Osmosis electric pressures

Nonporous Dense Membranes. Nonporous, dense membranes consist of a dense film through which permeants are transported by diffusion under the driving force of a pressure, concentration, or electrical potential gradient. The separation of various components of a solution is related directiy to their relative transport rate within the membrane, which is determined by their diffusivity and solubiUty ia the membrane material. An important property of nonporous, dense membranes is that even permeants of similar size may be separated when their concentration ia the membrane material (ie, their solubiUty) differs significantly. Most gas separation, pervaporation, and reverse osmosis membranes use dense membranes to perform the separation. However, these membranes usually have an asymmetric stmcture to improve the flux. 

Membrane Filtration. Membrane filtration describes a number of weU-known processes including reverse osmosis, ultrafiltration, nanofiltration, microfiltration, and electro dialysis. The basic principle behind this technology is the use of a driving force (electricity or pressure) to filter... 

One can transcribe the phenomenon in the form of an equation following the same thinking as for electro-osmosis. One says A current density j results not only from an electric field but also from a pressure difference AP, and, for small X and AP,... 

Electro-osmosis - the movement of liquid relative to a stationary charged surface (e.g. a capillary or porous plug) by an applied electric field (i.e. the complement of electrophoresis). The pressure necessary to counterbalance electro-osmotic flow is termed the electro-osmotic pressure. 

EMCPMT models wifi be described that can simulate transient electro-mechano-chemo diffusion, convection, and osmosis in one-dimensional FEMs composed of one and/or multiple layers of porous material with prescribed no(Xi) and FCD, < [ (X,) in the solid. The left (L) and right (R) interfaces are water baths containing prescribed concentrations of up to three charged species (p, m, b). Mechanical force (stress) or displacement fluid pressure, and electrical potential will also be prescribed on these interfaces. The first example is... 

Water transport in electrodialysis from the diluate to the concentrate process stream can affect the process efficiency significantly. If a convective flux as a result of pressure differences between flow streams can be excluded there are still two sources for the transport of water from the diluate to the concentrate solution. The first one is the result of osmotic-pressure differences between the two solutions, and the second is due to electro-osmosis that results from the coupling of water to the ions being transported through the membrane due to the driving force of an electrical potential. 

In electrodialysis, an applied electric field rather than a concentration gradient is used to draw ions across the membrane. Because it is faster than ordinary dialysis, electrodialysis is often used in biochemical analyses for purposes of fractionation, concentration, and desalting. Reverse osmosis (RO) is a process that uses semipermeable membranes to allow water permeation however, the membranes act as a barrier to the passage of dissolved and suspended particles. Typically, RO membranes are used to extract pure water from aqueous solutions of dissolved salts, such as seawater. The particle size cutoff is typically 0.0001 yum with driving pressures of 200 to 800 psi (1.4 to 5.5 MPa).61... 

As the quality of drinking water sources gets worse, the methods of water treatment or the traditional water treatment systems need to be modernized. Pressure-driven membrane systems such as reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) and electric-driven membrane system such as... 

Heat Thermal conduction, Jq = -keVT Chemical osmosis, JCQ = -CjCrKVTllh, where K is the hydraulic coefficient, nh the osmotic pressure head (Ilf = U/pg), (j the coefficient of osmotic efficiency Peltier effect, Jq=Lqlb T), where E is the electric field Thermal filtration... 

Membranes may be hastily classified according to the driving force at the origin of the transport process (1) a pressure differential leads to micro-, ultra-, nanofiltration, and reverse osmosis (2) a difference of concentration across the membrane leads to diffusion of a species between two solutions (dialysis) and (3) an electric potential difference applied to an ion-exchange membrane (lEM) leads to migration of ions through the membrane (electrodialysis, membrane electrolysis, and... 

Since the electrical resistance of the effiuent and parasitic currents are minimal at high level of impurities, specihc interest in electrically assisted membrane processes could increase due to more strict laws and legislation around effluents. The depletion of freshwater resources and the necessity to process brackish or seawater to produce potable water could promote the use of electrically assisted membrane processes in the future. Electrodialysis will have to compete with pressure-driven membrane processes such as reverse osmosis. The growing awareness of the unique cleaning ability of electrically ionized water (EIW) [47], a byproduct of electrodialysis, may be a factor to consider in the choice between ED and RO systems. NMR relaxation measurements were used to determine the water cluster size of electrically ionized water EIW. It is known that the water cluster size of EIW is signihcantly smaller than that of tap water. The smaller water cluster size is believed to enhance the penetration and extractive properties of EIW. Recently, EIW has been produced and used in several cleaning processes [47] in industry. 

Membrane processes are widely used in oil water separation. In general, a membrane is classified into two groups pressure-driven membrane and electrical membrane, known as electrodialysis. The most applicable process for oily wastewater removal is the former type. The pressure-driven membrane applications include microfiltration (MF), ultrafil-tration (UF), nanofiltration (NF), and reverse osmosis (RO). All of them are categorized by the molecular weight or particle size cut-off of the membrane as shown in Table 5. 

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