Adsorption Of Silver Ion Using A PVDF Separation Membrane Bearing Thiourea Groups

In this study a novel PVDF separation membrane bearing thiourea groups was successfully prepared for removal of Ag(I)from the aqueous solution by chemical grafting and phase transfer techniques with the polyvinylidene fluoride(PVDF)microspheres,dimethyl sulfoxide(DMSO),4-vinylbenzy chloride(VBC),benzoyl peroxide(BPO)and thiourea(TU)as main reagents.The purpose was to endow the adsorption function of the micro ultrafiltration membrane on the basis of filtration and retention,and then remove the silver ion(Ag(I))from the solution.Firstly,the morphology,chemical groups and components change before and after adsorption Ag(I)of the membrane were characterized using the characterization instruments,verified the thiourea groups were incorporated onto the PVDF chain and successfully adsorption Ag(I).simultaneously,density functional theory(DFT)was used calculate the chemical activity parameters to determine the reaction activity point of alkalized PVDF(APVDF),VBC and TU groups,and the optimum structure of TU-PVDF was determined by structural optimization.Secondly,the effects of p H,initial Ag(I)concentration,contact time,temperature and coexistence substances(Cu(II),Ni(II),Co(II),TA,EDTA,Na2S2O3)on Ag(I)uptake and the adsorption characteristics were investigated.TU-PVDF membrane more suitable for the treatment of low concentration Ag(I)-containing wastewater,and compared with three cations,the disturbing influences of three complexing reagents are very conspicuous.Then the hydrophilicity of the TU-PVDF membrane was characterized by contact angle meter,and the permeation flux,flux recovery ratio(FRR)and filtration resistance of the fabricated functional membrane were evaluated by bovine serum albumin(BSA)filtration experiment.The experiment results show that the contact angle,adsorption of BSA of the TU-PVDF membrane decreased by 38.8% and 61%,the pure water flux went up by 52% as compared as the pure PVDF membrane.The FRR value of TU-PVDF membrane(90%)is about as 2 times as that of the PVDF membrane(48%),the total filtration resistance is reduced by an order of magnitude.It suggests the membrane show a noticeable permeability and antifouling properties.Lastly,the breakthrough curves data obtained at different inflow velocities,membrane stack thicknesses,initial concentrations of Ag(I)were analyzed and fitted by Thomas model.On the basis of filtration test,the analysis of PDEs ascertains the distribution gradient of Ag(I)along longitudinal filtration direction of the membrane stack and verified by EDS.During the regeneration of TU-PVDF membrane,the eluent and silver were recycled and recovered(black Ag and Ag2S).Although this membrane and eluent were cycled 8 times,they also show an excellent reusability.Additionally,the potential application performance of the TU-PVDF membrane was evaluated by simulating non-cyanide electroplating silver rinsing wastewater.