A gram of activated carbon can have a surface area in excess of 500 m2 (5,400 sq ft), with 3,000 m2 (32,000 sq ft) being readily achievable. Carbon aerogels, while more expensive, have even higher surface areas, and are used in special applications.coalactivatedcarbon.com
Under an electron microscope, the high surface-area structures of activated carbon are revealed. Individual particles are intensely convoluted and display various kinds of porosity; there may be many areas where flat surfaces of graphite-like material run parallel to each other, separated by only a few nanometers or so. These micropores provide superb conditions for adsorption to occur, since adsorbing material can interact with many surfaces simultaneously. Tests of adsorption behaviour are usually done with nitrogen gas at 77 K under high vacuum, but in everyday terms activated carbon is perfectly capable of producing the equivalent, by adsorption from its environment, liquid water from steam at 100 °C (212 °F) and a pressure of 1/10,000 of an atmosphere.
James Dewar, the scientist after whom the Dewar (vacuum flask) is named, spent much time studying activated carbon and published a paper regarding its adsorption capacity with regard to gases. In this paper, he discovered that cooling the carbon to liquid nitrogen temperatures allowed it to adsorb significant quantities of numerous air gases, among others, that could then be recollected by simply allowing the carbon to warm again and that coconut based carbon was superior for the effect. He uses oxygen as an example, wherein the activated carbon would typically adsorb the atmospheric concentration (21%) under standard conditions, but release over 80% oxygen if the carbon was first cooled to low temperatures.
Physically, activated carbon binds materials by van der Waals force or London dispersion force.
Activated carbon does not bind well to certain chemicals, including alcohols, diols, strong acids and bases, metals and most inorganics, such as lithium, sodium, iron, lead, arsenic, fluorine, and boric acid.
Activated carbon adsorbs iodine very well. The iodine capacity, mg/g, (ASTM D28 Standard Method test) may be used as an indication of total surface area.
Carbon monoxide is not well adsorbed by activated carbon. This should be of particular concern to those using the material in filters for respirators, fume hoods or other gas control systems as the gas is undetectable to the human senses, toxic to metabolism and neurotoxic.
Substantial lists of the common industrial and agricultural gases adsorbed by activated carbon can be found online.
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can be used as a substrate for the application of various chemicals to improve the adsorptive capacity for some inorganic (and problematic organic) compounds such as hydrogen sulfide (H2S), ammonia (NH3), formaldehyde (HCOH), mercury (Hg) and radioactive iodine-131(131I). This property is known as chemisorption.
Iodine number
Many carbons preferentially adsorb small molecules. Iodine number is the most fundamental parameter used to characterize activated carbon performance. It is a measure of activity level (higher number indicates higher degree of activation) often reported in mg/g (typical range 500–1200 mg/g). It is a measure of the micropore content of the activated carbon (0 to 20 Å, or up to 2 nm) by adsorption of iodine from solution. It is equivalent to surface area of carbon between 900 and 1100 m2/g. It is the standard measure for liquid-phase applications.
Iodine number is defined as the milligrams of iodine adsorbed by one gram of carbon when the iodine concentration in the residual filtrate is at a concentration of 0.02 normal (i.e. 0.02N). Basically, iodine number is a measure of the iodine adsorbed in the pores and, as such, is an indication of the pore volume available in the activated carbon of interest. Typically, water-treatment carbons have iodine numbers ranging from 600 to 1100. Frequently, this parameter is used to determine the degree of exhaustion of a carbon in use. However, this practice should be viewed with caution, as chemical interactions with the adsorbate may affect the iodine uptake, giving false results. Thus, the use of iodine number as a measure of the degree of exhaustion of a carbon bed can only be recommended if it has been shown to be free of chemical interactions with adsorbates and if an experimental correlation between iodine number and the degree of exhaustion has been determined for the particular application.
Molasses
Some carbons are more adept at adsorbing large molecules. Molasses number or molasses efficiency is a measure of the mesopore content of the activated carbon (greater than 20 Å, or larger than 2 nm) by adsorption of molasses from solution. A high molasses number indicates a high adsorption of big molecules (range 95–600). Caramel dp (decolorizing performance) is similar to molasses number. Molasses efficiency is reported as a percentage (range 40%–185%) and parallels molasses number (600 = 185%, 425 = 85%). The European molasses number (range 525–110) is inversely related to the North American molasses number.
Molasses Number is a measure of the degree of decolorization of a standard molasses solution that has been diluted and standardized against standardized activated carbon. Due to the size of color bodies, the molasses number represents the potential pore volume available for larger adsorbing species. As all of the pore volume may not be available for adsorption in a particular waste water application, and as some of the adsorbate may enter smaller pores, it is not a good measure of the worth of a particular activated carbon for a specific application. Frequently, this parameter is useful in evaluating a series of active carbons for their rates of adsorption. Given two active carbons with similar pore volumes for adsorption, the one having the higher molasses number will usually have larger feeder pores resulting in more efficient transfer of adsorbate into the adsorption space.
Tannin
Tannins are a mixture of large and medium size molecules. Carbons with a combination of macropores and mesopores adsorb tannins. The ability of a carbon to adsorb tannins is reported in parts per million concentration (range 200 ppm–362 ppm).
Methylene blue
Some carbons have a mesopore (20 Å to 50 Å, or 2 to 5 nm) structure which adsorbs medium size molecules, such as the dye methylene blue. Methylene blue adsorption is reported in g/100g (range 11–28 g/100g).
Dechlorination
Some carbons are evaluated based on the dechlorination half-life length, which measures the chlorine-removal efficiency of activated carbon. The dechlorination half-value length is the depth of carbon required to reduce the chlorine level of a flowing stream from 5 ppm to 3.5 ppm. A lower half-value length indicates superior performance.
Apparent density
The solid or skeletal density of activated carbons will typically range between 2000 and 2100 kg/m3 (125–130 lbs./cubic foot). However, a large part of an activated carbon sample will consist of air space between particles, and the actual or apparent density will therefore be lower, typically 400 to 500 kg/m3 (25–31 lbs./cubic foot).
Higher density provides greater volume activity and normally indicates better-quality activated carbon. ASTM D 2854 -09 (2014) is used to determine the apparent density of activated carbon.
Hardness/abrasion number
It is a measure of the activated carbon's resistance to attrition. It is an important indicator of activated carbon to maintain its physical integrity and withstand frictional forces. There are large differences in the hardness of activated carbons, depending on the raw material and activity levels.
Ash content
Ash reduces the overall activity of activated carbon and reduces the efficiency of reactivation: the amount is exclusively dependent on the base raw material used to produce the activated carbon (e.g. coconut, wood, coal, etc.). The metal oxides (Fe2O3) can leach out of activated carbon resulting in discoloration. Acid/water-soluble ash content is more significant than total ash content. Soluble ash content can be very important for aquarists, as ferric oxide can promote algal growths. A carbon with a low soluble ash content should be used for marine, freshwater fish and reef tanks to avoid heavy metal poisoning and excess plant/algal growth. ASTM (D2866 Standard Method test) is used to determine the ash content of activated carbon.
Carbon tetrachloride activity
Measurement of the porosity of an activated carbon by the adsorption of saturated carbon tetrachloride vapour.
Particle size distribution
The finer the particle size of an activated carbon, the better the access to the surface area and the faster the rate of adsorption kinetics. In vapour phase systems this needs to be considered against pressure drop, which will affect energy cost. Careful consideration of particle size distribution can provide significant operating benefits. However, in the case of using activated carbon for adsorption of minerals such as gold, the particle size should be in the range of 3.35–1.4 millimetres (0.132–0.055 in). Activated carbon with particle size less than 1 mm would not be suitable for elution (the stripping of mineral from an activated carbon).
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For example:If your business is experiencing more demand for your product/service, thus the need for more skilled employees.If you’re having difficulty competing with big firms when recruiting top talent, which means you need help in attracting and landing better candidates.Recruitment specialist hiring tipsHere are a few strategies to help you find that great HR specialist.Make a detailed and compelling job descriptionA vague or poorly written job description won’t entice job seekers to apply, making it harder for you to find the best talent.
Worse, you might even hire the wrong person, which will be a costly mistake.A good job description identifies a role’s objectives, skills, experience, and tasks.
They also need to be proficient at technology, especially in HR tools like:Applicant tracking systemsPayroll processing softwareBenefits management platformsEmployee engagement toolsEmployee onboarding solutionsWith a strong grasp of these technologies, your HR staff will reduce the time they spend on administrative tasks, enabling them to focus more on acquiring the best talent, which will give you a huge competitive advantage.Get referralsReferrals from friends, family, and associates are a helpful resource when you’re looking for talented recruitment specialists.
In an HR setting, the most important of these include:Communication skills (e.g.
Synopsis:The global 5G market is anticipated to witness a significant growth during the forecast period.
Therefore, the optimization of internet network to bring in efficient telecommunications and addressing capacity needs has been attributed mandatory for the smooth working of machine-to-machine communication systems.Enhanced mobile broadband are likely to offer initial upside with respect to manifesting realistic expectations on their timeliness for proposition development.
The evolution of 5G is also expected to minimize the cost per gigabyte than the presently used 4G.The prevailing 2G, 3G, and 4G are primarily radio focused, while 5G will present a system comprising of radio, OSS, and telecom core.
This process will include new radio technologies, end-to-end orchestration and management, and a virtualized cloud-based core to facilitate automation and concepts like network slicing.
Service providers that understand 5G’s potential to revitalize their workflow will be best placed to optimize their ROI over the next decade.5G use cases are still in its nascent stage and have a long way to go before fully autonomous vehicles and remote surgeries become available commercially.
While 5G’s role is considered as a catalyst for IoT strategies, consumer connectivity and content is anticipated to hinge on significant refinements to the existing 4G-based value propositions.Regional Outlook:The North America region dominated the overall 5G market in 2019 as there has been a significant number of investments been made by the regional players and some of the key infrastructures is being materialized in the U.S.
Unless you are a pro Hookah smoker, decision-making confusion is common with everyone as there are so many options available in the market.
If you are not sure which one will work best, then this blog piece will come very handy as we break them down for you.Coconut Shell Charcoals: FlatsThese are the first Coconut Charcoal variants that came into the market.
However, nowadays they are available in more sizes to fit diverse hookah bowls and heat management devices like mini, standard, jumbo as well as large cubes.
In this case, the flats get red hot pretty fast.
This difference is a bit technical and can be observed when the coals are thoroughly lit.
On the other hand, the flats are lighter and thus less likely to press into the bowl and mess up your shisha.
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When rubber products tend to be molded, they can’t be eliminated due to the cohesive force possessed from the elastomer after being pressed under high pressure.
Therefore, when a rubber product is designed from the outset, regardless of the formula or mold, it is essential to carefully calculate the fit.
If not, the product size is likely to be unstable and the supplement quality is low.2.
Rubber is a hot melt thermosetting elastomer, even though plastic is hot melt along with cold curing.
Due to the the various models of vulcanizates, the temperature range for molding and curing of rubber is very different, and it can even be affected by weather changes and indoor temp and humidity.
Therefore, the production conditions of rubber products has to be adjusted appropriately at when.
