Ionic liquids and ultrasound in combination: synergies and challenges

Abstract

Ionic liquids, as reaction media, and sonochemistry are two recently developing fields of chemistry that present some similarities. Firstly, they constitute separately unconventional approaches to reaction chemistry that, in many cases, generate improvements in yield, rate and selectivity compared to classical chemistry, or even change the mechanisms or products expected. In addition, both are often associated with green chemistry concepts as a result of their properties and their possible eco-friendly uses. A recent trend has been to combine these two technologies in a range of different applications and the results demonstrate very significant and occasionally surprising synergetic effects. Here we critically review the advantages and limitations of the ionic liquid/ultrasound combination in different applications in chemistry, to understand how, and in which respects, it could become an essential tool of sustainable chemistry in the future. Many practical and theoretical aspects associated with this combination of techniques are not understood or resolved and we discus where fundamental studies might further advance this field.

Extraction, Preconcentration and Isolation of Flavonoids from Apocynum venetum L. Leaves Using Ionic Liquid-Based Ultrasonic-Assisted Extraction Coupled with an Aqueous Biphasic System

“…In addition, some other assisted technologies coupled with ILs, such as ionic liquid-based ultrasonic-assisted extraction (IL-UAE) [13], ionic liquid-based microwave-assisted extraction (IL-MAE) [14], and ionic liquid-based negative pressure cavitation-assisted extraction (IL-NPCE) [15], provide remarkable advantages in the extraction and separation field. In particular, IL-UAE is an innovative technology combining IL and ultrasonic extraction, which can produce clear synergies in some cases [16]. In the field of extraction of medicinal components from different herb sources, IL-UAE has been reported to be a comparatively more effective method for the extraction of various compounds, such as aesculin and aesculetin from Cortex fraxini [17], piperine from white pepper [18], ginsenosides from ginseng root [19], alkaloids from Catharanthus roseus [20], biphenyl cyclooctene lignans from Schisandra chinensis Baill [21], magnolol and honokiol from Magnoliae officinalis cortex [22].…”

Chemocatalytic hydrolysis of cellulose into glucose over solid acid catalysts

“…Compared to the above-mentioned dissolution/regeneration and ball-milling, ultrasound is a novel pretreatment technique of cellulose. The effects of ultrasound are the consequence of the cavitation phenomenon involving the formation, growth and collapse of microbubbles in the liquid phase [221]. By imploding, these microbubbles can create the locally high pressure (up to 1000 bar) and temperature (up to 5000 • C), leading to high-energy radical mechanisms and interesting physicochemical functions [222], hence, ultrasound-assisted pretreatment of cellulose has attracted much attention in recent years [223][224][225][226][227][228][229][230].…”

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

“…Despite the applications of ultrasound radiation in medicine, mainly for diagnosis, ultrasound has also paved its path in chemistry. [95] Currently, ultra sound is a laboratory tool used to dispersing nanoparticles and colloids, as well as driving chemical reactions. [96] Ultrasound offers a non-invasive control over the fabrication process of materials by generating localized heating and/or mechanical forces.…”