Process intensification in extraction by liquid emulsion membrane (LEM) process: A case study; enrichment of ruthenium from lean aqueous solution

Process intensification in extraction as a unit operation can be realized through liquid emulsion membrane (LEM) process by combining extraction and stripping in one stage eliminating the need of stripper. LEM technique is very useful to enrich very lean aqueous phase containing precious metal to aid the recovery process. The technique is illustrated by applying the same to enrich platinum group noble metal, ruthenium (Ru) from its aqueous solution. The liquid membrane phase consisted of extractant (trioctylamine) dissolved in liquid paraffin modified with 1-octanol and the surfactant used was Monemul 80. The strip phase found to be very effective was perchloric acid. To facilitate extraction tin(II) chloride was added to the aqueous feed phase containing Ru at 20 ppm level. Various process parameters affecting the performance of LEM process such as extractant, surfactant, strip phase concentrations, the batch extraction time, the treat ratio and the speed of agitation were studied at bench scale to aid process development.The maximum enrichment of Ru, obtained was almost 10.3 times, in the internal strip phase (2 mol L−1 of perchloric acid), from the feed phase containing Ru at 20 ppm level.