Reversible Chlorite/Chlorine Dioxide Anion Redox Couple for Low-Cost Energy Storage
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The ClO2-/ClO2 electrochemical reaction is shown to be highly reversible in acidic, near-neutral, and alkaline electrolytes while using low-cost carbon electrodes. Its equilibrium potential (0.954 V vs SHE) is pH-independent and enables high aqueous cell voltages of 1.38-2.15 V when used as a positive electrode with negative electrodes such as Zn, Fe, or S. This anion redox couple may enable low-cost aqueous rechargeable batteries free of resource-constrained metals, here demonstrated in prototype Zn-NaClO2 full cells. The rapid reaction kinetics and stability of the ClO2 phase at low temperatures also suggests that chlorite-based batteries may be favorable for applications in cold environments.Chlorine dioxide is being increasingly used as a water disinfectant. Residual chlorine dioxide may, however, be accompanied by traces of chlorite, which carries a possible health hazard. The method presented determines both forms, and also provides for the separate determination of any associated free chlorine and chloramines.
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To know the effects of combined disinfection on DBPs and enhance water quality safety,static pipe reactors were used and three kinds of commonly used pipe materials were selected to investigate the effects of pipe materials on chlorite formation in combined disinfection of chlorine and chlorine dioxide.Results indicated that the chlorite levels were the highest in PVC pipe and lower in metal pipes for both of the two kinds of combined disinfection.The difference between the two ways was that in the way of adding chlorine and chlorine dioxide together,chlorite levels in the ductile iron pipe increased with the increase of chlorine and decrease of chlorine dioxide in the mixed disinfectant.While,for the way of adding chlorine first and then adding chlorine dioxide,the chlorite levels were higher in ductile iron pipe than that in stainless steel from the beginning to the end.
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This paper was designed to study the concentration of chlorite and elucidate the factors on concentration of chlorite in drinking water pipe network disinfected by chlorine dioxide. The result showed that the lowest concentration of chlorite was connecting tube,elbow tube and branch in drinking water pipe network. The most important impact on chlorite was pipe sordes and flow rate. The transformation of chlorine dioxide disinfection byproducts in pipe network considered drinking water from safe to health play an important role.
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Chlorate
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Chlorate
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This paper aims to study the generating regularity of the inorganic by-product chlorite in the algae preoxidation with chlorine dioxide in drinking water processing.For this purpose,we have made an investigation over the generating regularity of chlorite under the conditions of different dosages of chlorine dioxide,contact time and pH.We have also studied the other influencing factors related to water quality,such as algal initial concentration,organic substances and ammonia nitrogen concentration on the generation of the by-product chlorite.The testing and investigation results show that the by-product chlorite increases with the increase of the dosage of chlorine dioxide.In addition,it is found that time is the key factor to influence the generation of chlorite.Actually,large amounts of chlorite would be resulted in 30 minutes.Two hours later,we may find that there would be generated chlorite which is 10 to 30 percent of chlorine dioxide,with an initial pH value beginning to generate the chlorite.The longer the contact time,the lower the initial pH would be.30 minutes later after a 10 minute reaction,the initial pH value would increase to 6.However,70 minutes later,the initial pH value would turn to be 3.9.Furthermore,the chlorite would gradually increase in the acidity condition while the pH value would change from low to high.Nevertheless,when the pH changes from neutral to alkalinity,little increase would be found of the chlorite in final analysis.But,when the algal chlorophyll-a concentration remains below 14.93 μg/L,no variation of the amount of by-product chlorite could be found with the initial algal concentration.However,when the algal chlorophyll-a concentration is greater than 14.93 μg/L,the chlorite tends to increase with the increase of the algal initial concentration.Though the organic matter is likely to promote the formation of chlorite,the chlorite wouldn't be found increasing with the increase of the concentration of the organic matter,which demonstrates a decreasing trend with the increase of the ammonia nitrogen concentration.And the residual chlorine dioxide is found decreasing with the time prolonging in the process of the formation of chlorite.Based on the regression analysis of the experimental data,the relation between the residual chlorine dioxide and the time to be elapsed seems to be a function of the power series in the generation of the by-product chlorite.
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Abstract Great concern has been risen due to the harmful by-product formation in chlorine dioxide disinfection. To control the by-product formation, we need to know the factor that make a great contribution to generate by-product in drinking water treatment. The Fe 2+ , Mn 2+ , organic matter and algae are the most presenting matters that could cause the formation of chlorite; thus, they were selected as factors in the study. The results showed that the amount of by-product chlorite produced increased along with the increase of the concentrations of organic matter, algae and Fe 2+ in water, but the presence of Mn 2+ didn’t impact on the formation of chlorite. In addition, the interaction between Fe 2+ and Mn 2+ was observed, but no obvious interaction between other factors was found. So when the concentration of above factors exceed the standard, the chlorine dioxide is not recommended in any step of the water treatment.
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Experiments were conducted by using raw water from a reservoir of south China to study consumption of chlorine dioxide and formation of chlorite.The results show that chlorine dioxide decays quickly in the beginning in samples,then the consumption is constant in first order-model.39.7%～57.9% and 48.0%～70.0% of chlorine dioxide consumption are converted into chlorite by means of the combinations of chlorine dioxide and chlorine,and pure chlorine dioxide,respectively.And the amount of chlorite formation is lower as micro-polluted raw water is treated by the comlinations.
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Although chlorine dioxide does not form trihalomethanes (THM) and produces very few non-volatile haloorganic materials in drinking water, intensive investigations bearing on the formation of chlorite by ClO2 disinfection reveal that the rate of chlorite formation reflects the rate of ClO2 consumption and as long as the amount of ClO2 applied is behind its demand, about 60% of the chlorine dioxide consumed is converted into chlorite. Mixtures of Cl2 and ClO2, which may successfully reduce the formation of haloorganic compounds, as well as of chlorite in the absence of bromide, fail to do this where water rich in bromide is concerned. As a result of bromide oxidation by chlorine, bromine is formed, which in turn reacts more intensively with organics than does chlorine and thus favours the formation of THM and other halogenated organic materials. This problem can, however, be circumvented if ClO2 is allowed to react in water with the organic precursors before chlorine is introduced. A pre-treatment with 1 ppm of ClO2 two hours before the application of 2 ppm Cl2, was found to reduce the formation of THM by 60% relative to its formation by chlorine alone, and the chlorite is reduced in this case by up to 90% relative to its formation by chlorine dioxide alone. This is of particular importance since it can solve some of the major problems bearing on the impact of disinfection upon the formation of undesirable by-products.
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