(727e) Modifying TiO2 Magnéli Phase Reactive Electrochemical Membranes with Pyrogenic Carbonaceous Materials for Adsorption and Electrochemical Removal of Water Contaminants

This study was focused on the synthesis, characterization, and performance evaluation of Ti₄O₇ reactive electrochemical membranes (REMs) amended with pyrogenic carbonaceous materials (PCMs). Among the Magnéli phases of TiO₂ (Ti_nO_2n-1 n= 4 to 10), Ti₄O₇ (n=4) is the most conductive phase and produces the highest yield of hydroxyl radicals. Ti₄O₇ possesses an electrical conductivity in the range of 1000-1500 S/m, but has limited adsorption capacity for organic contaminants. In this work, a method was investigated to improve the conductivity and adsorption capacity of Ti₄O₇ REMs and their performance for removal of different classes of water contaminants.

Two types of PCMs were added to REMs, 10 wt% multi-walled carbon nanotube (MWCNT)and 10 wt% powdered activated carbon (PAC). The composite PCM/Ti₄O₇ REMs were synthesized and characterized by a series of techniques (e.g., X-ray diffraction, thermal gravimetry analysis, Raman spectroscopy). Conductivity analysis showed that by adding MWCNTs and PAC, REM conductivity increased 3.3-fold and 2-fold respectively. Preliminary results indicated that a 10 wt% PAC and 10 wt% MWCNT loading to a Ti₄O₇ REM increased the adsorption capacity towards N-nitrosodimethylamine (NDMA)) by > 4.7-fold and > 7.1-fold, respectively. These results were determined by analyzing the time for permeate breakthrough curves to reach 50% of feed concentration.

By employing two different types of REMs, simultaneous chemical reduction/oxidation reactions and adsorption were used to separate and destroy different groups of dissolved water contaminants. For example, results showed for the Ti₄O₇ REM that steady state NDMA reduction was 60% during the three day experiment. By contrast, using 10 wt% PAC/Ti₄O₇ and 10 wt% MWCNT/Ti₄O₇ REMs, NDMA was no longer detected in the permeate during the three day experiment. These results indicated that the PCM/Ti₄O₇ composite REMs under cathodic potentials have potential for long-term removal of contaminants of concern.

Keywords: Separation, Water treatment, Reactive electrochemical membranes, pyrogenic carbonaceous materials.