Separate Beds Electrodeionization (edi) Technology To Prepare Ultrapure Water

Electrodeionization (EDI), known as a new technology for water purification, combines ion exchange and electrodialysis, which is to realize deeply desalting in low concentration solution. Based on the essential analysis of EDI, the separated bed EDI was put forward to overcome the shortages, such as low water throughput by unit memberane area, low current efficiency and low removal rate of weak electrolyte, which exist in traditional mixed-bed EDI on current.In this paper, four new styles of separated-bed EDI were schemed out, and the good results of desalting were achieved. In the same time, a new scheme of EDI with bipolar membrane process was contrasted experimentally.The feasibility of four new styles of separated-bed EDI process are proved. Result shows that the deeply desalting in low concentration solution can be realized in four new styles of separated-bed EDI process, the desalinization ratio up to 98% and the resistivity of product water can reach 4 MΩ·cm. But the long-term running indicated that the quality of product Water quality worsen and voltage of stack increased with the passage of time, the quality of water also can not reach the standard of the ultra-pure water. The further researches about new styles of separated-bed EDI should be done in the future. Then the experiment about EDI with bipolar membrane shows that the shotage of conventional EDI with bipolar membrane was conquered by the new scheme of EDI with bipolar membrane. The high quality water can be produced stably and continuously, the desalinization ratio up to 99.9% and the resistivity of product water can reach 17.5MΩ·cm. And then the experiment with multi-unit scheme of EDI with bipolar membrane was carried out and the resistivity of product water could reach over 18MΩ·cm, and the good prospect of EDI with bpolar membrane for industrial application was laid out.