Activity and resistance of iron-containing amorphous, zeolitic and mesostructured materials for wet peroxide oxidation of phenol

Iron-containing materials have been prepared following several strategies of synthesis and using different silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials was evaluated on the wet peroxide oxidation of phenol under mild reaction conditions (100 degrees C, air pressure of 1MPa and stoichiometric amount of hydrogen peroxide for the complete mineralisation of phenol). Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions, by-products distribution (aromatics compounds and carboxylic acids) and degree of metal leached into the aqueous solution. The nature and local environment of iron species is strongly dependent on the synthetic route, which dramatically influences their catalytic performance. Crystalline iron oxide species supported over mesostructured SBA-15 materials have demonstrated to be the most interesting catalysts for phenol degradation according to its high organic mineralisation, low sensitivity to leaching out and good oxidant efficiency.     

水中重金属离子吸附材料的研究现状与发展趋势

系统介绍了无机吸附材料（碳质类、矿物类、金属氧化物类）、有机高分子吸附材料（纤维素、壳聚糖、农林废弃物、离子交换树脂等）和复合型吸附材料（有机/有机型、无机/无机型、有机/无机型）等重金属离子吸附材料的物化特性和结构特点,对上述材料去除水体典型重金属离子的吸附容量、吸附机理、工程应用进展等进行了综述。阐述了纳米材料、离子选择性材料和可降解生物质材料等新型重金属离子吸附材料的研究现状及发展趋势。结果表明:开发价格低廉、吸附容量高、选择性高、可再生且环境友好的吸附材料是重金属离子吸附研究的重要方向;结合现代化检测技术和分析手段,探索吸附过程中吸附剂与重金属离子间相互作用的本质,对于拓展吸附机理和开发性能优良的吸附材料具有重要的理论和实际意义。     

The molecular size of natural organic matter (NOM) determined by diffusivimetry and seven other methods

The objectives of this work are to (1) determine the diffusion coefficients of natural organic matter (NOM) by diffusivimetry, (2) compare the results with diffusion coefficients determined by two other methods (fluorescence correlation spectroscopy (FCS) and dynamic adsorption experiments (DAM), (3) compare molecular weights derived from the diffusion coefficients to molecular weights determined by three different ultrafiltration experiments and high perfomance size exclusion chromatography (HPSEC). The diffusion coefficients determined in this work (stirred diffusion cell) are about 70% higher than that determined by DAM, and agree well with diffusion coefficients determined by FCS. Molecular weights determined by HPSEC are of the same magnitude as molecular weights derived from diffusion coefficients. Molecular weights determined by ultrafiltration vary considerably depending on the choice of membrane types. Membranes made of cellulose acetate generate results similar to results derived from diffusion coefficients. Membranes made of regenerated cellulose and polyether sulfone appear to retain too much of NOM, resulting in artificially high molecular weights.     

膨胀性黄土隧道钢拱架–格栅联合支护力学特性研究

为了研究膨胀性黄土隧道围岩与支护结构作用机制,解决膨胀力作用下的隧道支护难题,利用弹性薄壳理论建立了联合支护的力学分析模型,引入等效截面法和膨胀力参数得到了改进的围岩–支护特征曲线。基于上述模型和方法,对该黄土隧道初期支护的力学特性进行分析,提出适用于膨胀性黄土隧道的"格栅拱架+钢拱架+喷射混凝土"联合支护方式。结果表明:所建立的模型和方法对膨胀围岩条件下初期支护的力学特性分析具有较好的适用性,从理论角度解释该隧道原始初期支护发生破坏的原因;与"钢拱架+喷射混凝土"和"格栅+喷射混凝土"支护方式相比,提出的联合支护方式在膨胀性黄土隧道中更具优势,充分发挥了不同材料的承载特性,保证了隧道的稳定性。     

A quantitative property‐property relationship for the internal diffusion coefficients of organic compounds in solid materials

Indoor releases of organic chemicals encapsulated in solid materials are major contributors to human exposures and are directly related to the internal diffusion coefficient in solid materials. Existing correlations to estimate the diffusion coefficient are only valid for a limited number of chemical‐material combinations. This paper develops and evaluates a quantitative property‐property relationship (QPPR) to predict diffusion coefficients for a wide range of organic chemicals and materials. We first compiled a training dataset of 1103 measured diffusion coefficients for 158 chemicals in 32 consolidated material types. Following a detailed analysis of the temperature influence, we developed a multiple linear regression model to predict diffusion coefficients as a function of chemical molecular weight (MW), temperature, and material type (adjusted R² of .93). The internal validations showed the model to be robust, stable and not a result of chance correlation. The external validation against two separate prediction datasets demonstrated the model has good predicting ability within its applicability domain (>.8), namely MW between 30 and 1178 g/mol and temperature between 4 and 180°C. By covering a much wider range of organic chemicals and materials, this QPPR facilitates high‐throughput estimates of human exposures for chemicals encapsulated in solid materials.     

Measurement of biomass activity in drinking water biofilters using a respirometric method

A simple respirometric method was developed and applied for the measurement of biomass activity in bench-scale drinking water biofilters. The results obtained with the new method, i.e. biomass respiration potential (BRP), indicated a high sensitivity allowing the quantification of the activity of low amounts of biomass. The analysis of duplicate samples showed a reasonable reproducibility, i.e. average coefficient of variation of 14% (n = 19). The calculation of the ratio between biomass activity and the amount of viable biomass (phospholipid) at different filter depths indicated a substantial increase of this ratio with filter depth. This indicated an increased biomass activity per unit amount of viable biomass deeper in the biofilters, where biofilm thickness is low. The comparison of the filter profiles of biomass activity and dissolved biodegradable organic matter (BOM), expressed as theoretical oxygen demand, showed a high correlation between these profiles. Consequently, BRP results appear to be good indicators of the BOM removal capacity of the filter biomass. Therefore, BRP results can potentially be used in certain cases instead of BOM measurements for the assessment of the BOM removal capacity of drinking water biofilters, operated under different conditions. This is important because of the relative complexity of the measurements of BOM surrogates, e.g. assimilable organic carbon and biodegradable dissolved organic carbon, and BOM components.     

Using soil biomass as an indicator for the biological removal of effluent-derived organic carbon during soil infiltration

This study investigates the relationship between soil biomass and organic carbon removal during the infiltration of conventionally treated effluents used for groundwater recharge during soil-aquifer treatment (SAT). Investigations were conducted on samples collected from full-scale SAT sites, revealing a positive correlation between biodegradable organic carbon (BOC) concentrations in the recharged effluents and total viable soil biomass concentrations in the infiltration zone of soil samples collected from respective recharge basins. Findings of this study suggest that BOC limits soil biomass growth and was able to support a steady-state concentration of viable soil biomass that is characteristic to BOC concentrations introduced with the recharged effluents. All investigated sites indicate that BOC is primarily removed within 30 cm soil depth leading to a significant increase in soil biomass levels (measured as substrate induced respiration (SIR), total viable biomass, and dehydrogenase activity (DHA)). Controlled biological column studies revealed that the primary components of BOC in domestic effluents are organic colloids. Findings of this study support that hydrophobic acids, commonly believed to be recalcitrant, may also be attenuated by biological processes during soil infiltration.     

Biodegradable geotextiles – An overview of existing and potential materials

Geotextiles are a group of mostly thermoplastic polymers, which are processed to flexible material sheets, and are installed on various landscapes for reinforcing or protective purposes. Most applied materials in the field are non-degradable polymers, such as polyolefins or polyesters, which can implicate environmental problems concerning soil pollution and accumulation of micro plastics. Because of these drawbacks, for some applications time-consuming re-collection of the material becomes necessary. Hence, the development of more environmentally friendly and biodegradable geotextiles is of interest for several application purposes. In this review biodegradable alternatives to the conventional polymeric geotextile fibers are discussed. In general, there are two material classes available, which are natural fibers and biodegradable polymers. While there is already quite a number of natural-fiber-based geotextiles available on the market, the idea of applying industrial biopolymers for this purpose is relatively unexplored. Geotextile fabrics, made of plant fibers, represent a promising approach and were already successfully installed in several applications. However, the use of natural fibers also entails some limitations regarding water uptake and stability. Therefore, the potential use of a different material class, which comprises degradable, thermoplastic biopolymers, is discussed in this overview as well. There is only little information available on the use of these biopolymers in connection with geotextiles, thus their suitability regarding biodegradation, price and mechanical properties were evaluated.     

Mechanisms of Leakage through Synthetic Landfill Liner Materials

The introduction of synthetic lining materials for leachate containment and the prevention of groundwater contamination was an important development in landfill technology. These materials have a low hydraulic conductivity which results in minimal leachate release by bulk fluid flow (advection) provided that the barrier (and its construction) is free from defects. However, the effectiveness of these materials as barriers cannot be confirmed unless contaminant release by diffusion is also taken into consideration.
This paper reviews the mechanisms by which transport through barriers occur. It highlights the role of diffusion as a pathway for organic compounds to migrate through synthetic liners and indicates its importance in terms of environmental impact and landfill design.     

A stoichiometric model of bacterial growth

Numerous investigators have reported that the standard Monod model of bacterial growth does not adequately describe the transient response of activated sludge systems. By incorporating intracellular storage and extracellular release of shunted soluble carbon compounds in a model of bacterial growth and substrate utilization, a more accurate picture of the activated sludge process is obtained. The basic premise of the model developed in this paper is that a heterotrophic culture of bacteria will react with a carbonaceous substrate in the presence of oxygen and nutrients to produce more bacteria, carbon dioxide, water, various shunt products and storage products. The biomass is structured into three components: active biomass, stored biomass, and inert biomass. Three soluble components are considered: primary substrate, a secondary, shunted, biodegradable substrate and a shunted non-biodegradable substrate. Stoichiometric coefficients and rate forms have been proposed for the formation of each of these components and for the rate of oxygen utilization. The model is shown to be effective in simulating the step response to a recycle reactor, a batch test with a high initial substrate concentration and the step response of a chemostat.     

混凝土氯离子扩散系数测试方法的对比试验研究

采用交流电桥法和NEL法及自然扩散法对5种配合比的水工普通混凝土进行氯离子扩散性对比试验。通过测得和计算的氯离子扩散系数,分析3种试验方法测得的氯离子扩散系数与水灰比、孔隙率和强度之间的相关性。结论表明,混凝土的氯离子扩散系数与水灰比、强度及孔隙率之间均存在较好的相关性;自然扩散法测试的扩散系数都要明显大于交流电桥法测试的结果,NEL法和交流电桥法的结论近似。     

Radiation exposure in German dwellings,some results and a proposed formula for dose limitation

The results of our investigations in the Federal Republic of Germany on the indoor and outdoor exposure to natural radiation from gamma rays and radon and thoron daughters are presented. Indoor the median Rn-222 concentration was approximately four times higher than outdoors. A correlation analysis of the data obtained showed that indoors the equilibrium factor F is almost independent of ventilation, Rn-222 concentration and other parameters. The mean equilibrium factor was measured to be F = 0.3 in dwellings and approximately F = 0.4 outdoors. The results of our investigations on diffusion coefficients and exhalation rates showed, that the activity concentration in dwellings and in cellars can generally be explained by the radon exhalation from the building materials. Only in areas of high radon concentrations, the exhalation from the soil was a decisive factor. The mean effective dose equivalent by residence in dwellings amounted to 0.2 – 0.8 mSv/a for Rn-222 daughters and approximately 0.1 mSv/a for Rn-220 daughters. A relationship has been derived which permits the calculation of the expected average radiation exposure in dwellings by gamma radiation and by radon inhalation as function of the radionuclide concentration in building materials.     

击实粘性土分子扩散系数的测定

本文叙述了反映污染物在多孔材料中运移行为的对流扩散模型。根据以往的室内和野外试验结果，总结了各种岩土材料扩散系数的测定方法和具体数量范围。着重说明了一种新的分子扩散系数的测定方法及其试验装置和参数拟合过程，并报道了不同密实度的粘性土的试验结果。     

Synthesis of Nanozeolites/Carbon Composites for the Adsorptionof Bivalent Copper

Linde type A nanozeolite particles were successfully synthetized and supported over carbon-based materials in order to produce a hierarchical structured composite using a method based on the surface chemistry modification of carbon supports. Carbonaceous supports, exhibiting wide voids and openings, have been prepared using residues from agricultural activities such as cherry stones and hazelnut shells. Carbons using thermal treatment were produced and they were conditioned using polydiallyldimethylammonium chloride in order to promote the zeolites attachment onto the carbon surface. Supports were successfully covered with a consistent layer of zeolites and results showed that the chemical surface modification had a positive effect on the deposition of zeolites on carbons. In addition, copper adsorption experiments using these materials showed that the distribution of zeolite on a support improved their uptake efficiency from 73.80 to 288.22 mg·g^–1 for synthetic nanozeolite A. In addition, kinetic results showed that materials follow the pseudo-second order equation with high degree of correlation (R² > 0.97) suggesting that chemisorption is the rate-limiting step and it is more dependent on solid capacity than ion concentration in solution. Finally, equilibrium adsorption results showed a good adjustment of Langmuir model (R² = 0.96).     

Soft Tolerance: An Approach for Additive Construction on Site

Does high precision have to result in highly defined slick forms? Marta Malé-Alemany and Jordi Portell of the FABbots research studio describe their unique approach that relies on the customisation of existing mechanical devices and the use of locally available materials. Though exacting in their execution of machine code, they maintain a delight in the natural characteristics of materials that are shaped with a ‘soft tolerance’.     

A unified theory for extracellular polymeric substances,soluble microbial products,and active and inert biomass

We present a critical review of the relationships among three microbial products: extracellular polymeric substances (EPS), soluble microbial products (SMP), and inert biomass. Up to now, two different "schools" of researchers have treated these products separately. The "EPS school" has considered active biomass and EPS, while the "SMP school" has considered active biomass, SMP, and inert biomass. Here, we provide a critical review of each of the microbial products. Then, we develop a unified theory that couples them and reconciles apparent contradictions. In our unified theory, cells use electrons from the electron-donor substrate to build active biomass, and they also produce bound EPS and utilization-associated products (UAP) at the same time and in proportion to substrate utilization. Bound EPS are hydrolyzed to biomass-associated products (BAP), while active biomass undergoes endogenous decay to form residual dead cells. Finally, UAP and BAP, being biodegradable, are utilized by active biomass as recycled electron-donors substrates. Our unified theory shows that the apparently distinct products from the SMP and EPS schools overlap each other. Soluble EPS is actually SMP, or the sum of UAP and BAP. Furthermore, active biomass, as defined by the SMP school, includes bound EPS, while inert biomass includes bound EPS and the residual dead cells.     

Etude de l'inhibition de la nitrification par les composes organiques

Organic compounds likely to inhibit nitrification are numerous. The literature is rich in quantitative results but interpretation of these results is rarely attempted. Our study presents the inhibition constant determination of some phenolic and naphtholic products and proposes a theoretical approach of inhibition with emphasis on the structure.On a nitrifying mixed biomass, we have studied, in batch experiments, the effects of following organic pollutants on the nitrification: phenol; 2,4,5 trichlorophenol; 1-naphthol; 2 chloro-1-naphthol; 4 chloro-1-naphthol; 2,4 dichloro-1-naphthol. Our trials were conducted with mixed biomass (not only nitrifying bacteria) and, for the phenol, we observed inhibition that disappears when phenol is degraded. The phenol is highly toxic for nitrifying bacteria (Figs 1 and 2).For non biodegradable naphtholic components the model: allows the determination of K_I (inhibition constant) (Fig. 3).In dynamic experiments on biological filters, the study of the support role in nitrifying fixed bacteria inhibition has been carried out by comparing two different organics in particular: methanol (very little adsorbable aliphatic compound) and phenol (aromatic compound very well adsorbed on activated carbon). The two supports compared were expanded clay and activated carbon. The results obtained show that an adsorbing support can retain adsorbable compounds, removing toxicity observed for non supported or fixed or non adsorbing material ones (Fig. 4).For the naphthol family, we have calculated electronic structures using the M.N.D.O. method. We obtained also energies of low unoccupied molecular orbitals (L.U.M.O.) and high occupied-molecular orbitals (H.O.M.O.) Relations between the energy of L.U.M.O., the energy difference between the two frontier orbitals, pK_a and toxicity have been established. We show a correlation of K_i with pK and E_BV and ΔE (Fig. 5, Table 4).     

Measurement of diffusion coefficients of VOCs for building materials: review and development of a calculation procedure

The measurement and prediction of building material emission rates have been the subject of intensive research over the past decade, resulting in the development of advanced sensory and chemical analysis measurement techniques as well as the development of analytical and numerical models. One of the important input parameters for these models is the diffusion coefficient. Several experimental techniques have been applied to estimate the diffusion coefficient. An extensive literature review of the techniques used to measure this coefficient was carried out, for building materials exposed to volatile organic compounds (VOC). This paper reviews these techniques; it also analyses the results and discusses the possible causes of difference in the reported data. It was noted that the discrepancy between the different results was mainly because of the assumptions made in and the techniques used to analyze the data. For a given technique, the results show that there can be a difference of up to 700% in the reported data. Moreover, the paper proposes what is referred to as the mass exchanger method, to calculate diffusion coefficients considering both diffusion and convection. The results obtained by this mass exchanger method were compared with those obtained by the existing method considering only diffusion. It was demonstrated that, for porous materials, the convection resistance could not be ignored when compared with the diffusion resistance.     

基于多离子运移模型的混凝土电迁移试验数值分析研究

电迁移试验目前已经被广泛用来测试氯离子在混凝土中的扩散系数.离子在混凝土中的运移过程是个涉及离子与电场以及离子之间相互藕合作用的复杂过程,目前其具体运移过程仍不清楚.基于扩展Nernst-Plank方程和电中性条件建立多离子运移模型,通过计算预测电流和实测电流的最小误差确定离子扩散系数.该模型的主要优点是仅通过测试电流即可计算每个离子的扩散系数,且电流指标稳定,简单易测.数值分析详细给出了试样中电势分布、每个离子浓度、流量分布和其对电流的贡献情况,有助于深入理解电迁移试验中离子运移机理.     

煤层瓦斯运移机制的关键参数表征

 煤层的瓦斯扩散系数、浓度流动系数、初始运移强度系数和衰减系数,是煤体孔隙结构和煤质特性的力学表征。为研究煤层瓦斯运移机制,量化煤层瓦斯运移能力,依据Fick扩散理论和质量守恒方程,建立了描述煤体瓦斯浓度与扩散速率的计算模型,采用变量分离法进行数学求解,并通过数据迭代方法获取煤体内瓦斯的扩散系数和表面浓度流动系数;通过室内4种煤样瓦斯运移实验数据比较发现,煤体瓦斯质量增量与运移时间成负指数关系,且随煤阶升高而增大;瓦斯运移速度和衰减系数取决于煤的吸附能力和煤质组分,且煤种之间差异明显;渗透率与扩散系数成线性关系,与流动系数成二次函数关系,且随煤阶升高整体呈增加趋势。