WHAT IS ACTIVATED CARBON?
Each grainof activated carbon or charcoal is, in effect, a molecular sponge with atremendous area of internal surface in passageways so small that they cannot beseen by an optical microscope. It isthis surface that adsorbs and retains the odors, vapors, and gases. Even though the deposit of adsorbedcontaminant is only one or a few molecules deep, the amount of materialadsorbed can be surprisingly large because of the great internal surface. The grains in one pound of activated carbonhave an internal surface of about five million square feet.
It has beenknown since ancient times that carbon has the power to purify air andwater. Ordinarily carbon, as normallyproduced, possesses to a slight degree the power to adsorb and holdcontaminating materials. But by hightemperature steam activation, the process employed in the manufacture ofactivated carbon, the adsorption capacity is increased a hundredfold or more. New important methods of utilization as atotal purification treatment or as part of a treating system have beendeveloped. Activated carbon types arenow available which have low air resistance, high adsorptive capacity, andother characteristics especially suited to the treatment of industrial wastegases. For many problems, standardcommercially available activated carbon filter cells provide effective andeconomical solutions.
Everyone hashad some contact with activated carbon. Its use in gas masks, for water purification, and for deodorization iswell known. The public is now learningabout activated carbon through some of its new personal and householduses. Many are using filter tipcigarettes which contain activated carbon. Disposable activated carbon filters are being widely used in forced airfurnaces and air conditioners. Thepublic knows from popular articles that activated carbon helps the atomicsubmarines to stay under water for weeks or months and manned space capsules tostay in orbit for many days. Many havehad contact with activated carbon in its industrial applications, and know ofthe beneficial ways it can be used.
ACTIVATEDCARBON IS LIKE A MOLECULAR MAGNET. It isa form of carbon in which we create millions of tiny holes, which form aninternal structure of interconnected capillary passages not much larger thanthe molecules that it adsorbs. Althoughactivated carbon can be made from a variety of raw materials and by differentmethods of processing, we carefully select the material and processes thatproduce the combination of properties required for maximum effectiveness ineach of its many applications.
Adsorptionis commercially useful, because it can be used to remove impurities from air,gas and liquid mixtures even though the contaminants are present only in traceamounts.
Adsorptionis a physical action based on molecular forces. When an air, gas or liquid containing impurities is brought into contactwith it, the activated carbon attracts and holds the impurities on its internalsurfaces. The degree of adsorptiondepends on the relationship between the carbon pore structures and the size andshape of the contaminating molecules.
A tremendoussurface area is contained within a small volume of activated carbon. For example, the area in one quart (about onepound) of some types of carbon is as high as 9 million square feet. This makes absorption practical and one ofthe most effective methods of positive air purification known. Air purified with activated carbon isactually purer than much of the outside air we normally consider fresh andsweet.
Gas – Air and gases are purified byremoving organic and inorganic contaminants in high and very low concentrationsas small as one per billion.
Liquid – Activated carbon removesunwanted tastes, odors, colors, chlorine, and a wide range of contaminants fromwater and other liquids. Washed gradesare available for high purity requirements of medicinal, food and beverageapplications.
Air – Contaminated air is recoveredand recirculated at less cost than heating or cooling outside air. This improves indoor environment, stopspollution by exhaust air, improves neighborhood relations.
Solvents – Valuable solvents arerecovered from the air at a fraction of their original cost. This helps improve products by making thebest solvents economical to use.
Reclamation – Dry cleaning solutions,plating baths and degreasing solvents are reclaimed for reuse. By-product liquids, gases and waste productsare recovered for resale, reuse of simplified disposal.
Catalyst – Activated carbon is used tocatalyze a variety of specific chemical reactions. Activated carbon will decrease in catalyticactivity only when exposed to large quantities of high molecular weightmaterials and is not readily poisoned by the usual contaminants.
CatalystSupport – Activatedcarbon’s high adsorption capacity holds more metallic salts than othersupports. Its large internal structurealso effectively concentrates reactants and promotes catalysis.
Concentration – The high adsorptive capacityof activated carbon is used for concentrating many types of substances presentin dilute form in gases and liquids. Carbon adsorption is often faster and more economical than concentrationby evaporation, chemical reaction, ion exchange and other methods.
Fractionation – Activated carbons haveadsorbent capacity for a wide range of molecular sizes and shapes. By proper selection of carbon types andoperation of adsorptive equipment, it is possible to fractionate molecules,thereby separating one type or size from another. In specific cases, adsorption orchromatographic techniques will achieve a degree of separation usually notpossible with other methods.
ADSORPTIONEQUIPMENT FOR AIR POLLUTION CONTROL
Adsorptionis a physical phenomenon which permits the removal of contaminants from gasesand liquids. These contaminants can bereduces to as low a level as desired. The molecules of the contaminant are trapped and held by the internalsurface of the adsorbent. A number ofcommercial materials have the property of adsorption, including activatedcarbon, silica gel, activated alumina, molecular sieves, and certain clays.
Thisdiscussion relates primarily to activated carbon since it is the best known andmost effective adsorbent for air pollution control.
MANUFACTUREAND SELECTION OF ACTIVATED CARBON
Activatedcarbon is prepared from nut shells, wood, coal, or other carbonaceous material,and activated by the use of steam at high temperature to burn away part of thecarbon substance in a definite pattern to give a large amount of internalsurface, thereby imparting to the carbon the property of adsorption. We start with a crude carbon which has only afew pores or holes, due to the original structure of the carbonaceousmaterial. The rest of the carbon isrelatively solid. During activation, theblack grains become lighter in weight and acquire an internal pore structure havinga large surface. The more highlyactivated the carbon, the greater the surface and pore volume.
Theselection of the right grade to use depends on such factors as general class ofapplication, type and concentration of contaminants, efficiency required,resistance to liquid or gas flow, heat transfer, thickness of bed used, methodof support for carbon bed, and operating conditions. The final selection to determine the besttype and mesh size to use is ordinarily based on laboratory tests. It may be necessary to compare severalgrades. We can help you make theselection.
HOWACTIVATED CARBON IS USED FOR POLLUTION ELIMINATION
The basicprinciple for using activated carbon in the solution of adsorption problems issimple. Either move the fluid (gas orliquid) through the carbon or move the carbon through the fluid. The carbon can be used in either a fixed ormoving bed. It can be contained instandard filter cells or packed into adsorber vessels or towers.
Thepollutants are adsorbed by the carbon grains which increase in weight by theamount they adsorb. This continues untilthe capacity of the carbon is reached and then the pollutants are no longeradsorbed but are passed through the bed. At this point or before, the carbon must be replaced or reactivated. Activated carbon saturated with pollutantscan be reconditioned in high temperature steam reactivating furnaces similar tothose employed in the original manufacture of the carbon. In some cases, it is technically possible andeconomically feasible to desorb all or part of the pollutants with steam,direct heat, or solvent washing as part of the adsorption/desorption process(Solvent Recovery).
At ordinarytemperatures the so-called permanent gases are adsorbed to a minor extentcompared with those which have boiling points at room temperature orabove. The high molecular weightmaterials under certain conditions will displace smaller molecules which werealready adsorbed in activated carbon. Suppose, for example, we pass air containing butane, pentane, and hexanethrough a bed of activated carbon. Thecarbon will remove all three of the hydrocarbons until a breakthrough isreached, at which point some of the butane starts to come through, but theother hydrocarbons are completely adsorbed. If the adsorption is carried on for a sufficiently long time, the carbonwill contain mainly hexane with only small amounts of butane and pentane.
The initialefficiency of a fixed bed is a function of particle geometry and contacttime. For our purposes, contact time isthe bed volume in feet divided by the CFM; times 60. This is a standard concept of contact timeand is useful for our purposes. As arule-of-thumb, when the contact time is doubled, the loss (100 minus theefficiency) through the carbon bed is cut to one-tenth. Suppose we have a carbon bed with a volume ofa 8 f^3, CFM of 200, and an initial efficiency of 99%. The contact time is 2.4 seconds. If we double the contact time, making it 4.8seconds, by either cutting the CFM in half or by doubling the depth, we willreduce the loss from 1% to a tenth of 1%, making the initial efficiency99.9%. If, on the other hand, we cut thecontact time in half (to 1.2 seconds), by either doubling the CFM or cuttingthe thickness in half, we increase the loss from 1% to 10%, making theefficiency 90%. In general, contact timefor gas treatment operations vary from 1/10 to 10 seconds.
The initialefficiency does not measure the capacity of the ed to break-through orsaturation. These depends on the rate ofcontaminant flow, the mass of the carbon, and adsorption characteristics of thecarbon. The lower the amount ofcontaminants to be removed per minute, the greater the weight or volume of thecarbon, and the higher the adsorption capacity of the carbon; the longer willbe the service life of the bed.
For fixedbed installations, which handle large quantities of gas or liquid, and wherethen carbon layers can be used because a short contact time is suitable, anarrangement of vertical beds between screens or cylindrical beds may be used toadvantage. For the continuous operationof fixed bed systems, two or more vessels are required together with thenecessary interconnecting valves to switch the flow of material being treatedand, in some cases, the flow of the desorbing fluid.
Contact withoxygen, chlorine, and certain other gases at high temperatures should beavoided. Carbon is combustible, but noteasily ignited. In the absence of ablast of air, hot activated carbon supports combustion with difficulty andunder some conditions will go out on its own accord. Activated carbon is not ignited by highvelocity air at temperatures of 300˚F or less. With low air velocities, somewhat higher temperatures can be employed.
In problemswhere combustible materials are adsorbed from air, it is generally advisable tohandle mixtures that are below the lower explosive limit. If they are more concentrated, it may bedesirable to dilute them with additional air of inert gas. This adds to the size of the system, butmakes it safer.
If theconcentration of contaminant is high, it may be best to remove it in severaladsorption stages. For example, if acontaminant is present in a concentration of one part per million and it isdesired to reduce it to less than one part per billion, treatment by passingthrough a bed of activated carbon two or three feet thick may suffice. If, however, the contaminant is present in a1% concentration and it is desired to reduce it to less than one part perbillion, it might be well to do this in two separate stages.
Activatedcarbon is generally used as a concentration method so that vapors can bedisposed of in a concentrated form by other means such as burning or reuse in aprocess. There are a few exceptionswhere activated carbon is the carrier for disposal by dumping in the solid formor by flushing down the sewer, or where the carbon destroys the contaminant bycatalysis.
From anoperating cost point of view the contaminants should be eliminated either asclose as possible to the polluting source or as close as possible to where theair is used. By treating the air closeto the source, it is purified in the most concentrated form and the total loadof waste materials can be eliminated with the least expense. If the air is treated close to the use, it isnecessary to purify only that portion actually used (removing only a smalltotal amount of impurities), but the surrounding atmosphere iscontaminated. To do anything in betweenthese two extremes would mean purifying thousands of cubic yards of the atmosphereand in most cases would be impossible. Activated carbon is an excellent means of removing contaminants eitherat the source where they are concentrated or at the point of use where they maybe dilute.
Thecontinued success of an adsorption system depends on the regeneration ofrecharging the system. This can be doneseveral ways as follows:
1) Remove carbon in bulk
a) reprocess on site
b) return to factory
c) throw away and replace with new
2) Remove all cells
a) refill on site
b) return to factory for refill and servicing
c) use throwaway type cells
3) Regenerate in-place
a) steam, direct heat, recirculating vapor
b) reduce pressure
c) extract with solvent
VERSATILITYOF ACTIVATED CARBON
Activatedcarbon is a universal absorbent. It hasthe ability to remove from air or gas and hold within its capillary pores almostall types of objectionable gases and vapors. They are taken up because of the property of adsorption; the carbonremoves and retains within its microscopic porous structure almost all volatilematerials, whether they are chemicals, solvents, or mixtures of odor-causingsubstances. The only gaseous materialswhich it will not adsorb well are low molecular weight gases such as oxygen,nitrogen, carbon monoxide, and carbon dioxide. Even in this range, some compounds such as ammonia are adsorbed inreasonable quantities and adsorption is a satisfactory way of eliminating themif they do not constitute the major contaminating load. For some low molecular weight reactive gasesimpregnated carbon can be used to combine adsorption and chemical reaction.
The type ofapplication where activated carbon gives the most outstanding performance isthe removal of organic vapors with boiling points above room temperature. These include the essential oils, solvents,organic intermediates, organic waste materials, in fact most of the odors thatexist. Of these, activated carbon takesup a quantity equal to about one-third of its own weight and will adsorb thevapors completely from concentrations varying from pure vapor down to a levelso low that it can be neither smelled nor measured.
Activatedcarbon performs efficiently whether the contaminant concentration is high, low,or variable. No other elimination methodwill work with high efficiency on concentrations which may be as low as afraction of one part per million or billion. The same simple system can be used for hundreds of such problems.
Completetreatment with carbon is a widely used process method. Pass almost any exhaust mixture through adeep bed of activated carbon and everything of an obnoxious nature isremoved. You don’t necessarily have toknow what the pollutant is to remove it with activated carbon; it just does thejob. For example, we do not know exactlywhat Los Angelessmog is, but activated carbon eliminates it completely. If plant operating conditions should change,or if something unexpected should happen in the process, a carbon adsorptionsystem can be relied upon to purify the exhaust. By doing a 100% purification job, the air canbe returned to the building or process gas can be sent back to manufacturingprocess.
Activatedcarbon can be used to remove particulate material in conjunction with gas orliquid adsorption in certain instances. For this purpose it is necessary to use a rather deep bed compared withthat required for adsorption only. Thisprocedure is used in removing oil from compressed air, part of it is present asvapor and part as smoke. Both can beremoved if a deep bed of carbon is used. In the brewing industry, it is common practice to use activated carbonto completely decontaminate air, that is, remove all vapors and harmfulparticulate matter, including bacteria. In such a case, a very deep carbon bed is employed (about 10 feet) andexperience has shown that this does a good job of complete purification.
Because ofits simplicity, activated carbon adsorption can be used separately on each of abattery of fume emitting sources. Thissaves piping and other expenses. Forexample, carbon can be used in convenient adsorption traps to eliminatecontaminants being discharged from tank vents; there are no moving parts andthe trap can breathe freely in either direction. In addition to preventing contaminants fromleaving the tank to the atmosphere, it prevents the contamination of the tankcontents from impurities which may be in the air.
With thistype of venting, tanks can be placed inside of buildings in cases where itwould be more convenient. On submarines,the tanks which hold waste materials are equipped with carbon vents. If this were not done, there would be aserious odor problem. Also, onsubmarines, especially the atomic subs, carbon is used to purify the air usedfrom ventilation. This permits thesubmarines to stay down for more than a month using the same air over andover. The CO2 is removed by usualmethods, oxygen is added, and the carbon takes out the other contaminants.
ACTIVATEDCARBON IN CONJUNCTION WITH OTHER PURIFICATION SYSTEMS
Althoughactivated carbon will remove from exhaust air almost every type ofcontaminating substance, there are cases where the cost of operation can bereduced by removing part of the load ahead of the carbon beds by filtering orscrubbing. For example, it may befeasible to remove a major portion of the heavy contaminating load by scrubbingthe air with water in a packed tower. This may save carbon cost, and result in more economical operation ofthe system.
Activatedcarbon may be used as a final purification step in conjunction with a systemalready installed. For example, if acompany is using electrostatic precipitation and a caustic scrub to clean upits exhaust gases, and if the efficiency of the system is not 100%, it may bepossible to complete the job adding carbon filters.
An excellentcombination treatment method consists of two basic steps, scrubbing the gaswith water and activated carbon adsorption. The water removes particulate matter, some of the vapor if theconcentration is high, and cools the gas if it’s hot. The carbon removes any remaining vapors. Additional non-contaminated air is added tothe stream after the water scrubber so that the air entering the carbonabsorber is not completely saturated. This method is a logical answer to many pollution problems.
Depending onthe type of service, an activated carbon bed may be from ½” thick with 30 to 50feet per minute face velocity to several feet in thickness with velocity in therange of 30 to 200 feet per minute. Acarbon filter might last for a year or more in dilute and intermittent service,or might have to be desorbed as often as once an hour where contaminants arebeing recovered. The capacity ofactivated carbon for repeated adsorption and desorption is tremendous. When removing easily desorbed compounds itcan operate on one hour cycles for years. The installation cost of activated carbon treatment may vary from about$60.00 per thousand cfm to $25,000 per thousand cfm. In the higher brackets, part of the cost maybe in-place desorption equipment which produces values that offset the cost oftreatment. The operating cost per poundof contaminants removed may vary from a fraction of a cent per pound forintermittent standby service on dilute concentrations. These are wide limits, but activated carbonhas wide application.
Activatedcarbon should be considered either as a complete solution or as a treatmentstep for most pollution control problems. Although it will not be the best solution in all cases, it will often bethe best alternative. Its use isincreasing as its amazing capabilities become more widely known.
NEW EMPHASISON INDOOR AIR QUALITY
ACTIVATEDCARBON AIR PURIFICATION FOR HEALTH BENEFITS
Activatedcarbon adsorbs smog and organic vapors from polluted air. Wherever gaseous air contaminants produceirritation of the eyes, nose, throat, or lungs, proper use of the adsorbent mayrelieve such ailments in many individuals. Where irritations or allergic reactions are of concern, activated carbonis useful in removing odors that may arise in spaces that are shut tightly tokeep out the particles.
Activatedcarbon effectively removes odors and “stuffiness”, which may produce headachesand psychic distress in some individuals. It is also useful in hospitals and sick rooms to remove odors caused bydiseases, incontinence, and medication.
Activated carbonremoves from air practically all contaminants present in the form of gas orvapor, including odor, smog and toxic gases. The airstream passes through an activated carbon filter, where thecontaminants are removed and the air with all of its oxygen is recovered inpure form. To remove dust and pollen,one of the standard dust-arresting filters can be used on conjunction withactivated carbon. The combination ofactivated carbon and dust filters is used wherever the removal of both vaporsand particles is desired.
People whosuffer from irritation of the eyes, nose, throat and lungs, have reportedrelief through the use of activated carbon. Whether the irritant is an odor, vapor, smog, smoke or a combination,activated carbon equipment may give complete or partial relief.
Activatedcarbon has been used for years in hospitals. It effectively removes the odors of disinfectants, medicines, andchemicals, as well as other odors found in hospitals, doctor’s offices, andmorgues.
Contaminationof air in a living or working area can come from the outside or inside. Outside air contains smoke, smog, industrialwaste products, automobile exhaust fumes, dust and pollen. Indoor contamination can come from patients,personnel, cooking, pets, tobacco, perfumes, and cleaning compounds. All of these odors can be effectively removedwith activated carbon equipment.
Smog can becompletely removed by activated carbon. The irritant vapors in cigarette smoke can be taken from the air bycarbon adsorption. Activated carbon isnot a cure-all, but experience shows that in a high percentage of cases wherethere are definite irritants, positive benefits have been achieved.
BUILDINGCODE REGULATIONS OF RECIRCULATION OF AIR
Mostmunicipal building codes require minimum amounts of outside air for ventilationof occupied spaces. However, some alsoprovide for the elimination of all or part of such requirements wherever roomair is recirculated through properly installed and maintained odor-removingdevices using activated carbon. Anincreasing number of local authorities allow the substitution of activatedcarbon purified air for outside air, even though not provided for in theircodes, by interpreting purified room air to be the equivalent of outside airfor ventilation purposes.
Publichealth authorities long ago decided that building codes should provide forminimum standards of ventilation. Tothis end, they usually specified, often by an arbitrary rule of thumb, aminimum window area per occupant or per unit of floor area. As engineers developed mechanical means ofventilation, architects sought to use it in lieu of windows and otheropenings. At first, the codes were notchanged. Buildings had to have so manywindows, whether they were actually used or not. Eventually, the codes were altered to allowmechanical supply of a specified amount of air from outside.
In order tomake the minimum requirements less arbitrary, health authorities conductedtests to determine how much fresh air people really need. It was found that discomfort could be causedby excessive temperature, air stillness, humidity, smoke, dust and odors. Therefore, recirculation of room air throughfilters and control of temperatures and humidity could reduce the requirementsfor outside air, a certain amount of which was still considered necessary tosupply oxygen and to remove carbon dioxide and odors.
Next, it wasfound that plenty of oxygen and low enough concentrations of carbon dioxidewould exist in all but the most tightly sealed spaces, owing to normalinfiltration of air through doors and building joints. The ultimate limit in the reduction ofoutside air requirements was thus dictated by the need to eliminate odors from humanoccupancy. New minimums were drawn upthat were based upon the amount of outside air needed to dilute odors to theirthreshold level, or at least to a level that would not produce generaldiscomfort.
ODOR REMOVALBY ADSORPTION: We can nowremove odors by adsorption with activated carbon and eliminate mechanicallysupplied outside air. The technicalcapability of doing this has been proven. The only limiting factor is rigid interpretation of antiquated buildingand health codes.
As was oftenthe case with other forms of air treatment, activated carbon purification wasfirst installed not so much to eliminate outside air as to improve uponconditions. (The code requirements areconservative, as far as health is concerned, but they may permit odor conditionsthat are less than ideal.
COMMUNITIESACCEPTING ODOR ADSORPTION: The demand for reducing or eliminating the requirements foroutside air has been strongest where the cost savings could be the greatest,generally where the climate may be hot or cold. The quickest changing of the codes has been in those places and, also,in localities where the air out of doors may be obviously inferior to the airinside a conditioned space. In somesmog-ridden areas, codes now permit 100 percent recirculation. Where new codes have not been adopted, inspectorssometimes rule that air recirculated through properly installed and maintainedfilters of activated carbon, is in effect, outside air (as far asinterpretation of the code is concerned). Where inasmuch as other sections of the code require a minimum number ofdoors, fire exits, special vents.
Manylocalities have accepted the recommendation of the International Conference ofBuilding Officials, which allows 100 percent recirculation, or the Chicago code, whichallows up to 85 percent recirculation. In some cases, conformance with existing codes may be required, insofaras design and installation of the air conditioning system is concerned, but 100percent recirculation may be allowed in actual operation of the equipment.
Where theuse of activated carbon is contemplated and the situation is properly explainedto the code enforcement authorities, the requirement for outside air is usuallywaived. Members of the American Societyof Heating, Refrigeration and Air Conditioning Engineers usually accept theprinciple of odor adsorption as giving in the ASHRAE Guide and Data Books.
ACTIVATEDCARBON AIR PURIFICATION
Moderntechnology requires many production facilities that must be free of virtuallyall dust, lint, smoke particles, and corrosive or otherwise contaminating gasesand vapors. Such facilities are oftencalled “clean rooms” or “white rooms”. They may be required for the production, testing, or use of suchdelicate or sensitive equipment as missile guidance packages, electroniccomputers, micro chemical balances, optical devices, and space vehiclecomponents.
INCREASE INCLEAN ROOMS: More and more attention isbeing given to contamination control for at least five reasons (1) theprecision and sensitivity of the products needs to be greater (2) thereliability required is much greater (3) smaller and lighter products areneeded (4) more items of that type are being manufactured (5) air pollution isincreasing.
The initialobjectives for clean rooms were the exclusion of particulate matter and thecontrol of humidity and temperature. Particulate matter may be abrasive and may clog small openings anddelicate electrical contacts. High orvariable humidity may promote rusting and corrosion of metals, plus swelling,cracking and distortion in other materials. Variations in temperature may throw both the product and the tools forits manufacture out of alignment or balance.
Recently,contamination from corrosive, toxic, and reactive gases and vapors has beenrecognized as a growing problem; therefore, activated carbon is being usedincreasingly in contamination controlled facilities. Some authorities believe they cannot have areal clean room without it. Activatedcarbon adsorbs most of the gases and vapors that may interfere with clean roomoperations. In addition, it can be usedto reduce the cost of other types of air treatment for clean rooms bypermitting as much as 100% recirculation of the expensive, treated air. The gases that may cause corrosion includesulfur oxides, hydrogen sulfide, mercaptans, nitrogen oxides, hydrochloricacid, salt spray, halogen vapors, refinery gases, smelting gases and smog. Other gases and vapors also may interferewith clean room operations under special conditions. Some products can be contaminated by ordinaryodors and may have to be rejected on that account. In some cases, activated carbon is used whenit is not known what the troublesome contaminants are. Activated carbon removes all organic gasesand vapors and many inorganic types and is an excellent safety precaution toeliminate any extraneous compounds which might affect the work being done.
CARBONEFFICIENCY AND CAPACITY
Activatedcarbon has high efficiency for the removal of all such gases and vapors. It also has high capacity for most of them,including asphalt fumes, carbon didulfide, chlorinated hydrocarbons, tobaccosmoke vapor, smog and odors. The gasesand vapors for which activated carbon has a low capacity may need specialconsideration. They include some freons,formic acid, sulfur dioxide, some amines, some mercaptans, arsine, stibine,carbon dioxide, nitric acid, ammonia and formaldehyde. Standard carbon filters may be employeddirectly for their removal if the total amount of contaminant is small, thatis, if they are found either in low concentrations or in moderateconcentrations for a limited period of time. Special techniques, such as impregnation of the carbon with additives,increase absorptive capacity for some contaminants. Another technique that can be used in somecases is in-place regeneration of the carbon.
HOW WELLWILL ACTIVATED CARBON WORK FOR YOU?
Cigarettesmoke odor 4
Citrusand other fruits 4
Dieselfunes fumeodor 4
FilmProcessing Odors 3
Lubricatingoils and greases 4
Methylbuty ketone 4
Methylcellosolve acetate 4
Methylethy ketone 4
Methylisobuty ketone 4
Naptha(coal tar) 4
Packinghouse odors 4
Paintand redecorating odors 4
Pasteand glue 4
Popcornand candy 4
Spoiledfood stuff 4
Theatricalmakeup odors 4
Tobaccosmoke odor 4
Index # Meaning
4. Carbon works at High Capacity for all materials in thiscategory.
3. Carbon works at satisfactory capacity for all materials in thiscategory.
2. Carbon may or may not give satisfactory capacity for thesematerials.
1. Carbon absorption is low for these materials. Activated carbon cannot normally be used toremove these materials.
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