Abstract
This paper discusses the use of double- carrier supported liquid membrane (DCSLM) for extraction of Cr(III) ions, using the D2EHPA/CYANEX272 mixture as the carriers. Based on the calculated value of the activation energy and on the assumption that the result of transport process in the DCSLM, in particular, depends on the accumulation of intermediate products in the membrane, the mathematical model of the chromium(III) ions separation based on consecutive first-order reactions has been proposed. Transport kinetics of chromium(III) in studied system for different carriers concentrations ratio and their comparison with theoretical prediction was analyzed. The obtained results confirmed the presence of a synergistic effect of selected carriers in DCSLM. Verification of the proposed model has been carried out in the article. Mathematical model describes correctly the membrane transport process only for most effective carriers ratio. It was found that depending on the carriers ratio in DCSLM the transport processes may be controlled by both chemical reaction and diffusion. The described model can be a useful tool for quickly and approximate determination of the transport process parameters in experimental works but is too simple to correctly describe the Cr(III) ions pertraction in supported liquid membrane system under the full range of process parameters (especially concentrations and proportions of the used carrier).
Highlights
Chromium and its compounds are widely used in many industries
This paper discusses the use of double- carrier supported liquid membrane (DCSLM) for extraction of Cr(III) ions, using the di (2-ethylhexyl) phosphoric acid (D2EHPA)/CYANEX272 mixture as the carriers
In the discussed DCSLM system with D2EHPA/Cyanex272 mixture calculated value of the activation energy indicates that chromium(III) transport through membrane with optimum composition is controlled by chemical reaction occurring at interface of boundary layers
Summary
Chromium and its compounds are widely used in many industries (electroplating, tanning, dyes, textile). Chromium(III) is used as tannins, which enable the production of high-quality leather. Chromium helps to produce very tight and effective coatings [1]. In spite of the many advantages of chromium, spent tannings threaten environment, because of the toxic effect of chromium ions, in particular chromium(VI) ions. Wastewater containing chromium ions should be purified before discharge. According to the European Commission Report of 2010 [2], chromium belongs to the ‘‘critical elements.’’ This means, that it is characterized by limited resources and the lack of substitutes, while simultaneously being essential for economic and industry development. Taking into consideration the above factors, it requires the exploration and development of methods for the efficient separation of chromium from aqueous solutions
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