Ionic Liquids & Solid Waste Treatment
Solid waste treatment has become a major focus in the UK and EU. The implications from landfill, incineration and loss of resource value is not sustainable and is leading to issues such as; the production of GHG, reduction of air quality, land use, loss of critical materials and in general, unnecessary waste. Solid waste is difficult to treat, it can include mixed household waste, slags and mineral waste from mining, waste materials from manufacturing, and end-of-life products (batteries, electronics, vehicles, construction materials and more). Treatment with green chemistries is becoming more relevant, because of both economics and waste regulations. This page provides some tools for utilising green chemistries for solid waste treatment.
The use of ILs and DES have been gaining popularity by the properties that they present, and the ability to act as substitutes to hazardous or toxic materials. Applications for these chemistries are diverse and extend from phosgene replacement, cellulose dissolution, electroplating (including aluminium), paint additives, fuel cells, plasticisers, pharmaceutical production and single enantiomer drugs, (Plechkova & Seddon, 2007, Sekhon 2011, Kumar and Malhorta 2010) and many more developing technologies and uses.
The ability of ILs and DES to dissolve metals and exclusively select certain elements has provided opportunities for the recovery of metals from waste streams, removal of organic contaminants from a variety of media, and aid targeted selectivity of certain materials in waste media.
The identification and quantification of metal complexes in the solutions can be achieved through a variety of common techniques and lab instrumentation. These include ICP-MS and hyphenated ICP-MS techniques, NMR and EPR, hyphenated mass spectrometry approaches, UV-Vis and Raman spectroscopy among others.
Analytical methods for the quantification of metals and their complexes in solution are under development for ICP-MS and ILs and DES. Limitations and restrictions of the analysis are created by the viscosity of the samples and introduction to the instrument. Therefore to determine speciation and complexes, no dilution of the sample should occur. This inhibits the use of simple techniques such as ICP-MS with direct injection and favours techniques such as NMR and thermal desorption GC-MS techniques.
To quickly determine the presence of individual metal ions in solution, liquid-liquid extractions (LLE) can be performed to selectively remove ions, and allow them to be tested via routine analysis. By processes of elimination it is possible to determine the speciation of metals in a IL or DES solution without expensive analytical instrumentation.