Removal of the X-ray Contrast Media Diatrizoate by Electrochemical Reduction and Oxidation

Abstract

Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step.

Electrochemical oxidation of iodinated X-ray contrast media by boron-doped diamond electrodes

“…We observed exponential degradation kinetics of all six tested IXCM, which is in agreement with the results of previous studies (Radjenovic et al, 2013, Eversloh et al, 2014Del Moro et al, 2015). The pseudo first-order rates were determined from a linear plot of ln(c/c 0 ) against time and are shown in Table 3 in comparison with the rates from previous studies.…”

“…In this study, we observed kinetic values in the same order of magnitude as found by Eversloh et al (2014) and Radjenovic et al (2013), despite different experimental conditions. In contrast, Del Moro et al (2015) worked at extremely high current densities and absolute currents of about 7 A and therefore reported higher values.…”

Cathodic degradation of antibiotics: Characterization and pathway analysis

“…Based on the Cl À and F À recovery efficiency and electrons consumption, the coulombic efficiency for CAP and FLO reduction reaction were 11.74 ± 1.45% and 5.27 ± 0.87%, respectively according to a previously described formula (Radjenovic et al, 2012). Previous studies have proved that cathode providing electrons could dehalogenate 4-chlorophenol, trichloroethylene, pentachlorophenol, Iodinated X-ray contrast media diatrizoate and iopromide, halomethanes, haloacetonitriles, halopropanones, chloroform and trichloronitromethane (Aulenta et al, 2011;Huang et al, 2012;Kong et al, 2014b;Mu et al, 2011;Radjenovic et al, 2012Radjenovic et al, , 2013. However, this is the first report for the reductive dehalogenation of antibiotics CAP to AM and FLO to FLO-2ClF by the cathodic reduction.…”

Electrochemical dehalogenation of disinfection by-products and iodine-containing contrast media: A review

“…Such species include, among others, N-DBPs (e.g., haloacetonitriles and haloacetamides) and I-DBPs (e.g., monoiodoacetic acid (MIAA)) [7,8]. Some TrOCs groups, notably iodine-containing contrast media (ICMs) used in medical imaging [9,10] and frequently encountered in the environment [11,12] have been shown to be precursors of I-DBPs formed via the degradation of ICMs by halo-gen-based disinfectants or reactive oxygen species (ROS) formed in advanced oxidation processes (AOPs), as well as in EC treatment that involves both oxidation and reduction [13][14][15][16].…”