Energy-efficient removal of trace antibiotics from low-conductivity water using a Ti4O7 reactive electrochemical ceramic membrane: Matrix effects and implications for byproduct formation

The inevitably high energy consumption of traditional electrochemical processes to treat low-conductivity water has limited their wider application. Herein, we present an energy-efficient alternative, i.e. , a Ti 4 O 7 reactive electrochemical ceramic membrane (Ti 4 O 7 -REM) system with a superior mass transfer ability. For the removal of 10−200 μM norfloxacin (NOR) from low-conductivity (178−832 μS cm −1 ) water, the Ti 4 O 7 -REM system increased the kinetics rate constant by 4.3−34.0 times, thus decreasing the energy cost by 80.5−97.3% compared with a flow-by system. The rapid NOR removal was related to the enhanced direct electron transfer process in the Ti 4 O 7 -REM system, which allowed for higher resistance to HCO 3 − scavenging and a favorable reaction between NOR and the active sites. Meanwhile, this mechanism likely contributed to the less formation of inorganic chlorinated product, ClO 3 − , in the presence of Cl − . Although organic chlorinated byproducts were not detected during NOR degradation in the Ti 4 O 7 -REM system, Cl – influenced the speciation of the intermediates. A single-pass Ti 4 O 7 -REM system demonstrated 94−97% removal of trace antibiotics from real water samples in 30 s. The additional energy consumption (<0.02 kWh m −3 ) using a Ti 4 O 7 -REM system only contributed to 5.0−6.4% of the total in a typical tertiary wastewater treatment plant. Based on the above results, we can conclude that the convection-enhanced REM technique is viable for the purification of low-conductivity natural waters.