Preparation Of Bionic Superhydrophobic Three-Diamensional Porous Oil-Adsorption Sponges And Its Oil-Water Separation Performance

With the rapid development of globalized trade,social economy and industry are continuing in progress,the requirements for petrochemical products are increasing.While the oil spill accident and the large amount of oily wastewater from industry and daily life have seriously polluted and destroyed the ecological environment,even in greatly endangering human health.In view of the above problems,the efficient and rapid treatments of oily wastewater not only avoid the waste of petrochemical resource,but also protect the ecology and human health,which has great economic and ecological significance.With the interdisciplinary of bionics and interface theory,researchers have created superhydrophobic materials with selective absorption performance to oil and water,used to efficiently separate oil-contaminated wastewater.Superhydrophobic three-dimensional（3D）porous sponges possess the advantages of low density,high specific surface area and high adsorption capacity,showing a great potentiality in treating oily wastewater.However,most of the reported superhydrophobic 3D sponges have suffered from the expensive reagents,complex process,restrict experimental environment,or toxic solutions,which hindered its application.Based on the bionics and interface theory,this paper provided simple,green and environmentally friendly processes to control the micro-morphology and surface wettability,and then construct the multifunctional superhydrophobic 3D porous sponge,realizing the efficient separation of various types of oil-water mixtures with cyclic oil absorption.This paper is based on bionics and interface theory,adapting green methods to optimize the preparation process with water and ethanol as the basic solvents,synergistically regulating the micro morphology and surface chemical composition of 3D porous sponge,determining the optimal superhydrophobic modification conditions,verifying the improvement of surface wettability and oil absorption ability before and after modification,and elaborating on the oil-water separation mechanism of biomimetic superhydrophobic sponges,Realized the cyclic oil absorption and efficient separation of multiple types of oil-water mixtures.The research content of this paper is mainly divided into the following three parts:（1）To solve the problem of oil pollution in water and avoid the use of toxic reagents,this chapter uses citral as a green crosslinking agent,chitosan（CS）and bamboo fiber（BCF）treated with bamboo chopstick alkali as raw materials,and prepare superhydrophobic CS/BCF sponge materials（S-CS/BCF）through chemical crosslinking,freeze-drying,and chemical vapor deposition（CVD）in green strategy.Firstly,the lignin and hemicellulose of bamboo chopsticks are partially removed through alkaline treatment,and the BCF dispersion is obtained through mechanical stirring.The citral emulsion was added into the mixture of CS and BCF for crosslinking.After freeze-drying and chemical vapor deposition（CVD）treatment,S-CS/BCF sponge was prepared.The laminated CS cross-linked with citral and the bent BCF form an interconnected and stacked structure,resulting in a maximum irreversible deformation ratio of 14.56%for S-CS/BCF after 50 cycles of compression at 40%strain.It exhibits good mechanical properties and great potential for cyclic oil-absorption.Owing to the high porosity of S-CS/BCF,the sponge exhibits good oil absorption ability（17.95-44.57 g/g）.In addition,S-CS/BCF can effectively separate immiscible oil-water mixture,oil-in-water and water-in-oil emulsion through self-made peristaltic pump drive or self-made separation device gravity drive.More importantly,S-CS/BCF also exhibits good degradability.（2）In response to the problems of insufficient oil absorption capacity,complex preparation methods,poor durability,and difficulty in large-scale preparation of S-CS/BCF,this chapter selects melamine sponge as the skeleton material,adapted a simple dip-coating method to construct fluorine-free superhydrophobic TiO₂-HDMS/ER@MS sponge（SMS）in large-scale.Firstly,the hydrolysis and condensation of butyl titanate and hexamethyldisilazane（HDMS）generate a large amount of-Si（CH₃）₃ grafted onto the surface of titanium dioxide（TiO₂）,forming a TiO₂-HDMS suspension.After adding epoxy resin（ER）and polyamide resin curing agent to the suspension,ER/polyamide resin and TiO₂-HDMS were coated on the surface of the melamine sponge（MS）skeleton using a dip-coating method,and high-temperature curing was performed to obtain SMS.The cured ER has low surface energy due to its inclusion of dimeric fatty acids and long methylene chain hydrophobic segments.At the same time,it serves as an adhesive to improve the bonding force between hydrophobic TiO₂-HDMS and MS interface,forming a rough micro-nano composite structure,endowing the sponge with superhydrophobicity.The research results indicate that SMS has excellent superhydrophobic（air and oil phase）/superhydrophilic properties,with only slight plastic deformation（about 2%）after 1000 cycles of compression at 50%strain,demonstrating excellent mechanical properties.SMS exhibits excellent hydrophobic stability in complex and harsh physichemical environments,and higher oil absorption capacity（30.95-61.55 g/g）than S-CS/BCF,which can effectively recover floating oil and bottom oil for separating oil-in-water emulsions.In addition,SMS also exhibits good self-cleaning,photocatalysis,and bacterial filtration performance.（3）To overcome the hydrophobic coating of SMS increasing sponge density and reducing sponge adsorption performance,and the use of organic solvents,which limits the further large-scale preparation of sponges,this chapter uses water as the only solvent,and uses short carbon chain vinyl triethoxysilane（VTES）as the raw material for hydrophobic modification and micro/nano particles.Under alkaline conditions,the ethoxy group is removed to form VTES-OH with a large number of silicon hydroxyl groups,which condenses to form hydrophobic silica（HSiO₂）,and codeposited with prepolymerized dopamine onto MS surface to form HSiO₂-PDA@MS sponge.After the heat treatment,the catechins of polydopamine（PDA）oxidize to form quinone groups at high temperatures,improving the hydrophobicity of the surface.Combined with HSiO₂ particles and PDA to construct a micro-nano rough structure,superhydrophobicity HSiO₂-PDA@MS sponge（SPMS）was prepared on a large scale.Compared with the other two superhydrophobic sponges in this article,SPMS displays more excellent oil absorption ability（67.6-139.1 g/g）.After 100 compression unloading cycles at 80%strain,the residual non-invertible deformation is only 9.54%,demonstrating excellent mechanical properties.SPMS still maintains high hydrophobicity/superoleophilicity under corrosive/wear environments,different stress conditions,or compression cycles.In addition,SPMS is convenient for large-scale preparation,which can continuously remove oil slick and effectively separate multiple-types of oil-in-water emulsions.More importantly,SPMS has excellent flame retardancy,which can effectively absorb fuel,reduce combustion area,and decrease fire risk.The preparation of SPMS does not use toxic and harmful solvents,nor does it generate toxic by-products of secondary pollution.It is a simple,environmentally friendly,and cost-effective"green"production process that can be used for large-scale preparation of superhydrophobic sponges,and has enormous practical application potential in oil contaminated wastewater treatment.