European air quality maps 2005 including uncertainty analysis

The objective of this report is (a) the updating and refinement of European air quality maps based on annual statistics of the 2005 observational data reported by EEA Member countries in 2006, and (b) the further improvement of the interpolation methodologies. The paper presents the results achieved and an uncertainty analysis of the interpolated maps and builds upon earlier reports from Horalék et al. (2005; 2007)

Organic layers on silicon result in a unique hybrid fet

A Field-Effect Transistor (FET) is presented that combines the conventional lay-out of the silicon substrate (channel and source and drain connections) with a Si-C linked organic gate insulator contacted via an organic, conducting polymer. It is shown that this hybrid device combines the excellent electrical behavior of the silicon substrate and the ease of use and good properties of organic insulators and contacting materials.\ud Keywords: organic monolayer, FET, conducting polyme

Steering protein and salt ad- and desorption by an electrical switch applied to polymer-coated electrodes

Although solid-phase chromatography is a well-established method for protein separation, chemically intensive and often costly regeneration steps are needed to make reuse of the adsorbent possible. Here, we demonstrate the use of electrochemical principles as sustainable alternative. We make use of spontaneous adsorption of proteins to solid electrodes and reverse this process by applying an electric potential to regenerate the interface. This allows for adsorption of proteins to take place at 0 V difference between the electrodes, due to electrostatic interactions between the protein and the electrode surface. The desorption is then triggered by applying a potential difference (−1.2 V) between the electrodes.It is demonstrated that the incorporation of negatively charged polystyrene sulfonate (PSS) or positively charged polydiallyldimethylammonium chloride (PDMAC) in or on top of the respective activated carbon electrodes increases the amount of exchanged protein from 1 to 10 mg g−1, as compared to simple activated carbon electrodes. Interestingly, salt ad- and desorption occurs in opposite cycles compared to protein ad- and desorption, resulting in simultaneous concentration and desalting of the protein when 0 V is applied. On top of that, we also found that an enrichment in β-lactoglobulin could be achieved starting from whey protein isolate. These results clearly demonstrate that electrochemical technologies can be used not only for protein separation (including removal of salt), but also for protein fractionation, while not requiring solvent use

Covalently bound organic monolayers on silicon surfaces : visible light attachment, charaterization, and electrical properties

The full control over surface properties is a 'Holy Grail' in material science. A significant step forward in this area includes the modification of silicon surfaces, by the covalent attachment of organic monolayers. In this way receptors than can specifically bind with ions or molecules be attached to flat silicon surfaces.In this research, several facets have been studied that play a role in combining the world of organic chemistry (the monolayers) and the one of inorganic semiconductors (silicon). The development of a very mild method using visible light has been described. Via this method fragile sugar derivatives - which play an important role in cell recognition processes - have successfully been attached to silicon surfaces. Further the prevention of protein adsorption on modified silicon surfaces has been studied. In general, the adsorption of biomaterials adversely affects a diverse range of areas, e.g., the colonization of marine organisms on ship hulls or the fouling of filtration membranes. In addition, the electrical properties of organic monolayers have been described and finally the reaction mechanism of monolayer formation on porous silicon has been studied and discussed.With the combination of these studies a significant step forward has been made in the research on modified surfaces. We believe the work will stimulate the development of a variety of applications in the field of electrical devices and (medical) diagnostics

Modelling the required membrane selectivity for NO3⁻ recovery from effluent also containing Cl⁻, while saving water

We present a general outline for the selective recovery of NO3⁻ from a (waste) water stream also containing Cl⁻. The key element of the technology introduced and simulated here is a membrane unit demonstrating NO3⁻ over Cl⁻ permeation selectivity. The membrane is hypothesized to be hydrophobic and with that exploiting the difference in dehydration energy between NO3⁻ and Cl⁻. Apart from NO3⁻ recovery, the process also aims to reduce water consumption. Based on a generic outline of the process, the key parameters are defined, being the NO3⁻/Cl⁻ concentration ratio in the (waste) stream, the fraction of NO3⁻ and water recovered, and the selectivity of the membrane. The sensitivity of the separation process to these four parameters is evaluated. In the second part of the paper, the same principles are applied to a real-life process, i.e., NO3⁻ recovery from the effluent (waste) water of a fertilizer production plant. The aim was to calculate the membrane NO3⁻/Cl⁻ permeation selectivity required to recover 90% of NO3⁻, given a threshold value for the Cl⁻ concentration in the permeate stream and recycle 30% of the water, starting from two different NO3⁻/Cl⁻ concentration ratios in the effluent (waste) water. With 51 mM Cl⁻ in the effluent (waste) water and a Cl⁻ threshold of 9.9 mM, a membrane selectivity of 3 suffices. The required selectivity increases to 30 when the Cl⁻ in the effluent (waste) water is 200 mM and the Cl⁻ threshold is 4.2 mM. Reported NO3⁻/Cl⁻ membrane selectivities are still modest, with a maximal selectivity found in literature of 3. Strategies to develop membranes of significant higher selectivity are briefly discussed

Modelling the selective removal of sodium ions from greenhouse irrigation water using membrane technology

A model is presented for the Na+ and K+ levels in the irrigation water of greenhouses, specifically those for the cultivation of tomato. The model, essentially based on mass balances, not only describes the accumulation of Na+ but includes a membrane unit for the selective removal of Na+ as well. As determined by the membrane properties, some of the K+ is removed as well. Based on real-life process parameters, the model calculates the Na+ and K+ concentration at three reference points. These process parameters include the evapotranspiration rate, the K+ uptake by the plants, the Na+ and K+ content of the fertilizer, the Na+ leaching out from the hydroponic substrate material, and the Na+ and K+ removal efficiency of the membrane unit. Using these parameters and given a constant K+ concentration of the irrigation water entering the greenhouse of 6.6 mM (resulting in the optimal K+ concentration for tomato cultivation), the composition of the solution is completely defined at all three reference points per irrigation cycle. Prime aim of this investigation is to explore the requirements for the selective membrane that currently is developed in our lab. It is found that even for a limited Na+ over K+ selectivity of 6, after a number of cycles the Na+ level reaches steady state at a level below the upper (toxic) threshold for tomato cultivation (20 mM). Economic aspects and ways of implementation of such a system are briefly discussed

Modelling the selective removal of sodium ions from greenhouse irrigation water using membrane technology

A model is presented for the Na+ and K+ levels in the irrigation water of greenhouses, specifically those for the cultivation of tomato. The model, essentially based on mass balances, not only describes the accumulation of Na+ but includes a membrane unit for the selective removal of Na+ as well. As determined by the membrane properties, some of the K+ is removed as well. Based on real-life process parameters, the model calculates the Na+ and K+ concentration at three reference points. These process parameters include the evapotranspiration rate, the K+ uptake by the plants, the Na+ and K+ content of the fertilizer, the Na+ leaching out from the hydroponic substrate material, and the Na+ and K+ removal efficiency of the membrane unit. Using these parameters and given a constant K+ concentration of the irrigation water entering the greenhouse of 6.6 mM (resulting in the optimal K+ concentration for tomato cultivation), the composition of the solution is completely defined at all three reference points per irrigation cycle. Prime aim of this investigation is to explore the requirements for the selective membrane that currently is developed in our lab. It is found that even for a limited Na+ over K+ selectivity of 6, after a number of cycles the Na+ level reaches steady state at a level below the upper (toxic) threshold for tomato cultivation (20 mM). Economic aspects and ways of implementation of such a system are briefly discussed

Water desalination with nickel hexacyanoferrate electrodes in capacitive deionization : Experiment, model and comparison with carbon

Capacitive deionization (CDI) is a water desalination technology in which ions are removed from water by creating a potential difference between two capacitive electrodes. Porous carbon has been extensively used as an electrode material in CDI. However, recent developments in the field of intercalation materials have led to their application in CDI due to their large ion storage capacity. One such intercalation material, nickel hexacyanoferrate (NiHCF), was used in this study as the electrode material. A symmetrical cell was assembled with two identical NiHCF electrodes separated by an anion-exchange membrane. The effect of operational parameters such as current density, feed concentration and flow rate on the desalination characteristics of the cell was investigated. The highest salt adsorption capacity of ≈ 35 mg/g was measured at a current density of 2.5 A/m2 in a 20 mM NaCl feed solution. Furthermore, a Nernst-Planck transport model was successfully used to predict the change in the outlet concentration and cell voltage of the symmetric CDI cell. Finally, performance of the symmetric NiHCF CDI cell was compared with an MCDI cell with porous carbon electrodes. The NiHCF cell, on average, consumed 2.5 times less energy than the carbon-based MCDI cell to achieve similar levels of salt removal from saline water in CDI

Tailor-made functionalization of silicon nitride surfaces

This communication presents the first functionalization of a hydrogen-terminated silicon-rich silicon nitride (Si3Nx) surface with a well-defined, covalently attached organic monolayer. Properties of the resulting monolayers are monitored by measurement of the static water contact angle, X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRRAS). Further functionalization was performed by reaction of Si3Nx with a trifluoroethanol ester alkene (CH2=CH-(CH2)8CO2CH2CF3) followed by basic hydrolysis to afford the corresponding carboxylic acid-terminated monolayer with hydrophilic properties. These results show that Si3Nx can be functionalized with a tailor-made organic monolayer, has highly tunable wetting properties, and displays significant potential for further functionalization