Study On Electro Adsorption Technology Based On Desalination Of Alkali Drainage Ditches Water

The current situation of saline land in China is not optimistic。There are about 34.6 million hectares of saline land and the situation of soil salinization is deteriorating.People have invented various methods to reduce the salt in the land,When people handle saline land by water conservancy means,this will produce alkali drainage water containing a large amount of salt,which will pollute the land around the drainage and reduce biodiversity.Therefore,it is essential to find a suitable method to treat the alkali drainage water.In this study,from the actual treatment needs of alkali drainage water,the specific characteristics of agricultural water,such as low requirements for effluent quality,low operating costs and salt removal,were compared with various water treatment technologies,and electrosorption technology was selected as the treatment method for alkali drainage water.The activated carbon was modified and the electrodes were prepared on the basis of improving the performance of the activated carbon as an electrosorption electrode.SEM surface morphology comparison,contact angle analysis,specific surface area and pore size analysis,and FT-IR characterization of the activated carbon before and after modification demonstrated that the modification could improve the hydrophilicity of the activated carbon,and that changing the pore structure and microporous pore capacity of the activated carbon could improve the desalination capacity of the activated carbon as an electroadsorption electrode.This was also confirmed by the comparison of desalination experiments of the electrodes afterwards.Then a complete set of electroabsorption pilot equipment was built based on the electrode of the modified activated carbon.Finally,the effect of desalination of alkaline drainage water was tested with this electroabsorption pilot equipment.Firstly,single-factor experiments were conducted to determine the optimal range of the three operating conditions affecting the treatment of alkali drainage water by the electroabsorption module: the optimal range of interplate voltage: 1.6 V～2.0 V,the optimal range of inlet water flow rate: 15～25 m L/s,and the optimal range of treatment time: 17～19min;then the optimal operating conditions were determined by the response surface method: interplate voltage: 1.81 V,inlet water flow rate: 20.5 m L/s,and treatment time: 18 min.At this time,the conductivity,chloride ion,COD and total salt of the alkaline drainage water could be reduced from 6935 μs/cm,1351 mg/L,12.95 mg/L and 4780 mg/L to 1358.76 μs/cm,214.20 mg/L,9.72mg/L and 837 mg/L.The removal rates were in the following order The removal rates were: 80.41%,84.15 %,24.94 %,82.49 %.All the above indicators can meet the requirements in the Standard for Agricultural Irrigation Water Quality(GB5084-2021),and the treated alkali drainage water can be discharged directly,reused as washing water or reused as agricultural irrigation water.The desorption phase of the electroadsorption was investigated.The experiments yielded a desorption time of 3 minutes for the electroabsorption module and 21 minutes for the entire adsorption-desorption time.With the whole adsorption-desorption phase as the research target,experiments were conducted on the continuous operation of the electroabsorption to treat the discharge alkali canal water.The experiments showed that the desalination effect of the electroabsorption module could maintain 94% of the initial effect and still maintain 75.65% of the desalination rate after10 consecutive adsorption-desorption processes.The electrodes of the electroabsorption module were regenerated by acid washing with dilute hydrochloric acid after 10 cycles,and the results showed that the electrodes after acid washing and regeneration could recover99.31% of the initial desalination capacity.The water yield of electroabsorption was calculated,and the water yield of electroabsorption treatment of alkali drainage water was 67%.Based on the water yield,the economics of desalination of alkali drainage water by electrosorption was evaluated and the production cost per ton of fresh water was found to be about 0.7248 yuan.