Preparation And Properties Of Perfluorinated Sulfonic Acid Pervaporation Composite Membrane

In the process of industrial production,a lot of acid and alkaline waste liquid will be produced.How to deal with acid and alkali waste liquid effectively is an important subject.At present,there are some problems about the treatment of acid and alkali waste liquid,such as large investment,complicated process and low efficiency.Pervaporation has the characteristics of mild operating conditions and no influence of osmotic pressure threshold.It has great application potential in the concentration,reuse and reduction of acid and alkali waste liquid.However,at present,conventional pervaporation dense film materials cannot maintain long-term stability in strong acid and alkali environment.Therefore,we use perfluorosulfonic acid resin with good acid and alkali resistance as dense substrate.The specific research content of this paper is as follows:1.Due to the good acid and alkali resistance of perfluorosulfonic acid resin（PFSA）,PFSA is selected as the dense substrate of composite film,Polytetrafluoroethylene（PTFE）and PFSA have good compatibility,PTFE/PP as the supporting layer material,PFSA/PTFE/PP composite film is prepared by spraying process.The final composite membrane has a pure water flux of 45±1.2 kg/（m²·h）at 70℃.The acid and alkaline resistance of the intrinsic membrane and composite membrane was evaluated.It was found that the membrane was concentrated to 20 wt.%after 19 h long concentration operation at 70℃and the initial feed solution was 5 wt.% H₂SO₄ and 5 wt.%Na OH.The retention rate of acid and base can be kept above 99.9%.During the concentration of the acid solution,the structure of the dense layer is affected,and the pure water flux of the composite membrane is reduced,eventually maintaining around 32 kg/（m²·h）.However,during the process of alkali solution concentration,the pure water flux of the composite membrane will increase first and then decrease,and the final pure water flux of the composite membrane will remain around 40 kg/（m²·h）.2.By adding hydrophilic Titanium Dioxide（Ti O₂）particles into the dense layer as the modifier of the film,on the one hand,the stability of the film structure can be improved,and at the same time,the hydrophilic degree of the film can be increased.The water flux of PFSA-Ti O₂/PTFE/PP composite membrane was 70.33±1.05 kg/（m²·h）,and the membrane had good acid and alkaline resistance.The initial liquid was 5 wt.%H₂SO₄ and5 wt.%Na OH.The feed solution was enriched to 20 wt.%after a long concentration run of 12 h and 14 h respectively.The retention rate of acid and base concentration operation is above 99.9%,and the influence of acid and base on the structure of dense layer is weakened,and the water flux of the film is more stable during the operation of acid and base.