The "Scavenger" in Water - PVDF Water Treatment Membrane

Development status of PVDF water treatment membranes

With the increasing attention paid to urban sewage treatment and drinking water quality, and the rapid application of industrial wastewater, seawater desalination, medical membranes, and Bioenergy, water treatment membrane material technology has become an important development strategy in water resource treatment in China, and is a "member" of the national strategic emerging industry development plan. And PVDF resin has excellent comprehensive performance, forming an industrial chain consisting of membrane materials, membrane components, membrane components, membrane devices, and other elements, which is widely used in scientific research and industrial production.

Organic polymer membranes dominate the existing membrane market, such as polysulfone (PSF), polyethersulfone (PES), Polyacrylonitrile (PAN), polyamide, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). PVDF is one of the most commonly used membrane materials and has broad application prospects in the field of membrane separation.

             
Application of PVDF resin on water treatment membranes

The water treatment membrane separates liquid and mass through the pressure difference or power difference on both sides of the membrane boundary. Due to different filtration targets, impurities, macromolecular structures (proteins, colloids), small molecules or ions can be separated according to different sizes and chemical properties, which can be divided into microfiltration membrane, ultramicro membrane, reverse osmosis membrane, nanofiltration membrane, Electrodialysis membrane, etc. Microfiltration membranes are mainly used in fields such as sewage and wastewater treatment; Ultrafiltration membranes are widely used in the fields of sewage, wastewater treatment and reuse, and water purification; Nanofiltration membranes are mainly used in areas such as purified water, softened water, non ionic water, and seawater desalination; Reverse osmosis membranes can be applied in fields such as seawater desalination.

                              
Preparation method of PVDF water treatment membrane

PVDF belongs to crystalline polymers with high mechanical strength, good chemical resistance, thermal stability, and excellent aging resistance. It also exhibits good processing performance in the preparation of flat, hollow fiber, or tubular membranes. PVDF membranes are applied in the preparation of microfiltration (MF) and ultrafiltration (UF) water treatment processes, and membrane bioreactor (MBR) is a typical application of microfiltration and ultrafiltration.

PVDF membranes can be prepared by non solvent induced phase separation (NIPS), thermally induced phase separation (TIPS), vapor induced phase separation (VIPS), solution casting, electrospinning, and other methods.

Non solvent induced phase separation (NIPS) involves dissolving the polymer in a solvent to form a homogeneous solution, adding an extractant to extract the solvent, resulting in a two-phase structure of the polymer as a continuous phase and the solvent as a dispersed phase. After removing the extractant, a polymer with a certain pore structure is obtained.

Thermoinduced phase separation (TIPS) can prepare ultrafiltration/microfiltration membranes, usually with two different phase separation mechanisms: liquid-liquid phase separation, forming a dual continuous network pore structure, improving water flux and maintaining strength; Solid-liquid phase separation, forming a spherical packing pore structure.

The continuous Electrospinning technology can produce a variety of different types of nanofibers, enrich the application field of PVDF nanofiber membrane products, and is a widely used technology in cutting-edge research. ① A new type of photothermal conversion nanofiber membrane composed of electrospun acrylonitrile (PAN) nanofiber layer, polyvinylidene fluoride (PVDF), and antimony tin oxide (ATO). The PAN layer provides a hydrophilic water supply transmission channel to avoid salt precipitation, achieve efficient local heat transfer, and improve seawater desalination and water purification efficiency The electrospun PVDF SiO2 nanofiber membrane exhibits high hydrophilicity and poor lipophilicity, exhibiting good separation performance for different flow rates, initial oil concentrations, and oil-water systems. It has broad application prospects in the treatment of oily wastewater RGO/PVDF membranes with different concentrations of rGO prepared by electrospinning were applied in AGMD brine treatment systems, exhibiting high permeate water flux and desalination rate, as well as low permeate boron or salt concentration.

Future development will inevitably focus on reducing costs, improving performance, increasing stability, and extending service life Improve mechanical strength, anti-aging and weather resistance, and improve service life and treatment quality; ② Enrich the types of water treatment membranes, adapt to different water quality purification, and adapt to special working conditions such as high temperature, acid and alkali environments; ③ Hydrophilic performance modification improves pollution resistance, and adsorbed substances are easy to clean; ④ Reasonably design the size and arrangement of filter holes to increase the effective filtration area and membrane flux.