School of Chemistry - Theses

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Author: Bonggotgetsakul, Ya Ya Nutchapurida × Start date: 2000 × Subject: gold ×

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    The use of polymer inclusion membranes (PIMs) for the recovery of gold(III) from highly acid solutions and the preparation of monolayers of precious metal nanoparticles
    Bonggotgetsakul, Ya Ya Nutchapurida ( 2014)
    Polymer inclusion membranes (PIMs) have recently gained importance in solid phase extraction of both metallic and non-metallic species. The suitability of PIMs for gold recovery from acid digestion of electronic scrap was studied. PIMs containing Aliquat 336 or Cyphos® IL 104 incorporated in different polymer matrixes were studied for Au(III) extraction and back-extraction. The membranes containing 30 wt% Cyphos® IL 104 and 70 wt% PVDF-HFP has shown high Au(III) extraction rate and stability in aqua regia solution used for the digestion of electronic scrap. It was found that Na2SO3 could strip Au(III) efficiently from these PIMs. PIMs have been used as templates to prepare gold nanoparticles (Au NPs), silver nanoparticles (Ag NPs) and palladium nanoparticles (Pd NPs). [AuCl4]- was extracted into the membrane (20 wt%) Aliquat 336, 10 wt% 1-dodecanol and 70 wt% PVC) and subsequently reduced by L-ascorbic acid, tri-sodium citrate, NaBH4 or EDTA to form Au NPs. EDTA at pH 6.0 has been shown to be an effective reducing agent capable of forming a uniform monolayer of Au NPs of average size of 20 nm on the surface of the membrane. Similarly Ag+ or Pd2+ were extracted into PVC-based PIMs containing 45 wt% or 30 wt% D2EHPA, respectively, and subsequently reduced with different reducing agents. L-ascorbic was found to form nanoparticles on the surface with relatively uniform size of 360 nm for Ag and 38 nm for Pd. One hypothesis views PIMs as incorporating a network of nanosized channels. However, the use of surface imaging techniques has not clearly identified surface pores. A novel approach using the preparation of Au NPs on the membrane surface was proposed to study surface pore distribution of PIMs. Scanning Electron Microscopy (SEM) has been used to map the surface distribution of the Au NPs assuming that it is identical to the pore distribution.