Preparation Of Superhydrophobic Filter Media For Filtration High-humidity Dust And Research Of Its Filtration Performance

In recent years,due to the rapid development of industrialization and urbanization and the increase of energy consumption,air pollution caused by atmospheric particles has become more and more serious.Bag filter is widely used for industrial dust filtration because of its simple structure and high filtration efficiency.However,when bag filter deals with dust with high-humidity,it is easy to paste bags,increase pressure drop and reduce the service life of filter bags.So it is necessary to research the filter media of bag filter for filtration the dust with high-humidity.At the same time,the excellent hydrophobic characteristics of lotus leaves have always been of important scientific research value and status.Therefore,this study uses the hydrophobic mechanism of the lotus leaf surface to modify the surface hydrophobicity of the bag filter media to improve its filtration performance for high-humidity dust.Firstly,TiO₂sol was prepared by sol-gel method with tetrabutyl titanate as precursor and acetic acid as catalyst.γ-Methacryloyloxypropyl trimethoxysilane（KH570）was used to reduce its surface energy to prepare KH570-TiO₂modified superhydrophobic filter media.The wettability,surface morphology,chemical composition and filtration performance before and after modification were compared and analyzed.Secondly,by analyzing the KH570-TiO₂modified filter media,TiO₂-SiO₂@PDMS composite coating was selected to solve the phenomenon of partial cracking of hydrophobic coating.Meanwhile,its surface morphology,chemical composition,filtration performance and stability were compared with the unmodified and KH570-TiO₂modified filter media.Finally,the filter media model was established by Matlab based on SEM images of unmodified and TiO₂-SiO₂@PDMS modified.The filtration process of high humidity dust particles in the filter media was simulated by the coupling method of computational fluid dynamics and discrete element（CFD-DEM）.The effects of filtration velocity and surface energy between particle-particle and particle-fiber on the deposition of particles of filter media before and after modification were analyzed.The results show that:（1）The KH570-TiO₂ modified coating is uniformly deposited on the surface of the filter media,and the fiber surface is completely wrapped,with a water contact angle of 156.29°.By testing the filtration performance of the particles with the size of 0.3μm at the filtration velocity of 0.043～0.127m/s.Compared with the unmodified filter media,the filtration efficiency and quality factor of the modified are increased by an average of 2.767%and 0.34%respectively,which improves the filtration performance of the filter media.（2）After 50 times of sandpaper abrasion cycles,the water contact angle of KH570-TiO₂modified hydrophobic filter media decreases to 150.79°,and after soaking in acid-base solution for 24 hours,it decreases to 150.2°.Which means it has good mechanical and chemical stability,and it also has good self-cleaning performance by cleaning the surface of coal powder pollution.（3）The multi-layer micro nano structure constructed by TiO₂-SiO₂@PDMS composite coating is successfully treated on the fiber filter media and uniformly attached to the fiber surface,with a water contact angle of 158.29°.For the particles with the size of 0.3μm,at the filtration velocity of 0.043～0.127m/s,the filtration efficiency and quality factor of the modified filter media are increased by an average of 4.639%and 0.51%compared with the unmodified.It is higher than the filter media modified by KH570-TiO₂,so the filtration performance is further improved.（4）After 50 times of sandpaper abrasion cycles,the water contact angle of TiO₂-SiO₂@PDMS modified hydrophobic filter media decreases slightly from158.29°to 155.2°.After soaking in acid-base solution for 24 hours,the water contact angle decreases to 154.55°under strong alkali condition,but there is almost no change in strong acid solution.That is,the modified filter media has strong durability under harsh environmental conditions（such as mechanical wear,soak in strong acid or alkali solution）.Moreover,the coating has excellent self-cleaning performance.（5）The pressure and velocity gradient of the filter media before and after modification do not increase significantly when the filtration velocity is constant,that is,the modification of TiO₂-SiO₂@PDMS has little effect on the pressure and velocity gradient of the filter media.Under the same filtration velocity,compared with the unmodified filter media,the average adhesion of high-humidity particles per square meter on the surface of the modified can be reduced by 0.569mg,that is,reducing the surface energy of the filter media by TiO₂-SiO₂@PDMS can significantly reduce the adhesion of high-humidity dust.At the same time,the filtration efficiency of the modified filter media is 3.215%higher than that of the unmodified one.