Research On The Adsorption Mechanism And Application Of Capacitive Deionization In Concentrated Brine Treatment

The shortage of fresh water resources and the abundant sea water resources are the current status of water resources in China and many countries around the world.Therefore,it is very important to study a cost-effective concentrated brine reduction technology.Electro-adsorption technology（capacitive deionization technology）has the characteristics of high efficiency,stability,energy saving and environmental protection.It is favored by many water treatment workers as a technology for seawater desalination and concentrated brine reuse in the 21st century.Most of the research on electrosorption technology is still in the laboratory stage,and it is rarely applied to the treatment of actual wastewater.This study takes the actual water treatment objects and needs of the power plant as a starting point.Based on the treatment application research,it focuses on the quantitative analysis of the relationship between the adsorption mechanism,deionization effect,device structure and operating conditions of the electro-adsorption technology.This article mainly includes three parts:mechanism research,simulation analysis and application exploration.The mechanism research is mainly aimed at the adsorption stage of the electro-adsorption technology.On the basis of comparing and analyzing the existing electro-adsorption models,try to explain the adsorption process in the electro-adsorption technology through the force and motion analysis of ions The mathematical relationship between the ion removal rate of the adsorption device and the operating conditions（operating voltage,inlet water flow rate）.The simulation analysis mainly uses the salt solution prepared in the laboratory and a self-made electrosorption small test device to simulate the adsorption process,and at the same time,the established"electrosorption model based on the charged particle force analysis"is verified and optimized.In the application exploration part,this subject is based on the electro-adsorption pilot experimental project,to explore the effect of electro-adsorption technology on the treatment of reverse osmosis concentrated water in the power supply network of power plants,and to try to use Analyze and interpret the experimental results.The research conclusion and results of this article are as follows:（1）The electrosorption model based on the analysis of the force of charged particles takes the most unfavorable adsorbed ions in the concentrated brine flowing between the plates of the device as the research object.By calculating the relationship between its force and motion,the ion removal rateηand the operating voltage U are obtained.The mathematical relationship of is:η=（εne L²）U/[2H（H-2b）v²]-（εK₁t HL²）/[2H（H-2b）v²]（U>0）.The mathematical relationship between the ion removal rateηand the inlet water flow rate v is:η=[ne U-K₂t H)L²]/[2H（H-2b）v²]+ξ（v>0）.（2）The electro-adsorption model based on the change of device resistance is an electro-adsorption model that removes changes in ion rate caused by changes in resistance during adsorption.Through analysis and calculation,the mathematical relationship between the ion removal rateηof the electrosorption device and the operating voltage U is:η=φδV/（ctn FQ_v²（R+ΔR））U.The mathematical relationship between ion removal rateηand flow rate Qv is:η=φδVU/ctn F（R+ΔR）Q_v².（3）The electro-adsorption small test device was used to process the prepared salt solution.After fitting the experimental data,it was found that when the operating voltage of the small test device was between 0.2v and 1.2v,the mathematical relationship between the ion removal rate and the operating voltage basically conformed to a linear function relationship,The anastomosis is high.When the inlet water flow rate of the small test device is between 4 mm/s and 20 mm/s,the mathematical relationship between the ion removal rate and the inlet water flow rate is in good agreement with the model,and basically meets the form ofη=A/x²+B.（4）The pilot test of the electro-adsorption pilot plant to treat the power plant boiler feed water reverse osmosis concentrated water shows that the electro-adsorption device effluent is stable,and the maximum conductivity of the effluent in the test can be reduced by 1.021ms/cm,which has engineering application value.Optimizing the operating conditions of the device within a certain range is beneficial to improve the quality of the effluent and is consistent with the adsorption model.Moreover,the electro-adsorption technology has the characteristics of low operating cost,and after calculation,the electro-adsorption device only needs 0.98 yuan per ton of water.Compared with other technologies,electro-adsorption technology has economic advantages in the application of reverse osmosis concentrated water concentration reduction.（5）The conductivity,calcium ion,magnesium ion,sodium ion and chloride ion removal rate of boiler make-up water reverse osmosis concentrated water is proportional to the operating current and inversely proportional to the feed water flow rate;and the removal effect of calcium ion and magnesium ion is better than that of sodium ion.The test data combined with the"adsorption model based on ion force analysis"analysis shows that the electrosorption device preferentially adsorbs ions with high valence when adsorbing isoelectric ions.)In this pilot test,the optimal operating current is 37A,the optimal inlet flow is 26L/min,and the water yield is 50%.