Purification of metals using chemicals from biomass

What is it about?

A need exists to purify metals, often metals in wastes and in ores obtained from mining are in mixtures. By improving the processing of ores and wastes we will obtain a series of environmental advantages. For example at Dolaucathi the Romans were mining gold in Wales. The Romans used a range of primative methods to obtain gold, one method was to heat the ore with the sincere hope that the gold would melt and pool at the bottom of the furnace. I write "sincere hope" as much of the gold could be trapped in the porous ore and never be recovered. Another method they used was to crush lumps of ore or work on powdered ore by methods similar to gold panning. Here we obtain a separation which is based on a difference in density. Such density based methods are still being used in the mining sector using things like shaking tables. The problem with these mechanical processes and the simple heating methods is that it is hard to obtain a good purity of the product when the gold is present as an alloy containing other metals such as silver and gold. Also the high temperture methods such as melting gold / silver alloys with common salt (sodium chloride) which converts the alloy in to a mixture of metallic gold and silver chloride loaded salt requires large amounts of energy. A lower energy approuch to high purity metals is to use solvent extraction. Here the metals are converted into solution where they are dissolved in water mixed with acid. Next the metals are extracted into an organic layer normally using a mixture of a metal extracting agent and a diluting agent (organic solvent known as a diluent). Normally the diluent is about 70 % by volume of the organic layer, while a lot of work has gone into greener extraction agents much less has gone into greener diluents. Here in this paper we have concentrated on developing the use of a greener diluent. We have shown that petrokerosene can be replaced with a second generation biodiesel made by the hydrotreatment of lipids by Neste. This is sold under the name of HVO100 in Sweden and other parts of the world. We have also presented methods in the paper for the characterisation of new diluents which can be used by other workers in the future.

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Photo by Anthony Rampersad on Unsplash

Photo by Anthony Rampersad on Unsplash

Why is it important?

It is important that industry evolves from using petroleum and other fossil fuel based chemicals towards a the use of more sustainable non-fossil fuel derived chemicals. In this paper we show that a sustainable biomass derived biokerosene can be used as a replacement for petrokerosene. In this paper we should that a second generation biodiesel (HVO100) can be used as a replacement for aliphatic petrokerosene in solvent extraction experiments. We have shown that the HVO100 is a cheap diluent which is suitable for experiments which require high purity kerosene. In this paper we have shown that it is possible to purify impure scrap gold into high purity gold.

Perspectives