Carbon materials, prepared by using different methods with ionic liquids, are compared as electrocatalysts for the oxygen reduction reaction (ORR). Materials were synthesized through the hydrothermal carbonization of glucose and by using the same method in the presence of 1‐butyl‐3‐methylimidazolium methanesulfonate [bmim][MeSO3] as an additive. Another two carbon‐based materials were prepared by using ionic‐liquid‐based methods: ionothermal carbonization of glucose using [bmim][MeSO3] as a recyclable medium for the carbonization reaction and by direct carbonization of the ionic liquid in a one‐step method using [bmim][MeSO3] as the precursor for N‐ and S‐doped porous carbon (Carb‐IL). Characterization results showed the possibility of morphology and porosity control by using [bmim][MeSO3]. All materials were subsequently tested for the ORR in alkaline media. Carb‐IL showed enhanced and stable electrocatalytic ORR activity, even in the presence of methanol, ethanol, and borohydride, opening the possibility for its application in fuel cells.
In this study, four hydrophilic ionic liquids (ILs) containing 1-alkyl-3-methylimidazolim cation and either salicylate or chloride anions were synthetized and studied as new task-specific ionic liquids (TSILs) suitable for aqueous biphasic system (ABS) formation and selective one-step extraction of copper(II). TSILs are designed so that the anion is responsible for forming the complex with metal(II) and preventing hydrolysis of metal cations at very strong alkaline pH, whereas the cation is responsible for selective extraction of metal(II)-salicylate complexes. It was found that 1-butyl-3-methylimidazolium salicylate could be used for selective extraction of Cu(II) in the presence of Zn(II), Cd(II), and Pb(II) at very alkaline solution without metal hydroxide formation. It was assumed that formation of metal(II)-salicylate complexes prevents the hydrolysis of the metal ions in alkaline solutions. The determined stability constants for Cu(II)-salicylate complexes, where salicylate was derived from different ionic liquids, indicated that there was no significant influence of the cation of the ionic liquid on the stability of the complexes. The ABS based on 1-butyl-3-methylimidazolium salicylate has been applied as the sample preparation step prior to voltammetric determination of Cu(II). The effect of volume of aqueous sample and IL and extraction time were investigated and optimum extraction conditions were determined. The obtained detection limits were 8 ng dm. The optimized method was applied for the determination of Cu(II) in tap water, wastewater, and urine. The study indicated that application of the ABS based on 1-butyl-3-methylimidazolium salicylate ionic liquid could be successfully applied as the sample preparation method for the determination of Cu(II) from various environmental samples. Graphical abstract Aqueous biphasic system based on task-specific ionic liquid as a sample pretreatment for selective determination of Cu(II) in biological and environmental sample.
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