Alguacil Francisco J, Robla Jose I
Centro Nacional de Investigaciones Metalurgicas (CENIM-CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain.
Membranes (Basel). 2023 Feb 1;13(2):177. doi: 10.3390/membranes13020177.
An investigation of chromium(VI) transport across a supported liquid membrane containing the phosphine oxides Cyanex 921 and Cyanex 923 dissolved in Solvesso 100 as carrier phases was carried out in batch operation mode. Chromium(VI) transport was investigated as a function of different variables: hydrodynamic conditions in the feed (1000-1600 min) and stripping (600-1500 min) phases, HCl (0.25-2 M) and indium (0.01-0.1 g/L) concentrations in the feed phase, and carrier (0.01 M-0.75 M) concentration in the membrane phase. Indium was recovered in the stripping phase using hydrazine sulphate solutions, and, at the same time, chromium(VI) was reduced to the less harmful Cr(III) oxidation state. Models describing the transport mechanism comprising a diffusion process through the feed aqueous diffusion layer, fast interfacial chemical reaction, and diffusion of the respective chromium(VI)-phosphine oxide complexes across the membrane were developed. The equations describing the rate of transport correlate the membrane permeability coefficient with diffusion and equilibrium parameters, as well as the chemical compositions of the respective metal-carrier phases. The models were used to calculate diffusional parameters for each metal-carrier system, and the minimum thickness of the feed boundary layer was calculated as 1 × 10 cm and 6.3 × 10 cm for the Cr(VI)-Cyanex 921 and Cr(VI)-Cyanex 923 systems, respectively.
在间歇操作模式下，对铬（VI）通过负载液膜的传输进行了研究，该负载液膜含有溶解在Solvesso 100中的氧化膦Cyanex 921和Cyanex 923作为载体相。研究了铬（VI）传输与不同变量的函数关系：进料（1000 - 1600分钟）和反萃（600 - 1500分钟）相中的流体动力学条件、进料相中HCl（0.25 - 2 M）和铟（0.01 - 0.1 g/L）的浓度以及膜相中载体（0.01 M - 0.75 M）的浓度。使用硫酸肼溶液在反萃相中回收铟，同时，将铬（VI）还原为危害较小的Cr（III）氧化态。建立了描述传输机制的模型，该机制包括通过进料水相扩散层的扩散过程、快速界面化学反应以及相应的铬（VI） - 氧化膦配合物在膜中的扩散。描述传输速率的方程将膜渗透系数与扩散和平衡参数以及各金属 - 载体相的化学成分相关联。这些模型用于计算每个金属 - 载体系统的扩散参数，对于Cr（VI） - Cyanex 921和Cr（VI） - Cyanex 923系统，进料边界层的最小厚度分别计算为1×10⁻³ cm和6.3×10⁻³ cm。
