1、Chapter 8Chapter 8 Functional Polymers8.1 Introduction8.1.1 Definition of functional polymers Functional polymer according to IUPAC(a)a polymer bearing functional groups(such as hydroxyl,carboxyl,or amino groups)that make the polymer reactive,(b)a polymer performing a specific function for which it
2、is produced and used.A polymer that exhibits specified chemical reactivity or has specified physical,biological,pharmacological,or other uses 8.1.2 Classification of functional polymers Biodegradable polymer Conducting polymer Electroluminescent polymer Ferroelectric polymer Ferromagnetic polymer Im
3、pact-modified polymer Liquid-crystalline polymer Macroporous polymer Non-linear-optical polymer Optically-active polymer Photoelastic polymer Photoluminescent polymerPhotosensitive polymerPiezoelectric polymer PolyelectrolytePolymer sorbent Polymer compatibilizer Polymer drug Polymer gel Polymer mem
4、brane Polymer solventPolymer support Polymer surfactant Resist polymer Shape-memory polymer Superabsorbent polymer 8.1.3 Applications and outlook of functional polymers Applications:Organic catalysis(supported catalysts)Medicine(red-blood-cell substitutes)Optoelectronics(conducting polymersMagnetic
5、polymers and polymers for nonlinear optics)BiomaterialsPaints and varnishesBuilding materialsPhotographic materialsLube and fuel additives8.2 Membrane8.2.1 Introduction HistoryInitiator of all crossflow membrane technology Dr.Sourirajan,removed salt from seawater,in the late 1950s.Commercial RO&UF m
6、embranes occurred in the early 1970s.Crossflow membrane processes became well accepted in industry and medicine in the 1980s.Widely used today.History of membraneMembrane a selective barrier for separating certain species in a fluidNo phase changePore sizes determining the sieved particles Separatio
7、n,concentration,fractionation&purificationCharactersMembrane configurationsPorous membrane（多孔膜）（多孔膜）MF，UF，NFDense membrane（致密膜）（致密膜）ED，RO，GS，PV，VPClassification of membranesSymmetric membraneAsymmetric membraneStructure of porous membranesFig.5 Schematic diagram of a)a Fig.5 Schematic diagram of a)a
8、 symmetric and b)an asymmetric membrane symmetric and b)an asymmetric membrane Schematic diagram of the filtration behavior of Schematic diagram of the filtration behavior of a)an asymmetric and b)a symmetric membrane a)an asymmetric and b)a symmetric membrane a bClassification of membranes accordin
9、g to driving forceDriving forceProcessesPressureMicrofiltration,Ultrafiltration,Nanofiltration,Reverse OsmosisE l e c t r i c a l potentialElectrodialysisPartial pressurePervaporationConcentration gradientDialysisClassificationProcess of dead-end pressure-driven membrane filtration ClassificationPro
10、cess of cross-flow pressure-driven membrane filtration Classification8.2.2 Crossflow Membrane Technology Four categories:Osmosis(RO)Nanofiltration(NF)Ultrafiltration(UF)Microfiltration(MF)Crossflow Membrane TechnologyMicrofiltration(MF)Pore sizes:0.05 to 3 mTransmembrane pressures(TMP):550 psi(0.33.
11、3 bar)Cross-flow velocities:36 m/s in tubular modules Applications:starch,bacteria,molds,yeast and emulsified oils Crossflow Membrane TechnologyUltrafiltration(UF)Pore sizes:0.005 to 0.1 m Transmembrane pressures(TMP):Higher than MFCutoff molecular weight:About 1,000 to 500,000 Concentrate high mole
12、cular weight species while allowing dissolved salts and lower molecular weight materials to pass through the membrane.Crossflow Membrane TechnologyNanofiltration(NF)Pore sizes:close to one nanometer diameter(10)Transmembrane pressures(TMP):Higher than UFCutoff molecular weight:200 300 Application:Wa
13、ter softening Cheese-whey desalting RO pretreatment Pharmaceutical concentration Kidney dialysis units Maple sugar concentration.Crossflow Membrane TechnologyReverse osmosis(RO)Pore sizes:4 to 8 Transmembrane pressures(TMP):35100 atmCutoff molecular weight:25 and 150 Rejection mechanism:surface-forc
14、e-pore flow theory solution-diffusion theory Crossflow Membrane TechnologyTypical Operating Pressures-psig(bar*)RO-Seawater8001000RO-Waste and Process300600RO-Water Purification200350RO-Undersink(Home)50NF100200UF 25150MF(crossflow)10 25*14.5 psig=1 barCrossflow Membrane Technology Electrodialysis R
15、emoval of ionic species from non-ionic productsPervaporation Separation of liquid mixtures by partial vaporization through a permselective membrane Phase change occursCrossflow Membrane Technology Dialysis A concentration-driven diffusion Application:Separation of proteins and other macromolecules f
16、rom salts in pharmaceutical and biochemical applications,e.g.,hemodialysisCrossflow Membrane Technology8.2.3 Membrane materials Most of membranes are made of polymeric materials,e.g.Polysulfone(PSF)Polyethersulfone(PES)Polyphenylsulfone(PPSU)Polyvinylidene Fluoride(PVDF)Polypropylene(PP)Polyethylene
17、(PE)Cellulose and Cellulose acetates(CA)Polyamide(PA)Polyacrylonitrile(PAN)Polytetrafluoroethylene(PTFE)RO membrane materials CA membranes Tolerate chlorine at levels used for microbial control PA membranes Higher rejection and flux Tolerate a wider pH range Sulfonated PSF membranesNF membrane mater
18、ials PA membranes CA membranesUF membrane materials CA membranes PVDF membranes PSF membranes Tolerate a pH range of 0.5 to 13,temperatures to 85C(185F),and 25 mg/L of free chlorine on a continuous basis MF membrane materials PA membranes CA membranes PVDF membranes PC,PP,PE,PTFEOperating parameters
19、 for widely used polymeric RO and UF membranes Class Polymer type Max.temp.(psig)M a x.pressure(psig)O p t i m u mpHrange Max free chlorinec o n t i n u o u s(ppm)RO/NFc e l l u l o s eacetate(CA)401000 28 2polyamide(PA)651000211NONEUF(CA)60 200 29 3polysulfone(PS)1002000.513 25v i n y l i d e n efl
20、uoride(VF)80200112 50acrylonitrile(AN)80200 110508.2.4 Membrane elements Crossflow membrane configuration comparison DesignCharacteristicSpiral-woundFibersTubularPlate&frameCostLowLowHighHighPacking densityHighU F-H i g hRO Very highLowModeratePressure capabilityHighU F-L o wRO-HighU F-L o wRO-Mediu
21、mHighMembrane polymerchoicesManyFewFewManyFouling resistanceFairU F-G o o dRO-PoorVery goodFairCleanabilityGoodUF-Very goodRO-PoorVery goodGood8.2.5 Machines and systems A simple machine for membrane systems includes:A pump provide the driving pressure and crossflow velocity Housing elements Connect
22、ing plumbing Control valve(s)Pressure gauges Motor controls Membrane systems often need a pretreatment equipment to reduce membrane fouling They can be preceded or followed by other unit processes such as degasification or activated carbon adsorption e.g.,For ultrapure water applications,two-pass RO
23、 systems have replaced many RO-DI systems.8.2.6 Design consideration Important parameters A balance of flow and pressure Higher-pressure causes higher permeate,also causes more severe fouling Higher crossflow velocity reduces fouling.Recovery the ratio of permeate to feed volume Feedwater applicatio
24、ns:7580%machine recovery,Some UF and RO applications:5075%Seawater Desalting via RO is typically run as low as 40%due to the very high osmotic pressure generated as the salt in the feed stream is concentrated.Temperature The warmer the feed stream the higher the throughput Solution viscosity8.2.7 Ap
25、plications Hundreds of applications,falling in three broad categories:Water purification Manufacturing process separations Waste treatment.Water Purification Boiler feed Potable from brackish or alkaline source Color removal from surface water Microbial removal;bacteria,pyrogens,giardia and cryptosp
26、oridium cysts THM precursor and pesticide removal Potable from seawater Sodium and organics reduction for beverages Reconstituting food and juices Bottled water Can and bottle rinsingApplications:Water Purification Rinse water for metal finishing operations Spot-free car wash rinses Laboratory and r
27、eagent grade water USP Purified Water and Water for Injection Semiconductor chip rinsing Distillation and deionization system pretreatment Kidney dialysis Medical device and packaging rinse water Photographic rinse water Pulp and paper rinses and makeup water Dye vat makeup Applications:Water Purifi
28、cationProcess Juice and milk concentration Beer and wine finishing Beverage flavor enhancement Cheese whey fractionation/concentration of proteins and lactose Food oils,proteins,taste agents concentration Saccharide purification Maple sap preconcentration Enzymes and amino acids,purification and con
29、centrationApplications:Process Chemical dewatering Chemical mixtures fractionation Dye and ink Desalting Glycol and glycerin recovery ED paints recovery from rinses Medicine and vitamin concentration purification Blood fractionation Cell broth fractionation Cell concentration Photographic emulsions
30、concentration/purification Applications:ProcessWaste treatment Tertiary sewage water recovery Heavy metals and plating salts concentration BOD and COD concentration Dewatering liquid for reduced disposal volume Dilute materials recovery Radioactive materials recoveryApplications:Waste treatment Text
31、ile waste recovery for reuse Pulp and paper water recovery for reuse Dye and ink concentration and recovery Photographic waste concentration and recovery Oil field produced water treatment Lubricants concentration for reuse Commercial laundry water and heat reuse End of pipe treatment for water reco
32、very Applications:Waste treatment8.2.8 Recent advances Composite membranes RO,UF&NF Improved both flux and separation Increase chemical durability of membranes Surface treatment techniques Adding formal charges to change separation ability and reduce fouling tendency Enhanced systems controls improv
33、ed the operational efficiency Industrys evolving realization treatment systems are often most efficient if they combine several unit processes.Home RO units 8.3 Adsorptive Separation Polymers 8.3.1 Introduction Adsorption preferential partitioning of substances from the gaseous or liquid phase onto
34、the surface of a solid substrate Bone char decolorization of sugar solutions and other foods Activated carbon removing nerve gases from the battlefield Adsorption is different from absorption separation of a substance from one phase accompanied by its accumulation or concentration at the surface of
35、another.Adsorbent the adsorbing phase.Adsorbate the material concentrated or adsorbed at the surface of adsorbent.Physical adsorption caused mainly by van der Waals forces and electrostatic forces between adsorbate molecules and the atoms which compose the adsorbent surface.Thus adsorbents are chara
36、cterized first by surface properties such as surface area and polarity.8.3 Adsorptive Separation Polymers 8.3.1 Introduction Adsorption preferential partitioning of substances from the gaseous or liquid phase onto the surface of a solid substrate Bone char decolorization of sugar solutions and other
37、 foods Activated carbon removing nerve gases from the battlefield Adsorption is different from absorption separation of a substance from one phase accompanied by its accumulation or concentration at the surface of another.Adsorbent the adsorbing phase.Adsorbate the material concentrated or adsorbed
38、at the surface of adsorbent.Absorption a process in which material transferred from one phase to another(e.g.liquid)interpenetrates the second phase to form a“solution”.The term“sorption”is a general expression encompassing both processes of absorption and adsorption.Physical adsorption caused mainl
39、y by van der Waals forces and electrostatic forces between adsorbate molecules and the atoms which compose the adsorbent surface.Thus adsorbents are characterized first by surface properties such as surface area and polarity.Important indices A large specific surface area A suitable pore size distri
40、bution Surface polarity Polar adsorbents:Hydrophilic Nonpolar adsorbents:Hydrophobic8.3.2 Historical background Reference in Bible Aristotles experiment Practice in ancient Egypt,Grace and China Perhaps Dr.Gans in Germany was the first person who used ion exchanger(processed natural zeolite)to an in
41、dustrial scale,based on scientific understanding and technological maturity.Adams and Holmes synthesized organic ion exchangers called ion exchange resins in 1935.8.3.3 Classification Ion exchangers are generally insoluble solids or immiscible liquids(in case of liquid ion exchangers)capable of exch
42、anging ions with the surroundings Depending upon their ability of exchanging cations or anions the ion exchangers are either cation or anion exchangers respectively.A cation exchanger consists of a matrix with a negative charge.An anion exchanger consists of a matrix with a positive charge.The oppos
43、itely charged ions called counter ions,compensate the matrix charge.On the basis of the nature of the matrix an ion exchanger may be organic or inorganic In organic resins the matrix is a highly polymerized crosslinked hydrocarbon containing ionogenic groups.Inorganic ion exchangers are generally th
44、e oxides,hydroxides and insoluble acid salts of polyvalent metals,heteropolyacid salts and insoluble metal ferrocyanides.8.3.3.1 Synthetic Inorganic ION Exchangers The main emphasis has been given to the development of new materials possessing chemical stability,reproducibility in ion exchange behav
45、ior and selectivity for certain metal ions important from analytical and environmental point of view.Synthetic inorganic ion exchangers are generally produced as gelatinous precipitates by mixing rapidly the elements of groups 3,4,5 and 6 of the periodic table,usually at room temperature.8.3.3.2 Org
46、anic-inorganic ion Exchangers Traditional organic ion exchangers are found to be unsuitable at high temperatures and under strong radiation.Inorganic ion exchangers are reported to be not very much reproducible in behavior,and not very stable mechanically and chemically because of their inorganic na
47、ture.Interest has been developed to obtain some organic based inorganic ion exchangers,i.e.,hybrid ion exchangers.Fibrous ion exchange materials can be used in the form of various textile goods such as cloth,conveyer belts,nonwoven materials,staples,nets etc.consist of monofilaments of uniform size
48、ranging between 550 um.This predetermines short diffusion path of sorbent and high rate of sorption that can be of about hundred times higher than that of the granular resins with a particle diameter of 0.251 um,normally used.Has extremely high osmotic stability that allows them to be used in condit
49、ions of multiple wetting and drying occurring at cyclic sorption/regeneration processes in air purification.e.g.,A new class of highly crosslinked polymeric resins(Macronet resins)have been developed with surface areas as high as 1200 m2/g,which approach or exceed those of activated carbon in some c
50、ases.These resins can be easily regenerated in situ with simple aliphatic alcohols.The Macronet resins are available in a range of different functionalities and thus can be used for selective removal from multicomponent systems.8.3.4 Adsorbents Microporous,high specific surface material(200 2000 m2/
