Electroanalytical techniques applied to monitoring the electro-Fenton degradation of aromatic imidazolium-based ionic liquids

Abstract

In this study, the degradation of the ionic liquid (IL) 1,3-dicyclohexylbenzimidazolium chloride ([DCy6bim][Cl]) was carried out by applying an heterogeneous electro-Fenton (HEF) treatment using iron alginate spheres (FeAS) as catalyst. Initial trials were performed at current between 50 and 250 mA, different FeAS dosages (1-5 g), and [DCy6bim][Cl] concentrations (70-280 mg L −1 ) as key parameters for the characterization of the HEF process. Comparative experiments suggest that high current, low FeAS dosage and low [DCy6bim][Cl] concentration are the best conditions to yield near complete total organic carbon decay after 4 h. In order to evaluate the catalyst behaviour and iron leaching during the degradation of [DCy6bim][Cl], differential pulse voltammetry (DPV), a sensitive and selective electroanalytical technique, was used to monitor the IL degradation, by-products and iron evolution into the solution at high concentration levels. The profile of the voltammetric curves obtained by DPV suggests almost complete cleavage of the cation structure of [DCy6bim][Cl] during the first 120 min. At longer treatment times, DPV revealed the generation of iron complex with chloride and carboxylic acids. Finally, chromatographic analysis of these carboxylic acids and inorganic anions permitted to validate the results obtained by DPV and demonstrated the feasibility of the HEF process for IL degradation.Paper submitted to the "Special Issue of 10th World Congress on Chemical Engineering (WCCHE02)" for consideration by Journal of Applied Electrochemistry.

Towards a more realistic heterogeneous electro-Fenton

“…As for the catalyst, iron-containing alginate beads were prepared following a similar procedure to that found elsewhere [16]. Drops of a sodium alginate solution (2% w/v) were added into a 0.05 M Fe 3+ hardening solution prepared from iron(III) sulfate hydrate, keeping them in the iron solution for 1 h. After, they were filtered, washed repeatedly with distilled water and stored at 4°C [17]. The iron content of the catalyst obtained in this manner, which was determined to be of 4 mg Fe per gram of alginate beads, was obtained by performing an acid digestion of the alginate beads and measuring the iron concentration afterwards by ICP-OES.…”

“…Several investigations have focused on the preparation of efficient catalysts for EF using natural polymeric matrixes [15]. As an example, iron-containing alginate beads, gels obtained by cross-linking iron into an alginate structure, have demonstrated high catalytic activity for the degradation of various pollutants, like pesticides [16], ionic liquids [17] and dyes [18], showing reusability after several cycles [18,19]. Although heterogeneous EF suffers from slow kinetics (limited by the mass transfer of hydrogen peroxide to the catalyst surface) and the formation of catalyst agglomerations, those drawbacks could be overcome by the use of fluidizedbed Fenton reactors [20].…”

All-in-One Continuous Electrochemical Monitoring of 2-Phenylphenol Removal from Water by Electro-Fenton Treatment

“…However, these analytical techniques are highly solvent-dependent, sample destruction and time-consuming, as well as mostly expensive; additionally, in most cases, a sample pre-treatment is required (filtration and/or pH adjustment). Alternatively, electroanalysis is presented as a rapid (few minutes), sensitive, and majorly non-sample treatment method to follow a HEF reaction [36,37].…”