1. Chlorine dioxide generator
1.1 The nature and preparation of chlorine dioxide
Chlorine dioxide is an oxide of chlorine, with an irritating odor similar to chlorine, molecular formula ClO2, molecular weight of 67.457, melting point -59 ° C, boiling point of 11 ° C, exists in the form of a gas at room temperature, for a kind of yellowish green gas. When the concentration increases, the color changes to orange-red, gas chlorine dioxide is extremely unstable. Chlorine dioxide is soluble in water, the solubility of 107.98mg/L at 20°C, can be made into an unstable liquid, its liquid and gas are more sensitive to temperature, pressure and light, when the content of the air is higher than 10%, the spark can be detonated [1], chlorine dioxide is an unstable compound in water can be turned into HClO2 and HClO3.3., about 2-10% per day at room temperature The dissociation rate of [2], so it is not conducive to the preparation and transportation of large quantities, generally more in the use of the site now prepared.
Chlorine dioxide generator preparation of chlorine dioxide methods are mainly electrolysis and chemical methods, electrolysis is widely used in the diaphragm electrolysis, salt as raw material, under the action of the electric field to generate a mixture of chlorine dioxide containing sodium hypochlorite, hydrogen peroxide, ozone, the concentration of chlorine dioxide is generally only 10-30% or so, most of the chlorine gas. Chemical method mainly with sodium chlorate and sodium chlorite as raw materials for the two types of chlorine dioxide generation method. In the sodium chlorate method of production of chlorine dioxide process, if the chlorine ion as a reducing agent, the produced chlorine dioxide has the disadvantage of low purity, while the sodium chlorite method of chlorine dioxide has a high proportion of the general more than 90%.
1.2 Equipment and sterilization performance
The generators introduced from abroad are mainly Tetraralent, Rio Lindo, Germany's Prominent, etc., Li Lingwen et al [3] reported the synergistic sterilization effect of chlorine dioxide synergistic disinfector of Tetraralent, which utilizes electrolysis of the salt solution, and at the same time generates chlorine dioxide, chlorine gas, ozone and hydrogen peroxide, which are dissolved in water and synergistically sterilized, and its sterilizing effect is superior to any of the above mentioned disinfectants.The experimental results also indicate that the electrolysis voltage, current, electrolyte concentration and effective area of anode of electrolysis tank have an effect on the gas production of the sterilizer. Huan Pengcheng et al [4] on the United States Vulcan Rio Linda T140 chlorine dioxide generator for disinfection effect observation, the generator generates chlorine dioxide concentration can be adjusted in 2000-300mg / L, kill Escherichia coli, Staphylococcus aureus 1mg / L 3 minutes, kill Bacillus subtilis black variant spores 125mg / L 5 minutes, destroy HBsAg 125mg/L 2 minutes, the lowest concentration of energy experiments for 400 mg/L, 25% and 50% calf serum to protect the bacterial solution, then the bactericidal effect can be affected, the generator at a low concentration (10mg/L), on the copper sheet, carbon steel sheet, aluminum sheet is mildly corrosive, on the stainless steel sheet is basically non-corrosive.
Domestic chlorine dioxide generator development faster, the process is gradually mature [5]. At present, there have been used to produce chlorine dioxide through electrolysis of table salt, as well as sodium chlorate and sodium chlorite method of production of positive and negative pressure chlorine dioxide generator, some of which have been awarded a national patent. Ren Qingwei [6] according to the electrolysis method of preparation of chlorine dioxide mixed disinfection solution of the working principle and operating characteristics, the use of single-chip computer technology and residual chlorine detector, the realization of chlorine dioxide disinfection equipment, salt, alkali and operation of the whole process of regulation of automatic control, greatly improving the efficiency of disinfection and safe operation of the equipment. Chlorine dioxide produced by chemical method of higher content, Shi Lai-shun et al [7] developed a chemical method of chlorine dioxide generator, the iodine amount of chlorine dioxide composite disinfectant solution prepared by the generator determined that the effective chlorine content of 3246.1 mg / L. Detected by UV spectrophotometer and infrared spectrophotometer, the solution contains chlorine dioxide and chlorine, of which chlorine dioxide accounted for 60% -70% of the aqueous solution to the microorganisms. The killing effect of the aqueous solution on microorganisms, containing 4.5-5.0 mg/L active ingredient of Staphylococcus aureus, Escherichia coli and Candida albicans in the water for 1-2 minutes, containing 90 mg/L active ingredient of Bacillus subtilis black variant spores in the role of 5 minutes, the killing rate of 99.9% or more. Containing 400 mg/L active ingredient can destroy HBsAg antigenicity in 5 minutes. Chlorine dioxide generator chlorine dioxide disinfectant performance is more unstable [8], stored for 3 days, the degradation rate of 14.05%, such as the disinfectant solution plus analytical purity of sodium hydroxide, the PH value adjusted to 11.80, airtight and protected from light, stored at room temperature (18 ° C - 25 ° C) 18 months, the degradation rate of only 3.31%.
1.3 Application in disinfection
At present, chlorine dioxide generator is mainly used for drinking water disinfection and sewage treatment, etc., the traditional disinfection of drinking water disinfectant chlorine disinfectant in the treatment of raw water will have a large number of halogenated hydrocarbons, including trihalomethanes, such as chloroform, as well as chlorinated phenols and dichloroacetonitrile, etc. There are
.