Study On Transport And Separation Of Cd(Ⅱ) By A Tri-n-octylamine-Secondary Octyl Alcohol-Kerosene Hybrid Liquid Membrane

In this thesis cadmium(Cd2+) was transported by hybrid liquid membrane(HLM) where microporous polypropylene flat films and Tri-n-octylamine (TNOA, R3N)-secondary octyl-alcohol (ROH) kerosene were used as solid supports, membrane phase, respectively. The permeation of Cd2* is influenced by stirring speed in the feed and membrane solutions, HC1 and Cl~ concentration in feed phase, carrier concentration, membrane solvent. The experiments indicate that the transport of Cd2+ is coupled by the co-transport flow of protons. The theoretical equation of transport flux of metal ions across HLM has been deduced, treating the double solid membranes of HLM as a single membrane with twice the geometrical thickness of the polymer support. The experiment results well accord with the theoretical forecast. The uptake of TNOA content from membrane phase into feed phase and stripping phase is determined. The experiments indicate that HLM can prevent TNOA from loss out of membrane phase and prolong the lifetime of liquid membrane.The separation of Cd(II) and Zn(II) or Cd(II) and Fe(III) in the feed solution containing high concentration of HN03 and HC1 were successfully realized, adding stripping agent of liquid membrane system in the feed solution in order to control the transport of specific ions in the feed solution. The experiments indicate that the transport percentage of Cd2+ exceeds 92% and Zn2+ is only 3% after transport of 21 hours for binary Cd(II) and Zn(II) solution. Meantime, the transport percentage of Cd2+ is 100% and Fe3+ is nearly zero after transport of 25 hours for binary Cd(II) and Fe(III) solution .A hydrophilic cellulose acetate membrane(CA membrane) which had been synthesized in our lab was used to replacemicroporous polypropylene membrane in HIM system to separate Cd2+ from hydrochloric acid solutions. The experiments prove that CA membrane is similar to microporous polypropylene membrane when they were used in HLM system. The uptake of the carrier from the membrane phase into aqueous solution can be prevented completely by CA membrane.