Activated carbon absorption principle and type selection of activated carbon in syrup decolorization
The principle of decolorization of syrup by activated carbon
There are many fine pores inside the decolorising carbon particles, the pore diameter ranges from several micrometers to several micrometers, especially several to dozens of small e-pores, and the corresponding micropore surface area, which makes it have a large specific surface area, 1 gram of activated carbon with good activity Its surface area can reach about 1000 square meters. Because the atomic force field on the surface of activated carbon is not saturated and has residual cost power, the surface energy is considerable in such a large surface area. It is precisely due to adsorption that the unsaturated force field on the activated carbon surface is compensated to a certain extent, so that the surface can be Reduce, so that under a certain temperature and pressure, the surface of activated carbon can automatically absorb those substances that can reduce its surface energy.
However, the ratio of the number of different substances adsorbed by activated carbon from the solution is not consistent with the ratio of the concentration of these substances in the solution. It always tries to make the concentration of the solutes on the adsorption surface tend to be equal. In this way, even under the same adsorption power, the non-sugar content with a lower concentration in the sugar solution is easier to be adsorbed than the higher concentration of sucrose. The colored substances in the syrup generally have larger molecules and correspondingly larger molecular weights. Therefore, the surface energy of activated carbon can be reduced to a greater extent by adsorption, so that the syrup treated with activated carbon can be decolorized to a greater extent. It is precisely because activated carbon can decolorize and purify syrup, it has been well used in the advanced sugar industry abroad.
Activated carbon absorption speed
Put the re-dissolved syrup into the beaker, and at the same time, add the activated carbon particles and stir thoroughly. At this time, the important part of the syrup in contact with the activated carbon surface contains non-ferrous metal substances and other impurities. Then, the colored substances that we are far away from the activated carbon need to rely on convection to continuously move to the surface of the activated carbon and be adsorbed by it. Some of the substances adsorbed on the surface of these problems are adsorbed on the surface of the external environment of the particles, and the remaining part of the students move to the depths of the activated carbon particles through the pores in the analysis particles, are adsorbed on the pore walls, and diffuse through the research surface technology The effect is absorbed into the deep pores of the activated carbon particles. In this experiment, when the temperature of the re-dissolved syrup continues to rise, the decolorization treatment speed of the syrup by activated carbon can be obviously measured by using a spectrophotometer. This may be due to the company's gradual increase in working temperature, the increase in the average growth kinetic energy of the molecular industry, and the intensified Brownian motion, which is more conducive to the social convective movement of the colored substances in the syrup to the surface information of the activated carbon.
The choice of activated carbon type
Activated carbon has different physical and chemical properties due to different raw materials and manufacturing methods, which makes its adsorption capacity different. Generally, when the adsorbent is low-molecular, coconut shell activated carbon with micropores is more suitable, and the activated carbon of the coal system is more suitable for the solution of adsorbent materials from low-molecular to large-molecule.
The larger the specific surface area of activated carbon, the stronger the decolorization ability. However, in terms of chemical adsorption, it is not very accurate to select activated carbon only based on the general performance provided by activated carbon manufacturers, such as methylene blue adsorption capacity, iodine value, phenol value adsorption capacity and specific surface area. In particular, the functional groups of organic impurities in the syrup are mostly hydroxyl (phenol type) and carboxyl groups, which easily increase the polarity of the activated carbon surface. The surface of the activated carbon may be positively or negatively charged, thereby chemically combining with the organic impurities in the syrup. In this case, the appropriate activated carbon should be selected through the decolorization test of the actual syrup.
Selection of activated carbon adsorption decolorization device
When choosing a syrup decoloring device, the first things to consider are:
(1) Granular activated carbon or powdered activated carbon
(2) Adsorption decolorization method
(3) Pre-processing issues.
The choice of granular activated carbon or powdered activated carbon should be determined after comprehensive consideration of construction cost, construction land, utilization rate of activated carbon absorption and decolorization device, operation and management cost, source of activated carbon and other factors. At present, a ton of toner is only a few thousand yuan in the market, while a ton of granular toner can be sold for more than 10,000 yuan, and good quality toner can be sold for more than 20,000 yuan. Our factory uses powdered activated carbon, and the corresponding adsorption decolorization method is the adsorption decolorization of the stirring barrel. That is, the activated carbon is added to a mixing tank that has been poured into the redissolved syrup in a certain proportion, and then mechanically stirred to make it contact with the syrup. The adsorbed activated carbon can be separated by filtration, so it is also called contact filtration.
In addition, there are fixed bed adsorption decolorization, moving bed adsorption decolorization, fluid bed adsorption decolorization and so on. At the same time, various adsorption decolorization methods are divided into one tower decolorization method, downstream one-stage decolorization method, downstream multi-stage decolorization method and upstream multi-stage decolorization method.
It should be emphasized that the syrup must be pretreated before decolorization, and the suspended matter in the syrup is usually removed by filtration. In addition, due to different processing technologies, the final activated carbon product may be acidic or alkaline during the manufacturing process. For the sugar making process, sucrose is easy to transform under acidic conditions and easy to reduce under alkaline conditions, which is not conducive to the entire sugar making process. Therefore, the pH of activated carbon should be adjusted before use, so that the activated carbon supplier can adjust the pH of activated carbon to neutral.
The key to sugar production is decolorization and purification. Activated carbon has been widely studied and applied in the society for the analysis of many refined sugar production and processing processes due to its remarkable decolorization and purification effects. With the further improvement and development of sugar industry technology, activated carbon will have its own broader economic prospects for development.