Activated carbon can effectively adsorb chlorinated hydrocarbons, organophosphorus and carbamate insecticides, as well as phenyl ether, n-nitrochlorobenzene, naphthalene, ethylene, xylenol, phenol, DDT, aldrin, alkylbenzene Sulfonic acid and many esters and aromatic compounds. The secondary effluent also contains organic matter that is not adsorbed by activated carbon, such as intermediate degrading substances of protein, which is more difficult to be adsorbed by activated carbon than the original organic matter, and the removal ability of activated carbon to THMS is low, reaching only 23-60%. Activated carbon adsorption method combined with other treatment methods, ozone-activated carbon method, coagulation-adsorption activated carbon method, Habberer process, activated carbon-diatomite method, etc., so that the adsorption cycle of activated carbon is significantly prolonged, the dosage is reduced, the treatment effect and range substantial improvement.
The physical properties of activated carbon mainly refer to the pore structure and its distribution, which is also the main factor determining the adsorption performance of activated carbon. In the activation process of activated carbon, a large number of pores of various shapes and sizes are formed, and thus have a large surface area. In the process of carbon water contact, the great carbon water contact interface is the basis of the adsorption capacity of activated carbon.
Since the adsorption of activated carbon occurs on the surface of the adsorbent, the specific surface area of ​​the adsorbent is one of the important factors affecting the adsorption. The larger the specific surface area, the better the adsorption performance. Because the adsorption process can be regarded as three stages, the internal diffusion has a great influence on the adsorption speed, so the micropore distribution of activated carbon is another important factor affecting the adsorption. In addition, the surface chemistry, polarity and charge of the activated carbon also affect the adsorption effect.
Activated carbon for water treatment should have three requirements: large adsorption capacity, fast adsorption speed, and good mechanical strength. The adsorption capacity of activated carbon is related to the specific surface area of ​​activated carbon, and the specific surface area is large, the number of micropores is large, and the adsorbate adsorbed on the pore wall is more. The adsorption rate is mainly related to the particle size and pore distribution. The activated carbon for water treatment requires a transition hole (radius 20~1000A) to be developed, which is beneficial to the diffusion of the adsorption mass into the micropores. The smaller the particle size of activated carbon, the faster the adsorption speed, but the head loss should be increased, generally in the range of 8~30 mesh. The mechanical wear resistance of activated carbon directly affects the service life of activated carbon.
Granular columnar activated carbon, powdered activated carbon production is generally divided into two processes
In the first step, carbonization, the raw materials are dried at a temperature of 170 to 600, and 80% of the organic tissues are carbonized in the same amount.
In the second step, the carbonized material which has been carbonized in the first step is sent to the reaction furnace, reacted with the activator and water vapor to complete the activation process, and the finished product is prepared. In the process of endothermic reaction, columnar activated carbon mainly produces CO and H2 combination gas, which is used to heat the carbonized material to a suitable temperature (800 to 1000 degrees), remove all decomposable substances, and produce abundant pore structure and huge ratio. The surface area makes the activated carbon have a strong adsorption force. The activated carbon produced by different raw materials has different pore diameters, wherein the activated carbon with coconut shell as the raw material has the smallest pore size, the pore size of the wood activated carbon is generally larger, and the pore size of the coal activated carbon is between the two. Powdered activated carbon pore size is generally divided into three categories: large pore A transition hole: 20-1000A microporous: 20A According to the above characteristics, it can be seen that for different adsorption targets, the corresponding activated carbon should be selected to achieve the best cost performance. Therefore, generally, in the liquid phase adsorption, more activated carbon having a larger transition pore diameter and a larger average pore diameter should be used.
The raw materials of activated carbon are: activated carbon is mainly made of substances with high carbon content, such as wood, coal, nut shell, coconut shell, petroleum residue and so on.
The main use of granular powdered activated carbon: 1, air purification; 2, sewage treatment site exhaust adsorption; 3, beverage water treatment; 4, power plant water pretreatment; 5, wastewater recovery pretreatment; 6, biological sewage treatment; , toxic waste water treatment; 8, petrochemical alkali-free desulfurization; 9, solvent recovery; 10, chemical catalyst carrier; 11, canister; 12, gold extraction; 13, chemical storage and purification; 14, sugar, wine Class, MSG medicine, food refining, decolorization; 15, ethylene desalinated packing; 16, automobile exhaust gas purification; 17, PTA oxidation unit purification gas
Physical characteristics
Columnar activated carbon is a multi-aperture charcoal with a very rich pore structure, good adsorption characteristics, and its adsorption physical and chemical absorption.
The purpose and operation process of the powdered activated carbon process:
Zinc chloride method for intermittent production of powdered activated carbon, in order to reduce the investment in mechanical equipment, the mixture of wood chips and zinc chloride solution is not kneaded by a kneading machine, but a dip tank is adopted, and zinc chloride is impregnated. It penetrates into the wood chips and acts as a kneading machine.
The operation mode of the impregnation is slightly different from different manufacturers, but they are all similar. Impregnation of powdered activated carbon generally takes the immersion tank, also known as the immersion tank. It is a pool made of brick and acid-resistant cement on the ground. The pool is long, wide and deep. The outer surface of the tank is coated with acid-proof porcelain sheets to prevent corrosion, and a drain pipe is arranged at the bottom of the tank for discharging excess zinc chloride solution after immersion.
When impregnating the powdered activated carbon, the wood chips that meet the requirements are put into the immersion tank, and then the zinc water pump is started, and the prepared and tested zinc chloride solution is evenly poured on the wood chips until the zinc chloride solution covers the wood chips. So far, after the immersion - hour, the drain port at the bottom of the immersion tank is opened, and the excess zinc chloride solution is allowed to flow into the zinc pool. After a while, the zinc swarf material can be transported to the carbonization step for carbonization.
Those factories adopt a certain solid-liquid ratio to carry out the mixing, and the powdered activated carbon is mixed and evenly flooded for an hour, and needs to be turned over from time to time to obtain uniform mixing of the zinc chips. It is not necessary to add zinc solution to the zinc crumb mixture, and it is suitable to knead the cake by hand without dripping. Manufacture of activated carbon for different uses.
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