in recent years, along with growing and the pace of industrialization of our country's economic strength increasing, the large amount of industrial waste water due to industrial production has become one of the important source of the threat to the ecological environment. industrial wastewater is rich in all kinds of heavy metal ions, organic compounds and other substances, and some of them are highly toxic. once untreated, it will cause irreversible damage to the environment. for this reason, it is very urgent to strengthen the research of industrial waste water treatment technology, and activated carbon adsorption method as an effective industrial wastewater treatment technology should be brought to the attention of the society, and launches the thorough analysis of the specific application.
1. analysis of adsorption mechanism of activated carbon
activated carbon adsorption technology is to remove some or more harmful substances from industrial wastewater by adsorption and removal of certain substances or substances through the unique adsorption effect on the surface of activated carbon. in essence, the adsorption function of activated carbon mainly comes from two aspects:
(1) because the interior of the activated carbon molecules in each equal to the force, and its surface molecules in each to the uneven situation, so as to make the other substance molecules are easily adsorbed on the surface of activated carbon, under the action of force, it is a process for the physical adsorption; the reason lies in the fact that activated carbon can easily react with the adsorbent in a chemical reaction, thus achieving the effect of adsorption and purification. this process is chemical adsorption. the adsorption effect of activated carbon is the synthesis product of the above two adsorption processes.
when activated carbon adsorption efficiency with the parsing efficiency synchronization in the solution (per unit time activated carbon number of substances in the solution of the adsorption quantity is equal to parse) content in the material on the surface of activated carbon adsorption and solution will be in dynamic equilibrium, which is activated carbon adsorption equilibrium, the adsorbate concentration is the equilibrium concentration in the solution, we use q on behalf of the activated carbon adsorption capacity, its expressions:
q = v (co - c)/m
where: q represents the adsorption amount of activated carbon (a unit of the magazine quality of activated carbon), g/g;
v represents the total amount of wastewater to be purified, l;
c0 and c respectively represent the impurity mass concentration in the water before and after purification, g/l.
m represents the total amount of activated carbon added in the waste liquid, g.
and under the condition of constant temperature, activated carbon adsorption quantity q with purified water in the magazine the curve of mass concentration c is referred to as adsorption isotherm, for waste water treatment industry, the general selection ferrand lehi adsorption isotherm represents the size of the activated carbon adsorption function, its expression:
q ˙ c1 = k/n
where: k represents the coefficient related to the surface area and temperature of activated carbon; n is a constant associated with temperature.
2.analysis of advantages of activated carbon adsorption method
as an efficient adsorbent with many characteristics, such as multi-porosity, large surface area, high adsorption capacity and high stability, activated carbon has the following advantages.
（1） can be used independently
it is not necessary to add other flocculant or oxidant or other chemical reagents, but can be used for adsorption and purification directly through its own micropore characteristics.
（2） low production cost and simple use method
the production of activated carbon can be obtained only through wood, coal, etc., which is relatively low in cost and requires no other operation when it is used at the same time. it only needs to be put into waste liquid, and the operation process is simple and convenient.
（3） good adsorption effect
due to its unique large surface area and multi-pore characteristics, activated carbon has a good adsorption effect, especially for molecular impurities such as metal ions.
（4） it is not easy to cause secondary pollution
the adsorption process of activated carbon is mainly physical adsorption, and the adsorption of refractory magazines can be directly integrated with activated carbon for landfill, so as to avoid secondary pollution caused by redissolve into water.
（5） reusable
activated carbon, which has been purified from wastewater, can be recycled through chemical solution regeneration, thermal regeneration, electrochemistry and biological regeneration.
3. specific application of activated carbon adsorption method
（一） application in the purification of oily wastewater
oily water in industrial waste water not only yield huge and involved in many industries, such as oil exploration and refining, oil transport, shipping transportation, machinery manufacturing, food processing, etc., are in the process of its production operation can produce all kinds of different degrees of oily sewage, which cause serious damage to the ecological environment, especially the water resources environment.
activated carbon as a kind of hydrophilic material, can be spread in industrial waste oil, dissolve oil, emulsified oil, such as effective adsorption, but usually activated carbon adsorption capacity of oil limited (between 30 ~ 70 mg/g), combined with activated carbon is difficult to realize the secondary use after oil absorption, which makes its application in the oily wastewater purification cost is higher, so in oily wastewater purification treatment activated carbon usually only as a last level of processing, namely to trace pollutants removal in waste liquid, so as to realize the goal of deep purification.
generally speaking, the oil content in the waste water after activated carbon adsorption treatment can be less than 0.1 ~ 0.2 mg/l.
（二） application in the purification of dye wastewater
with the continuous development of modern textile industry, printing and dyeing industry has also achieved long-term progress. according to incomplete statistics, nearly 20,000 t dyes in the global printing and dyeing industry will enter the water directly into the natural environment in the form of waste water. the dye composition not only complex, deep chromaticity, high concentration and the making process is extremely cumbersome, a common processing methods include oxidation, flocculation, membrane separation, adsorption and biodegradation, including activated carbon adsorption process as a kind of more in-depth, application is very wide, is mainly used in the industrial wastewater cod and chroma removal, and in use will be more active carbon as catalyst carrier with other technology integrated application. in addition, in the purification treatment of dye wastewater, the decolorization rate is proportional to the temperature, which is independent of the ph value. therefore, the proper temperature selection is particularly important.
in general, with the recent condition of adsorption purification treatment after the decolorization rate of dye wastewater can reach 98%, nearly 50 times diluted times, the shade of the effluent cod quality content is less than 50 mg/l, meet the level of industrial wastewater discharge standard in our country.
（三） application in the purification of mercury and chromium waste water
（1） treatment of mercury containing wastewater
among many metal pollutants, metallic mercury is the most toxic, once it enters the human body, it will cause serious damage to the function of various proteins, thus endangering human health. although activated carbon for metallic mercury ion and its compounds have a certain ability of adsorption, but are relatively limited, multi-purpose at low purification treatment of wastewater containing mercury, or high concentrations of mercury in the last layer of multilayer liquid waste.
（2） treatment of chromium-containing wastewater
in recent years, with the rapid progress of the electronic industry, the electroplating industry has risen with it. according to the relevant investigation, metal chromium ions are not only highly toxic but also easily accumulated in various plants and animals, which leads to the introduction of biological chain into human body, causing serious injury to human respiratory tract and internal organs. however, the surface of activated carbon contains a large number of oxygen-containing groups, such as - cooh, - oh, etc., and the electrostatic adsorption function of these oxygen-containing groups has a strong chemical adsorption effect on metal chromium ions.
the results showed that when the amount of chromium contained in the chromium-containing wastewater was 50mg /l, the adsorption time was 1.5h, and the ph value =3, the purification effect of the chromium-containing wastewater treated by activated carbon adsorption was the best. in addition, activated carbon has been widely used in various industries for its advantages of simple operation, low cost and stable adsorption effect.
4. development of activated carbon adsorption combination technology
in practice, to better promote the industrial waste water purification effect, also can be activated carbon with other process to carry on the comprehensive utilization, so as to constitute a combination technique of activated carbon adsorption, a few of the more common as described below.
（1） combined process of activated carbon and ozone
ozone has strong oxidizing, has good sterilization effect on water body, not only to complement of purification of activated carbon, ozone and macromolecular organic matter decomposition, also can make it into a small molecules form, so as to facilitate its activated carbon adsorption, realize the activated carbon adsorption effect of ascension. through the combination of the two, the purification effect of industrial wastewater can be greatly improved.
（2） combined process of biological activated carbon
biological membrane purification process is a kind of commonly used means of organic cleaning water, let biofilm growth within the activated carbon by artificial means, and thus form a with activated carbon as the biofilm system, thus not only can greatly increase the contact time of biofilm with organic pollutants, still can better play to the active carbon adsorption effect, so as to realize "1 1 > 2" effect, promote industrial wastewater purification effect.
（3） activated carbon electrolysis
electrolysis is often used in the degradation of water impurities to purify, but limited by the electrode contact area, its purification effect of wastewater are relatively limited and large energy consumption, and active carbon has excellent electric conductivity, replace the traditional electrode with activated carbon, can make full use of the surface area and good adsorption characteristics of activated carbon, improve the electrolysis efficiency. according to relevant tests, the current utilization efficiency of electrolytic water treatment process using activated carbon as electrode has been greatly improved, which has become one of the current research hotspots.
5 the knot language
in a word, as an efficient and clean means of wastewater purification, activated carbon adsorption will be further expanded and improved with the further development of social economy. but it as a relatively new technology, no matter in theory or in practical application of certain deficiencies, especially lack of manufacturing process, make its are also relatively tight supply. in the face of these problems, the government and experts and scholars should be in the exploration of the positive work and constantly developing new activated carbon manufacturing and application technology, so as to better play its purification effect, promote to further improve the industrial waste water purification effect and perfect.
