Study On The Preparation Of Chlorine Dioxide And The Corrosion Characteristics Of Steel Materials During The Disinfection Process

Chlorine dioxide(ClO2)is widely used in paper and pulp bleaching,drinking water disinfection,food preservation,hospital disinfection,agricultural planting soil disinfection,industrial wastewater,circulating cooling water treatment and other fields due to its strong oxidizing properties,high efficiency,broad spectrum,and green safety.ClO2 is mainly used in the form of raw material on-site generation,chlorine dioxide tablets,and chlorine dioxide powder in different scenarios.In the process of use,the ClO2 solution prepared on site and prepared from the tablet powder product has a low pH and contains a large amount of impurities,causing varying degrees of corrosion to the metal appliances,equipment and pipes that are in contact in the use scene.This article selected a ClO2 powder product purchased on the market to study its corrosion of 20#steel,304 stainless steel and 316L stainless steel.It was found that in the ClO2 solution prepared by this product,when the solution concentration is 200 mg/L,20#Severe corrosion occurs;for corrosion-resistant 304 stainless steel and 316L stainless steel,when the solution concentration was 800 mg/L,severe corrosion also appeared.In order to solve the above problems,this research has developed a low-corrosion,environmentally friendly production method of ClO2 preparations,and studied the highprecision prepared by this method through static coupon weight loss method,potentiodynamic polarization curve method and scanning electron microscope-energy spectrum microanalysis.Corrosion of pure ClO2 solution to metal material 20#steel,304 stainless steel and 316L stainless steel.This article adopted the preparation process of the reaction of carbon dioxide(CO2)and sodium chlorite(NaClO2).The preparation process is simple,the raw materials are safe,and there is no need to provide an additional strong acid environment.At the same time,it solves many problems such as the recycling of ClO2.The process was further optimized,and the study found that the addition of catalyst can greatly increase the reaction rate.With the increase of the catalyst dosage,the temperature of the reaction solution and the increase of the reaction time,the y ield and purity of ClO2 showed a trend of first rose and then fell;the smaller the temperature of the absorption solution and the flow of CO2 within the research range,the more the ClO2 is collected.The higher the rate and purity.The optimal process parameters of this process are:the mass ratio of catalyst M2 to NaClO2 is 1,the reaction liquid temperature is 30℃,the reaction is 20 min,the CO2 flow rate is 0.5 L/min,and the absorption liquid temperature is 5℃.The ClO2 solution prepared with this process parameter has a yield of 93.39%,a purity of 98.78%,and apH>5.1.The corrosion of the prepared high-purity ClO2 solution on 20#steel,304 stainless steel and 316L stainless steel was studied.The study found that compared with the ClO2 powder products purchased on the market,the high-purity ClO2 solution prepared by this process significantly reduced the corrosion of 20#steel,and basically no corrosion to 304 stainless steel and 316L stainless steel.In the high-purity ClO2 solution,the corrosion rate of the three metals increases with the increase of the solution concentration,and decreases with the increase of the pH of the solution.The effect of pH on metal corrosion is weaker than that of the solution concentration.20#steel has no passivation in the high-purity ClO2 solution.When the solution concentration was 800 mg/L,the corrosion rate reached its peak.When the ClO2 concentration in the solution exceeded 800 mg/L,the corrosion products gradually changed from y-FeOOH It is a dense α-FeOOH,which hinders the contact between the corrosive solution and the metal matrix to a certain extent,and slows down the corrosion process.304 stainless steel has a passivation tendency in a solution of 200～1000 mg/L and has a low passivation potential.The passivation potential increases with the increased of the concentration,and decreases with the increase of pH,and it is easier to reach the passivation state.Mainly experienced the process of passivation film formation,gradual destruction and dissolution.The corrosion products are mainly composed of flake iron oxides and Cr2O3 microscopically,and there are also flowershaped substances composed of square NaCl and a small amount of SiO2.316L stainless steel appears twice in the high purity ClO2 solution of different concentrations.However,the passivation state is not completely formed,and the smaller the concentration,the lower the passivation potential.When the solution concentration is greater than 800 mg/L,slight pitting corrosion appears on the surface of 316L stainless steel microscopically,and the corrosion products are mainly small particles of iron oxide,flake and needle-like αFeOOH and NaCl.When the concentration of ClO2 solution is low,316L stainless steel will be passivated in acidic and alkaline solutions.