Experimental Study Of Fabricating Materials With Extreme Wettability Through Dip-coating For Oil/Water Separation

The discharge of industrial oily wastewater and the continual occurrence of oil spill accidents at sea cause huge waste of resources as well as heavy environmental pollution.How to solve the pollution and save the resources has always been the focus of scientific research.In recent years,extreme wettability materials have received more attention in the field of oil/water separation due to their opposite wettability to oil and water.However,there are some problems in the preparation of the materials,such as complex process,low efficiency and poor durability.In this paper,extreme wettability materials were prepared through dip-coating method and applied in oil/water separation research.The main research contents and results of the thesis are as follows:(1)The superhydrophilic and underwater superoleophobic stainless steel mesh was prepared through dip-coating method.The optimal mesh number and immersion time were first explored.Then the wettability,surface morphology and composition of the mesh were analyzed.According to the results,when the mesh number is 350 and the immersion time is 3 min,the mesh is covered with microscale granular bulge structure of chromium trioxide,which enables the mesh with good superhydrophilicity and underwater superoleophobicity.The water contact angle on the mesh in air is 0° and the contact angles of different oils on the mesh under water are all above 158°.Besides,the mesh behaves low adhesion to oil.The abrasion resistance and wettability stability test of the superhydrophilic and underwater superoleophobic stainless steel mesh shows that the mesh can maintain underwater superoleophobicity after 100 times of abrasion test or storage in water for 72 h.(2)The superhydrophilic and underwater superoleophobic stainless steel mesh was applied to oil/water separation and its oil penetration resistance,separation ability for different oil/water mixtures,reusability and separation ability under harsh environments were investigated.According to the results,the values of intrusion pressure on the mesh are all above 1.5 kPa to different oils.The mesh exhibits excellent separation efficiencies,rates and purities for different oil/water mixtures.The mesh can separate hexane/water mixture for 20 times and separate the mixtures of hexane and acid,alkali,salt solution as well as hot water with high efficiency.Thus,the mesh has broad application prospects in dealing with industrial oily wastewater.(3)The superhydrophobic and superoleophilic sponge was prepared through dip-coating method.The wettability,surface morphology and composition of the sponge were analyzed.According to the results,the skeleton of the sponge is covered with nano-scale needle-shaped structure of copper stearate,which enables the sponge with good superhydrophobicity and superoleophilicity.The water contact angle is 156° and the contact angles for different oils on the sponge are all 0°.Besides,the sponge behaves low adhesion to water.The abrasion resistance and wettability stability test of the superhydrophobic and superoleophilic sponge shows that the sponge can maintain superhydrophobicity after 100 times of abrasion test or storage in air for 12 months.(4)The superhydrophobic and superoleophilic sponge was applied to oil/water separation and its absorption capacity for different oils,reusability and absorption capacity under turbulent water were investigated.Based on the sponge,a device was designed to collect oil spills at sea.According to the results,the sponge has great absorption capacity and high absorption rate for different oils.The sponge can maintain good absorption capacity during the process of repeatedly absorbing diesel for 20 times or absorbing diesel under turbulent water.The oil skimmer on the basis of the sponge can simultaneously absorb and store oil,and does not need to recover oil by extrusion.Thus,the sponge has broad application prospects in dealing with oil spills at sea.