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Simple and selective reverse micelle mediated bulk liquid membrane extraction procedure is developed for the separation and simultaneous pre-concentration of precious metals from valuable wastes like spent auto mobile catalytic converters and gold jewelry washings. Quantification has been carried out using inductively coupled plasma optical emission spectrometry (ICP-OES). Tri octyl methyl ammonium chloride (TOAC), a cationic hydrophobic surfactant, forms reverse micelles after dissolution in trichloroethylene facilitating the extraction of platinum, gold and silver ions into the bulk liquid membrane. The procedure is based on the formation of extractable hydrophobic ion-associates between TOAC cationic reverse micelles and anionic metal ions. These hydrophobic ion-associates which are transported into the bulk organic membrane from an aqueous feed phase are subsequently stripped into a receiving solution in a unitary process. Optimum conditions for the overall transport efficiency of precious metals have...

A facilitated uphill transport for the separation and pre-concentration of platinum and palladium through a bulk liquid membrane procedure utilizing reverse mixed micelles as transport vehicles was developed. A mixed micellar solution in a liquid membrane process is a representation of mixed monolayer at the feed/membrane interface, and mixed bilayer aggregate in the membrane/receiving interface. A cationic hydrophobic surfactant along with, a nonionic surfactant was used to form reverse mixed micelles in trichloroethylene, which act as a carrier for extracting the metal ions into bulk liquid membrane. This procedure is based on the formation of hydrophobic ion-associates of platinum and palladium with the reverse mixed micelles in the presence of an acid mixture which are extractable into the membrane phase. The formation of reverse mixed micelles hastens the transport of platinum and palladium into the organic phase making room temperature extraction feasible providing an energy efficient extraction. These ion associates are then stripped into the receiving phase from these reverse mixed micelles. Several factors influencing the extraction efficiency, such as the acid concentration, surfactant concentration, extraction time and temperature were investigated and optimized for providing better recoveries. The formation of reverse micelles and reverse mixed micelles has been analyzed using TEM (transmission electron microscope). The preconcentration factors for both platinum and palladium individually were found to be 10 using this method. The accuracy of the procedure was validated by analyzing PTM-1a nickel–copper sulfide matte. The procedure has been utilized for the recovery of platinum and palladium from spent catalytic converters and environmental samples.

The carrier activity of 8-hydroxy quinoline (oxine) towards the facilitated transport of copper ions through chloroform bulk liquid membrane has been studied. The effects of pH of the source phase, the nature of stripping agents in the receiving phase, presence of other cations, nature of synergistic reagents on the transport were investigated. A solution of 0.1 M nitric acid (HNO 3 ) served as receiving phase for maximum transport of the metal ion. Addition of 2-amino pyridine to the membrane phase had a synergistic effect and caused a pronounced enhancement in the transport, while citric acid or glycine did not change the transport significantly. Maximum transport efficiency was observed for Cu 2+ ion when it was present in the concentration of 10 −4 M. Tolerance to the presence of Pb 2+ , Zn 2+ , Cd 2+ , Ni 2+ , Fe 2+ and Fe 3+ ions was investigated and it was found that Cu 2+ transport was not affected even in the presence of 10-fold concentration of these ions. This system was applied for the recovery of copper in electroplating industrial waste water samples.

A rapid phase transfer catalyst assisted directly suspended droplet micro-extraction (PTC-DSDME) procedure was developed for the separation and pre-concentration of hydrophilic ionic platinum from the digested geological and spent automobile converters prior to its determination by high resolution continuum source atomic absorption spectrometry (HR-CS AAS). The method is based on the formation of extractable hydrophobic species of anionic platinum with quaternary ammonium solubilising sites of a phase transfer catalyst in a bulk aqueous phase, in the presence of an acid mixture. The formed hydrophobic species are separated from the bulk aqueous phase and pre-concentrated into a micro-volume of suspended 1-undecanol droplet, avoiding the addition of an external chelating agent. Several factors influencing the extraction efficiency, such as the nature and volume of organic solvent, stirring rate, different PTCs and extraction time were evaluated and optimized. The proposed method was applied to synthetic samples, spent catalytic converters and geological samples. The spiked recoveries were in the range of 99–102%. Under the optimized conditions, a detection limit of 0.28 ng mL−1 and a good relative standard deviation of ±1.5% at 5.0 ng mL−1 were obtained (n = 6). The accuracy of the procedure was evaluated by analyzing Canadian certified reference materials such as PTC-1a copper–nickel sulphide concentrate and PTM-1a copper–nickel sulphide matte samples. The results showed that PTC-DSDME combined with HR-CS AAS is a rapid, sensitive, and low-cost procedure requiring minimum organic solvent and an efficient analytical method for the separation and determination of trace amounts of platinum from various matrices.