How Activated carbon be used in Water Treatment Plant

As a relatively special carbonaceous material, activated carbon is widely used in various fields such as environmental protection because of its developed pore structure, huge specific surface area, good stability, strong adsorption capacity and excellent regeneration capacity. Emphatically introduce the application of activated carbon adsorption technology in water treatment.

Physical and chemical properties of activated carbon

1.1 Activated carbon (AC)

Activated carbon is a commonly used non-polar adsorbent with stable performance and corrosion resistance, so it is widely used. It is a general term for carbon-based substances with adsorption properties. Heat and carbonize carbon-containing organic substances to remove all volatiles, and activate them with chemicals (such as ZnCl2, etc.) or water vapor to make porous carbon-structured adsorbents. There are two types of activated carbon, powder and granular, and granular activated carbon is mostly used in industry.

Due to different raw materials and production methods, the pore size distribution is different, generally divided into: carbon molecular sieve, the pore size is below 10×10-10m; activated coke, the pore size is below 20×10-10; activated carbon, the pore size is below 50×10-10m .

1.2 Activated Carbon Fiber (ACF)

Activated carbon fiber is a new type of adsorption functional material, which is made of lignin, cellulose, phenolic fiber, polypropylene fiber, pitch fiber, etc., through carbonization and activation. Compared with activated carbon, it has a unique microporous structure, higher external surface and specific surface area, and a variety of functional groups, and the average pore diameter is also smaller. It can be obtained in the fields of wastewater, waste gas treatment, and water purification through physical adsorption and physical chemical adsorption widely used.

The micropore volume of fibrous activated carbon accounts for about 90% of the total pore volume, and most of its micropore diameters are about 1nm, without excessive pores and macropores. The specific surface area is generally 600-1200m2/g, even up to 3000m2/g. The desorption regeneration rate of activated carbon fiber is fast, the time is short, and its performance is unchanged, which is better than activated carbon. Like activated carbon, activated carbon fibers are non-selective in adsorption, and are mainly used to adsorb organic pollutants, and are generally used for comprehensive wastewater treatment in refineries.

Adsorption and adsorption form of activated carbon

2.1 Activated carbon treatment

Refers to the process of using activated carbon as an adsorbent and catalyst carrier. It is mainly used in the deep purification of drinking water, urban sewage treatment, and industrial wastewater treatment.

2.2 Adsorption and adsorption form

The action of accumulating solutes on a solid surface is called adsorption. The surface of activated carbon has adsorption effect. Adsorption can be regarded as a surface phenomenon, so adsorption is closely related to the surface characteristics of activated carbon. Activated carbon has a huge internal surface and pore distribution. The effect of its outer surface area and surface oxidation state is small, and the outer surface provides many channels communicating with the inner cavity. The main role of surface oxides is to make the hydrophobic carbon backbone hydrophilic, giving activated carbon an affinity for many polar and non-polar compounds. Activated carbon has surface energy, and its adsorption is caused by the unbalanced force on the carbon atoms that make up the surface of the pore wall, thereby causing surface adsorption.

Application of activated carbon adsorption technology in water treatment

3.1 Overview of the application of activated carbon adsorption technology in water treatment

Practice has proved that activated carbon is an ideal adsorbent for water and wastewater treatment, and the use of activated carbon for water and wastewater treatment has been studied for ten years. In the past two decades, since the regeneration of activated carbon has been solved satisfactorily, and the manufacturing cost of activated carbon has also been reduced, activated carbon adsorption technology has been gradually popularized and used at home and abroad. Smelly. In the early 1960s, European and American countries began to use activated carbon adsorption as an effective means of water purification. my country has used activated carbon for carbon disulfide wastewater treatment in the 1960s. Since the early 1970s, granular activated carbon has developed rapidly in terms of technology, application range and treatment scale for industrial wastewater treatment. The treatment of oil refining wastewater, explosive wastewater, printing and dyeing wastewater, chemical wastewater, and electroplating wastewater has been applied on a large scale in production, and satisfactory results have been achieved.

3.2 Application of activated carbon in wastewater treatment

Activated carbon has different forms, and currently it is still mainly in granular form and powder form in water treatment. Powdered carbon is used for intermittent adsorption, that is, according to a certain proportion, powdered carbon is added to the water to be treated, mixed evenly, and the carbon and water are separated by sedimentation or filtration. This method is also called static adsorption. Granular carbon is used for continuous adsorption. The treated water passes through the carbon adsorption bed to purify the water. This method is exactly the same as the fixed bed in form, also known as dynamic adsorption. There are many substances that can be adsorbed by activated carbon, including organic or inorganic, ionic or non-ionic. In addition, the surface of activated carbon can also act as a catalyst, so it can be used in many different occasions.

Activated carbon has a strong adsorption capacity for dissolved organic matter in water, and is effective in removing most organic pollutants in water, such as phenol and benzene compounds, petroleum, and many other synthetic organic matter. Some organic pollutants in water are difficult to remove by biochemical or oxidation methods, but are easily adsorbed by activated carbon.

The cost of activated carbon adsorption treatment is higher than other general treatment methods. Therefore, when the concentration of organic matter in water is high, other more economical methods should be used to reduce the content of organic matter to a certain extent before processing. In wastewater treatment, the activated carbon adsorption process is usually placed behind the biochemical blowing process, which is called activated carbon tertiary wastewater treatment, which further reduces the content of organic matter in wastewater, removes pollutants that are not easily decomposed by microorganisms, and makes the water after activated carbon treatment It can meet the requirements of discharge standards, or make the treated water return to the production process for repeated use, so as to achieve the purpose of closed cycle of production water.

The ability of activated carbon to adsorb organic matter is very large. In the tertiary wastewater treatment, the COD adsorbed by each gram of activated carbon can reach dozens of percent of its own mass. The addition of tertiary wastewater treatment in the wastewater treatment plant can achieve 95% removal of BOD. Activated carbon removes organic matter in water in the form of physical adsorption, and the adsorbed properties do not change before and after adsorption. If a proper desorption method can be used, valuable substances in water can also be recovered. If the powdered activated carbon is put into the gas explosion equipment, the carbon powder and microorganisms form a kind of aggregate, which can make the treatment effect exceed the general secondary biological treatment method, and the effluent water quality is close to the tertiary treatment.

In addition, it can also make the activated carbon sludge dense and firm, reduce the turbidity of the effluent, and increase the hydraulic load of the secondary treatment. Powdered carbon can be added intermittently, and the treatment effect can be improved for existing secondary treatment plants without increasing investment in tertiary treatment.

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