Ziwei Lv,Hongxu Liu,Jingxuan Zhao,Ruijia Wang,Ting Xie,Yuchao Qi,Yang Yu,Xue Lv,Shulin Sun
In this paper, PVDF-g-PNIPAAm/GEP-PDA@ZnO composite membranes that can undergo light-induced structural response and photodegradation to achieve self-cleaning have been designed and applied to the separation and purification of dye wastewater. The membranes were prepared by blending graphene (GPE)-polydopamine (PDA)-coated zinc oxide (ZnO) core–shell particles into the PVDF-g-PNIPAAm matrix with a non-solvent induced phase separation technique. The GPE and ZnO are tightly bonded by highly adhesive PDA to form a “strawberry-like” core–shell structure. GPE absorbs light energy and converts it into heat, resulting in changes in PNIPAAm chain segments to expand the pore size for self-cleaning. While the membrane is warming up, GPE further promotes the activation of active groups on the surface of PDA@ZnO at high temperature, resulting in unique and excellent photothermal catalytic activity. As a result, the membrane achieves both self-cleaning and pollutant degradation, which results in an FRR of 99.6% after light cleaning. Moreover, the GPE-PDA@ZnO nanoparticle-modified PVDF-g-PNIPAAm membranes exhibit excellent cycling stability with a degradation flux recovery rate of more than 97% even after multiple UV cleaning. Thus, PVDF-g-PNIPAAm/GPE-PDA@ZnO composite membranes extend the versatility of PVDF-based membranes and show extraordinary potential for application in wastewater treatment.
Temperature-responsive separation membranes can significantly change their permeability and separation properties in response to changes in their surrounding temperature, improving efficiency and reducing membrane costs. This study focuses on the modification of polyvinylidene fluoride (PVDF) membranes with amphiphilic temperature-responsive copolymer and inorganic nanoparticles. We prepared an amphiphilic temperature-responsive copolymer in which the hydrophilic poly(N-isopropyl acrylamide) (PNIPAAm) was side-linked to a hydrophobic polyvinylidene fluoride (PVDF) skeleton. Subsequently, PVDF-g-PNIPAAm polymer and graphene oxide (GO) were blended with PVDF to prepare temperature-responsive separation membranes. The results showed that temperature-responsive polymers with different NIPAAm grafting ratios were successfully prepared by adjusting the material ratio of NIPAAm to PVDF. PVDF-g-PNIPAAm was blended with PVDF with different grafting ratios to obtain separate membranes with different temperature responses. GO and PVDF-g-PNIPAAm formed a relatively stable hydrogen bond network, which improved the internal structure and antifouling performance of the membrane without affecting the temperature response, thus extending the service life of the membrane.
Hongxu Liu,Junhao Xie,Jingxuan Zhao,Ruijia Wang,Yuchao Qi,Shulin Sun
Traditional water treatment membranes always face the problem of membrane contamination in the practical application. Those contaminants deposited on the membrane surface and inside the membrane pores make the filtration process more difficult. Herein, the temperature and photo sensitive nanocomposite membranes with superior wasterwater separation and light-cleaning capabilities were prepared by a non-solvent induced phase separation method, which combined the thermo-responsive property of poly(N-isopropylacrylamide) (PNIPAAm) grafted polyvinylidene fluoride (PVDF) and the high photothermal conversion character of core–shell structured BN@PDA-Ag nanosheets. The membranes can be heated to high temperature within a short period of light exposure due to the fast photothermal conversion capability of Ag and the excellent thermal conductivity of boron nitride (BN). The increase in temperature led to the contraction of PNIPAAm chains and bigger pore size. The microstructure, filtration, and cleaning performance of the nanocomposite membranes can be controlled by illumination, which allowed PVDF-g-PNIPAAm/BN@PDA-Ag membranes to achieve the effect of first interception and then cleaning. The membranes showed retention rates of 82, 99 and 95 % for BSA, oil–water emulsions and various dyes with flux recovery rates of > 90 % after light cleaning. This work provides a simpler, more efficient membrane cleaning strategy with superior potential for dealing with membrane contamination.
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