Preparation And Performance Study Of PVDF Functional Membranes Based On Dye Wastewater Treatment

With the rapid development of industrial technology in recent years,water pollution has become more and more serious.Among them,industrial wastewater discharge poses a serious threat to organisms and the environment.Membrane separation technology has been considered an effective way to solve water pollution.In this paper,the hydrogel（selection layer）is adhered to the surface of a commercial PVDF membrane（supporting layer）by way of surface coating for achieving the purpose of hydrophilic modification,and the as-prepared PVDF functional membranes with excellent separation performance.The specific experimental contents are as follows:（1）A composite separation membrane（PVDF-EX）with commercial polyvinylidene fluoride（PVDF）membrane as the substrate and hydrophilic calcium alginate-based hydrogel as the selective layer was prepared by surface coating.Tannic acid（TA）with abundant phenolic hydroxyl groups was used to improve the adhesion between layers,and multi-wall carbon nanotubes（MWCNTs）with high mechanical strength were used to improve the mechanical strength of the hydrogel layer.Compared with pure PVDF membranes,the surface hydrophilicity of PVDF-EX membranes was greatly improved,the static contact angle was reduced from 100.5°to 31.8°,and the dynamic contact angle was also significantly decreased at the same time.The interception rate of methylene blue（Me B）,rhodamine B（RB）,crystal violet（CV）and congo red（CR）can be increased to more than99%by the electrostatic adsorption andπ-πstacking interactions mechanism.The modified PVDF-EX membranes can achieve a pure water flux recovery rate of over 99%for cationic RB dyes after two cycles of filtration.In addition,after the oil-water separation and anti-oil-fouling adhesion test,it also proved that the surface is very highly hydrophilic.PVDF-EX membranes showed excellent separation performance through different interception mechanisms when filtrating Fe³⁺and oil-containing emulsions.These test results indicate that modified PVDF-EX membranes coated with Ca Alg-based hydrogel can handle more complex wastewater treatment environments.（2）The Na⁺MMT was pretreated by high-power ultrasonic to increase the adsorption sites on the surface and achieve uniform dispersion.Then,the Na⁺MMT was physically blended with SA and TA.And the Ca Alg-based hydrogel was successfully loaded on the commercial PVDF membrane by surface coating and ion crosslinking.Compared with the previous chapter,modified PVDF-MX membranes greatly improved the adsorption performance of dyes without damaging the dye retention effect.The adsorption rate of the modified membranes for cationic dyes,namely methylene blue（Me B）,auramine O（AO）,rhodamine B（RB）,and crystal violet（CV）can reach 98.94%,97.27%,98.3%and 99.23%,respectively.In addition,modified PVDF-MX membranes also have excellent anti-oil adhesion ability and oil-water separation effect.These tests show that the modified PVDF-MX membranes prepared by us have a broad development prospect in the field of wastewater purification.