Study On The Preparation Of Chlorine Dioxide With Sodium Chlorite

As an efficient disinfectant, chlorine dioxide was widely accepted and used, so there are many methods for chlorine dioxide preparation. The main purpose of this paper is to find a better method to produce chlorine dioxide. The main jobs are followed:Firstly, the five-step iodometry method was improved, made it proper to determine the concentrations of CIO2and CI2in this study. Secondly, the performance of NaC102activated by several acid activators was studied, a suitable acid activator was got, and some attempts in improving activation effect and raw materials utilization rate were done. Thirdly, by single-factor and orthogonal experiments, the performance of NaClO2activated by sodium persulfate and potassium peroxymonosulfate was studied, and some preliminary discussions on thermodynamics and kinetics of the reaction between NaClO2and Na2S2O8were studied, and also some attempts in optimizing reaction process were done.The results of pre-experiments show that, blowing-absorption-iodometry method can be used to determine the concentrations of CIO2and CI2.The results of acid activator activation experiments show that the activation effect is mainly determined by H+concentrations, oxalic acid is the strongest acid and its activation effect is the best in the three acid activators studied. In a suitable reaction condition, the rate transformed from NaClO2to ClO2is44.32%. In the reaction system, the added Cl-can improve the activation effect, especially activated with sodium bisulfate, the rate transformed from NaClO2to ClO2mounts from36.48%to49.96%, reach to its best theoretical value. The results also show that activator is not absolutely reacted in the reaction, and the activator left still can be used.The results of persulfate activation experiments show that the performance of NaClO2activated by potassium peroxymonosulfate is not good, but the activator of sodium persulfate is very good. The single-factor and orthogonal experiments indicate that reactor initial concentrations and reaction time are the most important matters that influence the reaction, and a optimal reaction condition was got:the reaction time is1h, reaction temperature is35℃, initial concentration of NaClO2is16.67g·L-1, the mass ratio of NaClO2:Na2S2O8is2:9, in this reaction condition, the yield of chlorine dioxide is82.39%, and purity is95.84%. Through the experiments between Na2S2O8and NaClO2, the reaction kinetic equation is established at pH7.0, and the reaction activation energy found is43.04kJ·mol-1. Some attempts of using metal salt and ClO-to increase the reaction rate were done, manganese salt has some effect.In this paper, some attempts in optimizing the process of chlorine dioxide preparation with acid activator were made, and these attempts can improve the activation effects. The experiments of NaClO2activated by Na2S2O8were also studied, the results indicate that this method is a good way to prepare chlorine dioxide, these results provide references for the practical production of chlorine dioxide.