Preparation Of PAA/PVDF-Fe~0 Hybrid For Cr(?) Removal From Aqueous Solution

In recent years,with the development of industrial,wastewater pollution of chromium is becoming more and more serious.Nanoscale zero-valent iron(Fe0)has received a great range of attention.Especially when hexavalent chromium(Cr(VI))remediation by nanoscale zero-valent iron,many ways have occurred.The smaller Fe0 particles,the larger specific surface area and the stronger reduction there are.But these have also led to oxidation and agglomeration easily.which diminished particles'reactivity.According to these characteristics,carrier have drawn scientists' eyes,especially PVDF membrane,which can improve the chemical property of material and efficiency of reaction to hexavalent chromium in aqueous solution.Unfortunately,the strong hydrophobic nature of PVDF membrane leads to only a small amount of immobilized Fe0 particles for decontamination of wastewater.Therefore,there is a major challenge in exploring a new approach for modification of PVDF films to improve its hydrophilicity.In this study,poly(vinylidene fluoride)(PVDF)microporous film was successfully synthesized by the phase inversion method and functionalized by poly acrylic acid(PAA)for immobilization of Fe0 particles.PAA was innovativeIy introduced onto PVDF film via in.situ polymerization of acrylic acid(AA)and followed by ion exchange procedure.The characteristic and removal effect of Cr(VI)by the as-prepared PAA/PVDF-Fe0 hybrids were tested.The removal mechanism and reaction kinetics of Cr(?)by PAA/PVDF-Fe0 hybrids were also explored.The main contents are as follows:(1)The morphology and surface functional groups of PAA/PVDF-Fe0 hybrids were studied by Scanning Electron Microscope(SEM).Fourier Transform Infrared(FT-IR)spectrometer and Energy Distribution Spectra(EDS),which indicated that the PVDF film by coating of PAA within its micropores and Fe0 particles are well immobilized onto the support.In addition,the surface hydrophilicity of PAA/PVDF film is improved obviously than PVDF film according to the contact angle measurement.(2)Over the reaction course,the resultant PAA/PVDF-Fe0 hybrids demonstrated high reactivity,excellent stability and reusability for Cr(?)removal.Compared with unsupported Fe0 particles,the removal efficiency of Cr(?)by PAA/PVDF-Fe0 hybrids under optimized conditions is increased by 52%.The effects of various factors(including initial pH,temperature,and initial concentration of Cr(?))on the removal efficiency were investigated.Results showed that lower pH,lower initial concentration and higher temperature facilitated the removal of Cr(?)by PAA/PVDF-Fe0 hybrids.(3)The activity of the regenerated PAA/PVDF-Fe0 hybrids toward Cr(?)was not appreciably deteriorated after 6-cycle use,suggesting that the PAA/PVDF-Fe0 hybrids retained most of the capacity for supporting nano-scale iron particles after being regenerated.(4)Compared with unsupported Fe0 particles,the PAA/PVDF-Fe0 hybrids resulted in a lower activation energy for Cr(?)removal.Mechanism analysis indicated that Cr(?)reduction process with PAA/PVDF-Fe0 hybrids is a surface-controlled chemical reaction.Moreover,a two-parameter pseudo-first-order model was provided and well-described the reaction kinetics of Cr(?)over PAA/PVDF-Fe0 hybrids under various conditions.