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A) Filtration

Filtration is a mechanical or physical process to separatesolidparticulatesfromfluids. Filtrate is a liquid that has passed through the filtration process. Residueis the material remaining after filtration.

Examples of filtration:

1. Thecoffee filterto keep the coffee separate from the grounds.

2. HEPAfilters inair conditioningto remove particles from air.

3. Belt filtersto extractprecious metalsinmining.

4. Whatman filter paper 40 is for separating crystals of CuSO4 from cold water.

5. Water filtrationsystem: Awater filtrationsystem generally makes use of a thick layer ofgranularmaterials, such as sand, gravel, and charcoal. Such a filter may be many feet thick and is known, therefore, as a deep-bed filter. When impure water passes through such a filter, suspended solids are removed, allowing relatively pure water to be collected at the bottom of the filter. In commercial water purification plants, the deep-bed filter may be modified to remove other impurities.

6. Furnaces use filtration to prevent the furnace elements from fouling with particulates.

7. Pneumatic conveying systems often employ filtration to stop or slow the flow of material that is transported, through the use of abaghouse.

8. In the laboratory, aBchner funnelis often used, with afilter paperserving as the porous barrier.

9. An experiment to prove the existence ofmicroscopic organismsinvolves the comparison of water passed through unglazedporcelain and unfiltered water. When left in sealed containers the filtered water takes longer to go foul, demonstrating that very small items (such asbacteria) can be removed from fluids by filtration.

10. In thekidney,renal filtrationis the filtration ofbloodin theglomerulus, followed by selective reabsorption of many substances essential for the body to maintain homeostasis.

11. DEfiltration: Filtration systems are varied in design, operation, and application. The most traditional system is diatomaceous earth (DE)filtration, in which DE is used to aggregate and collect suspended solids. The DE is collected on filter paper inside the pressure filter as the juice passes through the unit. The resulting juice is sparkling clear.

12. Gas masks: On the battlefield for respiratory support and other necessary equipment, decontamination solutions, and staff trained to decontaminate chemical warfare casualties. Collective protective shelters, complete with filters for airflow systems, have been provided to shield personnel in an otherwise contaminated area. Such shelters can provide a toxic-free area for person.

B) Sieving

Sieving involves using a screen or mesh to separate parts of a mixture. It can stop larger particles from going through and let the solution or the smaller pieces through.

If barrier is a mat of fibers or a porous polymer with small pore sizes, it is called filtration. If the barrier is of interwoven metal wire (screen); natural cloth (burlap, net); in a regular pattern and having regular, rather large, pore sizes, it is called sieving.

Examples of Sieving:

1. Screen wire can separate sand and rocks.

2. Very small porous screen wire separates water and rocks is also an example of sieving.

3. Sieving of flour.

4. Dimensional sorting of peas and beans.

5. Tea strainer, which is used to separate tea leaves from water. Sieves work because large particles cannot fit through the holes in a sieve, but small particles can.

6. Sieving is often used in preparing food, but it also has other uses. For example, very small sieves can separate viruses from bacteria.

7. Fishing net could be considered a very large sieve for catching fishes.

8. Cheese curd is separating via cloth.

9. Very small regular porous size screen wire can be used to separate juices from fruits.

10. Soot particles from smokestacks.

11. Regular size screen wire is used to separate large solid clots, formed in the mixture of sand and cement.

C) Dialysis

Dialysis is the transfer of solute (dissolved solids) across a semipermeable membrane. Strictly speaking, dialysis refers only to the transfer of the solute; transfer of the solvent is calledosmosis.If dialysis is done in the presence of electric current, then it is called electrodialysis.

Examples of Dialysis:

1. A solution of starch and sodium chloride in water can be separated by placing the mixture in a vessel on one side of a semipermeable membrane and placing pure water on the other side. The smaller particles of sodium chloride (which dissolve in water to form sodium and chloride ions) will diffuse across the membrane; diffusion of the much larger starch particles (which are not truly in solution but are in colloidal suspension) is hindered and may be completely prevented. By continuously or periodically replacing the solvent with fresh solvent, almost all of the sodium chloride can be removed. The method was originated by Thomas Graham.

2. Mixed macromolecules, such as proteins, may be similarly separated. By the use of graded semipermeable membranes chosen to allow successively smaller molecules to pass, mixtures can be separated into components of graded ranges of molecular weight.

3. Separation of enzymes from blood.

4. Separation of hormones by semipermeable membrane from blood and other fluids in the body.

5. Hemodialysisis a method in which kidney failure is treated with the process of dialysis. In hemodialysis, blood is removed, purified through dialysis, and returned to the bloodstream. In kidney failure, there is retention of salts and water, urea, and metabolic acids. The patient is then connected to a dialysis machine, which is also called a hemodialyzer. The blood flows through small channels made of semipermeable membranes. The dissolved substances like urea and salts pass through a sterile solution. Compounds like sugar and amino acids are added to the sterile solution. The dialysis solution is on the other side of the membranes, and the molecules flow through the membranes. The molecules diffuse from a higher concentration to low concentration area. The concentrations of molecules needed to be removed from the blood are zero in the dialysis fluid. The process of hemodialysis helps many patients who have kidney failure.

6. Peritoneal dialysis(PD) is a treatment for patients with severe chronic kidney disease. The process uses the patient'speritoneumin the abdomen as a membrane across which fluids and dissolved substances (electrolytes, urea, glucose, albumin and other small molecules) are exchanged from the blood. Peritonealdialysisis the dialysisthroughtheperitoneum,thedialyzingsolutionbeingintroducedintoandremove-dfromtheperitonealcavity, aseitheracontinuousoranintermittentprocedure.

7. Lymphdialysisremovalofureaandotherelementsfromlymphcollectedfromthethora-cic duct,treatedoutsidethebody,andlater reinfused.

8. Continuousambulatoryperitonealdialysis(CAPD)involvescontinuouspresenceofdial-ysissolutioninthe peritonealcavity. It can be used to remove metabolic wastes from kidney. e.g. urea, glucose, etc.

9. Continuouscyclingperitonealdialysis(CCPD)aproceduresimilartocontinuousambulatoryperitonealdialysisbuttakingplaceatnight,usingamachinetomakeseveralfluidexchangesautomatically. It can also be used to remove metabolic wastes from kidney. e.g. urea, glucose, etc.

10. Intermittentperitonealdialysis(IPD)anolderformofperitonealdialysisinwhichdialysissolutionisinfusedintotheperitonealcavity,allowedtoequilibratefor10to20minutes,andthendrainedout.

11. Colloidalmesoporoussilica nanoparticlesless than 20 nm in diameter are prepared bydialysis; this simplesurfactantremoval route can avoid aggregation by sedimentationredispersion and remove cationicsurfactantswhile retaining the originalcolloidalstate, which is applicable to the preparation of primarynanoparticlescarrying a functional organic substance.

D) Size Exclusion Chromatography

Size-exclusion chromatography (SEC)is achromatographicmethod in which molecules in solution are separated by their size, and in some casesmolecular weight.It is usually applied to largemoleculesor macromolecular complexes such as proteins and industrial polymers. Typically, when an aqueous solution is used to transport the sample through the column, the technique is known asgel-filtration chromatography, versus the namegel permeation chromatography, which is used when an organic solvent is used as a mobile phase.

Examples of Size-exclusion chromatography:

1. Biochemical applications: In general, SEC is considered a low resolution chromatography as it does not discern similar species very well, and is therefore often reserved for the final "polishing" step of purification. The technique can determine thequaternary structureof purified proteins that have slow exchange times, since it can be carried out under nativesolutionconditions, preserving macromolecular interactions. SEC can also assay proteintertiary structure, as it measures the hydrodynamic volume (not molecular weight), allowing folded and unfolded versions of the same protein to be distinguished. For example, the apparenthydrodynamic radiusof a typical protein domain might be 14 and 36 for the folded and unfolded forms, respectively. SEC allows the separation of these two forms, as the folded form will elute much later due to its smaller size.

2. Polymer synthesis: SEC can be used as a measure of both the size and thepolydispersityof a synthesizedpolymer, that is, the ability to be able to find the distribution of the sizes of polymer molecules. If standards of a known size are run previously, then acalibration curvecan be created to determine the sizes of polymer molecules of interest in the solvent chosen for analysis (oftenTHF). In alternative fashion, techniques such as light scattering and/orviscometrycan be used online with SEC to yield absolute molecular weights that do not rely on calibration with standards of known molecular weight. Due to the difference in size of two polymers with identical molecular weights, the absolute determination methods are, in general, more desirable. A typical SEC system can quickly (in about half an hour) give polymer chemists information on the size and polydispersity of the sample. The preparative SEC can be used forpolymer fractionationon an analytical scale.

3. High-pressuresize exclusion chromatography(HPSEC) is used for determining molecular weights of aquatic humic substances.

4. Determination of the porosities of monolithic columns by inversesize-exclusion chromatography.

5. Aqueous phasesize-exclusion-chromatography usedfor PLP-SEC studies into free-radical propagation rate of acrylic acid in aqueous solution.

6. Quantitation of aggregate levels in a recombinant humanized monoclonal antibody formulation by size-exclusion chromatography, asymmetrical flow field flow fractionation, and sedimentation velocity.

7. High-resolution length sorting and purification of DNA-wrapped carbon nanotubes bysize-exclusion chromatography.

8. Characterization of commercial and experimental sodium caseinates by multiangle laser light scattering andsize-exclusion chromatography

9. Purification of molecularly bridged metal nanoparticle arrays by centrifugation andsize exclusion chromatography

10. Absolute size-exclusion chromatography (ASEC) is a technique that couples adynamic light scattering(DLS) instrument to a size exclusion chromatography system for absolute size measurements of proteins and macromolecules as they elute from the chromatography system.

The definition of absolute used here is that it does not require calibration to obtain hydrodynamic size, often referred to as hydrodynamic diameter (DHin units of nm). The sizes of the macromolecules are measured as they elute into the flow cell of the DLS instrument from the size exclusion column set. It should be noted that the hydrodynamic size of the molecules or particles are measured and not their molecular weights. For proteins a Mark-Houwink type of calculation can be used to estimate the molecular weight from the hydrodynamic size. A big advantage of DLS coupled with SEC is the ability to obtain enhanced DLS resolution.

E) Centrifugation

Theprocessbywhichsubstancesareseparatedbycentrifugalforce toincreasetherateoffiltrationorsedimentationoftwo immiscibleliquidsoraliquidandasolid is called centrifugation.

Examples of Centrifugation:

1. Separating chalk powder from water.

2. Removing fat from milk to produce skimmed milk.

3. Separatingtextiles.

4. Removing water from lettuce after washing it in asalad spinner.

5. Separating particles from an air-flow usingcyclonic separation.

6. Theclarification and stabilization of wine.

7. Separation of water particles from clothes while spin-drying inwashing machines.

8. Separation of urine components and blood components in forensic and research laboratory.

9. Separation of cellular components e.g. lysosomes from other components.

10. Equilibrium-density-gradient centrifugation: aprocedureforseparatingparticlessuchasvirusesorribosomesormoleculessuchasDNAinwhichthesampleisplacedonapreformedgradientsuchassucroseorcesiumchloride.Uponcentrifugationeitherbyratezonalorequilibriumprocedures,themacromoleculesare'banded'inthegradientandcanbecollectedasapurefraction.

11. Isotope separation:

Other centrifuges, the first being the Zippe-type centrifuge, separateisotopesofchemical elements. These kinds of centrifuges are in use innuclear powerand nuclear weapons programs.

12. Human centrifuges are exceptionally large centrifuges that test the reactions and tolerance of pilots andastronautsto acceleration above those experienced in the Earth's gravity.

F) Masking

Masking is a pseudo-separation method in which a species is prevented from participating in a chemical reaction by binding it with a masking agent in an unreactive complex.

The reagent used to bind the species to be masked in an unreactive complex is called masking agent.

Technically, masking is not a separation technique because we do not physically separate the analyte and the interferent. We do, however, chemically isolate the interferent from the analyte, resulting in a pseudo-separation.

Examples of Masking:

Apassivationlayerthermally grown or deposited on wafers. It is resistant to high temperatures. Oxygen orwatervaporis used to grow silicon dioxide at temperatures above 900 degrees C. Silicon dioxide is used as a maskinglayeraswellas aninsulator.

A passivationlayerchemically deposited on awaferat temperatures of between 600 degrees C and 900 degrees C to protect thewaferfromcontamination. Silicon nitride is also used as a maskinglayerand as aninsulator.

Masking Agent

Elements Whose Ions Can Be Masked

CN

Ag, Au, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pd, Pt, Zn

SCN

Ag, Cd, Co, Cu, Fe, Ni, Pd, Pt, Zn

NH3

Ag, Co, Ni, Cu, Zn

F

Al, Co, Cr, Mg, Mn, Sn, Zn

S2O32

Au, Ce, Co, Cu, Fe, Hg, Mn, Pb, Pd, Pt, Sb, Sn, Zn

tartrate

Al, Ba, Bi, Ca, Ce, Co, Cr, Cu, Fe, Hg, Mn, Pb, Pd, Pt, Sb, Sn, Zn

oxalate

Al, Fe, Mg, Mn

thioglycolic acid

Cu, Fe, Sn

Examples of Selected Inorganic and Organic Masking Agents for Metal Ions

G) Distillation

Distillation is the technique of heating aliquidto createvaporwhich is collected when cooled separate from the original liquid.

Examples of Distillation:

1. Pure water can be separated fromsalt water through distillation.Salt wateris boiled to create water steam, but the salt remains in the solution. The steam is collected and allowed to cool back into salt-free water.

2. Fractional distillation is used to separate petroleum into its fractions.

3. Distillation is used to make any of the liquors that are stronger than wine.

4. Azeotropic distillation: If the azeotrope is not considered sufficiently pure for use, there exist some techniques to break the azeotrope to give a pure distillate. This set of techniques are known as azeotropic distillation. Some techniques achieve this by "jumping" over the azeotropic composition (by adding another component to create a new azeotrope, or by varying the pressure). Others work by chemically or physically removing or sequestering the impurity. For example, to purify ethanol beyond 95%, a drying agent or a desiccant(such as potassium carbonate) can be added to convert the soluble water into insolublewater of crystallization.Molecular sievesare often used for this purpose as well.

5. Pressure-swing distillation: One example of the application of pressure-swing distillation is during the industrial purification ofethyl acetateafter its catalytic synthesis fromethanol.

6. Distillation in food processing: Carbohydrate-containing plant materials are allowed to ferment, producing a dilute solution of ethanol in the process. Spirits such aswhiskeyandrumare prepared by distilling these dilute solutions of ethanol. Components other than ethanol, including water, esters, and other alcohols, are collected in the condensate, which account for the flavor of the beverage. Some of these beverages are then stored in barrels or other containers to acquire more flavor compounds and characteristic flavors.

7. Dry distillationordestructive distillation, despite the name, is not truly distillation, but rather achemical reactionknown aspyrolysisin which solid substances are heated in an inert orreducingatmosphere and any volatile fractions, containing high-boiling liquids and products of pyrolysis, are collected. The destructive distillation ofwoodto give methanolis the root of its common name wood alcohol.

8. Freeze distillationis an analogous method of purification usingfreezinginstead of evaporation. It is not truly distillation, but arecrystallizationwhere the product is themother liquor, and does not produce products equivalent to distillation. This process is used in the production ofice beerandice wineto increase ethanol andsugarcontent, respectively. It is also used to produceapplejack. Unlike distillation, freeze distillation concentrates poisonous congeners rather than removing them; As a result, many countries prohibit such applejack as a health measure. However, reducing methanol with the absorption of 4Amolecular sieveis a practical method for production.

9. Steam distillation is employed in the manufacture ofessential oils, for use inperfumes, for example. In this method, steam is passed through the plant material containing the desired oils.Eucalyptus oilandorange oilare obtained by this method on the industrial scale. Steam distillation is also sometimes used to separate intermediate or final products during the synthesis of complex organic compounds.

10. Steam distillation is also widely used inpetroleum refineriesandpetrochemicalplants where it is commonly referred to as "steam stripping".

11. Steam distillation also is an important means of separating fatty acids from mixtures and for treating crude products such astall oilsto extract and separatefatty acids,soapsand other commercially valuable organic compounds.

12. Extractive distillation: The separation of an azeotropic mixture of benzeneandcyclohexane, whereanilineis one suitable solvent.

H) Sublimation

Sublimationis the transition of a substance directly from thesolidto thegasphase without passing through the intermediateliquid phase.

Examples of Sublimation:

1. Solidcarbon dioxide(dry ice) sublimes everywhere along the line below the triple point (e.g., at the temperature of 78.5 C (194.65 K, 104.2F) atatmospheric pressure), whereas its melting into liquid CO2 can occur only along the line at pressures and temperatures above the triple point (i.e., 5.2 atm, 56.4 C)

2. Snowandicesublime, although more slowly, at temperatures below the freezing/melting pointtemperature line at 0 C for most pressures; see line below triple point.Infreeze-drying, the material to be dehydrated is frozen and its water is allowed to sublime under reduced pressure or vacuum.

3. Vacuum sublimation is the method of choice for purification of organic compounds for the use in theorganic electronics industry, where very high purities (often > 99.99%) are needed to satisfy the standards for consumer electronics and other applications.

4. Iodineproduces fumes on gentle heating. It is possible to obtain liquid iodine at atmospheric pressure by controlling the temperature at just above the melting point of iodine. Inforensic science, iodine vapor can reveal latentfingerprintson paper.

5. Naphthalene (M.P. 79 0C), ingredient inmothballs, also sublimes at 25 0C at 1 torr.

6. Arseniccan also sublime at high temperatures.

7. A useful analytical example of sublimation is the isolation of amino acids from fossil mollusk shells and deep-sea sediments.

8. Urea (M.P. 79 0C) sublimes at 50 0C at 1 torr.

9. Sulfur, benzoin and NH4NO3 are obtained readily in pure form by sublimation.

10. Iodine and camphor readily sublime at room temperatures and pressures.

11. Saccharin, quinine, cholesterol, and atropine are the additional examples of compounds that are conveniently separated by sublimation.