CO2 Capture Mechanism by Deep Eutectic Solvents Formed by Choline Prolinate and Ethylene Glycol

CO2 capture by imidazolium-based deep eutectic solvents: the effect of steric hindrance of N-heterocyclic carbenes

CO2 capture by deep eutectic solvents (DESs) formed between 1,3-bis(isopropyl)imidazolium 1,2,4-triazolide ([IiPim][Triz]) and ethylene glycol (EG) is investigated in this study. [IiPim][Triz]-EG DESs exhibit a capacity of ∼1.0 mol CO2 per mol DES at 1.0 atm and 25 °C. Surprisingly, mechanistic results disclose that CO2 reacts with EG but does not bind with the C-2 site of the [IiPim]+ cation, which may be due to the high steric hindrance of the C-2 site of the N-heterocyclic carbene IiPim present in [IiPim][Triz]-EG DESs.

Natural Deep Eutectic Solvents as Rust Removal Agents from Lithic and Cellulosic Substrates

The peculiar physicochemical features of deep eutectic solvents (DESs), in particular their tunability, make them ideal media for various applications. Despite their ability to solubilize metal oxides, their use as rust removers from valuable substrates has not yet been thoroughly investigated. In this study, we chose three known DESs, consisting of choline chloride and acetic, oxalic or citric acid for evaluating their ability to remove corrosion products from a cellulose-based material as linen fabric and two different lithotypes, as travertine and granite. The artificial staining was achieved by placing a rusty iron grid on their surfaces. The DESs were applied by means of cellulose poultice on the linen fabrics, while on the rusted stone surfaces with a cotton swab. Macro- and microscopic observations, colorimetry and SEM/EDS analysis were employed to ascertain the cleaning effectiveness and the absence of side effects on the samples after treatment. Oxalic acid-based DES was capable of removing rust stains from both stone and cellulose-based samples, while choline chloride/citric acid DES was effective only on stone specimens. The results suggest a new practical application of DESs for the elimination of rust from lithic and cellulosic substrates of precious and artistic value.