Kinetics of transport of sodium chloride using supported liquid pertraction

摘要

In the present work, the removal of NaCl using the present type of supported liquid membrane technique has been investigated. A simple apparatus devised and constructed was used to conduct the experiments. Various factors that would affect the progress of transport were studied and these were initial concentration (C-i) of simulated seawater in donor phase (DP), presence of mobile carrier (MC) in the liquid membrane (LM), concentration of MC in LM, presence of sequestering agent (SA) in the receptor phase (RP), and speed of stirring. The volume ratio of DP to RP was kept constant at 2:1. Type (1,2 dichloroethane (DCE)) and thickness (2mm) of LM were kept constant. Cellophane constituted the support for the LM. The most important findings emphasized the importance of the presence of a MC in the LM to enhance mass transfer through the LM and that an optimum concentration of MC existed. Also the importance of stirring in promoting mass transfer by minimizing the boundary layer intact to the cellophane support was elucidated. The best conditions arrived at were MC=0.0538mol/l (mol of dibenzo-18-crown-6/l of LM), SA=0.0617mol/l (mol of soluble starch/l of RP), slow stirring (100rpm) of DP, and using DCE as LM. The mass transfer of NaCl was analyzed based on kinetic laws of two consecutive irreversible first-order reactions, and kinetic parameters (k(1d), k(2m), k(2r), t(max)) for the transport of NaCl were investigated. The values obtained demonstrate that the process is diffusion-controlled. Results indicate that the membrane entrance and exit rate constants (k(1), k(2)) increase directly with C-i and inversely with quantity of SA.