Study On Enrichment Of Trace Heavy Metal Ions By EDI

With the increasing of the industrial and domestic waste, the problem of heavy metal pollution in water is very outstanding. Separating and recycling heavy metal is an important task in the field of wastewater treatment. Because of the properties of heavy metal ions are similar to each other, and the content of metal ion concentration is too low, and the composition in water is complicated. Separation and recovery of a particular ion from the mixed system of heavy metal ions is a difficult problem. Therefore, we urgently need to develop such a high-efficiency, cost-effective, manageable, non-polluting of heavy metal wastewater treatment method, which can recovery of valuable metals. Electrodeionization is a new kind of separation technology, electrodialysis and ion exchange skillfully combined organic membrane desalination technology. EDI has been widely used in pure water preparation field, at the same time, because it has a technical characteristic of high concentrated water concentration difference, EDI in low concentration of heavy metal wastewater treatment with good development prospects.This article used the self-made EDI stack. The condensed water is recycled. To simulate a heavy metal wastewater as the research object, researched and analyzed the effect of working current, feed flow rate and feed concentration to the enrichment performance of Cu2+ in the EDI process. Moreover, researched the effect of working current, feed flow rate, complexing agent and the pH of feed solution to separating of binary mixture of heavy metal ions.The results showed that, there was a balance of time in the process of EDI. Sampling after the balance time has the well stability. In the process of enrichment of Cu2+, beneficial to the improvement of the enrichment factor, if increased the working current and feed flow rate appropriately. By optimizing the operating conditions, the feed flow rate was 60 mL/min, the working current was 190 mA. After two hours of continuous running, the concentration of Cu2+ in the concentrated water was 9.45 mg/L, and the enrichment factor was 189.Researched the selective separation of heavy metal ions in the process of EDI. It was benefit to the selective separation of heavy metal ions, if increased the working current and feed flow rate appropriately. By optimizing the operating conditions, enrichment factor of Cu2+ was 214, the value of two kinds of ion separation ratio was 19.68. The results showed that, after the excess complexing agent is added to the feed water, the selectivity of Cu2+ in the EDI process is enhanced, and the value of Cu2+ and Co2+ separation ratio is increased. Added the excess complexing of EDTA, and remained the feed water neutral, the working current was 200 mA, the feed flow rate was 60 mL/min. After two hours of continuous running, the value of Cu2+ and Co2+ separation ratio was 37.92. The separation efficiency was improved remarkably. The result in this study was demonstrated that, there were a good concentration effect of trace heavy metal ion and a well performance of selective separation of heavy metal ions in EDI process.