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Pervaporation

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Title: Pervaporation  
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Subject: Membrane technology, Perstraction, Concentration polarization, Maxwell–Stefan diffusion, Membrane
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Pervaporation

Pervaporation (or pervaporative separation) is a processing method for the separation of mixtures of liquids by partial vaporization through a non-porous or porous membrane.

Contents

  • Theory 1
  • Applications 2
  • Materials 3
  • See also 4
  • External links 5
  • References 6

Theory

The term pervaporation is derived from the two steps of the process: (a) permeation through the membrane by the permeate, then (b) its evaporation into the vapor phase. This process is used by a number of industries for several different processes, including purification and analysis, due to its simplicity and in-line nature.

The membrane acts as a selective barrier between the two phases: the liquid-phase feed and the vapor-phase permeate. It allows the desired component(s) of the liquid feed to transfer through it by vaporization. Separation of components is based on a difference in transport rate of individual components through the membrane.

Typically, the upstream side of the membrane is at ambient pressure and the downstream side is under vacuum to allow the evaporation of the selective component after permeation through the membrane. Driving force for the separation is the difference in the partial pressures of the components on the two sides and not the volatility difference of the components in the feed.

The driving force for transport of different components is provided by a chemical potential difference between the liquid feed/retentate and vapor permeate at each side of the membrane. The retentate is the remainder of the feed leaving the membrane feed chamber, which is not permeated through the membrane. The chemical potential can be expressed in terms of fugacity, given by Raoult's law for a liquid and by Dalton's law for (an ideal) gas. During operation, due to removal of the vapor-phase permeate, the actual fugacity of the vapor is lower than anticipated on basis of the collected (condensed) permeate.

Separation of components (e.g. water and ethanol) is based on a difference in transport rate of individual components through the membrane. This transport mechanism can be described using the solution-diffusion model, based on the rate/ degree of dissolution of a component into the membrane and its velocity of transport (expressed in terms of diffusivity) through the membrane, which will be different for each component and membrane type leading to separation.

Applications

Pervaporation is effective for diluting solutions containing trace or minor amounts of the component to be removed. Based on this, aqueous solutions.

Pervaporation is a very mild process and hence very effective for separation of those mixtures which can not survive the harsh conditions of distillation.

  • Solvent Dehydration: dehydrating the ethanol/water and isopropanol/water azeotropes
  • Continuous ethanol removal from yeast fermentors.
  • Continuous water removal from condensation reactions such as esterifications to enhance conversion and rate of the reaction.
  • Membrane introduction mass spectrometry
  • Removing organic solvents from industrial waste waters.
  • Combination of distillation and pervaporation/vapour permeation
  • Concentration of hydrophobic flavour compounds in aqueous solutions (using hydrophobic membranes)

Recently, a number of organophilic pervaporation membranes have been introduced to the market. Organophilic pervaporation membranes can be used for the separation of organic-organic mixtures, e.g.:

  • Reduction of the aromatics content in refinery streams
  • Breaking of azeotropes
  • Purification of extraction media
  • Purification of product stream after extraction
  • Purification of organic solvents

Materials

Hydrophobic membranes are often polydimethylsiloxane based where the actual separation mechanism is based on the solution-diffusion model described above.

Hydrophilic membranes are more widely available. The commercially most successful pervaporation membrane system to date is based on polyvinyl alcohol. More recently also membranes based on polyimide have become available. To overcome the intrinsic disadvantages of polymeric membrane systems ceramic membranes have been developed over the last decade. These ceramic membranes consist of nanoporous layers on top of a macroporous support. The pores must be large enough to let water molecules pass through and retain any other solvents that have a larger molecular size such as ethanol. As a result, a molecular sieve with a pore size of about 4 Å is obtained. The most widely available member of this class of membranes is that based on zeolite A.

Alternatively to these crystalline materials, the porous structure of amorphous silica layers can be tailored towards molecular selectivity. These membranes are fabricated by sol-gel chemical processes. Research into novel hydrophilic ceramic membranes has been focused on titania or zirconia. Very recently a break-through in hydrothermal stability has been achieved through the development of an organic-inorganic hybrid material.Citation needed

See also

External links

  • www.membrane-guide.com suppliers, products, news and facts for engineers involved in the design or the operation of pervaporation systems.
  • [1] Introduction to pervaporation and vapor permeation with ceramic membranes.
  • [2] Environmental Importance & as a Green Chemistry solution.
  • Hybrid silica Applications, technology and background information.

References

  • require('Module:No globals')

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   local title = mw.title.getCurrentTitle()
   local namespace = title.namespace
   if namespace == 0 then

return ''

   elseif namespace == 2 and not title.isSubpage then

return ''

   else

return ''

   end

end

local function viafLink( id )

   if not string.match( id, '^%d+$' ) then
       return false
   end
   return '.. id .. ' ' .. id .. '' .. getCatForId( 'VIAF' )

end

local function kulturnavLink( id )

   return '.. id .. ' id' 

end

local function sikartLink( id )

   return '.. id .. '&lng=en ' .. id .. '' 

end

local function tlsLink( id ) local id2 = mw.ustring.gsub(id, '%s', function(s) return mw.uri.encode(s, 'WIKI') end)

   return '.. id2 .. ' ' .. id .. '' 

end


local function ciniiLink( id )

   return '.. id .. '?l=en ' .. id .. '' 

end

local function bneLink( id )

   return '.. id .. ' ' .. id .. '' 

end


local function uscongressLink( id )

   return '.. id .. ' ' .. id .. '' 

end

local function narapersonLink( id )

   return '.. id .. ' ' .. id .. '' 

end

local function naraorganizationLink( id )

   return '.. id .. ' ' .. id .. '' 

end

local function botanistLink( id ) local id2 = mw.ustring.gsub(id, '%s', function(s) return mw.uri.encode(s, 'PATH') end)

   return '.. id2 .. ' ' .. id .. '' 

end

local function mgpLink( id )

   -- TODO Implement some sanity checking regex
   return '.. id .. ' ' .. id .. '' 

end

local function rslLink( id )

   -- TODO Implement some sanity checking regex
   return '.. id .. '&CON_LNG=ENG ' .. id .. ''

end

local function leonoreLink( id ) -- Identifiants allant de LH/1/1 à LH/2794/54 (légionnaires) -- Identifiants allant de C/0/1 à C/0/84 (84 légionnaires célèbres) -- Identifiants allant de 19800035/1/1 à 19800035/385/51670 (légionnaires décédés entre 1954 et 1977, et quelques dossiers de légionnaires décédés avant 1954)

   if not string.match( id, '^LH/%d%d?%d?%d?/%d%d?%d?$' ) and
      not string.match( id, '^C/0/%d%d?$' ) and
           not string.match( id, '^19800035/%d%d?%d?%d?/%d%d?%d?%d?%d?$' ) then
       return false
   end
   return '.. id .. ' ' .. id .. '' 

end

local function sbnLink( id )

   if not string.match( id, '^IT\\ICCU\\%d%d%d%d%d%d%d%d%d%d$' ) and not string.match( id, '^IT\\ICCU\\%u%u[%d%u]%u\\%d%d%d%d%d%d$' ) then
       return false
   end
   return '.. id .. ' ' .. id .. '' .. getCatForId( 'SBN' )

end

local function nkcLink( id ) return '.. id .. '&CON_LNG=ENG ' .. id .. '' end

local function nclLink( id )

   if not string.match( id, '^%d+$' ) then
       return false
   end
   return '.. id .. '&CON_LNG=ENG ' .. id .. '' 

end

local function ndlLink( id ) return '.. id .. ' ' .. id .. '' end

local function sudocLink( id )

   if not string.match( id, '^%d%d%d%d%d%d%d%d[%dxX]$' ) then
       return false
   end
   return '.. id .. ' ' .. id .. '' 

end

local function hlsLink( id )

   if not string.match( id, '^%d+$' ) then
       return false
   end
   return '.. id .. '.php ' .. id .. ''

end

local function lirLink( id )

   if not string.match( id, '^%d+$' ) then
       return false
   end
   return '.. id .. '.450.0.html ' .. id .. ''

end

local function splitLccn( id )

   if id:match( '^%l%l?%l?%d%d%d%d%d%d%d%d%d?%d?$' ) then
       id = id:gsub( '^(%l+)(%d+)(%d%d%d%d%d%d)$', '%1/%2/%3' )
   end
   if id:match( '^%l%l?%l?/%d%d%d?%d?/%d+$' ) then
        return mw.text.split( id, '/' )
   end
   return false

end

local function append(str, c, length)

   while str:len() < length do
       str = c .. str
   end
   return str

end

local function lccnLink( id )

   local parts = splitLccn( id )
   if not parts then
       return false
   end
   local lccnType = parts[1] ~= 'sh' and 'names' or 'subjects'
   id = parts[1] .. parts[2] .. append( parts[3], '0', 6 )
   return '.. lccnType .. '/' .. id .. ' ' .. id .. '' .. getCatForId( 'LCCN' )

end

local function mbLink( id )

   -- TODO Implement some sanity checking regex
   return '.. id .. ' ' .. id .. '' .. getCatForId( 'MusicBrainz' )

end

--Returns the ISNI check digit isni must be a string where the 15 first elements are digits local function getIsniCheckDigit( isni )

   local total = 0
   for i = 1, 15 do
       local digit = isni:byte( i ) - 48 --Get integer value
       total = (total + digit) * 2
   end
   local remainder = total % 11
   local result = (12 - remainder) % 11
   if result == 10 then
       return "X"
   end
   return tostring( result )

end

--Validate ISNI (and ORCID) and retuns it as a 16 characters string or returns false if it's invalid --See http://support.orcid.org/knowledgebase/articles/116780-structure-of-the-orcid-identifier local function validateIsni( id )

   id = id:gsub( '[ %-]', ):upper()
   if not id:match( '^%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d[%dX]$' ) then
       return false
   end
   if getIsniCheckDigit( id ) ~= string.char( id:byte( 16 ) ) then
       return false
   end
   return id

end

local function isniLink( id )

   id = validateIsni( id )
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       return false
   end
   return '.. id .. ' ' .. id:sub( 1, 4 ) .. ' ' .. id:sub( 5, 8 ) .. ' '  .. id:sub( 9, 12 ) .. ' '  .. id:sub( 13, 16 ) .. '' .. getCatForId( 'ISNI' )

end

local function orcidLink( id )

   id = validateIsni( id )
   if not id then
       return false
   end
   id = id:sub( 1, 4 ) .. '-' .. id:sub( 5, 8 ) .. '-'  .. id:sub( 9, 12 ) .. '-'  .. id:sub( 13, 16 )
   return '.. id .. ' ' .. id .. '' .. getCatForId( 'ORCID' )

end

local function gndLink( id )

   return '.. id .. ' ' .. id .. '' .. getCatForId( 'GND' )

end

local function selibrLink( id ) if not string.match( id, '^%d+$' ) then

       return false
   end
   return '.. id .. ' ' .. id .. '' .. getCatForId( 'SELIBR' )

end

local function bnfLink( id )

   --Add cb prefix if it has been removed
   if not string.match( id, '^cb.+$' ) then
       id = 'cb' .. id
   end
   return '.. id .. ' ' .. id .. ' .. id .. ' (data)' .. getCatForId( 'BNF' )

end

local function bpnLink( id )

   if not string.match( id, '^%d+$' ) then
       return false
   end
   return '.. id .. ' ' .. id .. '' .. getCatForId( 'BPN' )

end

local function ridLink( id )

   return '.. id .. ' ' .. id .. '' .. getCatForId( 'RID' )

end

local function bibsysLink( id )

   return '.. id .. '&feltselect=bs.autid ' .. id .. '' .. getCatForId( 'BIBSYS' )

end

local function ulanLink( id )

   return '.. id .. ' ' .. id .. '' .. getCatForId( 'ULAN' )

end

local function nlaLink( id ) return '.. id .. ' ' .. id .. '' .. getCatForId( 'NLA' ) end

local function rkdartistsLink( id ) return '.. id .. ' ' .. id .. '' .. getCatForId( 'RKDartists' ) end

local function getIdsFromWikidata( item, property )

   local ids = {}
   if not item.claims[property] then
       return ids
   end
   for _, statement in pairs( item.claims[property] ) do
         if statement.mainsnak.datavalue then
          table.insert( ids, statement.mainsnak.datavalue.value )
         end
   end
   return ids

end

local function matchesWikidataRequirements( item, reqs )

   for _, group in pairs( reqs ) do
       local property = 'p' .. group[1]
       local qid = group[2]
       if item.claims[property] ~= nil then
           for _, statement in pairs ( item.claims[property] ) do
                if statement.mainsnak.datavalue ~= nil then
                        if statement.mainsnak.datavalue.value['numeric-id'] == qid then
                        return true
                end
            end
           end
       end
   end
   return false

end

local function createRow( id, label, rawValue, link, withUid )

   if link then
       if withUid then
           return '* ' .. label .. ' ' .. link .. '\n'
       else
           return '* ' .. label .. ' ' .. link .. '\n'
       end
   else

return '* \n'

   end

end

--In this order: name of the parameter, label, propertyId in Wikidata, formatting function local conf = {

   { 'VIAF', 'VIAF', 214, viafLink },
   { 'LCCN', 'LCCN', 244, lccnLink },
   { 'ISNI', 'ISNI', 213, isniLink },
   { 'ORCID', 'ORCID', 496, orcidLink },
   { 'GND', 'GND', 227, gndLink },
   { 'SELIBR', 'SELIBR', 906, selibrLink },
   { 'SUDOC', 'SUDOC', 269, sudocLink },    
   { 'BNF', 'BNF', 268, bnfLink },
   { 'BPN', 'BPN', 651, bpnLink },
   { 'RID', 'ResearcherID', 1053, ridLink },
   { 'BIBSYS', 'BIBSYS', 1015, bibsysLink },
   { 'ULAN', 'ULAN', 245, ulanLink },
   { 'HDS', 'HDS', 902, hlsLink },
   { 'LIR', 'LIR', 886, lirLink },
   { 'MBA', 'MusicBrainz', 434, mbLink },
   { 'MGP', 'MGP', 549, mgpLink },    
   { 'NLA', 'NLA', 409, nlaLink },
   { 'NDL', 'NDL', 349, ndlLink },
   { 'NCL', 'NCL', 1048, nclLink },
   { 'NKC', 'NKC', 691, nkcLink },
   { 'Léonore', 'Léonore', 640, leonoreLink }, 
   { 'SBN', 'ICCU', 396, sbnLink },     
   { 'RLS', 'RLS', 947, rslLink },

{ 'Botanist', '[[Author ci

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