Preparation Of Oil Resistant Hierarchical Metal Hydroxide Composite Metal Mesh And Its Oil-water Separation Performance

The pollution of oil-bearing wastewater derived from the development of industrial production and human life is becoming more and more serious.It is of great significance to develop efficient recycling technology to realize the reuse of wastewater and efficient recovery of oil products.Oil/water separation membrane has attracted much attention in the field of wastewater treatment because of its advantages such as high separation efficiency,low energy consumption and no secondary pollution.However,there are problems of surface oil adhesion and membrane pore plugging pollution in the use of oil-water separation membrane,which greatly attenuates its separation efficiency and service life,and seriously hinders the practical application of oil/water separation membrane.Therefore,it is very important to improve the oil resistance of the oil/water separation membrane.The crux to achieve super oil resistance of the membrane lies in the fabrication of the surface hydrophilic micro/nano hierarchical structure of membrane,which improves the wettability and water capture ability of membrane material,and reduces the contact area between the membrane and oil.In this paper,the hierarchical metal hydroxide composite metal meshes with ultrahigh oil resistance were prepared by hydrothermal method,and their oil/water separation related properties were studied.The specific research contents are as follows:The nickel-doped copper hydroxyl sulfate@copper hydroxide/copper mesh（NBCHCM）was prepared by chemical oxidation and hydrothermal synthesis.Firstly,the copper hydroxide nanoarrays grow radially along the surface of the copper wires in an alkaline aqueous solution.Then,the nickel-doped copper hydroxyl sulfate nanosheets were grown on the surface of the copper hydroxide arrays by low temperature hydrothermal method.The interlaced embedded nanosheets@nanoarrays hierarchical composite structures were established on the surface of copper mesh through the above two-step method.The results show that the composite copper mesh with reaction time of 3 hours（NBCHCM-3 h）expresses optimal superhydrophilicity/under superoleophobicity and water capture ability,and ultrahigh oil resistance.The prepared copper mesh shows high rejection（>99.99%）and high flux(>28543L m^-2 h^-1)for a variety of oil/water immiscible mixtures,shows high rejection over 99.98%for various oil-in-water emulsion.Meantime,the prepared copper mesh shows stable separation performance after continuous separation of oil/water mixture for 20 times,which still has behaved good cycling stability.In addition,the prepared copper mesh has excellent mechanical stability,acid resistance,and alkali resistance,which expresses obvious selectivity to oil and water under a variety of harsh conditions.The hierarchical cobalt-nickel bimetallic hydroxide/stainless steel mesh（Co Ni-OH/SSM）was prepared by one-step hydrothermal synthesis.The hydrophilic double metal cobalt-nickel hydroxide（Co Ni-OH）nanothorns@nanosheets hierarchical structures fabricated on the surface of stainless steel mesh（SSM）endow the SSM with superhydrophilicity/underwater superoleophobicity.The results show that the SSM modified by Co Ni-OH with a growth time of 4 h（Co Ni-3 h）shows the optimal water capture ability and ultrahigh oil resistance.The prepared mesh shows high rejection（>99.95%）and high flux(>37227 L m^-2h^-1)for various oil/water immiscible mixtures,the mesh also expresses rejection more than 94.25%for a variety of oil-in-water emulsion.The cyclic separation test results show that the prepared SSM has maintained good separation performance after more than 20 cycles with stable flux of 37000 L m^-2 h^-1,and rejection of 99.90%.Besides,the prepared SSM has excellent mechanical stability,and corrosion resistance,and still shows obvious oil/water selectivity in acidic,alkaline,saline and other harsh conditions.In conclusion,in this study,the Ni-doped copper hydroxyl sulfate nanosheets@copper hydroxide nanoarrays and cobalt-nickel bimetallic hydroxide nanothorns@nanosheets hierarchical structures were modified on the surface of the metal mesh,respectively,and the NBCHCM and the Co Ni-OH/SSM were successfully prepared,and the oil/water separation performance were studied.The fabrication of these two kinds of micro-nano hierarchical structures makes the metal mesh both show high separation efficiency,ultrahigh underwater oil resistance,good mechanical stability,and durability,and can achieve effective separation of the oil/water immiscible mixture and oil-in-water emulsion.