A performance comparison of a novel electrochemical-membrane process operated in two modes for separating nanoscale TiO2 from the solution

摘要

In this work, two schemes of the simultaneous electrocoagulation/electrofiltration (EC/EF) process were tested to compare their performance in the treatment of nanosized TiO2-containing wastewater in terms of permeate flux and quality. Experimental results of the recirculation mode have shown that the residual COD (chemical oxygen demand) of permeate in the early treatment stage decreased as the applied electric field strength (AEFS) increased. The removal of COD might reach up to 97.3%. But this phenomenon vanished as the AEFS was greater than 166.7 V/cm. As for turbidity, electric conductivity, total dissolved solids (TDS), and Ti content, their removal efficiencies were determined to be 98.7 %, 95.1%, 95.8%, and 99.9%, respectively. It was also noticed that the filtration rate in the early treatment stage increased as the AEFS increased. Again, as the AEFS increased to be greater than 166.7 V/cm, the filtration rate began to drop to a steady flux of 6.00 x 104 L/m2h. Therefore, 166.7 V/cm was determined to be the critical electric field strength. By using the non-circulation mode while keeping the other operating conditions the same as the recirculation mode, the removal efficiencies of COD, turbidity, electric conductivity, TDS, and Ti content were determined to be 92.0%, 98.1%, 92.3%, 93.1%, and 99.9%, respectively. Its steady flux for each treatment module was found to be 6.38 x 104 L/m2h. In summary, no matter it was operated using the recirculation mode or non-circulation mode, the EC/EF treatment system is capable of removing COD and turbidity to satisfactory levels and yielding permeate suitable for recycling.