Introduction
Recently, water shortage problem becomes more and more serious in the world [1]. The desire to make a drinking water by treating a ground water, a surface water, a sea water and so on has been increasing. An electrodialysis (ED) is one of the useful methods and has applied to make the drinking water as well as RO and NF membranes [2~5].
ED is an electrical system utilizing ion exchange membranes. Ion exchange membranes have permselectivity similar to RO and NF membranes [6]. It is very important to understand the mechanism of permselectivity of ion exchange membranes to design ED system. The transport number ratio between target ion and standard ion has been treated to discuss the permselectivity of ion exchange membrane in ED system [7]. Recently, it was found that the ratio of transport number of several anions to chloride ion changed with the progress of electrodialysis. In this paper, a mechanism of permselectivity of ions in the electrodialysis system is theoretically discussed to make clear the reason why the transport number ratio changes with the progress of deionization in electodialysis process. In addition, the simple way to simulate ED system is proposed.
2. Theoretical
2.1 Model of electrodialysis system
The ratio of transport number of anion a and chloride ion, PaCl is defined by eq.(1) [7].
Here, ta and tCl denotes the transport number of anion a and Cl ion, respectively. [a]B and [Cl]B are the concentration (eq/m3) of anion a and Cl in the diluted compartment, respectively. [Ja] (eq/m2s) denotes the flux of anion a and[Js] the sum of all ion fluxes through the anion exchange membrane. Thus, PaCl defined by eq.(1) shows the transport number ratio of anion a and Cl at ...
... middle of paper ...
... the transport number ratio depends on only the total electrolyte concentration in the diluted compartment, CB. PaCl is determined by the membrane resistances of ions transport in the system where CB is sufficiently high. On the other hand, in the system where CB is sufficiently low, PaCl is determined by the equivalent conductance of electrolytes in the diluted compartment. Thus, PaCl changes with the progress of electrodialysis, since the electrolyte concentration in the diluted compartment decreases with time. The transport number ratio was analyzed with this model and it was shown that the model explained the experimental results very well.
It was also possible to simulate ED system after the electric resistances of the equivalent circuit were obtained from the analysis of the time course of PaCl. The simulation results agreed with ED data very well.
The pump exchanges three sodium molecules for two potassium molecules. In doing so an electrical gradient is formed across the basolateral membrane of the cell due to the imbalance of charge generated. The interior of the cell is negative by about 80mV in relation to the outside...
Cyclic voltammetry makes possible the elucidation of the kinetics of electrochemical reactions taking place at the electrode surface [31, 32]. In a typical voltammogram, there can be several peaks. From the sweep-rate dependence of the possible to investigate the role of adsorption, diffusion and coupled homogeneous chemical reaction mechanism. [33]
resting membrane voltage than perhaps other ions -> Ek for other ions using Nernst at values
Active transport is the mediated transport of biochemical, and other atomic molecular substances across membrane. This process requires the expenditure of cellular energy to move molecules uphill against a gradient. It is also involves the use of a protein carrier to transfer a specifics substance across the membrane, but against its concentration
In life, it is critical to understand what substances can permeate the cell membrane. This is important because the substances that are able to permeate the cell membrane can be necessary for the cell to function. Likewise, it is important to have a semi-permeable membrane in the cell due to the fact that it can help guard against harmful items that want to enter the cell. In addition, it is critical to understand how water moves through the cell through osmosis because if solute concentration is unregulated, net osmosis can occur outside or inside the cell, causing issues such as plasmolysis and cytolysis. The plasma membrane of a cell can be modeled various ways, but dialysis tubing is especially helpful to model what substances will diffuse or be transported out of a cell membrane. The experiment seeks to expose what substances would be permeable to the cell membrane through the use of dialysis tubing, starch, glucose, salt, and various solute indicators. However, before analyzing which of the solutes (starch, glucose, and salt) is likely to pass through the membrane, it is critical to understand how the dialysis tubing compares to the cell membrane.
The transport proteins tend to be specific for one molecule (a bit like enzymes), so substances can only cross a membrane if it contains the appropriate protein. As the name suggests, this is a passive diffusion process, so no energy is involved and substances can only move down their concentration gradient. There are two kinds of transport protein:Channel Proteins form a water-filled pore or channel in the membrane. This allows charged substances (usually ions) to diffuse across membranes. Most channels can be gated (opened or closed), allowing the cell to control the entry and exit of ions.Carrier Proteins have a binding site for a specific solute and constantly flip between two states so that the site is alternately open to opposite sides of the membrane. The substance will bind on the side where it at a high concentration and be released where it is at a low
Active transport can be put into two categories. These categories include primary active transport and secondary active transport. Secondary active transport can also be know as cotransport. Primary active transport uses chemical energy when moving molecules across a membrane gradient. An important factor in primary active transport is the sodium-potassium pump. Secondary active transport does know require a
E_cell^o was determined to be 0 V since the same metal was used as the electrodes. In doing so, the differences in the standard reduction potentials was 0 V. The R value, the ideal gas constant is given in 8.314 J/(mol K), T is the temperature at standard conditions (298.15 K), n is the number of electrons transferred (2 in this case), and F is the Faraday Constant of 96485.3399 J/(V mol). The reaction quotient, Q, was determined to equal the concentration of the concentrated Copper ion divided by the diluted Copper ion concentration (Q=([Cu_diluted^(2+)])/([Cu_concentrated^(2+)])= .05 M). The average corrected Ecell was found to be .042 V, givng a 10.52% error when compared to the theoretical
The first terms of equations (4) and (5) log (Knel) and ΔGnel respectively arises from the non-electrostatic interactions which is independent of salt concentration whereas the second term – ZΨ × log [NaCl] reflects ΔGel which is the electrostatic component of the Gibbs energy originating from the release of the counterions which depends on the salt concentration. From the plot of log Kb vs. log [NaCl] ZΨ was obtained from the slope of this curve and the intercept gives log Knel value.
For this laboratory experiment, the objectives are to describe the seats of electromotive force or EMF, and to know the difference between the EMF and terminal voltage. Also, one of the objectives of this experiment is to know the significance of internal resistance and how this internal resistance differentiate a real battery from an ideal battery. These objectives can be accomplished by knowing how to measure the EMF of a battery and by calculating the internal resistance of the battery.
The electrical conductivity (EC) for all water samples varied from 25 - 1,108 μs/cm reflecting the different amounts of the total dissolved ions in
Electrolysis is a chemical reaction caused by electricity in solutions. Electrolysis can separate molecules (like separating water into hydrogen and oxygen gas, which is called electrolysis of water), electroplate a metal, can be used for welding, and can even be used for hair removal. Electrolysis was discovered by Alessandro Volta. The materials to cause electrolysis are a source of direct current (like batteries), electrolyte, and two electrodes.
It also decreases the amount of sludge, which needs to be disposed. Electrocoagulation is a technology that removes components from wastewater by applying a strong electric field that produces a series of oxidation and reduction reactions. By decomposing the electrodes, the metallic ions produced are subject to fast hydrolysis and the products of the hydrolysis neutralize the charge of the suspended particles driving them to a fast coagulation and sedimentation. Electrodes consist of iron and aluminium have special coagulation properties and are very efficient in decolouring industrial wastewater. In recent years, the EC has been successfully tested to decolourization of dye-containing solutions. Applied electrodes in EC process are usually iron or aluminium. The dye in coloured wastewater is coagulated by iron and aluminium hydrates or hydroxides produced from the sacrificial anode. EC technology, compared with other techniques, enjoys some advantages like plain equipment, easy functionality, short resistance time, no need of chemicals, low sludge production, sludge stability, suitable sedimentation of sludge, dewatering and environmental compatibility. EC process is being used for the removal of ions, organic matters, colloidal and suspended particles, dyes, oil and heavy metals from aqueous
This filtration system serves the same purpose, and had the ability to remove chemical components like lead and arsenic from the raw water. This is shaping up to be a cheap and effective filtration system to help the process of purifying water. Researchers in Mumbai, India discussed how here are several approaches to the purification of water with the use of nanotechnology that are currently being investigated and have the potential to be ready for use very soon, and some that are already being implemented into the
Reverse osmosis has been applied for different type of industrial waste water. In these RO system we are used two type of membranes 1. Flat sheet 2. Spiral Membrane. This type of RO membrane is used to remove parameter like calcium, zinc, Sulphate, Chloride, Magnesium Ammonia and others.