Surface complexation modeling of Yb(III) sorption and desorption on hematite and alumina

Sorption and desorption of Yb(III) were studied on hematite and on alumina using a surface complexation model. The experimental methodology was conceived to allow an analysis of the data using a constant capacitance model. The FITEQL code was used for the calculations.The experimental results tend to show reversibility of sorption when the surface loading is small, and irreversibility when the surface loading is high. Surface complexation modeling gives a good interpretation of these two phenomena, taking into account hydroxylation of the surface complexes. In these two cases, it is possible to describe sorption and desorption curves with the same surface stoichiometries and the same surface complexation constants. The existence of these surface complexes depends on the pH of the solution, surface loading, and reaction direction.     

Analysis of surface and aerosol polarized reflectance for aerosol retrievals from polarized remote sensing in PRD urban region

A precise estimate of polarization induced by surface is crucial for polarized remote sensing dedicated to monitoring aerosol properties over urban area. The accurate knowledge of interaction between surface and aerosol polarized reflectance is essential for accurately achieving aerosol properties. In order to study surface and aerosol polarized reflectance for aerosol retrievals over urban area, a new airborne directional polarimetric camera (DPC) with high spatial resolution (4 m at 4000 m a.g.l) was developed. The surface polarized reflectance over distinct surface covers of urban area (forest, shrub, and soil) were studied using DPC measurements during a field campaign in the Pearl River Delta (PRD), China. The large variations were found in surface polarized reflectance of distinct urban covers due to surface type variability. For all surface types, the empirical BPDF model cannot describe accurately surface polarized reflectance at all possible illumination and observation geometries. From the quantitatively study of relationship between surface and aerosol polarized contribution to DPC measurements, we show that the polarized contributions of aerosol, which optical properties were defined by ground-based measurements, are much larger than the polarized contribution of surface, and found that the polarized contribution of surface covers increases with decreasing NDVI. The effect of polarization accuracy of measurements on aerosol retrieval was also investigated using DPC measurements, and found that 0.1% polarization accuracy of measurements can be neglected when AOD is retrieved using polarized measurements. Based on the information of effects of polarized reflectance differences between distinct surface covers and polarization accuracy of polarized measurements on retrieved aerosols over urban area, we found that the accuracy of aerosol retrieval over forest covers is higher than other surface types using polarized remote sensing.     

Numerical studies of the heterogeneous combustion of char using detailed chemistry

The oxidation of graphite is used as a model system for the combustion of char. In order to understand this oxidation process a stagnation-point flow of an oxygen stream on a graphite surface is investigated numerically. The chemical reactions in the gas phase as well as on the surface are modelled by a series of elementary steps. The surface reactions take into consideration the different surface complexes formed, the influence of the geometry of the graphite surface and the interaction of gas-phase molecules with surface complexes. The rate coefficients used are estimated by applying methods of the microkinetic analysis of heterogeneous catalytic reactions. The mechanism is used to simulate the combustion rate of a graphite surface and the ratio of CO to CO2 formed on the surface. The simulation results are compared with experimental data and a good agreement is achieved. Furthermore, the fraction of char-bound nitrogen converted to N2 and N2O is calculated.     

Measurement of the Oxygen Mass Transfer Through the Air-Water Interface (5 pp)

Goal, Scope and Background Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. Methods A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer.Results Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be.Conclusion A simple technique for measuring oxygen diffusion parameters through the air-water solution surface has been developed. Derived equations enable the calculation of diffusion parameters of the surface layer at current conditions. These values of the parameters permit one to compare the resistances of the gas–liquid interface to oxygen mass transfer in the case of adsorption of different substances on the surface layer. Recommendation and Outlook This simple technique may be used for a determination of oxygen permeability of different water-solution surface layers. It enables one to measure the resistance to the oxygen permeability of all inflowing wastewater surface layers in the wastewater treatment plant, and to initiate a preliminary cleaning of this wastewater if required. Similarly, we can measure oxygen permeability of natural waterbodies. Especially in the case of pollution, it is important to know to what extent the oxygen permeability of the water surface layer has been decreased. Based on the tehnique presented in this research, fieldwork equipment will be developed.     

Adsorption/desorption properties of copper ions on the surface of iron-coated sand using BET and EDAX analyses

This study was conducted to develop a heating process for coating hydrated iron oxide on the sand surface to utilise the adsorbent properties of the coating and the filtration properties of the sand. BET and scanning electron microscope (SEM) analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used for characterising metal adsorption sites on the iron-coated sand surface. The results indicated that the iron-coated sand had more micropores and higher specific surface area because of the attachment of iron oxide. Copper ions could penetrate into the micropores and mesopores of iron oxide on sand surface, and the regeneration of the iron-coated sand could be achieved by soaking with pH = 3.0 acid solution. Besides, the results of EDAX analysis showed that copper ions were chemisorbed on the surface of iron-coated sand. Results of the study developed an innovative technology for coating iron oxide on sand surface for the treatment of heavy metal in water.     

Analysis of the sensible heat flux from the exterior surface of buildings using time sequential thermography

In this study, the distribution of surface temperature on the surface of two buildings having different characteristics was measured using a thermal infrared camera. Measurements were made in the summer, the period in Japan during which heat flux from buildings is of major interest, and again in the winter for comparison purposes. The heat characteristics of each building were obtained throughout the day by time-sequential thermography (TST), and the surface temperature of each physical element was classified according to temperature, shape, material and position. When the temperature of a surface could not be determined by an infrared camera mounted on the top of a building or a pole, temperature measurements were made using a hand-held IR camera. In addition, the sensible heat flux from each surface was calculated using TST and the surface area of each element as calculated from blueprints of the buildings.     

A new approach for modelling potential effects in cation adsorption onto binary (hydr) oxides

The current approach for modelling ion adsorption onto binary (hydr)oxides using homogeneous surface complexation models involves the assumption of either an ideal mixture of the two surfaces (i.e. two surface sites on one surface) or a patchwise surface (i.e. two surfaces with one surface site on each surface). As the physical truth should be between these two limiting cases, a model which assumes a patchwise surface constituted of three patches is proposed. Two patches represent the distinct (hydr)oxides, and the third one a mixture of these distinct (hydr)oxides. Using the diffuse layer model, the three approaches are applied to literature data for Cd adsorption onto binary mixtures of alumina-coated silica at total constant Cd concentration and varying amounts of alumina coatings. For Cd adsorption onto these binary (hydr)oxide systems, the new approach explains the observed potential effects. The proposed model, which contains two additional adjustable parameters in terms of site concentrations or one adjustable parameter in terms of specific surface area, is more successful than the two limiting cases. The new model is then validated by predicting Ca and Zn behaviour on the same binary (hydr)oxide system.     

City ventilation of Hong Kong at no-wind conditions

We hypothesize that city ventilation due to both thermally-driven mountain slope flows and building surface flows is important in removing ambient airborne pollutants in the high-rise dense city Hong Kong at no-wind conditions. Both spatial and temporal urban surface temperature profiles are an important boundary condition for studying city ventilation by thermal buoyancy. Field measurements were carried out to investigate the diurnal thermal behavior of urban surfaces (mountain slopes, and building exterior walls and roofs) in Hong Kong by using the infrared thermography. The maximum urban surface temperature was measured in the early noon hours (14:00–15:00 h) and the minimum temperature was observed just before sunrise (5:00 h). The vertical surface temperature of the building exterior wall was found to increase with height at daytime and the opposite occurred at nighttime. The solar radiation and the physical properties of the various urban surfaces were found to be important factors affecting the surface thermal behaviors. The temperature difference between the measured maximum and minimum surface temperatures of the four selected exterior walls can be at the highest of 16.7 °C in the early afternoon hours (15:00 h). Based on the measured surface temperatures, the ventilation rate due to thermal buoyancy-induced wall surface flows of buildings and mountain slope winds were estimated through an integral analysis of the natural convection flow over a flat surface. At no-wind conditions, the total air change rate by the building wall flows (2–4 ACH) was found to be 2–4 times greater than that by the slope flows due to mountain surface (1 ACH) due to larger building exterior surface areas and temperature differences with surrounding air. The results provide useful insights into the ventilation of a high-rise dense city at no-wind conditions.     

The humidity dependence of ozone deposition onto a variety of building surfaces

Measurements of the dry deposition velocity of O₃ to material samples of calcareous stone, concrete and wood at varying humidity of the air, were performed in a deposition chamber. Equilibrium surface deposition velocities were found for various humidity values by fitting a model to the time-dependent deposition data. A deposition velocity-humidity model was derived giving three separate rate constants for the surface deposition velocities, i.e. on the dry surface, on the first mono-layer of adsorbed water and on additional surface water. The variation in the dry air equilibrium surface deposition velocities among the samples correlated with variations in effective areas, with larger effective areas giving higher measured deposition velocities. A minimum for the equilibrium surface deposition velocity was generally measured at an intermediate humidity close to the humidity found to correspond to one mono-layer of water molecules on the surfaces. At low air humidity the equilibrium surface deposition velocity of O₃ was found to decrease as more adsorbed water prevented direct contact of the O₃ molecules with the surface. This was partly compensated by an increase as more adsorbed water became available for reaction with O₃. At high air humidity the equilibrium surface deposition velocity was found to increase as the mass of water on the surface increased. The deposition velocity on bulk de-ionised water at RH=90% was an order of magnitude lower than on the sample surfaces.     

Evaluation of surface runoff and road dust as sources of nitrogen using nitrate isotopic composition

Stable nitrogen and oxygen isotope ratios of nitrate (δ¹⁵N-NO₃ and δ¹⁸O-NO₃) have recently been used to identify nitrogen sources in water environments. However, there have been no investigations designed to determine nitrate isotopes in non-point sources in urban areas for evaluating the impact of surface deposits on nitrogen in surface runoff. In this study, we collected rainwater, surface runoff and surface deposits (road dust, roof dust and soil) to evaluate the nitrogen sources in surface runoff using nitrate isotopes. There were no large differences in δ¹⁵N-NO₃ among rainwater (−0.3‰ to 1.5‰), surface runoff (−2.7‰ to 0.4‰), leachates from road dust (−5.8‰ to 6.2‰) and soil (−11.5‰ to 0.6‰). In contrast, the δ¹⁸O-NO₃ in surface runoff (28.5-47.9‰) was lower than that in rainwater (62.7-78.6‰), and higher than that in leachates from road dust (6.1-27.6‰) and soil (−1.1‰ to 6.6‰). δ¹⁸O-NO₃ is a useful indicator for evaluating the NO₃-N sources in surface runoff. Using this indicator, NO₃-N from road dust was estimated to account for more than half of the NO₃-N in surface runoff. This is consistent with a result based on a comparison of their loads per unit surface between rainwater and surface runoff, which also showed that most of the nitrogen in surface runoff was derived from surface deposits.     

诱导结晶工艺中诱晶载体的选择与改性

以含铜废水为处理对象,重点考察了诱晶载体的表面性质及表面负荷对诱导结晶过程的影响。结果表明,在工艺启动初期,白云石以及碱式碳酸铜为诱晶载体时,铜的去除率在90%以上,石英砂对铜的去除率较低,但石英砂经表面改性后对铜的去除效率亦可达90%以上。在运行稳定后,几类诱导载体对铜的去除率皆能稳定在95%,说明诱晶载体的表面性质对诱导结晶工艺的影响主要在于反应启动初期,选择与目标结晶产物结构、成分相同或相似的诱晶载体有利于诱导结晶过程的进行。此外,研究结果还表明,诱晶载体表面负荷对结晶过程影响较大,诱导结晶除铜工艺中载体表面负荷不宜高于0.054 g Cu/(m2.d)。     

诱导结晶工艺中诱品载体的选择与改性

以含铜废水为处理对象，重点考察了诱晶载体的表面性质及表面负荷对诱导结晶过程的影响。结果表明，在工艺启动初期，白云石以及碱式碳酸铜为诱晶载体时，铜的去除率在90％以上，石英砂对铜的去除率较低，但石英砂经表面改性后对铜的去除效率亦可达90％以上。在运行稳定后，几类诱导载体对铜的去除率皆能稳定在95％，说明诱晶载体的表面性质对诱导结晶工艺的影响主要在于反应启动初期，选择与目标结晶产物结构、成分相同或相似的诱晶载体有利于诱导结晶过程的进行。此外，研究结果还表明，诱晶载体表面负荷对结晶过程影响较大，诱导结晶除铜工艺中载体表面负荷不宜高于0．054gCu／（m2·d）。     

不同再生工艺对活性炭吸附性能的影响分析

吸附法油气回收技术中,吸附剂的再生是一个难点和研究重点。微波加热作为一种新的再生技术,受到人们日益的重视。实验利用比表面积及孔隙分析仪测定了经多次微波真空,加热真空和加热再生后的活性炭的表面结构变化,通过对比分析,探讨了3种工艺多次再生活性炭对活性炭表面结构的影响。结果表明,3种工艺均对活性炭结构都有所破坏,但微波真空再生对活性炭比表面积和孔容破坏最小,净吸附容量最大,从效率及能耗上都比较好。     

Investigating activated sludge flocs using microanalytical techniques: demonstration of environmental scanning electron microscopy and time-of-flight secondary ion mass spectrometry for wastewater applications.

Environmental scanning electron microscopy (ESEM) with an energy-dispersive X-ray spectrometer (EDS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were demonstrated to be useful analytical tools for investigating surface and bulk components of individual floc particles from both full- and bench-scale activated sludge systems. Detailed surface imaging of various hydrated biological floc particles by ESEM revealed substantial differences in surface features between treatment systems, while EDS identified spatial differences in the iron and the aluminum distributions. The ToF-SIMS spectra had signature fragments of protein and polysaccharide material from the floc surface, suggesting that this technique is capable of surface profiling extracellular polymeric substances. Principal-component analysis of the positive ion ToF-SIMS spectra from the mixed-liquor-suspended solid (MLSS) samples and reference aquatic organic materials found slight differences between the full- and bench-scale MLSS surface properties but substantial differences among MLSS and treated effluent from the same facility.     

Impact of atmospheric deposition of anthropogenic and natural trace metals on Northwestern Mediterranean surface waters: a box model assessment

Under stratified oligotrophic conditions (May-November), the surface mixed layer of the Northwestern Mediterranean constitutes a homogeneous water volume of 10-30 m depth. In other respects, the mean residence time of Ligurian surface waters (0-200 m) is 102 days. It is therefore possible to quantify the extent to which atmospheric deposition of trace metals affects surface waters. On the basis of literature data on anthropogenic and natural trace metals, we demonstrate that the ratios between total seawater labile atmospheric deposition during 102 days (Δc) and dissolved TM concentrations in Ligurian surface waters (c) illustrate the impact of atmospheric deposition on surface seawater (Δc/c). High ratios indicate surface TM enrichments, while low ratios indicate surface TM depletion, due to the quasi-complete sorption and removal of TMs by plankton during spring bloom. The simple box model proposed here may be used for other marine regions where hydrodynamical and physico-chemical constraints are well defined.     

Influence of dense surface meteorological data assimilation on the prediction accuracy of ozone pollution in the southeastern coastal area of the Korean Peninsula

In order to clarify the influence of surface meteorological data assimilation with various resolutions on the photochemical ozone concentration in the southeastern Korean Peninsula, several numerical experiments were conducted. The meteorological and photochemical reaction models used in this study are the fifth-generation mesoscale model (MM5) and the three-dimensional photochemical urban airshed model (UAM-V), respectively. Dense meteorological data make it easier to obtain accurate estimates and surface characteristics than coarse-resolution data. As a result, the estimated temperature obtained from high resolution surface data assimilation in the Busan and Ulsan metropolitan areas is higher than that obtained from coarse resolution surface data assimilation. These high temperatures resulted in strong winds from the sea and a significant dispersion of ozone. In analyses involving an index of agreement (IOA) and root mean square deviation (RMSD), the temperature and wind speed estimated with dense surface data assimilation agreed well with those obtained from observations.However, the influence of dense surface data assimilation tends to be stronger in the flat Ulsan metropolitan area than in the mountainous Busan metropolitan area. This is caused by the heterogeneity of the surface characteristics, including the topography. If the surface parameters induced by regional circulation, such as the topography and land use, are complex and heterogeneous, the efficiency of observational data on data assimilation has to be verified before air pollution is assessed.     

RES3T-Rossendorf expert system for surface and sorption thermodynamics

This paper presents a digitized version of a thermodynamic sorption database, implemented as a relational database with MS Access. It is mineral-specific and can therefore be used for additive models of complex solid phases such as rocks or soils. An integrated user interface helps users to access selected mineral and sorption data, to extract internally consistent data sets for sorption modeling, and to export them in formats suitable for other modeling software. Data records comprise mineral properties, specific surface area values, surface binding sites' characteristics, sorption ligand information, and surface complexation reactions. An extensive bibliography is included, providing links not only to the above listed data, but also to background information concerning surface complexation model theories, evidence for surface species, and sorption experimental techniques.     

REST-Rossendorf expert system for surface and sorption thermodynamics

This paper presents a digitized version of a thermodynamic sorption database, implemented as a relational database with MS Access. It is mineral-specific and can therefore be used for additive models of complex solid phases such as rocks or soils. An integrated user interface helps users to access selected mineral and sorption data, to extract internally consistent data sets for sorption modeling, and to export them in formats suitable for other modeling software. Data records comprise mineral properties, specific surface area values, surface binding sites' characteristics, sorption ligand information, and surface complexation reactions. An extensive bibliography is included, providing links not only to the above listed data, but also to background information concerning surface complexation model theories, evidence for surface species, and sorption experimental techniques.     

Pore structure of soot deposits from several combustion sources

Soot was harvested from five combustion sources: a dodecane flame, marine and bus diesel engines, a wood stove, and an oil furnace. The soots ranged from 20% to 90% carbon by weight and molar C/H ratios from 1 to 7, the latter suggesting a highly condensed aromatic structure. Total surface areas (by nitrogen adsorption using the Brunauer Emmett Teller, BET method) ranged from 1 to 85 m2 g(-1). Comparison of the surface area and meso-pore (pores 2-50 nm) surface area predicted by density functional theory (DFT) suggested that the soot was highly porous. Total meso-pore volume and surface area ranged from 0.004-0.08 cm3 g(-1) and from 0.33-6.9 m2 g(-1) respectively, accounting for up 33% of the BET surface area. The micro-pore volume (pores <2 nm) calculated from CO2 adsorption data (by DFT) ranged from 0.0009 to 0.013 cm3 g(-1) and micro-pore surface area was 3.1-41 m2 g(-1), accounting for 10-20% of the total intra-particle (meso-plus micro-pores) pore volume and 70-90% of the total intra-particle surface area. Higher pore volume and surface area values were computed using the Dubinin Radushkevich plot technique; ranging from 0.004-0.04 cm3 g(-1) to 11-102 m2 g(-1) for micro-pore volume and surface area, respectively. Comparison of the C/H ratio and the micro-pore structure showed a strong correlation, suggesting a relationship between the condensation of the skeletal structure and micro-porosity of the soot. These data contradict literature reports that soot particles are non-porous and are consistent with recent literature reports that soil organic matter has large micro-pore surface areas.     

活性炭改性研究进展

本文从表面结构特性、表面化学性质和电化学性质 3个方面叙述了国内外在活性炭改性方面的研究进展。表面结构特性改性主要是从增大比表面积和控制孔径分布两方面展开 ,从而增大吸附量 ;表面化学性质改性主要是通过氧化还原改变表面含氧酸性、碱性基团的相对含量以及负载金属改性 ,从而改变对极性、极性较弱或非极性物质的吸附能力 ;电化学性质改性主要是通过加微电场改变活性炭表面的带电性和由此而产生的化学性质的变化 ,从而改变吸附性能。最后 ,本文还从活性炭的吸附性质方面 ,客观地提出了今后发展方向