Abstract
AbstractThis work reports the electroreduction of a volatile organic halide (trichloromethane) from an airborn stream. In the past years, we highlighted the role of polycrystalline silver as powerful electrocatalyst for the electroreductive hydrodehalogenation of volatile organic halides (VOH) in water/organic solvent mixtures, from 0 to 100 % of the aqueous component. The successful conversion of trichloromethane and 1,1,1‐trichloethane to the relevant dehalogenated compounds, methane and ethane have prompted us to extend the investigations to the treatment of gaseous effluents, adopting a silver Gas Diffusion Electrode (Ag‐GDE) and the appropriate cell design. In the field of electroreduction processes the possibility of using GDE to treat gaseous effluents for the removal of volatile organic pollutants represents an electrochemical challenge, and the treatment of N2/CHCl3 gas mixtures fed into the cathodic Ag‐GDE compartment demonstrates the feasibility of the electroreductive detoxification process. Our results will be presented and discussed in terms of CHCl3 removal efficiency, selectivity and energy consumption in preparative electrolyses.
Highlights
The electroreduction of organic halides has played a key role in organic electrochemistry[1,2] since the early works of Winkel and Proske[3] and of von Stackelberg and Stracke[4] on the treatments of organic halocompounds
Rodrigo et al largely investigated the coupling of two or more electrooxidation processes, such as photo-electrooxidation coupled to zero-valent iron (ZVI), resulting in a very high removal of chloro-containing compounds in both drinking water and soil effluents.[30,31,32]
The electrolysis progress was followed by monitoring gaseous effluent by GC/ FID, whose typical data are presented in Figure 3, for an AgGDE at the first run
Summary
Short lifetime that hinder their industrial applicability.[20]. Rodrigo et al largely investigated the coupling of two or more (photo-) electrooxidation processes, such as photo-electrooxidation coupled to zero-valent iron (ZVI), resulting in a very high (around 100 %) removal of chloro-containing compounds in both drinking water and soil effluents.[30,31,32] their potential scale-up is still rather difficult. Electroreductive processes have gained a large scientific attention due to either their potentiality in chemical recovering/recycling or in the value-added substance productions,[33,34,35,36,37] in particular when halocompounds in wastewater streams have to be treated.[38,39] on one hand, the cathodic reaction can be used to produce energy as molecular hydrogen, while performing the solution decontamination via the anodic process, on the other it can concomitantly play a pivotal role in the degradation of organics .[19] Both the direct reduction of the pollutant at the cathode and the electrogenerated H2O2-mediated decontamination are the two most relevant cathodic processes.[20]. The electrolyte side was covered by a slurry containing Vulcan XC72R® + PTFE (1 : 1), B-GDE, or Ag + Vulcan XC72R® and PTFE (1 : 1), see Figure 2B This last ink was prepared as follow: 1.5 g of microcrystalline Silver was mixed with 6 g of Vulcan XC72R and dispersed in Milli-Q water. All chemical reagents were provided by Sigma-Aldrich and used as received
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