Materials With Special Wettability And Its Application In Oil-water Separation

Recently,materials with special wettability for oil/water separation have received a high level of attention.Due to their opposing affinities towards water and oil,such as hydrophobic and oleophilic,or hydrophilic and oleophobic,such materials can be used to remove only one phase from the oil/water mixture,and simultaneously repel the other phase,thus achieving selective oil/water separation.In this thesis,composite sponge with superhydrophobicity and underwater superoleophobic mesh coating were synthesized successfully through sonochemistry method.The composition,structure and wettability of the obtained materials were characterized by XRD,XPS,SEM and contact angle measurements.At the same time,the adsorption capacity and oil/water separation efficiency of these products were also tested.The main works are summarized as follows:1.A recyclable,stable and cost-effective superhydrophobic reduced graphene oxide modified melamine foam（RGMF）was prepared through ultrasonic-microwave synergistic method for the first time.In the synthesis process,ultrasonic and microwave irradiation not only shortened the reduction time of graphene oxide（GO）with the existence of reducing agent,but also considerably enhanced the firmness of reduced graphene oxide（rGO）anchored onto the melamine foam（MF）.The structure and property of the obtained RGMF were characterized by XRD,Raman,SEM and contact angle measurements.The results showed that the skeletons of MF were completely covered with rGO layers which were compact and full of wrinkles.The as-prepared RGMF was superhydrophobic without further modification.Moreover,the RGMF showed excellent selective adsorption capacity of various oils and organic solvents from water.The maximum oil adsorption capacity was112 times of the weight of the initial MF,and the adsorption capacity of the RGMF did not deteriorate after it was reused 20 times.More importantly,the RGMF showed good stability against cavitation erosion for 2h and corrosion liquids,including strong acidic,strong alkali and high density salt aqueous solutions.All these features made the as-prepared material an ideal candidate for removal and collection of oils and organic solvents from water.2.Bi₂O₃ was fixed to glass substrate by spin-coating method,forming a kind of coating and its underwater oleophobicity was tested.The CAs of a series of typical oil droplets on the coating were given,such as soybean oil,gasoline and n-hexane,which were all over 150°.From the results above,it can be concluded that bismuth material has potential in oil/water separation because of its underwater super-oleophobicity.Therefore,Bi₂O₃、BiOCl、Bi₂O₂SO₄ and BiVO₄ were anchored on the stainless steel mesh,forming the oil/water separation membrane.To test these membranes’stability,their underwater oil contact angle was calculated after being placed for 15 days in air.And result showed that the contact angles of all membrane were reduced in different degrees,but the minimal change was shown in the BiVO₄ coated mesh,hence BiVO₄ was chosen as the typical bismuth material,which can be used in oil/water separation.3.An underwater superoleophobic BiVO₄ coated mesh with sunlight-driven self-cleaning property for oil/water separation was prepared by ultrasonic irradiation.The as-prepared coating has micro/nano hierarchical structures and shows underwater superoleophobicity for various oils and organic solvents.It also exhibits excellent durability against abrasion,cavitation erosion and ultra-low temperature.Such coating can be used to separate oil/water mixtures effectively and further applied in a continuous oil-water separation system.And the aqueous pollutant in water could be degraded with the existence of the as-prepared mesh under simulated solar irradiation.More importantly,the BiVO₄ coating can decompose organic contaminants which absorbed on its surface under simulated solar irradiation,and thus recover its original oil-water separation ability.All these features make the BiVO₄ coated mesh an ideal candidate for potential application in water contamination treatment.