Determination method of chromaticity in water and water

      

　　What is the color of water?

　　Pure water is colorless. When it contains a lot of impurities, water will produce color. For example, water containing more mud and sand will appear yellow; water containing a lot of mud and sand and humus will appear brown or yellowish brown; water containing colloidal iron will be light yellow or yellowish brown; water containing algae will be green or brown, etc. Therefore, based on the color of the water, the composition or degree of pollution of the contaminants in the water can be roughly inferred.

　　The chromaticity of water is one of the important indicators of drinking water quality. This is mainly because chromaticity can cause adverse reactions to human visual senses, and can make water taste unpleasant when drinking, and produce aversion.

　　At the same time, due to the impurities that cause the chromaticity of aquatic products, they will clog the pores of the ion exchanger used for water treatment, pollute the resin, and pollute the water quality, causing the deterioration of the water quality. Therefore, industrial water has stricter requirements for the chromaticity of water.

　　How should the color of water be expressed?

　　In the analysis of water quality, "true color" is generally used to represent chromaticity, that is, the color of the water after the suspended solids in the water are removed. Therefore, before the water sample is measured, the suspended solids in the water should be removed by clarification or ion deposition. If the water sample contains inorganic or organic substances with too small particles and is not easy to remove by centrifugation, it can be measured

　　"Appearance", that is, the color of the water sample without removing suspended solids, and the measurement results need to be indicated in the test report.

　　Usually measuring the water chromaticity, platinum cobalt colorimetry can be used: 1.246g potassium chloroplatinate (K2PtCl6) and 1.000g of crystalline cobalt dichloride (CoCl2 · 6H20) dissolved in water containing 100ml_ concentrated HCl and diluted to 1L, this standard solution is equivalent to 500 degrees (1mg/L platinum in the form of chloroplatinum cobalt acid ions produced by the color of l degrees), and then use this standard to prepare a 5-70 degree step standard color scale (Table 1-19), visually compare the water sample and platinum cobalt standard color scale, and record the water sample color.

　　For industrial wastewater with high isochromaticity, other waters exceeding 70 degrees can also be diluted by multiple method.

　　What methods can be used to remove the color in water?

　　Commonly used methods of color removal include:

　　(1) Coagulation treatment

　　When the chromaticity impurities in water are mainly suspended and colloidal organic matter, after coagulation, clarification and filtration treatment. Generally, about 75% to 90% can be removed. The coagulant can be commonly used aluminum sulfate, or basic aluminum chloride [Aln (OH) mCl3n-m], and an organic polymer flocculant can be used appropriately. See Table 1-20 for the chromaticity effect.

　　(2) Chlorination treatment

　　When the water's chromaticity (mainly organic matter) content is large, after chlorination treatment, the "chromaticity" removal rate is about 80%. When chlorinated, the remaining chlorine should be greater than O. 5mg/L. Chlorination treatment is carried out faster at low pH value, therefore, chlorination should be placed before coagulation treatment. The remaining chromaticity (mainly organic matter) after chlorination can be further removed in coagulation, and the residual chlorine in water should be removed before entering the ion exchange process.

　　(3) Adsorption treatment

　　Adsorption treatment is a treatment method that uses porous solid substances to remove the chromaticity impurities of water by adsorbing on the solid surface. Commonly used adsorbents include granular activated carbon, macroporous adsorbents, etc.

　　Activated carbon layer filtration, generally when the chromaticity value of water is low, the granular activated carbon layer is 0.6 to 1.5m high; when the chromaticity value of water is high, the layer height is 1.5 to 3.Om, and the running flow rate

　　10~ 12M/h. The removal effect of granular activated carbon layer is shown in Table 1-21.

　　Macroporous adsorbent is a bead-like macroporous polymer. It can adsorb and resolve some specific components in aqueous solution, so it can remove "chroma" impurities in water well.