Preparation Of Bionic Superwetting Material And Its High Viscosity Crude Oil-Water Separation Performance

The increasingly serious oil pollution problems,especially the high viscosity crude oil pollution,cause serious waste of natural resources and seriously destroy the balance of ecological environment.Traditional oil-water separation methods usually have their own limitations,such as secondary pollution,high cost,high labor intensity,long time consumption,low selectivity,low efficiency and so on.In recent years,biomimetic superwetting surfaces have been successfully introduced into the field of oil-water separation,and great research progress has been made.However,compared with common low viscosity petroleum products,crude oil is easily adhered to or blocked the separation materials due to its high viscosity and low fluidity,which limits the application of the superwetting surface in crude oil-water separation or in situ adsorption and recovery of crude oil.For high viscosity crude oil-water mixtures that are easy to be pre-recovered,designing and constructing superhydrophilic/underwater superoleophobic surfaces with stable water retention layers as the separation barrier between the oil and the separation membrane surfaces is a effective way.But,there are still drawbacks such as complicated preparation process,high cost,not durable and not environmentally friendly.As for the crude oil spills that are inconvenient for pre-recovery,it is a very effective solution to realize in-situ recovery by reducing the viscosity of crude oil through heating effect.However,achieving excellent Joule heating performance at lower voltage inputs is challenging for composites made of commonly used non-conductive polymer foams.In addition,obstacles such as high preparation costs and complex preparation processes still exist.Moreover,from the point of view of being more environmentally friendly and energy efficient,materials with photothermal and Joule heating effects simultaneously can realize all-weather crude oil water separation while conserving resources as much as possible,showing greater attraction.Based on this,a series of superwetting materials inspired by the surface of organisms with special wettability in nature were designed and prepared to solve the above problems.The main work and related results are as follows:（1）In order to solve the problems faced by superwetting surfaces in the separation of high-viscosity crude oil-water mixtures that are easy to be pre-recovered,superhydrophilic and underwater superoleophobic surfaces（named MCC-LS-CM）were successfully prepared by a simple,green and environmentally friendly one-step dip coating method inspired by fish scale surface,in which microcrystalline cellulose with-OH hydrophilic functional groups is introduced into the coating with the aid of an inorganic adhesive.In the whole preparation process,water was the only solvent.Besides being highly resistant to low viscosity oils and achieving effective oil-water separation,the MCC-LS-CM also effectively resisted crude oil adhesion and achieved high viscosity crude oil-water separation.And,the surface of MCC-LS-CM indicates abrasion resistance.Moreover,the method exhibits universality on multiple substrates.It is expected that such fabrication strategy can provide a low cost,green and environmentally friendly approach to construct superhydrophilic and underwater superoleophobic surfaces to achieve super anti-crude oil-fouling and（crude）oil-water separation.（2）Aiming at the problems faced by superwetting surfaces in the application of separation of high viscosity crude oil-water mixtures that are not easy to be pre-recovered,superhydrophobic and superoleophilic PDMS@NiO@NF was prepared inspired by the surface of lotus leaves.Nickel foam（NF）with a three-dimensional mesh structure acted as the substrate and nickel oxide（NiO）was on its surface by simple,controllable,and large-area-preparation laser etching,and further surface modification was performed by polydimethylsiloxane（PDMS）.Thanks to the excellent ferromagnetism and wettability of the NF substrate,PDMS@NiO@NF can achieve non-contact,controlled recovery of low viscosity heavy or light oil.In addition,it can also achieve all-weather rapid high viscosity crude oil-water separation assisted by the Joule heating effect to reduce the viscosity of crude oil under safe voltage input.（3）In order to achieve more energy saving and environmental protection purposes,carbon felt（CF）with excellent Joule heating performance was selected as the substrate,and uniform molybdenum disulfide（MoS₂）was prepared on its surface by one-step hydrothermal method,and superhydrophobic and superoleophilic carbon felt（PDMS@MoS₂@CF）was prepared by combining it with surface modification.It also exhibits significant photothermal and Joule heating capabilities at safe low voltages benefiting from the excellent electrical properties of CF itself and the exceptional photothermal and electrical properties of MoS₂.In addition to low viscosity oil recovery,PDMS@MoS₂@CF can also reduce the crude oil viscosity and effectively achieve crude oil recovery assisted by photothermal and Joule heating effects.Meanwhile,the two effects can complement each other,realizing all-weather high viscosity crude oil water separation while saving energy.（4）In order to be able to adapt to the complex and changeable practical application environment,3D porous superhydrophobic and superoleophilic foams（LMP-Foam）have been successfully prepared by combining the sacrificial template method and laser etching.The PDMS which has low surface energy,excellent elasticity,and abrasion resistance,and the multi-walled carbon nanotubes（MWCNT）were used together as the skeleton structure of foam.Here,MWCNT do not exist as a coating around the foam surface,but as the main component constituting the foam skeleton,so the foam shows excellent mechanical property,low temperature resistance,high temperature resistance,salt resistance and abrasion resistance.Taking the advantage of the addition of MWCNT,the foam shows excellent photothermal effect and Joule heating effect.Besides low viscosity oil recovery,it can achieve rapid crude oil spill recovery under the photothermal effect or Joule heating effect.The combination of the two effects can be used for efficient all-weather high viscosity crude oil-water separation under different weather conditions.This foam is expected to be an ideal material for all-weather dealing with oil spills.