Electrodialysis(EDI) system
Overview:
Eectrodialysis(EDI)is a method of seawater desalinatio using ion exchange membranes. lon exchange membrane is a functional membrane,which is divided into an ion exchange membrane and cation exchange membrane,[referred to as negative membrane and positive membrane].The positive membrane only allows cations to pass through,and the negative membrane only allows anions to pass through,which is the selective permeabiity of the ion exchange membrane.Under the action of an external electric field,the anions and cations in the aqueous solution will move towards the anode and cathode respectively.If an exchange membrane is added in the middle,the purpose of separationand concentration may be achieved.Electrodialysis uses this principle.
Use:
polyethylene heterogeneous ion exchange membranes contain enough fixed groups and dissociable ions,which have certain selective permeability and conductivity for ions in solution.It is widely used inelectrochemical departments to separate different types of ions.For example,desalination of seawater and brackishwater,desalting concentration of solution,electrolytic preparation of inorganic compounds and recoveryand purifcation of radioactiveelements,softening and desaltingof boilerwater, processing of industrial products such as metallurgy,coal,electronics,medicine,chemical industry and food.
Advantages:
No chemical consumption,simple equipment,easy to operate.
Application:
Electrodialys is method was first used for desalination of seawater,making drinking water and industrial water,concentrating seawater to make salt,and combining with other technologies to make high-purity water,and later has been morewidely used in wastewater treatment.
The most common way to use the electrodialys is in wastewater treatment:
1、Treat alkali papermaking waste liquid,recovering alkali from the concentrated liquid and recovering lignin from the diute liquid;
2、Separateand concentrate heavy metalions from wastewater containing metal ions,and then further treat or recycle concentrated liquid
3、Separate radioactive elements from radioactive wastewater
4、Prepare sulfuric acid and sodium hydroxide from the waste liquid of glauberite;
5、Preparesulfuricacidand deposit heavy metal ions from picking waste liquid;
6、Treat electroplating wastewater and waste liquid.Metal ion wastewater including Cu2+,Zn2+,Cr(IV), Ni2+ is suitable for electrodialysis treatment,which is more widely used in recovering nickel from nickel plating waste liquid.Many factory practices have shown that this method can achieve closed-oopcirculation.
