Development of a Spacer for the Diluting Compartment of EDI-LB (Electrodeionization-Layered Bed) Device

Yiqing Li, Shan Guan, Enqi Tang
2010 Journal of Sustainable Development  
With the product water from a one-stage reverse osmosis (RO) process as the feed water, ultrapure water has been prepared by a self-designed module for one-stage one-pass RO/EDI/LB filtration system (the thickness of spacer for diluting compartment is 10 mm). This paper evaluates the changes in voltage-current, resistivity of product water and conductivity of concentrate water, and achieves a proper spacer for diluting compartment. This spacer ensures an even distribution of fluid in diluting
more » ... fluid in diluting compartment, effectively avoids the intermixing between different layers, and realizes the deep removal of ions. It indicates that the resistivity of product water is higher than 17 MΩ·cm, water output per effective membrane area reaches 5.5×10 -5 m 3 /(cm 2 ·h), and power consumption per ton water is less than 0.7 kW·h when the module is assembled with the modified spacer. Preface EDI (electrodeionization), an advanced membrane separation technology, has been widely applied in the preparation of ultrapure water. At present, EDI process mainly consists of mixed bed EDI and layered bed EDI. Ion exchange resins in diluting compartment of mixed bed EDI module are mixed packed, which leads to adverse effects on the desalination efficiency, output of product water, tightness and etc.; whereas, ion exchange resins in LB-EDI module are layer packed, which results in positive effects on the resistivity of product water, product flux per effective membrane area, tightness and etc.. Therefore, more and more attention is being given to the development of LB-EDI technology (Kunin, R et al, 1950, p. 109; Walters, W R et al, 1955, p, 61-67). The design of spacer for the diluting compartment is one of the essentials of EDI technology. Reasonably designed spacer has good hydrodynamic performances, ensures uniform contact between the fluid and resin, eliminates the channeling, improves the ion exchange properties, minimizes the adverse effects on ion exchange caused by alluvial sediments of resin, avoids the blockage of the channel entrance and exit by resin particles, and increases the tightness of ion exchange membrane. The strict control on the length, width and thickness of compartment and subcompartment, as well as the structure of catchment channel network play important roles in the design of spacer for the diluting compartment (Giuffrida, A J et al, 1986; Ganzi, G C et al, 1987, p. 43-50; Kitty, K S et al, 1988; Keith, A P, 1989; Parsi, E J et al, 1991) . As for LB-EDI process, besides the above-mentioned requirements, the spacer should have no intermixed area among various resin layers under the force of the current so as to ensure the stratification of bed. This paper compares the different spacers, and achieves a reasonably designed spacer, which is valuable for broader applications. Experiment device and process flow Experiment device EDI module: a self-designed one-stage one-pass module and a diluting compartment. Spacer for the diluting compartment: blind pass, loop-free, 325.44 cm 2 of effective membrane area, 10 mm of thickness, and ABS resin plate as a plating material. Spacer for the concentrate water compartment: blind pass, loop-free, 4 mm of thickness, and ABS resin plate as a plating material. Spacer for the electrolyte water compartment: 0.5 mm of thickness, and equipped with in-built inert screen. Journal of Sustainable Development March, 2010 203
doi:10.5539/jsd.v3n1p202 fatcat:oxxqemmhdvb7tk5xytribi5iw4