Degradation of imidazolium-based ionic liquids by catalytic wet peroxide oxidation with carbon and magnetic iron catalysts

Abstract

BACKCGROUND: The ‘green’ image of ionic liquids (ILs) has changed in the last few years since numerous works have evidenced their non-biodegradability, persistence and high ecotoxicity, particularly for the most common imidazolium-based ILs. In this work, the feasibility of catalytic wet peroxide oxidation for the degradation of imidazolium-based ILs of different alkyl chain lengths has been studied under selected operating conditions (1000 mg L−1 IL, stoichiometric H2O2 dose, 2 g L−1 catalyst, pH 3 and 90 °C temperature) using different catalysts such as magnetic iron (Fe3O4) supported on γ-Al2O3 and activated carbon (AC) as well as bare carbon materials (graphite, AC). The catalytic activity and stability and the efficiency of H2O2 consumption have been evaluated. RESULTS: Although both AC-based catalysts led to the conversion of the IL, they yielded a low H2O2 consumption efficiency (24% and 45% with AC and Fe3O4/AC, respectively) due to the fast decomposition of H2O2 and the recombination of radical species into H2O and O2, non-reactive species under the operating conditions. In contrast, graphite and Fe3O4/γ-Al2O3 showed high activity allowing complete conversion and relatively high mineralization degrees of all the ILs tested in 1 h reaction time. Among those catalysts, Fe3O4/γ-Al2O3 exhibited a considerably greater stability upon four successive uses where iron leaching was negligible and the magnetic properties were maintained. CONCLUSIONS: Catalytic wet peroxide oxidation has proved to be an interesting alternative for the treatment of imidazolium-based ILs in water. The application of Fe3O4/γ-Al2O3 is particularly promising due to its high activity, remarkable stability and easy magnetic recoveryThis research has been supported by the Spanish MINECO through the project CTQ2013-4196-R and by the CM through the project S2013/MAE-271

Screening of Activated Carbons for the Treatment of Highly Concentrated Phenol Solutions Using Catalytic Wet Peroxide Oxidation: The Effect of Iron Impurities on the Catalytic Activity

“…Bearing this in mind, the ratio between TOC and H 2 O 2 conversions (X TOC /X H2O2 ) was used to study the efficiency of H 2 O 2 consumption. Indeed, this has been the most common strategy to quantify the overall efficiency of CWPO [14,27]. As observed, X TOC /X H2O2 values above 0.5 are obtained with all catalysts, except for C-GRAN.…”

“…Bearing this in mind, the ratio between TOC and H2O2 conversions (XTOC/XH 2 O 2 ) was used to study the efficiency of H2O2 consumption. Indeed, this has been the most common strategy to quantify the overall efficiency of CWPO [14,27]. As During CWPO, pollutant and H2O2 molecules compete for the available active sites at the surface of the solid catalyst.…”

“…Bearing this in mind, the ratio between TOC and H2O2 conversions (XTOC/XH 2 O 2 ) was used to study the efficiency of H2O2 consumption. Indeed, this has been the most common strategy to quantify the overall efficiency of CWPO [14,27]. As Regarding mineralization levels, TOC conversions obtained with the commercial ACs are always lower than phenol removals (cf.…”

Effects of sodium persulfate and hydrogen peroxide on imidazolium ionic liquid degradation by simulated solar light in aqueous ZnO suspension

“…Up to now, various techniques have been studied for the ionic liquids removal from wastewater, including ultrasonic, 5–7 electrolytic, 8–14 fenton, 15–19 electro‐fenton, 20,21 biological process, 3 photocatalysis, 22,23 and advanced oxidation process 24–27 . Kaabeche et al.…”

Biological oxidation of choline‐based ionic liquids in sequencing batch reactors

“…Formerly, ILs were typically eliminated through Advanced Oxidation Processes (AOPs). Thus, ILs can be efficiently removed from water by Fenton oxidation, catalytic wet peroxide oxidation, electroxidation or photodegradation . Specifically, Munoz et al, 2015, studied the Fenton oxidation of the IL choline chloride (CholineCl) at an initial concentration of 1000 mg L −1 with a stoichiometric dose of H 2 O 2 and 50 mgFe 3+ L −1 at pH 3 at 70 °C; they obtained a very low mineralization rate in terms of TOC removal (36.1%) relative to ILs from other families such as EmimCl (65.3%) and BmpyCl (43.7%) under identical conditions .…”