Research On The Preparation And Performance Of Oil-water Separation Materials Based On ZnO Nanostructures

The high-water content in crude oil will increase the power consumption during the crude oil transport process.It will also reduce the utilization rate of equipment and pipelines in the gathering and refining process,which further affects the regular operation of crude oil gathering and refining process by causing fouling and corrosion in metal pipelines and equipment.Currently,most of China’s oil fields have entered the tertiary oil recovery period,in which high-water content in crude oil is widely existed.It is urgent mission to develop novel efficient and stable oil-water separation technology.Among the various methods of oil-water separation,the membrane separation materials with special wettability have be-come an effective candidate due to their simplicity of use and no secondary pollution.So fat,the effective regulation of the surface wettability of materials is vital in improving the oil-water separation performance.This paper has constructed tunable nanoarray structures on fiber felt substrates.By experimental and theoretical analysis,we performed a systematic investigation on oil-water separation process,coalescing and demulsification of emulsified droplets.A microscopic mechanism of the emulsion droplet coalesce and demulsify process is revealed.The material surface structures have been optimized and the oil-water separa-tion properties of the materials have been improved further.The main contents and results of this study are as follows:（1）Nanostructure preparation.Herein,a ZnO nanostructure was prepared by a two-step sol-gel process and was grown from the liquid phase.It would be used to investi-gate the effects of different preparation parameters（pulling times,growth precursor concen-trations,growth temperature conditions,and growth time conditions）on the ZnO nanostructures.The aspect ratio of ZnO nanostructures increased with the concentration of the growth precursor.The same trend was observed for the case with different gaps in the nanoarray structure.Furthermore,the array density of ZnO nanostructures increased with the number of film pulls.Meanwhile,the growth temperature determined the formation and stability of the nanoarray structure.In addition,the increase in growth time led to a decrease in the diameter of the nanostructure and its top agglomeration.（2）Surface wettability of the filter material.The wettability of the nanoarray structures was analyzed,which was prepared under different conditions.The experimental results in-dicated that the designed ZnO nanostructured fiber felts were superhydrophobicity and su-peroleophilicity in the air.Water or oil droplets rapidly spread on the surface of ZnO nanostructured fiber felts.The contact angle of the material surface was close to 0°.The ZnO nanostructured fiber felts were prepared under the conditions of 2 pulling times,0.05mol/L concentration of growth solution,90°C,and 3 h growth time.We achieve both a su-perhydrophobicity in oil and a superoleophobic property in water,and the contact angle was above 150°.（3）Oil-water separation.We investigated the oil-water separation performance of coated fiber felts in oil-in-water and oil-in-water emulsions.Our experimental results demonstrated that the oil-water separation efficiency of the coated fiber felts in oil-in-water emulsions was around 98%.The separation flux was up to 3139 L·m^-2·h^-1.The oil-water separation efficiency of the coated fiber felts was 98%in water-in-oil emulsions,with a separation flux of up to 960 L·m^-2·h^-1.The coated fiber felts showed excellent separation performance and stability in recycling separation experiments.（4）Mechanism study.The emulsified droplets’dynamic behavior and their coalescing and demulsifying on the surface of fiber felts were investigated by an ultra-deep 3D digital microscope.The different oil-water emulsions in contact with the surface of the fiber felts result in the main phase of the oil-water mixture to be adsorbed on the surface of the filtra-tion material and finally form a liquid layer.In contrast,the impurity phase was selectively rejected.By the transmembrane pressure difference,the main phase was separated from the oil and water through the separation material.