Spectroelectrochemical monitoring of contaminants during the electrochemical filtration process using free-standing carbon nanotube filters

Abstract

Real-time process monitoring is still relatively scarce but is fundamental to provide in-situ information about different chemical and electrochemical processes. Particularly, electrochemical filtration has received growing attention in recent years due to the wide range of applications in which it can be successfully employed. Electrochemical removal is considered as an attractive methodology for the treatment of wastewater due to its efficiency in the removal of a huge number of contaminants. In this work, the development of a new device based on the use of UV–vis bare optical fibers in long optical pathway configuration allows us to monitor continuously the electrochemical degradation process during the filtration of different compounds. Spectroelectrochemistry additionally supplies quantitative information allowing us to calculate the efficiency of the electrochemical filtration process. The material selected to fabricate the electrochemical filter was single-walled carbon nanotubes that display not only high physical and chemical stability, but also high electrical conductivity. Therefore, the combination of electrochemical degradation methods, free-standing single-walled carbon nanotube filters and operando spectroelectrochemical techniques makes this outstanding device very interesting in the study of different molecules. As proof of concept, three different systems have been studied to validate the cell and demonstrate the good performance of the spectroelectrochemical device: o-tolidine (reference system), indigo carmine (organic dye), and 4-nitrophenol (hazardous pollutant).