Extraction of cadmium from aqueous solutions by emulsion liquid membranes using a stirred transfer cell contactor

Abstract

Foi estudada a extração de íons cádmio(II) a partir de soluções aquosas ácidas, usando, em uma cela de transferência sob agitação, uma membrana líquida em emulsão, (MLE) preparada pela mistura de querosene com D2EHPA (um ácido alquilfosfórico) como carregador móvel e Span-80 como surfactante. A membrana MLE permitiu transporte eficiente do metal, da solução de alimentação para o extrato de coleta em experimentos realizados a 25 ºC. As variáveis significativas no transporte de cádmio através da membrana foram a concentração do extrator e a quantidade de metal na solução alimentadora. A concentração de HCl como agente de coleta afetou somente a taxa inicial de extração do metal, mas não a extensão da extração. A quantidade de surfactante usada neste estudo estabilizou a membrana adequadamente, mas o uso de uma quantidade maior produziu uma menor taxa de extração inicial devido à resistência inferfacial mais alta. Os resultados experimentais sugerem a possibilidade de recuperação ou remoção de metais tóxicos de soluções aquosas diluídas em um extrator baseado em membranas líquidas emulsificadas.It is studied the extraction of cadmium(II) ions from acidic aqueous solutions using a stirred transfer cell-type emulsion liquid membrane (ELM) prepared by dissolving in kerosene, with D2EHPA (an alkylphosphoric acid) as mobile carrier and Span-80 as surfactant. The ELM allowed efficient metal transport from the feed solution to the stripping liquor in experiments carried out at 25 ºC. The significant variables on cadmium transport through the membrane were extractant concentration and metal content in the feed metal-donor solution. Concentration of HCl as stripping agent affected only the initial metal extraction rate but not the extraction extent. The surfactant content used in this study stabilized the membrane adequately, but the use of a higher content produced a smaller initial extraction rate due to higher interfacial resistance. The experimental results suggest the possibility of recovering or removing valuable or toxic metals from dilute aqueous solution in an extractor based on emulsified liquid membranes.

Effect of modification of environmentally friendly biosorbent wheat (Triticum aestivum) on the biosorptive removal of cadmium(II) ions from aqueous solution

“…Cadmium is present as free Cd 2+ species along the whole acid pH range. Above pH 7.5, it starts to precipitate as Cd(OH) 2 and thus, no more 'available' for biosorption [34]. Thus upper pH limit is decided by the precipitation of metal ions.…”

Emulsion Liquid Membrane for Cadmium Removal: Determination of Liquid Membrane Components

“…The distribution coefficient (K D ) of cadmium prepared by D2EHPA concentration could be obtained from the plot of log (D2EHPA) versus log K D slope of the line is equal to the number of carrier molecules associated with a metal atom in the extracted species. It was found in Figure 2 that the obtained slope was almost equal to 2, indicating that one mole of cadmium would react with two moles of D2EHPA as mentioned by Basualto et al 30 Based on these result, the distribution coefficient of various D2EHPA concentration was evaluated by the following equation:…”

Kaolinite and Cd2+ Transport and Interaction in Sand Media: Batch and Column Experiments

“…CaCl 2 was used as the background ions because Ca 2+ is one of the most common divalent cations found in natural waters. In addition, Cd is predominantly present as Cd 2+ in the acidic pH range for low Cl -(1 mM) concentrations (Basualto et al 2006). The highest chloride ion concentration in the co-transport experiments was 0.6 mM.…”