Back membrane technology

Constmction of new power plants in the coal region of the western United States presents serious problems in states whose laws dictate zero effluent. In these plants, cooling-tower water withdrawn from rivers cannot be returned to them. In these situations, cooling-tower effluent is purified by distillation (vapor-compression plants have predominated) and by a combination of distillation and membrane technology. The converted water then is used as boiler feedwater the plant blowdown (effluent) is evaporated from open-air lined pools, and pool sediment is periodically buried back in the coal mine with the flue ashes. 

Fuel Cell Technology Onsite Generation Systems Proton Exchange Membrane Technology Back-Up Power Systems... 

Polyamide membranes were developed in an effort to improve upon the performance of CA membranes. In particular, the higher operating pressure and relatively low salt rejection of CA membranes were holding back RO technology from becoming more commercially viable. 

Membrane technology is a well-established technology for the immobilization of enzymes [233] since Degussa [234] introduced a continuous acylase process employing an enzyme-membrane reactor for the enantiomeric production of pure L-amino acids in 1981. Polymer membranes configured into hollow-fiber modules are, by far, the most widely used membrane where the enzyme is held back by the low cutoff of the membrane. 

Nanofiltration. The nanofiltration process is, along with baclq)ulse filtration (Section 7.5.4.3), another example of the new possibilities in processing that are due to recent developments in the field of membrane technology. At conditions intermediate between those used in ultrafiltration and RO, this technology can selectively reject multivalent ions such as 804 while passing monovalent ions [147-149]. The process therefore can remove sulfate and other multivalent anions selectively from alkali chloride brines. Since the equivalent amount of alkali metal ions is held back by electrostatic forces, the net effect is the removal of M2SO4. 

Membrane technologies have a particular advantage over SX techniques as membrane systems often allow for extraction to be coupled in the same system with simultaneous back-extraction, rather than the extraction and back-extraction being conducted in sequential steps as is necessary in SX operations. Where a membrane acts as the organic phase, which separates two distinct aqueous phases, the phase from which the solute is extracted is referred to as the source phase and the aqueous phase into which the solute is back-extracted is called the receiving phase. 

The soluble ions of iron and aluminium are usually reduced to a minimum by adjusting the electrolyte pH. For the removal of solid iron hydroxide and aluminium hydroxide Bayer decided to use a new pre-coat-free brine purification technology -back-pulse filtration using GORE-TEX membrane filter cloths. 

The final principles of back-pulse filter technology are the nature and properties of the GORE-TEX membrane. The membrane is composed of expanded polytetra-fluoroethylene, or e-PTFE. The membrane traces its roots to the invention of e-PTFE by Robert W. Gore in 1969. Since that time, e-PTFE has found application in many areas including medical devices, electronics, fabrics and fuel cells to name a few. In the filtration area, e-PTFE is used in the form of a membrane to capture and remove particles from both gaseous and liquid streams. 

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