Production Of High Purity Water By Membrane-free Electrodeionization(MFEDI)

Membrane-free electrodeionization (MFEDI) is a novel technique for water treatment, which simply uses strong DC electricity to regenerate exhausted resins without membranes. MFEDI is much simpler in structure, easier operation, without frequent disassembly, better high purity water quality and more economical in investment than traditional EDI (electrodeionization). The influences of several important operating variables (resins ratio, flow velocity, current density, height of resin layer) and parameter variations (pH, concentrate conductivity and regeneration voltage) versus regeneration time were investigated; the possibility of producing high purity water via MFEDI and the efficiency of high purity water production were assessed by calculating the removal ratio, water recovery ratio and energy consumption; the performance of the resins and the Ti/IrO2-SnO2-Sb2O5electrode under DC electricity were also evaluated in this study.It was shown that the optimal operation conditions of MFEDI were:550A-D113volume ratio3:1, resin layer height80cm, current density200A/m" and flow rate15m/h; high purity water with a conductivity of0.056-0.066μs/cm was obtained when feed conductivity was5-20μs/cm, and the removal ratio, water recovery rate and energy consumption were calculated to be about98.78-99.70%,92.3-96.9%and0.60-1.56kWh/m3water respectively; the exchange capacity and thermodynamic properties of the resins as well as the performance of Ti/IrO2-SnO2-Sb2O5electrode kept unchanged in the accelerate life test for600hours, and the results revealed that MFEDI can stay stable in the long term operation.