact with hypoxic sediments. During one summer, when the oxygen system was turned off for a month, the soluble Mn in the bulk hypolimnion increased substantially. Oxygen concentrations were quickly restored after the system was turned back on, but elevated levels of soluble Mn persisted until the sedimentation rate of detritus through the hypolimnion increased. When operated without interruption, the oxygenation system was able to reduce the bulk average hypolimnion soluble Mn concentration by up to 97%, indicating that source water control of soluble Mn and Fe can be accomplished with hypolimnetic oxygenation in water-supply reservoirs.     

Decomposition of trichloroethylene and tetrachloroethylene in drinking water by a combined radiation/ozone treatment

The decomposition of small amounts (100 ppb) of tri- or perchloroethylene in drinking water has been investigated. The combined action of γ-radiation and ozone results in a considerable synergistic effect. Furthermore, the presence of ozone eliminates completely the formation of nitrite occurring under γ-irradiation alone.     

矿物材料的前景展望

矿物材料（ MineraI Materials）是 70年代末由地质学工作者提出的一个新概念,并很快发展成为一门相对独立的学科。 　　不同的学者对矿物材料有不同的定义,笔者建议将矿物材料定义为：在工农业生产和日常生活中具有应用价值的天然矿物、岩石及其制成品和仿制品。其含义包括四个方面：①能被直接利用或经过简单的加工处理（如破碎、选矿、切割、改性等）即可利用的天然矿物、岩石;②以天然的非金属矿物、岩石为主要原料,通过物理化学反应（如焙烧、熔融、烧结、胶结等）制成的成品或半成品材料;③人工合成的矿物或岩石;④这些材料的…     

Degradation of soil-sorbed trichloroethylene by stabilized zero valent iron nanoparticles: effects of sorption, surfactants, and natural organic matter

Zero valent iron (ZVI) nanoparticles have been studied extensively for degradation of chlorinated solvents in the aqueous phase, and have been tested for in-situ remediation of contaminated soil and groundwater. However, little is known about its effectiveness for degrading soil-sorbed contaminants. This work studied reductive dechlorination of trichloroethylene (TCE) sorbed in two model soils (a potting soil and Smith Farm soil) using carboxymethyl cellulose (CMC) stabilized Fe-Pd bimetallic nanoparticles. Effects of sorption, surfactants and dissolved organic matter (DOC) were determined through batch kinetic experiments. While the nanoparticles can effectively degrade soil-sorbed TCE, the TCE degradation rate was strongly limited by desorption kinetics, especially for the potting soil which has a higher organic matter content of 8.2%. Under otherwise identical conditions, ∼44% of TCE sorbed in the potting soil was degraded in 30 h, compared to ∼82% for Smith Farm soil (organic matter content = 0.7%). DOC from the potting soil was found to inhibit TCE degradation. The presence of the extracted SOM at 40 ppm and 350 ppm as TOC reduced the degradation rate by 34% and 67%, respectively. Four prototype surfactants were tested for their effects on TCE desorption and degradation rates, including two anionic surfactants known as SDS (sodium dodecyl sulfate) and SDBS (sodium dodecyl benzene sulfonate), a cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide, and a non-ionic surfactant Tween 80. All four surfactants were observed to enhance TCE desorption at concentrations below or above the critical micelle concentration (cmc), with the anionic surfactant SDS being most effective. Based on the pseudo-first-order reaction rate law, the presence of 1×cmc SDS increased the reaction rate by a factor of 2.5 when the nanoparticles were used for degrading TCE in a water solution. SDS was effective for enhancing degradation of TCE sorbed in Smith Farm soil, the presence of SDS at sub-cmc increased TCE degraded by ∼10%. However, effect of SDS on degradation of TCE in the potting soil was more complex. The presence of SDS at sub-cmc decreased TCE degradation by 5%, but increased degradation by 5% when SDS dosage was raised to 5×cmc. The opposing effects were attributed to combined effects of SDS on TCE desorption and degradation, release of soil organic matter and nanoparticle aggregation. The findings strongly suggest that effect of soil sorption on the effectiveness of Fe-Pd nanoparticles must be taken into account in process design, and soil organic content plays an important role in the overall degradation rate and in the effectiveness of surfactant uses.     

Electrochemical generation of the Fenton's reagent: application to atrazine degradation

The degradation of refractory chemicals in water requires chemical oxidation by hydroxyl radicals. Among the systems that may be used to generate OH(o), the Fenton's reagent consists of the mixing of ferrous iron and hydrogen peroxide. Even though this system is very simple, the oxidation of an organic compound is difficult to control and the ferrous iron regeneration is limited. Very recently, electrochemical systems have merged that allow the electrochemical production of ferrous iron and/or hydrogen peroxide, thereby allowing the generation of OH(o). So a simple electro-Fenton system has been used and tested for its efficiency in producing hydroxyl radicals. Atrazine was chosen as a model organic compound as its reaction with OH(o) has been extensively studied. Comparison with the classical Fenton system gives advantage to the electrochemical system, due to a more thorough oxidation of atrazine.     

小城镇污水处理适用技术的比较分析

针对小城镇污水处理筛选出来的、典型的污水生物处理技术的特点进行分析，采用综合指标-分值比较的方法，对处理小城镇污水的适用性进行了阐述，并确定了应用小城镇污水处理适用技术的基本条件与要求。     

Comparison of trichloroethylene reductive dehalogenation by microbial communities stimulated on silicon-based organic compounds as slow-release anaerobic substrates

Microcosm studies were conducted to demonstrate the effectiveness of tetrabutoxysilane (TBOS) as a slow-release anaerobic substrate to promote reductive dehalogenation of trichloroethylene (TCE). The abiotic hydrolysis of TBOS and tetrakis(2-ethylbutoxy)silane (TKEBS), and the biotic transformations of the hydrolysis products from both were also investigated. Comparison of TCE reductive dehalogenation was performed with microbial communities stimulated from three different sites: Site 300 Lawrence Livermore National Laboratory (LLNL), CA, Point Mugu Naval Weapons Facility, CA, and the Evanite site in Corvallis, OR. Poisoned microcosms showed that 1 mol of TBOS slowly and abiotically hydrolyzes to 4 mol of 1-butanol, while the live microcosms showed the 1-butanol ferments to butyrate and/or acetate, producing H₂. The hydrolysis of TBOS and TKEBS was abiotic and not enhanced by biotic processes under the anaerobic conditions of these tests. Hydrogen consumption was correlated with reductive dehalogenation, indicating it served as an electron donor for reductive dehalogenation. TBOS was found to be a slow-release anaerobic substrate to support long-term dechlorination of TCE to ethylene in Point Mugu microcosms, and in the LLNL microcosm bioaugmented with the Evanite culture. Electron mass balances showed most of the electron flow went into the creation of organic acids, especially acetate, and the production of methane. Electron efficiencies for reductive dechlorination were as high as 14% based on the electrons used for dechlorination to the total electrons associated with the mass of TBOS and TKEBS hydrolyzed. Rates of TBOS hydrolysis increased with greater TBOS concentrations as a light nonaqueous-phase liquids (LNAPL). These results indicate that TBOS has promise as an effective anaerobic substrate for remediating a wide range of CAH concentrations at different CAH contaminated sites.     

Comparison of the ozonation and Fenton process performances for the treatment of antibiotic containing manure

An integrated treatment method based on magnesium salt extraction followed by chemical oxidation was used for the treatment of a veterinary antibiotic, oxytetracycline (OTC) contaminated cow manure since animal manure can be an important source for antibiotic pollution in the environment. Pretreatment with magnesium salt enhanced the efficiencies of subsequent oxidation processes by extracting 63.9% of OTC from the manure thereby making it more favorable for oxidation with the hydroxyl radicals produced by the Fenton and ozone oxidation processes. Both the 24 h Fenton oxidation process with 434 mM H₂O₂ and 43.4 mM Fe²⁺ doses and the 1-h ozonation process with an applied ozone dose of 2.5 mg min^− 1 provided more than 90% OTC removal from the manure slurry. However, the second-order OTC removal rate constant of Fenton process (119 M^− 1s^− 1) was remarkably lower than that obtained with the ozonation process (548 M^− 1s^− 1). The oxidant dose was a significant factor for the efficiency of the Fenton treatment but not for the ozone treatment. The efficiencies of both the Fenton and ozone oxidation processes were not affected by the pH adjustment of the manure slurry.     

羟基氧化铁的制备影响及污水处理中的应用

介绍了羟基氧化铁的种类、结构、表面物理化学性质,讨论了羟基氧化铁制备时反应物(如铁盐种类、沉淀剂)与反应条件(如温度、pH值、表面活性剂等)对产物的影响。最后,对羟基氧化铁在污水处理中的应用进行概述,对实际工程的应用具有重要意义。     

矿物纤维在沥青混凝土路面处理中的应用

介绍了矿物纤维的性能特征及其在国内外的发展现状,并针对其在路面处理中的应用及需要注意的问题进行了分析,说明了矿物纤维在我国具有广阔的发展前景。     

Pilot studies for in-situ aerobic cometabolism of trichloroethylene using toluene-vapor as the primary substrate

In-situ pilot studies of aerobic cometabolism were conducted to evaluate the injection of toluene-vapor and air into TCE-contaminated aquifer. Delivery of primary substrate (toluene) in a vapor state with air enhanced the growth of indigenous toluene-utilizing bacteria that would degrade TCE by aerobic cometabolism. Meanwhile, delivering toluene in a vapor state effectively reduced potential clogging near the injection points due to excessive microbial growth, which was observed in the field when the injection of neat toluene was employed. Over 90% removal of TCE was achieved with primary substrate (toluene) degraded to a concentration below 10 microg/L.