Enrique Alvarez-Guerra

Ionic liquids in the electrochemical valorisation of CO2

The development of electrochemical processes for using captured CO2 in the production of valuable compounds appears as an attractive alternative to recycle CO2 and, at the same time, to store electricity from intermittent renewable sources. Among the different innovative attempts that are being investigated to improve these processes, the application of ionic liquids (ILs) has received growing attention in recent years. This paper presents a unified discussion of the significant work that involves the utilisation of ILs for the valorisation of CO2 by means of electrochemical routes. We discuss studies in which CO2 is used as one of the reactants to electrosynthesise value-added products, among which dimethyl carbonate has been the focus of particular attention in the literature. Approaches based on the electrochemical reduction of CO2 to convert it into products without the use of other carbon-based reactants are also reviewed, highlighting the remarkable improvements that the use of ILs has allowed in the CO2 electroreduction to CO. The review emphasises on different aspects related to process design, including the nature of IL anions and cations that have been used, the working conditions, the electrocatalytic materials, the electrode configurations, or the design of electrochemical cells, as well as discussing the most relevant observations, results and figures of merit that the participation of ILs has allowed to achieve in these processes. Several conclusions are finally proposed to highlight crucial challenges and recommendations for future research in this area.

Ionic Liquid-Based Three Phase Partitioning (ILTPP) for Lactoferrin Recovery

A novel technique called ionic liquid-based three phase partitioning (ILTPP) that combines the interesting properties of ionic liquids as extracting solvents and the advantages of interfacial partitioning for protein recovery is presented in this work. The ternary system BmimBF4/NaH2PO4/H2O is used to accumulate lactoferrin (a bovine whey with important nutraceutical properties) at the liquid-liquid interface. Between 74% and 99% of the lactoferrin is recovered at the interface, depending on the temperature, the ionic liquid content, and, especially, the salt concentration. Consequently, ILTPP can be seen as a promising technique that may overcome the drawbacks of conventional techniques to recover lactoferrin.

Separation of Proteins by Ionic Liquid-Based Three-Phase Partitioning

Ionic liquid-based three-phase partitioning (ILTPP) is presented in this chapter as a novel technique to recover proteins from waste streams or complex media that overcomes the main drawbacks of conventional methods. This technique uses ionic liquid-based aqueous two-phase systems (ILATPS) to obtain results that are characteristic of three-phase partitioning (TPP). The chapter describes both ILATPS and TPP and studies the suitable systems to carry out ILTPP and the influence of its operating variables. ILTPP can accumulate most of the target protein at the liquid–liquid interface, which makes its recovery easier. The selectivity of the process can be tuned to the operating conditions (e.g., pH) so the applicability of ILTPP is broadened, since it may be applied to enrich the concentration of an individual protein or recover simultaneously a group of them. The separation of lactoferrin from whey is analyzed as an interesting case of ILTPP application.

Optimization of ionic liquid recycling in Ionic Liquid-based Three Phase Partitioning processes

The economic viability of Ionic Liquid-based Three Phase Partitioning (ILTPP) processes, which have been proposed to recover proteins from waste streams, highly depends on the recyclability of the salt and, especially, the ionic liquid used in this technique. For this reason, the economic optimization of the recovery of ILTPP reagents is carried out, considering the main operational costs (reagents and energy). Results show that the process configuration with which costs are minimized is based on the use of vacuum evaporation to remove water from the salt-rich phase of the process. Therefore, the increase of salt concentration is not an economically efficient alternative to recycle the ionic liquid, even though this alternative is usually proposed in the literature. The optimum costs vary between 51.5 – 307 € kg protein−1 for almost all protein concentrations in the feed stream, which are significantly lower than the lowest price reported for the target protein (lactoferrin), so ILTPP processes seem to be economically viable. In addition, the price of reagents and energy has very little influence on the optimum solutions, because very large changes of prices are required to modify the obtained results.