Method for reducing the desalination time in a “flow-through” CDI-water clearance equipment

The work of the CDI salt water distiller based on the principle of bulk deionization by creating a double electric layer on the porous structure of the electrode was investigated. The possibility of increasing the efficiency of desalination by reducing the time of discharge diffusion processes in high-porous electrodes is studied. In the experiments, a flow-through type was used, the pumping of the solution in which is carried out through porous electrodes separated from each other by a permeable separator, without the use of ion-exchange membranes. The analysis of possible pore sizes for various sorbing materials is carried out and estimates of the duration of the corresponding pulses of the control voltage are performed. Preliminary experiments carried out on a model CDI cell allowed us to optimize the choice of electrophysical parameters for carbon felt electrodes of the “Carbopon-Active” type and the “AUT-M-2” fabric produced by OJSC “SvetlogorskKhimvolokno”. A method is proposed for reducing the discharge cycle time by supplying a series of pulses of reverse polarity voltage to the electrodes of a desalter. When matching the characteristics of the porosity of the electrode material and the duration of the pulses, it is possible to achieve accelerated removal of salt ions by increasing the electric field strength from the depth of the pores to the outside, into the interelectrode gap. The estimated pore size was ~ 100 μm; therefore, in a relatively long interelectrode gap of ~ 1 mm, the main mass of ions during the pulse does not have time to reach the surface of the electrodes. This made it possible to maintain the high efficiency of the CDI desalination process. Experiments on a model cell and a full-scale CDI-desalter demonstrated a 2.5-fold decrease in the discharge cycle time in the regime of superposition of control pulses in comparison with the short-circuit mode of electrodes.

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