Performance relations in Capacitive Deionization systems

Capacitive Deionization (CDI) is a relatively new deionization technology based on the temporary storage of ions on an electrically charged surface. By directing a flow between two oppositely charged surfaces, negatively charged ions will adsorb onto the positively charged surface, and positively charged ions will adsorb onto the negatively charged surface. To optimize CDI design for various applications, performance relations in CDI systems have to be understood. CDI performance is determined by two factors, adsorption capacity and adsorption rate. The adsorption capacity is important for performance because only a limited amount of ions can be adsorbed onto an electrically charged surface; after the total adsorption capacity is reached the surface has to be discharged. The adsorption rate is important for performance because a higher adsorption rate results in faster removal of ions from a certain stream. The objective of this thesis is to relate the performance of a CDI unit to the specifications of the influent stream and the design aspects of the unit, such as the used electrode materials in the CDI unit. To obtain these relations, the focus in this thesis is on using electrochemical characterization techniques to obtain CDI performance in terms of charge transport, and furthermore linking this charge performance to desalination performance. By using this approach, we found that the total adsorption capacity of a CDI unit is determined by the double-layer area present in the used electrodes, where a higher double-layer area gives a higher adsorption capacity. The adsorption capacity of the double-layer area is in turn dependent on the applied potential and the chemical and physical properties of the treated water. This analysis can be used to screen for activated carbons with a high amount of double-layer area. We found that materials with a high amount of pores with a size around 1.6 nm have a high double-layer area. The adsorption rate of a CDI unit is mainly determined by the absolute conductivity of the influent stream. This relation can be used to optimize spacer and electrode thickness for various influent streams. The charge efficiency, i.e. the amount of ions adsorbed per amount of charge adsorbed, is limited by counter ion expulsion. It could be improved by placing ion-exchange membranes in front of the electrodes. By integrating all obtained relations in a mathematical model, deionization performance could be predicted for CDI systems with and without ion-exchange membranes. This model can be used to predict deionization performance for any operational condition, as well as to identify and resolve bottlenecks in the operation of the CDI system. <br/

Modeling of evaporation processes in glass melting furnaces

The majority of glass furnaces worldwide, apply fossil fuel combustion to transfer heat directly by radiation from the combustion processes to the melting batch and glass melt. During these high temperature melting processes, some glass components, such as: sodium, potassium, boron and lead species will evaporate from the glass melt. There are three main motives to study evaporation processes in glass furnaces. In the first place evaporation of volatile components from the glass melt surface is one of the main causes of particulate and heavy metal emissions of industrial glass furnaces. Secondly, incongruent evaporation of glass melt components might cause depletion of volatile glass compounds at the surface layer of the melt. This process may be a source for glass failures and inhomogeneities in the glass product. Thirdly, volatilization of glass melt components may lead to the formation of aggressive vapors, such as alkali or lead vapors, reacting with the superstructure silica based refractory materials or refractories in the flue gas system. The evaporation rates depend on the process conditions in the glass furnace, like: • Glass melt composition (at the surface); • Temperature of the glass melt surface; • Composition of the atmosphere. Especially the water vapor (air-fuel versus oxy-fuel) and the carbon monoxide contents just above the melt are important; • Exposure time of a glass melt volume to the combustion atmosphere and • Local gas velocities and turbulence intensity just above the glass melt surface. For different glass types, the interaction between furnace atmosphere and the glass melt surface as well as the different evaporation reactions were summarized and discussed qualitatively, by many investigators. However, a universal and accurate mathematical evaporation model to predict evaporation rates of volatile glass components in industrial glass melt furnaces as well as laboratory glass melt furnaces quantitatively, was hardly available so far. Objective The main goal of this study is the development of a general applicable evaporation model, for different types of glass furnaces and different glass compositions. This model should be based on validated mass transfer relations and simulation of the thermodynamic properties of multi-component silicate melts. With this evaporation model the evaporation rates of volatile species from different types of glass melts can be predicted. The model is meant to investigate quantitatively the impact of different process parameters on the evaporation rates of different volatile glass species and depletion of these glass components in the surface layer of the melt. The investigations in this study primarily focus on evaporation from multicomponent silicate glass melts used for the industrial production of glass articles. Approach In this study an evaporation model has been developed and validated by laboratory evaporation tests. For the evaporation model developed here, 5 different steps were required: I. Identification of the main volatile species and dominant evaporation reactions at prevalent conditions for the investigated glass melts. II. Modeling of the mass transport of volatile glass components in the glass melt. The second diffusion law of Fick in combination with known interdiffusion coefficients (from experiments, models or literature) of volatile glass compounds, to describe the diffusion mass transport in a static melt. Additional to this, Computational Fluid Dynamics (CFD) are applied to describe both, the convective and diffusive transport of volatile species from the bulk to the surface of the melt. III. Modeling of mass transport in the gas phase, describing the transport of volatile species from the glass melt surface into the gaseous atmosphere for laminar and turbulent gas flows. IV. Thermodynamic Associated Species Model (ASM) to calculate the chemical activities of volatile glass components in the melt and at the surface of the melt. V. Calculation of the evaporation rates. From the evaporation reaction, its chemical equilibrium constant and the chemical activities of the volatile glass components at the surface of the melt, the saturation pressure of the gaseous reaction products can be determined. The local evaporation rates of individual species, are calculated from the local mass transfer relations or local Nernst boundary layer thickness in the gas phase, the local saturation vapor pressures of the volatile species and the vapor pressures of these species in the bulk gas flow. The local Nernst boundary layer thickness of the Modeling of evaporation processes in glass melting furnaces gas phase above the melt can be determined from the velocity profiles in the gas phase derived from CFD modeling, even for turbulent flows in combustion chambers. Laboratory-scale transpiration evaporation experiments have been used to: A) validate the evaporation modeling results and B) to study evaporation kinetics for sodium-silicate melts, multi-component alkali-lime-silicate melts and alkali-free borosilicate melts. In the transpiration set-up the furnace atmosphere composition, temperature level and gas velocity are controlled. Evaporation rates were measured for sodium, potassium, boron, chloride and sulfur species released from different well defined glass types, with known compositions. As will be shown later on in this summary, a procedure has been developed to derive chemical activities from the evaporation rates, measured during transpiration experiments. The validation of the evaporation model exists of a comparison between the experimentally and from thermodynamic modeling (ASM) derived chemical activities of volatile glass components. Mass transport relations for the gas phase Mass transfer relations and procedures were derived to describe the mass transport of volatile glass components or their volatile reaction products from liquids or melts into the gaseous atmosphere. These mass transfer relations and procedures are developed for the applied laboratory transpiration experiments as well as for industrial glass furnaces. CFD modeling appears to be a useful tool to predict the mass transport of volatile species into a carrier gas for a complex geometrical configuration of a transpiration test set-up. Such CFD models are applied to describe and to understand the fluid dynamics in the gas phase and distribution of volatile species in this phase. Water is used as model liquid to investigate these mass transfer processes in transpiration evaporation tests. Results of the CFD-modeling for water evaporation tests at room temperature have been validated by transpiration experiments. Excellent agreement was found between model results and experiments, as the differences between the experimental measured evaporation rates and the CFD modeling results are less than 2 %. The results of CFD modeling and the results of simple water transpiration evaporation experiments at room temperature are used to obtain relatively simple mass transport relations for a fixed geometry of the transpiration test set-up. It has been shown in this study that these Sherwood relation are applicable for other evaporating liquids and temperatures as well when using the same equipment

Control by atomic layer deposition over the chemical composition of nickel cobalt oxide for the oxygen evolution reaction

Anion exchange membrane water electrolysis (AEMWE) is a promising technology for renewable electricity-driven water splitting toward hydrogen production. However, application of AEMWE at industrial scale requires the development of oxygen evolution reaction (OER) electrocatalysts showing long-term stability under mild alkaline conditions. Among these, nickel cobalt oxide thin films are considered promising candidates. The ideal chemical composition of these oxides remains debatable, with recent literature indicating that rock-salt NiCoO2 may exhibit similar OER activity as the traditional spinel NiCo2O4. In this work, we present the development of a plasma-enhanced atomic layer deposition (ALD) process of nickel cobalt oxide thin films (∼20 nm) with focus on the role of their chemical composition and crystal structure on the OER activity. The film composition is tuned using a supercycle approach built upon CoOx cycles with CoCp2 as a precursor and O2 plasma as a co-reactant and NiOx cycles with Ni(MeCp)2 as a precursor and O2 plasma as a co-reactant. The films exhibit a change in the crystallographic phase from the rock-salt to spinel structure for increasing cobalt at. %. This change is accompanied by an increase in the Ni3+-to-Ni2+ ratio. Interestingly, an increase in electrical conductivity is observed for mixed oxides, with an optimum of (2.4 ± 0.2) × 102 S/cm at 64 at. % Co, outperforming both NiO and Co3O4 by several orders of magnitude. An optimal electrocatalytic performance is observed for 80 at. % Co films. Cyclic voltammetry measurements simultaneously show a strong dependence of the OER-catalytic performance on the electrical conductivity. The present study highlights the merit of ALD in controlling the nickel cobalt oxide chemical composition and crystal structure to gain insight into its electrocatalytic performance. Moreover, these results suggest that it is important to disentangle conductivity effects from the electrocatalytic activity in future work

Using an emergent system concept in designing interactive games for autistic children

This paper features the design process, the outcome, and preliminary tests of an interactive toy that expresses emergent behavior and can be used for behavioral training of autistic children, as well as for an engaging toy for every child. We exploit the interest of the autistic children in regular patterns and order to stimulate their motivational, explorative and social skills. As a result we have developed a toy that consists of undefined number of cubes that express emergent behavior by communicating with each other and changing their colors as a result of how they have been positioned by the players. The user tests have shown increased time of engagement of the children with the toy in comparison with their usual play routines, pronounced explorative behavior and encouraging results with improvement of turn taking interaction

Comparative genome and methylome analysis reveals restriction/modification system diversity in the gut commensal Bifidobacterium breve

Bifidobacterium breve represents one of the most abundant bifidobacterial species in the gastrointestinal tract of breast-fed infants, where their presence is believed to exert beneficial effects. In the present study whole genome sequencing, employing the PacBio Single Molecule, Real-Time (SMRT) sequencing platform, combined with comparative genome analysis allowed the most extensive genetic investigation of this taxon. Our findings demonstrate that genes encoding Restriction/Modification (R/M) systems constitute a substantial part of the B. breve variable gene content (or variome). Using the methylome data generated by SMRT sequencing, combined with targeted Illumina bisulfite sequencing (BS-seq) and comparative genome analysis, we were able to detect methylation recognition motifs and assign these to identified B. breve R/M systems, where in several cases such assignments were confirmed by restriction analysis. Furthermore, we show that R/M systems typically impose a very significant barrier to genetic accessibility of B. breve strains, and that cloning of a methyltransferase-encoding gene may overcome such a barrier, thus allowing future functional investigations of members of this species.</p

Cardiopulmonary resuscitation practices in the Netherlands: results from a nationwide survey

Background: Survival rates after in-hospital cardiac arrest are low and vary across hospitals. The ERC guidelines state that more research is needed to explore factors that could influence survival. Research into the role of cardiopulmonary resuscitation (CPR) practices is scarce. The goal of this survey is to gain information about CPR practices among hospitals in the Netherlands. Methods: A survey was distributed to all Dutch hospital organizations (n = 77). Items investigated were general hospital characteristics, pre-, peri- and post-resuscitation care. Characteristics were stratified by hospital teaching status. Results: Out of 77 hospital organizations, 71 (92%) responded to the survey, representing 99 locations. Hospitals were divided into three categories: university hospitals (8%), teaching hospitals (64%) and non-teaching hospitals (28%). Of all locations, 96% used the most recent guidelines for Advanced Life Support and 91% reported the availability of a Rapid Response System. Training frequencies varied from twice a year in 41% and once a year in 53% of hospital locations. The role of CPR team leader and airway manager is most often fulfilled by (resident) anaesthetists in university hospitals (63%), by emergency department professionals in teaching hospitals (43%) and by intensive care professionals in non-teaching hospitals (72%). The role of airway manager is most often attributed to (resident) anaesthetists in university hospitals (100%), and to intensive care professionals in teaching (82%) and non-teaching hospitals (79%). Conclusion: The majority of Dutch hospitals follow the ERC guidelines but there are differences