Investigation Of DO Removal In Recycled Water On Modified Activated Carbon

There is a serious shortage of water resources in the Shanxi Province Taiyuan,as an energy and chemical base,industrial water consumption is very large.If you can put the discharge of urban sewage for recycling for industrial water,The recycling municipal wastewater can be used in urban greening,toilet flushing,road watering and cleaning and other situation of using miscellaneous water.A great number of industrial water consumption in Taiyuan can be seen.If we can use the recycling municipal wastewater as industrial water,not only municipal wastewater can be recycled,but also the shortage of Taiyuan's water resources can be solved.However,it will spend a large number of money in building a specific pipe to convey recycling water.Because of low temperature in winter,those homes in the most areas of northern China are warmed up by central heating with the heating pipe;however,the heating pipe will be idled in other seasons.In fact,the quality of recycling municipal wastewater is closed to the standard of Design Code of District Heating Network.In this case,with the suitable treatment,it is possible for conveying industrial water by using the heating pipe.But the prerequisite is that the original heat pipe network system can not be corroded,affecting the subsequent heating,oxygen corrosion is the most important cause of pipeline corrosion,chloride ion(C1-)can also cause pipeline corrosion,so the DO removal of sewage reclaimed water is very important.The traditional methods of DO removal are physical,chemical and catalytic methods,and the catalytic process is widely concerned because of the rapid reaction but not the increase of toxic substances into the water body.In order to obtain the best performance of modified activated carbon,in this paper,the raw activated carbon was modified by using high pressure hydrothermal system,the method of impregnation and the combine of them;and then used as catalysts into the chemical reaction between hydrazine(N2H4)and dissolved oxygen(DO)in water.The removal rate and removal amount of dissolved oxygen is investigated in this study.The study concludes that:1)the raw activated carbon modified by using high pressure hydrothermal system has the best catalysis effect at 270?,removal rate can be nearly 53.07%;2)for those raw activated carbon modified by using the method of impregnation,raw activated carbon was dipped by Ni(NO3)2 solution,when soaking temperature of 60?,soaking time for 3 hours and content of metal is 5%;removal effect of dissolved oxygen is the best,removal rate can be nearly 85.92%;3)for those raw activated carbon modified by combine of two methods mentioned above,activated carbon modified by high pressure hydrothermal system firstly and the method of impregnation secondly shows the best catalysis,effect removal rate can be nearly 98.56%.The study chose GS270-5-Ni-60-3,a kind of modified activated carbon with best catalysis effect,as catalysts to investigate the influences of temperature,pH,flow rate,the amount of catalysts and other operating conditions that can affect experimental results.The research concludes that:1)the higher temperature,the faster chemical reaction rate,and the higher the removal rate of dissolved oxygen can be found;removal effect of dissolved oxygen is the best at 45 ?,removal rate can be nearly 99.46%;2)alkaline condition is favourable for the catalysis effect of modified activated carbon,removal effect of dissolved oxygen is the best at the point of pH=13,removal rate can be nearly 99.64%;3)when the amount of catalysts is 7g/L,the removal effect of dissolved oxygen is the best,removal rate can be nearly 99.64%;4)it shows when flow rate is 5L/h,catalytic performance is the best.The optimal experimental condition in which dissolved oxygen is removed by modified activated carbon optimized and selected by orthogonal test is temperature of 45 ?,pH=13,flow rate of 5L/h,the amount of catalysts of 7g/L;under these conditions,removal rate can be nearly 99.82%.The method of nitrogen cryogenic adsorption,SEM,FTIR were used in this study to analysis raw activated carbon and modified activated carbon.According to the study of nitrogen cryogenic adsorption method,1)high pressure hydrothermal system significantly improve pore structure of activated carbon;2)when comparing the effect of using sequence between high pressure hydrothermal system and isovolume impregnation method,using high pressure hydrothermal system firstly shows more the amount of loaded metal.This phenomenon is because some data which stands for character of modified activated carbon using this sequence is less than that of another sequence.These characters include the number and volume of mesopore,total micropore volumes and BET surface areas.According to the study of SEM and EDS elements analysis method,this sequence shows an significant improvement of the amount of loaded Ni.This is because the method combines all advantages of high pressure hydrothermal system and isovolume impregnation method;in addition,after using high pressure hydrothermal system,modified activated carbon shows larger pore size and uniform distribution of pore structure.According to the study of FTIR characterization analysis,using high pressure hydrothermal system,isovolume impregnation method and the combine of them can change the number of functional groups rather than the type of them.Specifically,they can improve the number of NH and C-O-C-O-C which can contribute to improve catalytic performance of activated carbon.This dissertation provides a systematically research of preparation of modified activated carbon,practical operation conditions and reaction mechanism of removal dissolved oxygen in water.However,it still involves some shortages such as the research of catalytic mechanism.In this case,further study is needed.