Activated charcoal is carbon that has been treated with oxygen. The treatment results in highly porous charcoal. These tiny holes give the charcoal a surface area of 300-2,000 m2/g, allowing liquids or gases to pass through the charcoal and interact with the exposed carbon. The carbon adsorbs a wide range of impurities and contaminants, including chlorine, odors, and pigments. Other substances, like sodium, fluoride, and nitrates, are not as attracted to the carbon and are not filtered out.

Since adsorption works by chemically binding the impurities to the carbon, the active sites in the charcoal eventually become filled. Activated charcoal filters become less effective with use and have to be recharged or replaced.

What Activated Charcoal Will and Won’t Filter

The most common everyday use of activated charcoal is to filter water. It improves water clarity, diminishes unpleasant odors, and removes chlorine. It’s not effective for removing certain toxic organic compounds, significant levels of metals, fluoride, or pathogens. Despite persistent urban legend, activated charcoal only weakly adsorbs alcohol and it not an effective means of removal.

• Chlorine
• Chloramine
• Tannins
• Phenol
• Some drugs
• Hydrogen sulfide and some other volatile compounds that cause odors
• Small amounts of metals, such as iron, mercury, and chelated copper

It won’t remove:

• Ammonia
• Nitrates
• Nitrites
• Fluoride
• Sodium and most other cations
• Significant amounts of heavy metals, iron, or copper
• Significant amounts of hydrocarbons or petroleum distillates
• Bacteria, protozoa, viruses, and other microorganisms

Activated Charcoal Effectiveness

Several factors influence the effectiveness of activated charcoal. The pore size and distribution varies depending on the source of the carbon and the manufacturing process. Large organic molecules are absorbed better than smaller ones. Adsorption tends to increase as pH and temperature decrease. Contaminants are also removed more effectively if they are in contact with the activated charcoal for a longer time, so flow rate through the charcoal affects filtration.

Activated Charcoal De-Adsorption

Some people worry that activated charcoal will de-adsorb when the pores become full. While the contaminants on a full filter aren’t released back into the gas or water, used activated charcoal is not effective for further filtration. It is true that some compounds associated with certain types of activated charcoal may leach into the water. For example, some charcoal used in an aquarium might start to release phosphates into the water over time. Phosphate-free products are available.

Recharging Activated Charcoal

Whether or not you can or should recharge activated charcoal depends on its purpose. It’s possible to extend the life of an activated charcoal sponge by cutting or sanding off the outer surface to expose the interior, which might not have fully lost its ability to filter media. Also, you can heat activated charcoal beads to 200 C for 30 minutes. This will degrade the organic matter in the charcoal, which can then be rinsed away, but it won’t remove heavy metals.

For this reason, it’s generally best to just replace the charcoal. You can’t always heat a soft material that has been coated with activated charcoal because it might melt or release toxic chemicals of its own, basically contaminating the liquid or gas you want to purify. The bottom line here is that you possibly could extend the life of activated charcoal for an aquarium, but it’s inadvisable to try to recharge a filter used for drinking water.

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Message Body:
Hello,

we are looking for (waterproof) activated carbon honeycomb blocks 50*50*50mm or 100*x100*x50mm for air filtration purposes.

our main focus is ozone reduction, can you help us with this?

How much can you deliver asap?
What Incoterms can you offer? DAP, DDP?
We would love express delivery, means the fast the better. possible for you?

best regards,
Franziska Fisches

Geschäftsführerin

MAVENET GmbH
Tel.: +49 30 398 204 401
www.mavenet-innovations.com

Handelsregister: Amtsgericht Charlottenburg, HRB 166140B

3 Dec 2020, 05:47

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Petroleum coke, also called pet coke or petcoke, is a solid carbon material that resembles coal; it is a product of oil refining

Would like to have the contact details of  equipment manufacturers / suppliers where pet coke is used as raw material alternative to shell Charcoal , Wood Charcoal and Coal

Somasekhar Reddy Nelvoy   somasekharreddyn  @ googlemail

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Hoping you will be fine,

We intend to purchase the given below items urgently against 100% irrevocable LC at sight basis. Kindly send us urgently your lowest and competitive proforma invoice on ex-work/FOB as well as CIF basis against 100% LC at sight basis alongwith COA/printable brochures/specification sheets exactly according to our below required specifications. The detail of the urgently required items is as under:-
Sr. #. Description of Item Required Quantity
1. Carbon Molecular Sieve————3600Kg(3.6Tons)
Chemical Name: Activated Carbon > 95% wt/wt
CAS #. C (7440-44-0)
For the Production of pure N2 gas from air by using adsorption process Product Name: MOLSIEVON 3A (Shirasagi MSC-3A) or Equivalent
Specific Gravity (Water=1)2.0-2.1
Pore Size: 3A
Solubility in Water: Insoluble
Shape= Cylinderical, Dia= 2.0-2.5mm, Length= 5mm
Made: Japan/China/Europe OR Equivalent

2. Molecular Sieve——560Kg
Type: 10X Size: 8-12 mesh #
Origin: America/Europe/China or Equivalent
Packing: In Poly lined Hard Fiber/Paper/Composite Drums

3. Molecular Sieve———–420Kg
Type: 13X
Size: 4-8 mesh #
Origin: America/Europe/China or Equivalent
Packing: In Poly lined Hard Fiber/Paper/Composite Drums

Note-1:- Please clearly write the Country of Origin, Product number, Brand Name and COA/brochures/Technical specifications(exact according to our required specifications) of the quoted item.
Note-2:-  Prices/P.I and COA/brochures/printable technical specifications must be attached separately.
Note-3:- Kindly send us your offer alongwith COA/brochures/printable technical specifications only on our given below e-mail address instead of Made in China or Alibaba’s account I.D.
Note-4:- Payments through  Alibaba Cashier Account/TT/Wire Transfer/Advance payments are prohibited from Pakistan now after 1st JAN-2019. Now according to the new international trade policy of Pakistani Govt., only 100% LC at site is allowed and we are unable to import in Pakistan now w/o 100% LC even US$1.00.

**Payments can be sent from anywhere, but Pakistani-customs is not clearing any shipment without bank’s EIF(I-Form). As we already told you that  payments through Alibaba Cashier Account/TT/Wire Transfer/Advance payments was possible till December-2018 and payments through Alibaba Cashier Account/TT/Wire Transfer/Advance payments are prohibited from Pakistan now after 1st JAN-2019 and it is not possible now. Without Bank involving or 100% LC the bank could not issue the I-Form. (EIF/I-form means the Payment transaction proof against shipment) and without bank’s issued I-form Custom will not clear any shipment. We already faced the same problem in last of December-2018, when the policy was being changed. So kindly quote only against 100% LC at sight basis.

Note-5:-  Kindly quote prices against 100% Irrevocable LC at sight basis. (LC means that our bank will collect payment from us against your sent Proforma Invoice and the payment from our bank will be sent to your bank against shipment’s documents. We will send you the LC Draft for your approval before opening an Original Bank LC. All LC Charges will be born by us in our Bank and you will receive your actual amount from your Bank).
Note-6:- Our final destination port is Karachi, Pakistan.
Note-7:- The quoted product must be according to our required specifications instead of others.
Note-8:- Kindly send us two offers one for packed into 25Kg/50Kg polylined PP bags and the other for packed into 25Kg/50Kg polylined Hard fiber/composite/Paper Drums.

Waiting for your early response impatiently,

Thanking you with best regards,

Your’s Truly,

Saad Sindhu
Legal Scientific Company.
P-489, Near Gaus-e-Azam Chowk, Shadman-City, Phase-I,
Civil Hospital Road, Bahawalpur, Pakistan.
Ph/Fax:+92-62-2720258, Cell:+92-306-0780958
E-Mail: legalscientific[DOT]co[AT]gmail[DOT]com

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1. Iodine value (400 ~ 1300): refers to the amount of iodine adsorbed by activated carbon in 0.02N12 / KL aqueous solution. The iodine value is related to the pore surface area with a diameter greater than 10A. The iodine value is one of the criteria for judge the price of activated carbon.

2. Butane value: Butane value is the amount of butane adsorbed per unit weight of activated carbon after saturated air and butane pass through the carbon bed at a specific temperature and specific pressure.

3. Ash content (6-16): There are two types of ash of activated carbon, one is surface ash and the other is internal ash content. Normally, the ash of activated carbon refers to internal ash.

4. Water content (<5): It is a measure of how much water is contained in carbon, that is, the percentage of the weight of water adsorbed in activated carbon.

5. Hardness: The hardness value refers to the resistance of the granular activated carbon to the decay movement of the steel ball in the RO-TAP instrument. Hardness is an indicator for measuring the mechanical strength of activated carbon.

6. Carbon tetrachloride CTC (%): The carbon tetrachloride value is an indicator of the total pore volume, which is measured with a saturated CCI4 gas flow of zero degrees Celsius through a 25 degree carbon bed. That is, the adsorption function of activated carbon depends on the carbon tetrachloride value. The measurement method is to use activated carbon to adsorb carbon tetrachloride, and the measured result is the adsorption rate of activated carbon. Generally, the highest carbon tetrachloride value of activated carbon is 80. Activated carbon manufacturers in Beijing and Hebei have more than 80% to reach 60%.

7. Molasses value:  The molasses value is a method to measure the relative decolorization ability of activated carbon in boiling molasses solution. The molasses value is interpreted as a surface area with a pore diameter greater than 28A. Because molasses is a mixture of multiple components, this parameter must be tested in strict accordance with the instructions. The molasses value is obtained by calculating the ratio of the optical density of the filter by treating the molasses liquid with a standard sample of activated carbon and a sample of activated carbon to be tested.

8. Bulk weight (400-600): Bulk weight is a method of measuring the quality of a specific amount of carbon. By gradually adding activated carbon to a graduated drum to 100cc, and measuring its mass. This value is used to calculate the amount of activated carbon needed to fill a specific adsorption device. Simply put, the bulk weight is the weight of activated carbon per unit volume.

9. Particle density – The particle density is the weight of the particulate carbon per unit volume, excluding the particles and the space between cracks greater than 0.1 mm.

10. Methythioninium Chloride (100-300):   The Methythioninium Chloride value refers to the number of milligrams of Methythioninium Chloride absorbed when a solution of 1.0 g of carbon and a concentration of 1.0 mg / L of Methythioninium Chloride reaches equilibrium.

11. Wear value

The wear value is an index for measuring the wear resistance of activated carbon. The wear value of granular activated carbon indicates that the particles reduce the resistance of the particles during the treatment process. It is calculated by determining the ratio of the average diameter of the final particles to the average diameter of the original particles.

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The chemical composition of charcoal is very similar to graphite. Useful properties of activated charcoal can be contributed to the huge number of pores and hence activated charcoal exhibits very high absorbent and catalytic properties.

Activated carbon is used in methane and hydrogen storage,  air purification, decaffeination, gold purification, metal extraction, water purification, medicine, sewage treatment, air filters in gas masks and respirators, filters in compressed air, teeth whitening, and many other applications.

Activated carbon industrial application

One major industrial application involves use of activated carbon in metal finishing for purification of electroplating solutions. For example, it is the main purification technique for removing organic impurities from bright nickel plating solutions. A variety of organic chemicals are added to plating solutions for improving their deposit qualities and for enhancing properties like brightness, smoothness, ductility, etc. Due to passage of direct current and electrolytic reactions of anodic oxidation and cathodic reduction, organic additives generate unwanted breakdown products in solution. Their excessive build up can adversely affect plating quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level.

Medical uses

Activated charcoal for medical use

Activated carbon is used to treat poisonings and overdoses following oral ingestion. Tablets or capsules of activated carbon are used in many countries as an over-the-counter drug to treat diarrhea, indigestion, and flatulence.

However, activated charcoal shows no effect of intestinal gas and diarrhea, and is, ordinarily, medically ineffective if poisoning resulted from ingestion of corrosive agents such as alkalis and strong acids, iron, boric acid, lithium, petroleum products, or alcohol. Activated carbon will not prevent these chemicals from being absorbed into the human body.

It is particularly ineffective against poisonings of strong acids or alkali, cyanide, iron, lithium, arsenic, methanol, ethanol or ethylene glycol.

Incorrect application (e.g. into the lungs) results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not initiated.

Activated Charcoal is a powerful tool for emergency cleansing of the gastrointestinal tract, perhaps the most effective remedy known today. It can be used in cases of poisoning from virtually any toxic substance. Activated charcoal reduces the absorption of poisonous substances up to 60%.

One teaspoon of activated charcoal has a surface area of approximately 10 000 square feet. It adsorbs and helps eliminate toxins, heavy metals, chemicals, pharmaceutical drugs, morphine, pesticides from your body.

Activated carbons can be also use to whiten tooth

Benefits of Activated Charcoal and Its Uses:

• Poisoning by various chemical substances, drugs, toxic heavy metals, alkaloids
• Overall body detoxification
• Food poisoning
• Treating stomach pain caused by excess gas, diarrhea, or indigestion.
• Body odor and bad breath
• Hepatitis: chronic and acute viral
• Withdrawal syndrome (as a rule, is used for drinking, not for drug addiction)
• Intoxication caused by chemotherapy or radiotherapy
• Various skin ailments
• Inflammation
• Helps lower cholesterol, triglycerides and lipids found in the blood.

Analytical chemistry applications

Activated carbon, in 50% w/w combination with celite, is used as stationary phase in low-pressure chromatographic separation of carbohydrates (mono-, di-trisaccharides) using ethanol solutions (5–50%) as mobile phase in analytical or preparative protocols.

Environmental applications

Activated carbon is usually used in water filtration systems. In this illustration, the activated carbon is in the fourth level (counted from bottom).

Carbon adsorption has numerous applications in removing pollutants from air or water streams both in the field and in industrial processes such as:

• Spill cleanup
• Groundwater remediation
• Drinking water filtration
• Air purification
• Volatile organic compounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes.

During early implementation of the 1974 Safe Drinking Water Act in the US, EPA officials developed a rule that proposed requiring drinking water treatment systems to use granular activated carbon. Because of its high cost, the so-called GAC rule encountered strong opposition across the country from the water supply industry, including the largest water utilities in California. Hence, the agency set aside the rule. Activated carbon filtration is an effective water treatment method due to its multi-functional nature. There are specific types of activated carbon filtration methods and equipment that are indicated – depending upon the contaminants involved.

Activated carbon is also used for the measurement of radon concentration in air.

Agriculture uses

Activated carbon (charcoal) is an allowed substance used by organic farmers in both livestock production and wine making. In livestock production it is used as a pesticide, animal feed additive, processing aid, nonagricultural ingredient and disinfectant. In organic winemaking, activated carbon is allowed for use as a processing agent to adsorb brown color pigments from white grape concentrates.

Activated carbon has been used as a purification agent since ancient Egypt and India. It was introduced to the modern world via the sugar refineries of 1800s Europe, and its use quickly swept the globe. Rapidly evolving technology has led to its expansion ever since, and today activated carbon plays a key role in a vast number of industries, from wastewater treatment to pharmaceutical manufacturing. It is also used in agriculture to improve crop yields.

activated carbon adsorbs and removes targeted compounds along its vast surface area. Although it has been used in modern agriculture for only a decade or so, research shows that activated carbon can boost agriculture in several important ways.

Seed Protection

Fungicides and herbicides are absolutely essential to modern agriculture, preventing harmful species from taking over and destroying crops. Unfortunately, these products can also be damaging to newly planted seeds. When mixed with fertilizer or used to coat vulnerable seeds, activated carbon can ensure the survival of the vast majority of seeds. The surface chemistry of the activated carbon can even be manipulated to ensure the best pH for different types of seeds. In some cases, activated carbon can also be mixed into the soil to protect fields from accidental spills of fungicides or herbicides.

Time-Release Nutrient Delivery

Although most popular applications of activated carbon involve removing toxic or noxious compounds, activated carbon’s tremendous storage abilities also allow it to deliver helpful compounds on a timed basis. For agriculture, activated carbon can store nutrients that are essential to plant health and then release them over time. For example, activated carbon can be impregnated with ethylene, the naturally occurring hormone that causes plants to ripen. The ethylene can then be delivered to help all of the fruits in a crop ripen at the same time.

Herbicide Catalyst

Activated carbon is a powerful catalyst for oxidation, and can be used for this purpose in the production of herbicides. It is important to choose a powdered activated carbon (PAC) with strong characteristics of filtration and sedimentation. When specifically prepared for this purpose, PAC can help to create a highly effective herbicide.

Purification and Decolorization

Like any other chemical product, agrochemicals need to be pure and clean to create the desired results. Colorization also matters in consumer preferences, with homogeneously colored products being seen as more desirable.  Activated carbon is used in the agrochemical industry to remove unwanted compounds and create the pure, decolorized products that consumers deserve.

Agriculture is a relative newcomer to the list of industries that have been revolutionized by the use of activated carbon. Yet research shows that it works across a wide range of agricultural applications. Activated carbon comes in many types and forms, each with its own unique characteristics. For the best results, it is important to consult with an activated carbon expert who can help you sort through the options and select just the right product to meet your needs.

Are you interested in purchasing activated carbon for a specific application? Do you require expert guidance in choosing the right impregnation for your needs? With more than 70 years of experience in the activated carbon industry, Oxbow Activated Carbon is proud to provide the most diverse line of activated carbon products on the market today. We provide both standard and custom impregnations, spent carbon disposal and reactivation, and numerous other specialized services. We pride ourselves on our individualized customer service, and we look forward to becoming your one-stop shop for all your activated carbon needs.

Distilled alcoholic beverage purification

Activated carbon filters (AC filters) can be used to filter vodka and whiskey of organic impurities which can affect color, taste, and odor. Passing an organically impure vodka through an activated carbon filter at the proper flow rate will result in vodka with an identical alcohol content and significantly increased organic purity, as judged by odor and taste.^{[citation needed]}

Fuel storage

Research is being done testing various activated carbons’ ability to store natural gas^[2][1] and hydrogen gas.^[1][2] The porous material acts like a sponge for different types of gases. The gas is attracted to the carbon material via Van der Waals forces. Some carbons have been able to achieve bonding energies of 5–10 kJ per mol. The gas may then be desorbed when subjected to higher temperatures and either combusted to do work or in the case of hydrogen gas extracted for use in a hydrogen fuel cell. Gas storage in activated carbons is an appealing gas storage method because the gas can be stored in a low pressure, low mass, low volume environment that would be much more feasible than bulky on-board pressure tanks in vehicles. The United States Department of Energy has specified certain goals to be achieved in the area of research and development of nano-porous carbon materials. All of the goals are yet to be satisfied but numerous institutions, including the ALL-CRAFT program,^[1][2][13]are continuing to conduct work in this promising field.

Gas purification

Filters with activated carbon are usually used in compressed air and gas purification to remove oil vapors, odor, and other hydrocarbons from the air. The most common designs use a 1-stage or 2 stage filtration principle in which activated carbon is embedded inside the filter media.

Activated carbon filters are used to retain radioactive gases within the air vacuumed from a nuclear boiling water reactor turbine condenser. The large charcoal beds adsorb these gases and retain them while they rapidly decay to non-radioactive solid species. The solids are trapped in the charcoal particles, while the filtered air passes through.

Chemical purification

Activated carbon is commonly used on the laboratory scale to purify solutions of organic molecules containing unwanted colored organic impurities.

Filtration over activated carbon is used in large scale fine chemical and pharmaceutical processes for the same purpose. The carbon is either mixed with the solution then filtered off or immobilized in a filter.

Mercury scrubbing

Activated carbon, often infused with sulfur^[14] or iodine, is widely used to trap mercury emissions from coal-fired power stations, medical incinerators, and from natural gas at the wellhead. This carbon is a special product costing more than US$4.00 per kg.

Since it is often not recycled, the mercury-laden activated carbon presents a disposal dilemma. If the activated carbon contains less than 260 ppm mercury, United States federal regulations allow it to be stabilized (for example, trapped in concrete) for landfilling. However, waste containing greater than 260 ppm is considered to be in the high-mercury subcategory and is banned from landfilling (Land-Ban Rule). This material is now accumulating in warehouses and in deep abandoned mines at an estimated rate of 100 tons per year.

The problem of disposal of mercury-laden activated carbon is not unique to the United States. In the Netherlands, this mercury is largely recovered and the activated carbon is disposed of by complete burning, forming carbon dioxide (CO2).

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Coconut shell based activated carbons has Lower Ash Content, Higher Amount of Micropores, Higher Iodine Number, Excellent Hardness and it is very efficient in the removal of small size organic impurities.

Activated carbon from coconut shell has predominantly pores in micro pore range. Almost 85-90% surface area of coconut shell activated carbon exists as micro-pores. These small pores match the size of contaminant molecules in drinking water and therefore are very effective in trapping them.

Macro-pores are considered as an access point to micro-pores. Meso-pores do not usually play an important role in the adsorption unless the surface area of these pores is large, 400 m2/g or more. The predominance of micro-pores in coconut shell carbon gives it tight structure and provides good mechanical strength and hardness and also high resistance to resist attrition or wearing away by friction.

Coconut shell-based AC has the most micropores. Micropores are defined as pores less than 20-angstrom units (two nm) in diameter.  Coconut shell based carbons are excellent for Point of Use (POU) and Point of Entry (POE) applications because of lower ash content and excellent microporus structure.

The very large internal surface areas characterized by microporosity along with high hardness and low dust make these coconut shell carbons particularly attractive for water and critical air applications as well as point-of-use water filters and respirators.

Coconut Activated Carbon Hardness Number is around 98 but Bituminous Coal Activated carbons hardness number is only 85 – 90.

Some of other features which carbon industries, see as a great advantage in favour of coconut carbon are as follows:

• Coconut is a renewable source of carbon
• Coconuts grow throughout the year, with harvesting generally occurring 3-4 times in a year
• Coconut tree can be preserved for many years

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Activated carbon features great adsorptive ability and reflects a wide array of dissolved chlorine and organics. You can custom-make activated carbon to fit your particular requirements.

Activated carbon

Any organic material with high contents of coal, peat and coconut shells can be used to make this type of carbon. This kind of carbon is also called activated charcoal, a content that makes the end product highly porous. It features big surface area exposed for adsorption and chemical reactions. With high level micro-porosity, one gram of active carbon has a surface area of around 2.17 tennis courts. The surface area is determined by nitrogen gas adsorption.

Advanced chemical treatments can increase the adsorbing elements of the material, however proper activation of relevant applications is accessible from high surface areas only. Thermal decomposition done in a heat furnace can transform the carbon based material into activated carbon. Controlled heat and environment is employed to operate the heat furnace.

The end point residue generally has a big surface area per unit volume to facilitate adsorption as it has large network of submicroscopic pores. The walls of the pores offer needed adsorption to the surface molecules.

Uses of activated carbon 

• It is mainly used to remove odors and chemicals that color the water.
• It can remove strong smelling natural gases like hydrogen sulphide from water contents.
• It is capable to remove little volumes of iron, mercury and chelated copper.
• Chlorine from water is absorbed and removed while leaving an aspect called ammonia.
• It can decrease or remove volatile organic chemicals, pesticides, radon, herbicides, benzene and many other compounds and solvents.

During the activation process, a lot of pores, made of molecular dimensions are developed within the structure. The structure can contain a large internal surface that enormously attracts molecules of its surrounding gases and liquids. The whole power of this force is equal to the molecular system of the atmospheric medium. Moreover, this content is a technique that can remove various factors from a given mixture.

These are employed as de-coloring and cleansing agents in a lot of processes because they are capable to absorb 10% to 90% impurities from different Aquarius solutions. Activated carbon works in purification process that involves getting the organic compounds attracted to the activated carbon as the water pass through the filter, and two contents get reaction in form of being chemically bounded to each other.

Pollutants don’t get into the sink or glass as the pores of the filter does not allow big molecules to pass through. Get more information about the forms, process and reason behind activated carbon and its ideas.

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Materials for activated carbon in use worldwide are as follows:

Coconut shell

Powdered activated carbon Raw Materials

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Activated carbon can be considered as a material of phenomenal surface area made up of millions of pores – rather like a “molecular sponge”.  Activated carbon is a microporous inert carbon matrix with a very large internal surface (700 to 1 500 m²/g). The internal surface is ideal for adsorption. Activated carbon is made from materials containing amorphous carbon, such as wood, coal, peat, coconut shells… It is formed via a thermal process, where volatile components are removed from the carbon-laden material (raw material) in the presence of oxygen.

The process by which such a surface concentrates fluid molecules by chemical and/or physical forces is known as ADSORPTION (whereas, ABSORPTION is a process whereby fluid molecules are taken up by a liquid or solid and distributed throughout that liquid or solid).

In the physical adsorption process, molecules are held by the carbon’s surface by weak forces known as Van Der Waals Forces resulting from intermolecular attraction. The carbon and the adsorbate are thus unchanged chemically. However, in the process known as CHEMISORPTION molecules chemically react with the carbon’s surface (or an impregnant on the carbon’s surface) and are held by much stronger forces – chemical bonds.

In general terms, it is necessary to present the molecule to be adsorbed to a pore of comparable size.  In this way the attractive forces coupled with opposite wall effect will be at a maximum and should be greater than the energy of the molecule.

For example, a fine pored coconut shell carbon has poor decolorizing properties because color molecules tend to be larger molecular species and are thus denied access to a fine pore structure. In contrast, coconut shell carbons are particularly efficient in adsorbing small molecular species. Krypton and Xenon, for instance, are readily adsorbed by coconut shell carbon but readily desorb from large pored carbons such as wood.

Maximum adsorption capacity is determined by the degree of liquid packing that can occur in the pores. In very high vapor pressures, multi-layer adsorption can lead to capillary condensation even in mesopores (25A).

Activated Carbon Adsorption Capacity

The effectiveness at which activated carbon can remove contaminants from a stream is not based on the quantity of carbon, but, the activated carbon adsorption capacity. The greater the capacity, the more contaminants the activated carbon will be able to adsorb in volume. However, due to natural carbon’s limitations, it is not able to adsorb certain contaminants, as there molecular weight are to low to be treated through this process alone.

Active carbon is most effective against compounds that hold a high molecular weight and low solubility due to activated carbon having a high molecular weight as well. If there is ever an uncertainty if a specific contaminant will be removed in the adsorption process, referral is to be made to the solubility and molecular weight of said containment.

If adsorption capacity is plotted against pressure (for gases) or concentration (for liquids) at constant temperature, the curve so produced is known as an ISOTHERM. Adsorption increases with increased pressure and also with increasing molecular weight, within a series of a chemical family. Thus, methane (CH4) is less easily adsorbed than propane (C3H8).

Efficiency is determined by the type of pollutant, the type of activated carbon which is used and the temperature and humidity of the waste gases. An effective installation can be expected to realise a yield between 95 – 98 % for input concentrations of 500 – 2 000 ppm.

If effective, concentrations can typically be brought from 400 – 2 000 ppm to under 50 ppm.

In foundries, an end concentration of 20 mg/Nm³ VOC has been established

Mercury can be brought down to less than 0.05 mg/Nm³. Dioxins to less than 0.1 ng TEQ/Nm³ and, for odour and H₂S, yields of 80 – 95 % have been established

This is a useful fact to remember when a particular system has a number of components.

Activated carbon adsorption mechanism

After equilibrium, it is generally found that, all else being equal, the higher molecular weight species of a multi-component system are preferentially adsorbed. Such a phenomenon is known as competitive or preferential adsorption – the initially adsorbed low molecular weight species desorbing from the surface and being replaced by higher molecular weight species. Physical adsorption in the vapor phase is affected by certain external parameters such as temperature and pressure.

The adsorption process is more efficient at lower temperatures and higher pressures since molecular species are less mobile under such conditions. Such an effect is also noticed in a system where moisture and an organic species are present. The moisture is readily accepted by the carbon surface but in time desorbs as the preferred organic molecules are selected by the surface.

This usually occurs due to differences in molecular size but can be also attributable to the difference in molecular charge. Generally speaking, carbon surfaces dislike any form of charge – since water is highly charged (ionic) relative to the majority of organic molecules the carbon would prefer the organic to be adsorbed.

Primary amines possess less charge on the nitrogen atom than secondary amines that in turn have less than tertiary amines. Thus, it is found that primary amines are more readily adsorbed than tertiary amines.

High levels of adsorption can be expected if the adsorbate is a reasonably large bulky molecule with no charge, whereas a small molecule with high charge would not be expected to be easily adsorbed.

Molecular shape also influences adsorption but this is usually of minor consideration. In certain situations, regardless of how the operating conditions can be varied, some species will only be physically adsorbed to a low level. (Examples are ammonia, sulfur dioxide, hydrogen sulfide, mercury vapor and methyl iodide). In such instances, the method frequently employed to enhance a carbon’s capability is to impregnate it with a particular compound that is chemically reactive towards the species required to be adsorbed.

Since carbon possesses such a large surface (a carbon granule the size of a “quarter” has a surface area in the order of ½ square mile!) coating of this essentially spreads out the impregnant over a vast area. This, therefore, greatly increases the chance of reaction since the adsorbate has a tremendous choice of reaction sites. When the adsorbate is removed in this way the effect is known as CHEMISORPTION.

Unlike physical adsorption the components of the system are changed chemically and the changed adsorbate chemically held by the carbon’s surface and desorption in the original form is nonexistent. This principle is applied in many industries, particularly in the catalysis field, where the ability of a catalyst can be greatly increased by spreading it over a carbon surface.

The effect of activated carbon on the adsorbate in water comes from two aspects: on the one hand, physical adsorption, the internal force of the activated carbon is in a balanced state under the force from all directions of the water body, and the external molecules are not balanced, so that the molecules adsorb to the activated carbon On the surface; on the other hand, it is chemical adsorption, because there is a chemical interaction between activated carbon and the adsorbed substance.

The adsorption of activated carbon on pollutants in water is the result of the combined action of the above two kinds of adsorption. There are four steps in the adsorption process of activated carbon on the adsorbate in water: first, due to the convection effect of the water body, the adsorbate diffuses onto the surface of the activated carbon; second, the adsorbate molecules diffuse into the large pores of the activated carbon through the liquid film; Third, the adsorbate molecules reach the micropores due to surface diffusion; fourth, the adsorbent molecules in water are adsorbed on the surface of the activated carbon pores.

Activated carbon adsorption equilibrium is a state of dynamic equilibrium. When the adsorption rate and the desorption rate of activated carbon in the solution are equal, that is, when the amount of activated carbon adsorption per unit time is equal to the amount of desorption, the concentration of the adsorbed substance in the solution and the concentration on the surface of the activated carbon will no longer change. For adsorption equilibrium.

Adsorption capacity and adsorption speed are two important indicators to measure the adsorption process of activated carbon. The adsorption capacity is reflected by the adsorption amount qe, which is mainly affected by the pore size and structure of activated carbon. In addition, temperature and pH value also affect the adsorption capacity of activated carbon.

Adsorption speed refers to the amount of material adsorbed per unit weight of adsorbent per unit time, which is mainly determined by the contact time of water and adsorbent. Because the adsorption reaction is an exothermic reaction, low temperature is usually beneficial to accelerate the adsorption rate.

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