Preparation, Modification And Adsorption Properties Of Carbon Nanomaterials/polyvinylidene Fluoride Blend Membranes

In recent years,membrane distillation technology is widely used in water treatment,oil and water separation,catalyst and so on.However,the higher cost and lack of membrane materials restrict the development of membrane in industry.Polyvinylidene fluoride(PVDF)has a good thermal stability,mechanical properties and chemical stability,and has been regarded as a common and ideal membrane material in a field of ultrafiltration and microfiltration.However,PVDF membranes are highly hydrophobic and easy to be attached to the contaminants leading to a lower water flux.Therefore,in order to solve these problems that the PVDF membrane is vulnerable to be polluted in long-term water treatment operation process,we explored blending modification method with the additions of MWCNTs-COOH to improve the hydrophilicity and anti-foluing of PVDF membranes.The main content of this paper is divided into two parts:firstly,a simple tactic that concerned with enhancing pore size/porosity and hydrophobicity of MWCNT/PVDF blended membrane was investigated,using different time of alkali-treated or plasma irradiated.Then the pretreated membranes were grafted by immersing into various concentrations OTS(Octadecyltrichlorosilane)or APTE solution to vary anti-wetting property.Secondly,integration of multiwalled carbon nanotube(MWCNT),grapheme oxide(GO)and reduction graphene oxide(RGO)with polymers to construct network porous structure by swelling and freeze-drying method,which has attracted considerable attention for both fundamental studies and diverse technological applications.In this paper,a simple method to prepare large-scale network pores and sponges using the solvent/nonsolveent(DMF/H2O)system to swell blended membrane,after which freeze blended membrane in liquid nitrogen bath is presented.The membranes were characterized by FT-IR,WAC,BET,mercury intrusion porosimetry,and SEM to test the changes of surface morphology,chemical composition,hydrophobicity,porosity and pore size of PVDF blend membranes.The analysis results indicated membranes grafted 5wt%OTS impels water contact angle increasing greatly from 90° to 141.90 after modification,and the optimum concentration of OTS and alkaline treatment time were 5wt%and 10 min.At the same time,the changes of surface pore size/porosity,mechanical property and hydrophobicity of the membranes can be observed.The effects of DMF content in the solution,swelling time and freezing time of MWCNT-GO-RGO/PVDF membranes on the crystallization properties,surface morphology and hydrophobicity,and adsorbing performances were comprehensively investigated by X-ray diffraction(XRD),field emission scanning electron microscope(SEM),the contact angle analysis(WCA),and the ultraviolet spectroscopy.Based on the SEM observation,the process conditions of PVDF blend membrane greatly affect the pores structure,and network pores were presented obviously on MWCNT/PVDF membranes after being swollen for 15 min by 4wt%DMF/H2O and frozen for 1.5 h in liquid nitrogen,and RGO/PVDF membrane swollen for 15 min by 8wt%DMF/H2O and frozen for 0.5 h.Moreover,the adsorption properties of above blended membranes containing RGO and MWCNT were 0.6,1.03 mg/g,respectively.