Preparation Of PTFE-based Photothermal Nanofiber Membrane And Study Of Its Membrane Distillation Performanc

Solar energy holds great promise for sustainable seawater desalination and alleviating the world’s water shortage.In recent years,solar evaporators have received much attention due to high solar energy utilization,however,their vapor collection efficiency is low due to the lack of effective vapor condensation and clean water collection systems.In recent years,a new photothermal membrane distillation（MD）process has come into being,which realizes the simple and efficient integration of clean vapor generation,condensation,and collection.The integration of photothermal materials into membranes to prepare functional MD membranes can make full use of solar energy to achieve local heating at the membrane-feed side interface through the photothermal effect,providing an efficient temperature gradient across the membrane for vapor transfer,effectively solving the problems of high energy consumption,heat loss and temperature polarization of the traditional MD process.and becoming an important research direction in membrane distillation in recent years.Photothermal membrane distillation has become an important research direction in the field of membrane distillation in recent years.Based on the electrostatic spinning and electrostatic spinning derivative technology,the superhydrophobic CB/PTFE photothermal nanofiber membranes and the pro/hydrophobic photothermal composite membranes with stable high flux and excellent salt cut-off rate were prepared based on polytetrafluoroethylene（PTFE）with very low surface energy and the photothermal properties of carbon black,respectively,with the aid of nano-doping technology and layer-by-layer composite technology,which provide new ideas for the development of new PTFE-based photothermal membrane distillation This study provides new ideas for the development of new PTFE-based membranes for photothermal membrane distillation.The details of the research are as follows:（1）CB/PTFE composite nanofiber membranes were prepared by introducing carbon black into PTFE spinning liquid system using the electrostatic solution-blowing technique,combined with the roasting process at 390℃.The best overall performance was achieved with the addition of carbon black at 2%,and the membrane showed a rough nanofiber and microsphere structure with uniform fibers,moderate microsphere size,and good morphology;achieved superhydrophobic properties with a static contact angle of 161.0±2.6°,a rolling contact angle of 7.7±1.5°and a roughness of 4.07±0.33μm;exhibited excellent light absorption performance with an average absorbance in the240～2600 The average light absorption rate in the wavelength band of 240～2600 nm is99.97%;Under the irradiation of 1 k W m^-2 light intensity,the surface temperature of the CB/PTFE composite membrane increased by 13°C relative to the pure PTFE membrane,showing excellent light absorption and photothermal conversion performance,and its permeation flux is 1.42 L m^-2-h^-1,the salt rejection is above99.99%.（2）Based on electrostatic spinning technology and layer-by-layer composite process,CB/PVA as the hydrophilic photothermal layer,PVDF as the intermediate binder layer,and PTFE as the hydrophobic base layer,the CB-PVA/PVDF/PTFE pro/hydrophobic photothermal composite film was successfully prepared.When the addition amount of carbon black is 15%,the fiber has good overall morphology and excellent light absorption and photothermal conversion ability,and the average absorbance can reach 99.96%in the wavelength range of 240～2600 nm.Under 1 k W m^-2 light intensity,the membrane surface temperature can be increased by 22.9℃compared with the pure PVA membrane,its permeation flux can reach 1.51 L m^-2-h^-1after membrane stabilization,and the salt rejection is more than 99.99%.The CB/PVA hydrophilic photothermal layer has good hydrophilicity,and it is easy to form a hydration layer with pollutants,and the anti-fouling performance test and SEM characterization,compared with pure PTFE membranes,CB-PVA/PVDF/PTFE membranes showed good anti-pollution performance for feed liquids containing pollutants and could maintain high water flux and retention rate with long-term stable operation,indicating that composite membranes with hydrophobic substrate and hydrophilic surface layer have the strong anti-pollution capability in MD membranes and have great potential in treating high salinity polluted wastewater.