Preparation Of Porous Membrane Materials Using Waste Plastic As Raw Material And Its Treatment Of Oily Wastewater

With the improvement of life quality,the application of plastic has dramatically increased,which would lead to huge white pollution.On the other hand,petroleum fuel,as the largest energy consumption in the world,is widely used in industry,agriculture,national defense,transportation,and daily life.Meanwhile,oil spill accidents in the process of offshore oil exploration and transportation have caused serious environmental pollution.Therefore,in order to reduce environmental pollution and achieve the purpose of "use of waste materials for wastewater treatment ",this paper takes waste plastic Kevlar and polyethylene(PE)as the research object to explore the high-value recycling of plastic and prepare porous aerogel membranes with different wettability for emulsion separation.The separation property and recyclability of aerogel membranes are studied in detail,which are mainly as follows:1.The dispersed aramid nanofibers(ANFs)based on the raw material of waste plastic of Kevlar was obtained using a KOH/DMSO solvent system for treatment.The aerogel membrane with superhydrophilic/underwater superoleophobic was fabricated via combining solvent replacement and freeze-drying route.The structure and composition of the material were characterized,focusing on exploring the wettability and oil/water separation performance of ANFs aerogel membrane,and preliminarily exploring the separation mechanism of an oil-in-water emulsion.ANFs aerogel membrane can achieve the separation of oil-in-water emulsion stabilized by surfactants under gravity drive,and the separation efficiency is over 98%.In addition,it still maintains a high separation efficiency of more than 98.0% after 10 subsequent cycles,implying its outstanding recyclability.2.In order to expand the recycling of plastics,waste domestic plastic PE was selected as the raw material.A waste PE-derived aerogel membrane via swelling,solvent extraction,and followed by freeze-drying.The structure and composition of the material were characterized,and the wettability and oil/water separation performance of the material was explored.For water-in-oil emulsion under complex environments,the corrosion resistance,separation,and regeneration properties of aerogel membranes were investigated.Besides,the separation mechanism of the water-in-oil emulsion was preliminarily explored.Most interestingly,the waste PEMA can be recycled and regenerated as a raw material for preparing new PEMA to form closed-loop recycling as an environmentally friendly and sustainable model.Meanwhile,PE aerogel membrane has great application potential in emulsion separation even under complex conditions.3.Carbon nanotubes with low density and high elastic modulus are considered to improve the mechanical properties of ANF aerogel membranes.Multi-walled carbon nanotubes(MWCNTs)were treated with concentrated nitric acid to remove impurities and improve their dispersivity in DMSO/KOH system.A hydrophilic/underwater superoleophobic ANFs/CNTs composite aerogel membrane was prepared by mixing dispersed aramid nanofibers and CNTs as the stock solution.It not only maintains the three-dimensional porous structure and excellent separation property of ANFs aerogel membrane but also realizes the separation of water-in-oil emulsion with surfactant stability under gravity.In addition,the ANFs/CNTs composite aerogel membrane and the ANFs aerogel membrane was tested through the tensile strength.Compared with the raw material,the tensile strength value of the ANFs/CNTs composite aerogel membrane is increased by the addition of CNTs.Besides,it exhibits certain flexibility,which greatly improves the mechanical properties of ANFs aerogel membrane.4.To expand the wettability of the PE aerogel membrane and avoid it being polluted by oil fouling in emulsion separation,PE aerogel membranes are prepared from a precursor of waste polyethylene plastic,and the interface wettability of PE aerogel membranes is modified by non-thermal plasma in one step process.The structure and composition of the material were characterized,and the wettability and oil-water separation performance of the material were emphatically explored.By lowtemperature plasma modification,the modified PE aerogel membrane has superhydrophilic/underwater superhydrophobic wettability,which shows good separation performance and stability in water-in-oil emulsion separation.This modification method can not only achieve uniform material surface modification but has the advantages of energy saving and time,easier control,high efficiency and no pollution.It is believed that the hydrophilic aerogel membrane and non-thermal plasma modification strategies developed herein are expected to be applicable to the wettability modification of other plastic-based materials for potential practical application in oilin-water emulsion treatment.