Treatment Methods Of The Residue From Chlorine Dioxide Generator

Chlorine dioxide is applied in disinfection process widely due to its advantages of efficient and fast disinfection effects and less disinfection by-products.However,during the preparation process of chlorine dioxide adopting compound methods,harmful pollutant of concentrated chlorate is always existing in its residue.But there is not a suitable treatment way of the residue.Chlorate in the residue is hazard to the environment.Ion-exchange technology and redox methods can be used to remove chlorate depends on that chlorate belongs to the oxoanion and it has strong oxidation.So in this study,the rule of concentrated chlorate removal was explored by ion-exchange and iron powder reduction technology.An efficient and harmless treatment process for residue of chlorine dioxide generator is estanblished on the basis of the comparison of various processes.In this research,separation and enrichment of chlorate by using anion-exchange membrane from the residue of chlorine dioxide generator were investigated.The operational condition parameters including exchanging solution composition and concentration,stirring intensity,temperature,pH,co-existing anions and influent flow were surveyed by a sery of batch tests.When the initial concentration of sodium chloride as exchange-solution was 270.0 g/L,the temperature was 25±1 ?,pH of the solution was 7.0 and the strring intensity was 200 r/min.The experiment results demonstrated that anion exchange membrane could effectively separate and enrich chlorate from the residue of chlorine dioxide generator for 288 hours under the best condition,and 87% efficiency was achieved,which enrich the concentrated chlorate in 7.5 times as the influent.The effects and influence factors of anion-exchange membrane on chlorate were investigated.The static and dynamic experiments of ion exchange resin for the treatment of chlorate were carried out.The results indicated that the resin has large adsorption capacity,which was 1.25 g Cl O3-/g,and the removal efficiency was higher than 95%.Pseudo two order kinetics model was found to be fit in the adsorption process.The dynamic experimental results showed that the efficient volume of ion exchange column increases with the decrease of the empty bed residence time.Besides,the higher concentration of the inflow and the smaller of the ion exchange column,the shorter of the breakthrough time.Desorption experiments showed that desorption concentration reached the maximum of 23.51 g/L at 100 min and renewable resins could recycle.The effect factors and mechanism of the iron powder for removing chlorate in acidic condition were conducted.The results suggested that iron powder could effectively remove chlorine ions at pH=2.0,and the removal efficiency of 99% was reached.In addition,increasing temperature,shocking speed and iron dosage could improve the reduction speed and rate.Pickling pretreatment is another way to improve the reduction speed and rate.Further more,iron powder could be recycled for 15 times.Comparing above results and the actual residue processing requirements,iron powder is observed to be the most efficient for the disposal of chlorate and it is recommended to be applied to treat the residue in chlorine dioxide generators.Treatment system is established of iron powder,and the treated liquid could be used as flocculating agent after oxidation by ozone.Eventually,efficient and harmless disposal of the residual liquid is achieved.