Simultaneous Adsorption and Electrochemical Reduction of N-Nitrosodimethylamine Using Carbon-Ti₄O₇ Composite Reactive Electrochemical Membranes

Abstract

This study focused on synthesis and characterization of Ti 4 O 7 reactive electrochemical membranes (REMs) amended with powder-activated carbon (PAC) or multiwalled carbon nanotubes (MWCNTs). These composite REMs were evaluated for simultaneous adsorption and electrochemical reduction of N-nitrosodimethylamine (NDMA). The carbon-Ti 4 O 7 composite REMs had high electrical conductivities (1832 to 2991 S m −1 ), where carbon and Ti 4 O 7 were in direct electrical contact. Addition of carbonaceous materials increased the residence times of NDMA in the REMs by a factor of 3.8 to 5.4 and therefore allowed for significant electrochemical NDMA reduction. The treatment of synthetic solutions containing 10 μM NDMA achieved >4-log NDMA removal in a single pass (liquid residence time of 11 to 22 s) through the PAC-REM and MWCNT-REM with the application of a −1.1 V/SHE cathodic potential, with permeate concentrations between 18 and 80 ng L −1 . The treatment of a 6.7 nM NDMA-spiked surface water sample, under similar operating conditions (liquid residence time of 22 s), achieved 92 to 97% removal with permeate concentrations between 16 and 40 ng L −1 . Density functional theory calculations determined a probable reaction mechanism for NDMA reduction, where the rate-limiting step was a direct electron transfer reaction.

An Organic Chemist’s Guide to N-Nitrosamines: Their Structure, Reactivity, and Role as Contaminants

“…In one example, powderactivated carbon was used to adsorb NDMA to a reactive membrane, where it was then electrochemically reduced. 163 Given the difficulties and costs of remediating nitrosaminecontaminated water, the adage that an ounce of prevention is worth a pound of cure rings strikingly true here. Prevention of nitrosamine formation is arguably the most important aspect of long-term control of nitrosamine contamination in many situations.…”

“…Treatment of contaminated waters with ozone/hydrogen peroxide (O 3 /H 2 O 2 ) is more effective at degrading nitrosamines than conventional ozonation, but this technique may have limited practical application as a result of the risk of carcinogenic bromate formation under these conditions . Electrochemical oxidation and reduction of aqueous NDMA have been reported, and several metals have been demonstrated to catalyze the reduction of nitrosamines in water. − Various methods utilizing bioremediation (e.g., bacterial degradation) of nitrosamines in water have shown promise . One such method, propane biosparging, has been demonstrated in the field for the in situ treatment of an NDMA-contaminated aquifer .…”

“…Physical removal techniques can be paired with destructive methods. In one example, powder-activated carbon was used to adsorb NDMA to a reactive membrane, where it was then electrochemically reduced …”

Advanced Nanowood Materials for the Water–Energy Nexus

“…Emerging contaminants such as pharmaceuticals, personal care products, pesticides, and endocrine disrupting compounds pose major human health risks but only have low concentrations in water. [ 92 ] Recent research on poly‐ and perfluoroalkyl substances, [ 93 ] nitrosodimethylamine, [ 94 ] and microplastics [ 95 ] have drawn increasing attentions. To make the nanowood materials carry specialized functions and test their feasibility in real world conditions, more testing and modifications will be desired using actual contaminated water samples and operate reactors in engineering related conditions.…”

Chlorinated Byproduct Formation during the Electrochemical Advanced Oxidation Process at Magnéli Phase Ti4O7 Electrodes

“…The KH 2 PO 4 electrolyte was used because it is relatively inert to electrochemical oxidation. The solution conductivity value was chosen to mimic that of typical natural waters 41 and was measured using a conductivity probe (PC2700, Oakton, Cole-Parmer, IL, USA). Control oxidation experiments were performed with either 1 mM resorcinol or NaCl (1 and 5 mM) to determine a baseline for resorcinol oxidation and inorganic chlorinated byproduct formation.…”