Research On Composite Membrane Based On Heavy Metal Ion Detection And Adsorption Function

Fluorescent carbon dots(CDs)is a new fluorescent carbon material with the diameter less than 10 nm,which has advantages of low toxicity,good fluorescence stability and high fluorescence intensity compared with traditional metal quantum dots and organic fluorescent dyes,but it’s not conducive to the realization of industrial application for its strong water solubility.Attapulgite(ATP)is a kind of one-dimensional nano-sized hydrated magnesium aluminum silicate minerals,which is widely used in many fields for its excellent chemical stability,large surface area,strong adsorption ability and so on,especially for the field of mental ions adsorption.However,the powder ATP is bad for recovery and easy to cause secondary pollution.Therefore,the membrane material which can be used for fluorescence detection of heavy metal ions was prepared by grfting CDs on PVDF membrane and the separation membrane material with dual functions of heavy metal ions detection and adsorption can be prepared by selecting PVDF membrane as the carrier of ATP and grafting with CDs at the same time.The membrane material named PVDF-g-PAA-CDs was successfully prepared by grafting CDs on the modilfied PVDF membrane surface.And the basic properties and fluorescence properties were characterized.The results showed that the membrane retained the fluorescence properties of CDs,such as excitation-dependent photoluminesccnt behavior,emitting bright blue under ultraviolet light and easy to be quenched by nmetal ions.The membrane material can be usecd for the detection of Cu2+,Hg2+ and Fe3+,and would not be affected by the commion ions in water such as Na+,K+,Cl-.We concluded that the fluorescence detection concentration of Cu2+ and Hg2+can reach 1 nmol/L,Fe3+ can reach 1 μmnol/L through the changes of the fluorescence spectrum.PVDF-g-PAA-CDs membrane had advantages of fast,stable,efficient,convenient,green for the detection of heavy metal ions as membrane material,and avoided the shortage of losing of CDs in water,which was a very promising fluorescent detection material.Then a membrane material PVDF/ATP-CDs with dual functions of metal ions detection and adsorption was prepared by loading ATP ancd CDs into PVDF membrane.And tlhe properties were characterized,which proved that the membrane material retained the inherent properties of ATP and CDs.On the one hand,the membrane material had certain adsorption capacity for heavy metal ions,which was mainly attributed to the adsorption ability of ATP.Also,it overcame the difficult reclaim of adsorbent and avoided the secondary pollution.On the other hand,the membrane material possessed the function of fluorescence detection of heavy metal ions.The fluorescence response models belonged to fluorescence on-off and the fluorescence quenching mechanism was mainly ascribed to the electron,charge or energy transfer rooted in the selective interaction between CDs and metal ions.The PVDF/ATP-CDs membrane material broke the defect of simply detection or adsorption of metal ions,realized dual functions of metal ions detection and adsorption.