The synthesis and optimization of polymeric inclusion membranes (PIMs) for the transport of Cd(II) and Pb(II) and their separation from Zn(II) in aqueous saline media are presented. The effects of NaCl concentrations, pH, matrix nature, and metal ion concentrations in the feed phase are additionally analyzed. Experimental design strategies were used for the optimization of PIM composition and evaluating competitive transport. Synthetic seawater with 35% salinity, commercial seawater collected from the Gulf of California (Panakos®), and seawater collected from the beach of Tecolutla, Veracruz, Mexico, were employed. The results show an excellent separation behavior in a three-compartment setup using two different PIMs (Aliquat 336 and D2EHPA as carriers, respectively), with the feed phase placed in the central compartment and two different stripping phases placed on both sides: one solution with 0.1 mol/dm3 HCl + 0.1 mol/dm3 NaCl and the other with 0.1 mol/dm3 HNO3. The selective separation of Pb(II), Cd(II), and Zn(II) from seawater shows separation factors whose values depend on the composition of the seawater media (metal ion concentrations and matrix composition). The PIM system allows S(Cd) and S(Pb)~1000 and 10 < S(Zn) < 1000, depending on the nature of the sample. However, values as high as 10,000 were observed in some experiments, allowing an adequate separation of the metal ions. Analyses of the separation factors in the different compartments in terms of the pertraction mechanism of the metal ions, PIMs stabilities, and preconcentration characteristics of the system are performed as well. A satisfactory preconcentration of the metal ions was observed after each recycling cycle.
Esta obra está bajo licencia internacional Creative Commons Atribución-NoComercial-CompartirIgual 4.0 Internacional 52 Ciencia, Ingenierías y Aplicaciones, Vol. 2(2): 51-79 • Notas Técnicas reformado catalítico.
AbstractUsed mainly as fuels in internal combustion engines, gasolines are complex mixtures of hydrocarbons that include in their composition different additives that improve their stability and performance. Its chemical composition is not only diverse but also variable, depending on the crude oil origin, the obtaining process and the existing regulations, which fix the maximum allowed content of certain compounds that should be limited due to their toxicity. Gasolines are obtained by fractional distillation of petroleum and also from heavier fractions of petroleum by thermal or catalytic cracking, processes that together with catalytic reforming will have a direct impact on their composition. The objective of this review is to address the complex composition of gasoline, as well as some basic processes of oil refining, which largely determine its composition and which are closely related to the emission of polluting substances. In this way, we provide a more accurate context on the pollutants of gasoline and its impact on the environment, while we highlight the need for advanced regulations to regulate the composition of fuels.
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