Activated carbon is a natural raw material
The natural substance activated carbon is refined by CARBONIT using a unique and internationally patented process. All raw materials processed by CARBONIT are residue-controlled and LGA-monitored. They comply with strict European standards for water filters. The latest technology ensures unparalleled performance. CARBONIT water filters combine an exceptional filter fineness of up to 0.45 µm with the high adsorption effect of activated carbon. Like spring water from the tap. No need to carry heavy water crates.
Activated carbon is a material based on natural raw materials that binds chemical compounds and molecules due to its porous structure and the resulting extremely large internal surface. Activated carbon is traditionally used in many processes in the chemical industry. Due to its high adsorptive properties, it is mainly used for cleaning exhaust air, drinking water and waste water, as well as in food technology, pharmaceuticals and chemistry.
The starting materials for the production of activated carbon are carbonaceous raw materials such as wood, peat, lignite, hard coal, fruit kernels or coconut shells. But other carbonaceous materials, such as plastic waste or petroleum products, can also be processed into activated carbon due to their high carbon content. These carbonaceous materials are obtained in a similar way to charcoal production and then, as the name suggests, activated. This activation process increases the adsorptive properties of the carbon and leads to an improvement in the cleaning performance compared to conventional charcoal.
Activated carbon consists of an irregularly arranged crystal lattice of carbon atoms. These randomly shifted lattice planes lead to a very porous structure and thus a large internal surface. In commercially available activated carbon, this can be in the range of 500 to 1500 square meters per gram.
For comparison: 4 to 5 grams of activated carbon contain the area of an entire football field. The inner surface of the activated carbon is characterized by the pore system; in simple terms, a distinction is made between pores of different sizes and diameters. A distinction is made between macropores (the supply pores into the grain interior) and adsorption pores (i.e. the pores in which the actual attachment of the molecules to the inner surface takes place).
The structure of the pore system influences the transport of the sorptives from the grain edge into the grain interior as well as the adsorption properties of the respective substance on the surface.
surface properties of activated carbon
In addition to the pore structure, the chemical properties of the surface also have a decisive influence on the adsorption capacity of activated carbon. Given the abundance of contaminants that can occur in water or air, the cleaning performance of activated carbon is in practice geared towards very specific groups of substances. A selection of problem substances that can occur in drinking water purification, for example, is listed below:
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odors and flavors,
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Colors,
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mineral oil hydrocarbons,
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halogenated organic hydrocarbons,
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organic hydrocarbons,
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Chlorine, chlorine dioxide, ozone, permanganate,
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heavy metals,
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ammonium, nitrate,
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pharmaceutical active ingredients.
Since each of these compounds has a different adsorption behavior and binding capacity due to its chemical composition, the physical properties such as grain and pore size are combined with the chemical properties of the surface. This ultimately leads to optimal cleaning performance in the respective application.
adsorption
Adsorption is a process in which substances attach themselves to a surface (Fig. B). There are two types of adsorption. Firstly, there is physical adsorption, which is mainly caused by van der Waal's forces. Van der Waal's force is a very weak force of attraction, but it is sufficient to hold molecules or atoms to a surface (adsorb them) due to their charge. This force is reversible, i.e. if a stronger force occurs, e.g. Brownian molecular motion when the temperature increases, the adsorbed substance can be dissolved again. The situation is different with chemical adsorption, also known as chemisorption. Here, as with all chemical reactions, an activation energy must be overcome so that the impurity (adsorptive) forms a chemical bond with the surface of the activated carbon (adsorbent). Chemisorption is a stronger bond than physical adsorption. In principle, however, desorption (re-dissolution) of the substances can also occur here if the binding forces of other groups of substances are more pronounced. If the capacity (absorption capacity for pollutants) of an activated carbon filter is exhausted, this is referred to as a loaded filter. However, loaded filters do not necessarily have to be disposed of. The activated carbon contained in the filter can often be regenerated by removing the adsorbed substances from the surface of the activated carbon. This desorption process (i.e. the reverse adsorption process) can be brought about, for example, by reducing the pressure or increasing the temperature. However, after repeated desorption or when adsorbing substances that are difficult to desorb, the loaded activated carbon must be fully reactivated. The loaded activated carbon undergoes a new - albeit shorter - activation process with the aim of raising the inner surface back to its original level. Another way of regenerating loaded activated carbon is extraction. The adsorbed substances are removed from the surface of the carbon using an organic solvent. Microorganisms can also regenerate (macroporous) activated carbon by biologically breaking down organic compounds that are easily desorbed. Regenerated activated carbon is used in industrial applications in particular, for example in printing works, in food technology, drinking water treatment and wastewater treatment. Valuable substances can often be recovered through desorption, as demonstrated by the adsorptive recovery of toluene in printing works, where the toluene recovered from the exhaust air is fed back into the printing process.
manufacturing process
Activated carbon can be made from almost any carbon-containing material. These starting materials can be in uncharred form or in the form of coal and coke. The basic principle of activation is to selectively break down part of the carbon under suitable conditions. The selective breakdown results in the escape of volatile substances, creating numerous pores, gaps and cracks in which the adsorption of substances can take place. There are two methods for producing activated carbon: chemical activation and gas activation. In chemical activation, uncharred raw materials such as peat or sawdust are mixed with a dehydrating agent (water-removing), e.g. zinc chloride or phosphoric acid, and then activated at temperatures of 400 - 600 °C. This mainly produces coarse-pored activated carbon, which, due to its properties, can be used, for example, to decolorize liquids.
The second variant is gas activation. This generally uses already carbonized natural products such as charcoal, peat coke, coconut shell coke, hard coal or lignite. These already have a few small pores before activation and thus an initial, albeit still poorly developed adsorption surface. The activation process significantly increases the number of pores and thus the size of the surface. Activation is carried out at temperatures of 700 - 1000 °C and using steam and carbon dioxide. The steam and carbon dioxide lead to partial oxidation, particularly of the non-crystalline carbon. This expels tar-like products that clog the fine pores and largely exposes the carbon framework. The desired pores for fine-pored activated carbon are now formed inside the raw material. Since activation requires a high temperature, the use of rotary kilns, multi-story or shaft furnaces has become established in industry. Here, activated carbons and their pore distribution can be tailored to the various applications.
Activated carbon is sold as powdered or granular carbon or shaped carbon. In the production of shaped carbon, e.g. for water filters (activated carbon block filters), the carbonized semi-finished product is pulverized, activated and then mixed with a binding agent and extruded or sintered as required. The granular carbon, which is a few millimeters in size, is available as broken particles or as rod-shaped pellets. Granular carbon is used in adsorber containers through which the gas or liquid stream to be purified is passed. The broken, sharp-edged activated carbon is preferably used for water purification. Thanks to its compact design, an activated carbon block filter replaces voluminous loose beds of powdered carbon. The capacity to absorb undesirable substances is also significantly increased and the tendency to release substances that have already accumulated (so-called chromatographic effect) is lower. In addition to chemical-physical adsorption, fine-pored block filters with a high filter fineness also have good mechanical filtration properties against particles and microorganisms.
drinking water treatment
Drinking water is usually obtained from aquifers, but also in regions with poor groundwater, for example from the bank filtration of rivers. A large proportion of the compounds and contaminants that humans release into nature are biologically broken down by soil bacteria as they seep into the water. Nevertheless, the legal limits are repeatedly exceeded, which means that the water obtained must be treated before being fed into the drinking water network. The filters used for this are called single-layer or multi-layer filters.
The single-layer filters consist entirely of just one filter material, whereas the multi-layer filters are made up of a combination of different filter materials. The multi-layer filters usually consist of a layer (e.g. sand) to retain coarse particles and a layer of activated carbon. Since suppliers are legally only able to guarantee the quality of drinking water up to the house connection, drinking water filters are also increasingly being used in private homes.
These filters are designed to eliminate particles, bacteria, odorous and flavoring substances, and heavy metals that may be introduced through the pipe network. It can also happen that pollutants are not completely retained in the waterworks. These can be pesticides, drug residues, or even hormonal substances that enter the groundwater through diffuse entry and pass through the waterworks unhindered. Unsuitable or outdated domestic installations can release heavy metals into the drinking water. If the local differences in drinking water quality are not taken into account when selecting the pipe materials, heavy metal ions can be released. These are ions of the elements copper, nickel, zinc, and lead. In all of these cases, it is advisable to install an activated carbon filter directly in front of the drinking water tap, which can remove these heavy metals, drug residues, and pesticides from the drinking water (Fig. F). The minerals, salts, and trace elements that are essential for the human organism remain unaffected. Due to their small size and good mobility, they pass through the filter and are therefore also available after filtering.
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