Recently, the Functional Textile Material Group led by Prof. Bin Ding in our college has made a breakthrough in the area of air filtration membranes releasing negative ions.This work was published with the title of “Low-Resistance Dual-Purpose Air Filter Releasing Negative Ions and Effectively Capturing PM2.5” in ACS Applied Materials & Interfaces, which isa world authoritative academic journal in the field of material interfaces research(ACS Appl. Mater. Interfaces 2017, 9, 12054−12063).
The severe air pollution poses a great threat to human health. Therefore,the development of a functional air filter material that can release negative ions has become one of the most important directions in the field of air filtration. Moreover, negative ions as a functional material are called “air vitamin”, which can contribute to the synthesis and storage of vitamins in the body and have an important effect on human life.However, electret melt-blown fibrous materials present the advantage of high initial filtration efficiency, but their use is impeded due to the charge dissipation and without the function of releasing negative ions. Electrospun nanofiber materials, which can overcome the drawbacks of materials above due to the ultrathin diameters, small pores, high porosity and easy function modification, have attracted the widespread concern of researchers. However, how to achieve high filtration efficiency and low air resistance of fibrous membranesat the same time, and improve their function of negative ion releasing, is still a critical issue in air filtration.
Schematic illustrationof the air purification mechanismand the performance demonstration of effectively capturing PM2.5.
Therefore, the researchers developed a low-resistance air filter capable of releasing negative ions (NIs) and efficiently capturing PM2.5 by electrospinning polyvinylidene fluoride (PVDF) fibers doped with negative ions powder (NIPs). The decrease of air-resistance for polysulfone, polyvinyl butyral, and PVDF fibrous membranes was investigated. The air-resistance of fibrous membranes decreased by 36% with the reduction of fiber diameters due to the “slip effect” of PVDF fibers.Furthermore, the single PVDF/NIPs fiber was endowed with stronger surface potential tested using atomic force microscopy due to the higher electronegativity of fluorine atom, resulting in higher releasing amounts of NIs (RANIs). More importantly, the reduced fiber diameter was in favor of alleviating the shielding effect towards potential difference of NIPs and promoting the RANIs from 798 to 2818 ions cc-1.Ultimately, the resultant fibrous membranes exhibited high PM2.5 purification efficiency of 99.99%, a low pressure drop of 40.5 Pa, and high RANIs of 2818 ions cc-1. This functional material, which has excellent filtration performance, is of great significance to the development of the functional integrated material in air filtration.
This work is supported by the Key Technologies R&D Program of China (Nos. 2015BAE01B01 and 2015BAE01B02), the National Natural Science Foundation of China (Nos. 51673037 and 51503030), the “DHU Distinguished Young Professor Program”, the Fundamental Research Funds for the Central Universities (No. 16D110115), and the Shanghai Sailing Program (No. 15YF1400600).
