Powdered activated carbon, also known as PAC, or PAC carbon has been applied in the field of water treatment for more than 100 years.. Abroad, the use of powder activated carbon to remove organic matter, color, and smell substances in water has achieved successful experience and good removal effect. For example, in Chicago, USA in the 1920s, the combination of powder activated carbon adsorption process and slow sand filtration process has been successfully used to prevent chlorophenol pollution of drinking water; in East Prussia, powder activated carbon has been used to eliminate seasonal raw water algae odor, etc.
The application of activated carbon adsorption technology in this field has also been paid more and more attention by the majority of science and technology and engineering technicians.
1. Types and adsorption properties of PAC PAC particles are 10 to 50 microns, and the density is 0.36 to 0.74 g/m3. It is a porous adsorption material with weak polarity, strong adsorption capacity and stable activity. The pore size of activated carbon varies greatly, and the removal effect of organic matter with a relative molecular mass of 500-3000 is better. At present, the activated carbons in engineering applications mainly include wood carbon, nutshell carbon and coal-based carbon, and studies have shown that the adsorption performance of wood-based carbon and nutshell carbon is significantly better than that of coal-based carbon [2]. Research on water purification efficiency of powdered activated carbon The adsorption of solute molecules in water by powdered activated carbon is a complex process, which is the result of the combined action of several forces, including ionic attraction, van der Waals force, and chemical hybrid force. According to the double-rate diffusion theory of adsorption, adsorption is a double-rate process consisting of two stages of rapid diffusion and slow diffusion. Rapid diffusion is a process in which solute molecules diffuse in large pores with small resistance uniformly distributed along the radial direction within the carbon particle. These large pores create radial diffusion resistance. When the molecules further diffuse from the macropores into the micropores that communicate with the macropores, it is extremely slow due to the great resistance generated by the narrow pore size. The micropores are also uniformly distributed in the carbon particles, but do not constitute radial diffusion resistance. The factors affecting the adsorption of powder activated carbon involve the polarity, molecular weight and spatial structure of solute molecules, which depend on the characteristics of water quality. Activated carbon has selective adsorption to different substance molecules. 2. PAC application technology
2.Selection of dosing process Foreign experts have analyzed and studied the application of powdered activated carbon, and believed that the adsorption and removal of artificially synthesized chemicals by powdered activated carbon mainly depends on the type of the compound. When selecting the dosing point, the degree of mixing and treatment contact time must be considered to minimize the interference of water treatment chemicals on adsorption. When selecting the powder activated carbon process, the main consideration is ; (1) There must be sufficient stirring conditions at the dosing point, so that the powder activated carbon can be quickly mixed and contacted with the treated water. (2) Try to prolong the contact adsorption time of powdered activated carbon and water body, make full use of the adsorption capacity of powdered activated carbon, and improve the adsorption rate.
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