Research On Surface Design And Oil-water Separation Performance Of Permanent Mercaptosilane-based Super-wetting Composites

In recent years,oil spills occur frequently accompanying with the development of the petroleum industry,which generate a large amount of oily pollutants(mainly oily wastewater).In addition,its external environment is becoming more and more complex,resulting in difficulties in post-processing,which will cause damage to the ecological environment and threaten the safety of human life and property.How to deal with the oil-water mixture quickly and efficiently to reduce the environmental impact and economic loss has become the focus of society.With the development of science and technology and the continuous innovation of materials,the emergence of super-wetting materials has provided new methods for the field of oil-water separationSuper-wetting materials can selectively absorb or repel oil stains,and successfully separate and recover them from water due to its special wetting properties.Among them,superhydrophobic/superlipophilic materials and intelligent switchable wetting materials have attracted extensive attention and research due to their advantages such as simple preparation,high efficiency,and low cost.At this stage,super-wetting materials have made great progress in terms of preparation,performance,and application,but there are still many shortcomings,such as complex preparation processes;difficult recovery after oil absorption;It is easy to lose the super-wetting property under high salinity,strong acid and alkali and extreme temperature;the separation effect is reduced in the face of complex multiple oil-water systems;etc.To overcome these shortcomings,based on porous materials such as melamine foam and cotton fabrics,a variety of super-wetting materials have been prepared herein:(1)Superhydrophobic materials prepared in a simple one-step method;(2)Durable magnetic superhydrophobic materials;(3)Low-cost and harsh environment-resistant superhydrophobic material;(4)Ultra-fast pH responsive switchable wetting materials.Meanwhile,the preparation methods,mechanism,wettability,oil-water separation performance and durability,etc.were studied(1)Starting from commercially available melamine foam(MF)and cotton fabrics,different concentrations of ?-mercaptopropyltriethoxysilane(MPTES)were used for hydrolysis and condensation under alkaline conditions to prepare different surface morphologies and wettability composites.The Fourier-transform infrared(FTIR),X-ray photoelectron spectroscopy(XPS)and scanning electron microscopy(SEM)measurement results demonstrated the MPTES Successful grafting onto MF.The composite material has good superhydrophobic/superlipophilicity,oil-absorbing ability,mechanical properties and durability.It has excellent absorption to various types of oils or organic solvents and can be reused.In addition,due to the large number of thiol groups on the surface,the composite material can also be used for the adsorption of heavy metal ions and re-modification to obtain different functionalized super-wetting materials.Therefore,the superhydrophobic composite material has wide application prospects(2)The superhydrophobic fabric was fabricated by surface modification with MPTES to incorporate thiol groups,and subsequent thiol-ene click chemistry with methacryloxypropyltrimethoxysilane(MPS)modified SiO2@Fe3O4 nanoparticles(MPS-SiO2@Fe3O4).The FTIR,XPS and SEM measurement results demonstrated the MPS-SiO2@Fe3O4 nanoparticles were strongly grafted onto the fabric surface via chemically covalent bond and constructed hierarchical micro/nanoscale structure combined with the inherent microstructure of pristine fabric.Under combination of such hierarchical structures and the inherent low surface energy of hydrophobic Si skeleton and alkyls groups,the resulting fabric exhibited superhydrophobicity and could be used to separate oil from oil/water mixture accompanying with high separation efficiency,permeate flux and excellent recyclability.Furthermore,the as-prepared fabric displayed excellent superhydrophobic durability against tape-peeling,abrasion and chemicals like strong acidic and alkaline solution Therefore,this work not only provided a facile,environmentally friendly and versatile strategy for fabricating the superhydrophobic composites,but also opened a door to preserve the durable superhydrophobicity,exhibiting promising prospect in the application of oil/water separation(3)The superhydrophobic foam was fabricated by surface modification on MF with MPTES,followed by thiol-ene click with MPS modified nano-silica particles(MPS@SiO2)in the assistance of ultraviolet light.The silica nanoparticles were strongly grafted onto the foam surface via chemically bond,which not only increased the foam surface roughness,but also decreased its surface free energy,resulting in the foam superhydrophobicity.The foam could be used as the absorption material to collect oil from oil-water mixture.Meanwhile,the foam possessed good elastic property and remained good recyclability in oil-water separation.Furthermore,the as-prepared foam displayed high stability even in 250? muffle furnace for 2 h and liquid nitrogen treatment,the foam surface remained superhydrophobic,implying the foam could be used for oil-water separation in harsh conditions,which even control the spread and extinguishment of fires containing oil.Therefore,this facile,environmentally friendly,low cost and versatile method exhibites great potential in the preparation of robust superhydrophobic coatings(4)A commercially available MPS-modified silica(MPS@SiO2)and oleic acid were grafted onto the surface of a mercaptosilane-modified MF via thiol-ene click chemistry to obtain a pH-responsive ultrafast wettability transition material.The FTIR,XPS and SEM measurement results demonstrated MPS@SiO2 and oleic acid have been successfully grafted onto the MF surface via chemically covalent bond.The composite material is superhydrophobic/superlipophilic in acidic and neutral condition,and has good separation ability for heavy oil/water systems.It exhibits superhydrophilic/underwater superoleophobicity under alkaline conditions,and light oil/water system has good separation ability.And the wetting transition speed is very fast,only 2.7 s at pH=13,which is better than most literature reports.The material also has good cycle stability and absorption capacity(k).In addition,the mechanism of pH-induced wettability transition of the material is also studied,and the model of the surface wettability of the material under different pH conditions is analyzed,which provides theoretical guidance for future work.