Printing and dyeing wastewater is mainly composed of desizing wastewater, bleaching wastewater, dyeing wastewater and printing wastewater. Printing and dyeing wastewater generally has the characteristics of high concentration of pollutants, various types, toxic and harmful components and high chroma. Therefore, an effective method should be adopted for processing. There are many activated carbon treatment methods for printing and dyeing wastewater, including decolorization with soft plasmid-like activated carbon, decolorization with hard-plasma activated carbon, ozone-activated carbon treatment, and activated carbon-biofilm method. The soft and hard plasmid-like activated carbon decolorization method is as follows:
Printing and dyeing wastewater was decolorized with soft plasmid-like activated carbon. The properties of petroleum pyrolysis plant by-product oil slag charcoal are similar to those of high-temperature activated activated carbon. Toyota and others in Japan have carried out experiments on the treatment of printing and dyeing wastewater with this oil-slag charcoal. Based on this, many plants such as Japan Red Sanlili Factory The actual treatment device was constructed, in which the water quality of the dyeing wastewater activated carbon treatment device of the dyeing company was treated with soft plasmid-like activated carbon to basically meet the requirements. Compared with the conventional coacervation method, the method has the advantages of good decolorization effect, no sludge formation, and certain adaptability to water quality changes.
Printing and dyeing wastewater was decolorized with hard-plasmid activated carbon. Hard-like activated carbon has the advantages of high physical strength, small pressure loss, good heat resistance, and complete regeneration at 1000 ° C. It has been used in the decolorization of refined sugar factories and chemical plants. Later, Hollitex The carpet grindstone company used it in dyeing plant wastewater treatment and further application. The use of hard activated carbon in the treatment of printing and dyeing wastewater has a lower replenishment rate than soft activated carbon, so the operating cost is not high.
Activated carbon adsorption:
Adsorption properties are the primary property of activated carbon. Activated carbon has crystallites like graphite grains but irregularly arranged. During the activation process, pores with different shapes and sizes are produced between the crystallites. It is assumed that the pores of the activated carbon are cylindrical pore shapes, and the radius of the pores calculated by the activated carbon according to a certain method can be divided into two categories:
(1) According to IUPAC:
Micropore <1.0nm
Middle hole 1-25nm
Large pores > 25 nm.
(2) According to custom:
Micropores <150nm
Middle hole 150-20 000nm
Large pores > 20 000 nm.
Due to these pores, especially micropores provide a large surface area.
The pore volume of activated carbon micropores is generally only 0.25-0.9mL / g, the number of pores is about 1020 / g, and the total pore surface area is about 500-1500m2 / g, usually measured by BET method, also known as up to 3500-5000 m2 / g. Almost 95% of the surface area of ​​activated carbon is in the micropores, so in addition to some macromolecules, micropores are an important factor in determining the adsorption performance of activated carbon. The pore volume of the mesopores is generally about 0.02-1.0 mL/g, and the surface area is up to several hundred square meters, generally only about 5% of the total silkworm species of activated carbon. Its function can adsorb steam and provide a channel for the adsorbate to enter the micropores, and can directly adsorb larger molecules.
The pore volume of macropores is generally about 0.2-0.5 mL/g, and the surface area is only about 0.5-2 m2/g. The first effect is to make the adsorbate molecules rapidly penetrate into the smaller pores inside the activated carbon; the second is to act as a catalytic carrier. The catalyst is usually precipitated in the micropores in a small amount, and most of them are precipitated in the macropores and mesopores.
The surface area of ​​the activated carbon should include the internal surface area and the external surface area. In fact, the adsorption property mainly comes from the huge internal surface area, so it cannot be mistaken that the grinding of the activated carbon will significantly increase the surface area and increase the adsorption force.
Many adsorptions are reversible physical adsorption, that is, the adsorbed material is a fluid, which is adsorbed by activated carbon under a certain temperature and pressure, and is desorbed by the adsorbate at high temperature and low pressure, and the inner surface of the activated carbon is restored to its original state. This is a widely used physical adsorption, also known as van der Waals adsorption.
Activated carbon mechanical:
(1) Particle size: A set of standard sieve sieving method was used to determine the weight of activated carbon remaining in and passing through each sieve to indicate the particle size distribution.
(2) Static density or bulk density: the weight of the activated carbon per unit volume of the dietary pore volume and the interparticle void volume.
(3) Bulk density and particle density: the weight of the activated carbon per unit volume of the dietary pore volume without the intergranular void volume.
(4) Strength: the crushing resistance of activated carbon.
(5) Abrasion resistance: that is, wear resistance or anti-friction performance.
These mechanical properties directly affect the application of activated carbon, for example: density affects the size of the container; the thickness of the powder affects the filtration; the particle size distribution of the carbon affects the fluid resistance and pressure drop; the fracture affects the service life of the activated carbon and the regeneration of the waste carbon.
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