Leicester Ionic Liquids Group
Green Solutions
University Home Department of Chemistry University Index University Search University Help

Research

The main research interests of the group are firmly based around green chemistry with particular emphasis on electrochemical processes. It is active in developing novel solvent systems with industrial applications such as metal deposition and dissolution. It collaborates strongly with industry and much of the work to date has been in the development of novel processes using ionic liquids.

>>>Podcast: ionic liquids as green solvents.

Ionic Liquids and Deep Eutectic Solvents

An ionic liquid is a salt in which the ions are poorly coordinated, which results in these solvents being liquid below 100°C, or even at room temperature (room temperature ionic liquids, RTILs).

Cu2+ in various ionic liquids and Deep Eutectic Solvents.

Ionic liquids are electrically conductive and have extremely low vapor pressure. Their other properties are diverse. Many have low combustibility, excellent thermal stability, a wide liquid range, and favorable solvating properties for diverse compounds. Many classes of chemical reactions, such as Diels-Alder reactions and Friedel-Crafts reactions, can be performed using ionic liquids as solvents. The miscibility of ionic liquids with water or organic solvents varies with sidechain lengths on the cation and with choice of anion. Because of their distinctive properties, ionic liquids are attracting increasing attention in many fields, including organic chemistry, electrochemistry, catalysis, physical chemistry and engineering.

While a huge amount of academic studies have been carried out into ionic liquids consisting of discrete anions such as PF6- or (CF3SO2)2N- each new salt is a chemically new entity for which the toxicological properties are unknown so every new compound has to go through registration. In our work we are generally focusing on large-scale applications where such costs would be excessive. All of our work focuses on eutectic based ionic liquids meaning that we have tonne-scale processes using these liquids.

>>> Find out more about our Deep Eutectic Solvents...

Novel Materials — Salt Modified Starch

Rubber (left) and rigid plastic (right) made from salt modified starch.

In our research we have tried to emulate nature in the formation of starch blends by adding more complex mixtures of chemicals that mimic the natural fluids found in cells. By varying the composition and constituents it is possible to change the elastic modulus of the finished product from that of a stretchy rubber to a rigid plastic. We have been able to plastic materials that are rigid, transparent sheets by curing the material at elevated temperature and moderate pressure. This is a markedly different material than has ever been cast from starch before.

What is potentially controversial about this technology however is the debate of whether it is more beneficial to use crops for plastics or food? One of the possible advantages of this research is that it is possible to use crops for both in as much that preliminary studies have shown that waste starch such as banana skins and orange peel can be used as sources of starch from which to make plastics. Since agriculture and the food processing industry produce vast amounts of waste starch this could act as an alternative source of raw materials. This is the equivalent of making medium density fibreboard (MDF) where softwood wood fibres are glued together with a resin binder.

Ultimately our modern lives can only be made sustainable by decreasing our dependency on oil based chemicals and in particular polymers for packaging. Starch is certainly one alternative source of renewable and sustainable polymers but others such as cellulose and chitin will also play an important role in polymers of the future.

>>> Find out more about novel materials...

Electroplating

Zn/Sn coated pieces (left) and nickel and silver coated brass (right).

A viable alternative to Cr(VI) has been developed. It offers high current efficiency using either soluble chrome anodes or DSAs. Hard, black or decorative (bright) chrome coatings are possible. Processes have been developed for the deposition of Cr, Al, Co, Ni, Cu, Zn, Sn, Pb, Pd, and Ag. Alloys such as Cu/Zn, Zn/Co and Zn/Sn have also been deposited on a wide range of substrates without special pre-treatment. Stable colloidal suspensions can be made and incorporated into metallic coatings to produce hard composites.

>>> Find out more about electroplating...

Immersion Coatings

Silver coated printed circuit board (left) and silver coated copper pipe (right).

An immersion Ag process has been developed giving a high quality solderable Ag finish for PCB applications. This is now a viable alternative to conventional acid-based autocatalytic electroless coatings. Immersion coatings of Cu on Al and alloys are also now made possible using the same liquid / process technology.

>>> Find out more about immersion coating...

Electropolishing

Polished (top left) and unpolished (bottom left) bolts and partly polished stainless steel tube (right).

The benefits of the new electropolishing technology are a higher current efficiency when compared with the traditional process, excellent surface finish, drop-in replacement for current acid based solutions and the liquid is noncorrosive.

>>> Find out more about electropolishing...

Metal Oxide Processing

Range of metal oxides dissolved in Deep Eutectic Solvents.

These ionic liquids dissolve a wide range of metal oxides and can be used to selectively extract metals from complex matrices. We have a pilot plant in operation to extract a range of metals from waste substrates.

>>> Find out more about metal oxide processing...