Preparation Of TiO₂-based Materials With Special Wettability In Response To Light And Study On Oily Wastewater Treatment Performance

With the continuous improvement of people's awareness of environmental protection,oil-water separation has become the focus of attention in the world in recent years.The production of oily sewage mainly includes two aspects:industrial production discharge and oil spill at sea,which brings great harm to human health and ecological environment.Although the traditional oil-water separation process is mature,most of them are accompanied by high energy consumption and secondary pollution.Therefore,it is very important to find a new way of oily wastewater treatment.It is found that materials with special wettability can overcome the above problems and achieve efficient treatment of oily wastewater,which will play an important role in the field of oily wastewater separation.In order to make the material surface have special wettability,it is necessary to control the surface energy and surface roughness structure.In this paper,micron and nano-scale TiO₂ is used to increase the surface roughness of the material,and low surface energy modifier is used to obtain appropriate surface energy.Because of its non-toxicity,easy preparation and low cost,TiO₂ is one of the commonly used materials,and can be synthesized by different synthetic methods to obtain different size and morphology of particles,which can meet the needs of various types of oily wastewater treatment processes.In addition,the Photoresponse of TiO₂ is helpful for the separation of oily wastewater.On the one hand,under ultraviolet irradiation,TiO₂has photohydrophilicity,which can reverse transformation the wettability of the material surface,make a separation material have the ability to separate different kinds of oily wastewater,realize the continuous separation process,and greatly improve the separation efficiency.On the other hand,TiO₂ also has photocatalytic activity,which can degrade soluble organic pollutants in water at the same time of oil-water separation process,and further improve the purity of filtrate.Therefore,using titanium dioxide as the base material,rough surfaces were formed on different materials?copper mesh,sponge,cellulose acetate filter membrane?to make them have special wettability and oil-water separation properties were studied.The main contents of this paper are as follows:?1?A simple and environmentally friendly hydrothermal method was used to construct massive TiO₂ on the surface of 300 mesh copper wire mesh?CWM?.The formed TiO₂ has two different sizes,one with an average particle size of 1?m and the other with an average particle size of 50 nm.The micro-nanostructured bulk titanium dioxide significantly improves the surface roughness of the CWM and determines the surface wettability by measuring the contact angle.The obtained TiO₂@CWM was immersed in the low surface energy modifier stearic acid?STA?solution to obtain a filter with superhydrophobic surface wettability,remember to S-TiO₂@CWM.The separation rate and efficiency of the filter were calculated by separating the heavy oil-water layered mixture,and its heavy oil-water separation ability was tested.On the other hand,when it is necessary to separate light oil-water layered mixture,the surface wettability of the filter is changed from superhydrophobic to superhydrophilic by utilizing the hydrophilic oxygen vacancies produced by TiO₂ under UV irradiation,remember to U-TiO₂@CWM,and the separation rate and efficiency are calculated to test its light oil-water separation ability.The experimental results show that the prepared filters exhibit opposite wettability under different modification conditions,and can separate different types of oily wastewater,thus increasing the scope of practical application.In addition,the wettability conversion can be repeated by changing the modification conditions several times,and the prepared filter also has certain mechanical strength and self-cleaning ability,which is expected to be applied in practical industrial production.?2?Melamine sponge?MF?adhering to titanium dioxide and dopamine?PDA?was prepared by a simple and easy to operate dipping-pulling method,remember to TiO₂/PDA@MF.TiO₂ is evenly distributed on the surface of the sponge frame structure,which improves the roughness.Then perfluorodecyl trichlorosilane,a low surface energy modifier,is used to modify the wettability of the sponge into superhydrophobic,remember to TiO₂/PDA@MF.Finally,the wettability of one surface of the sponge is converted into superhydrophilic by using the photohydrophilicity of TiO₂,which is modified into Janus sponge.The oil absorption capacity of the TiO₂/PDA@MF was tested.Diesel oil,gasoline and vacuum pump oil were taken as examples.The results show that the modified sponge can effectively adsorb the layered oil floating on the surface of water body,and can recover the adsorbed oil by mechanical extrusion.After many adsorption processes,it can maintain good oil absorption and drainage capacity.For crude oil with high viscosity,the adsorption process is carried out after the temperature are increased and viscosity is reduced of crude oil by the good light absorption and heat transfer capacity of TiO₂and PDA.In addition,because of the hydrophilicity of Janus sponge,it can effectively prevent the sponge from being affected by natural factors such as wind and wave in the absorption process,and improve the possibility of practical application.?3?Reduced TiO₂?r-TiO₂?nanoparticles were prepared by a simple solvothermal reaction.The r-TiO₂ particles and chitosan?CS?were attached to cellulose acetate membrane?CAM?by vacuum filtration remember to r-TiO₂/CS@CAM.The results show that the average particle size of r-TiO₂ is 10 nm,and the band gap is narrowed because of the oxygen vacancy,which makes it able to degrade organic matter under visible light,thus greatly reducing the use of energy.By changing the amount of r-TiO₂ attached,the modified membranes with different r-TiO₂ contents were obtained.The synergistic effect of surface r-TiO₂ micro-nanostructure and chitosan demulsification effect was used to separate the emulsion under gravity.The oil contact angle and the emulsion separation test of different r-TiO₂/CS@CAM was tested showed that the emulsion separation capacity of r-TiO₂/CS@CAM with r-TiO₂content of 0.3 mg mL^-1 was the best.The r-TiO₂/CS@CAM with a content of 0.3 mg mL^-1 of r-TiO₂ was taken as an example for the separation of different oil emulsion and repeated separation experiments were carried out.The results show that the r-TiO₂/CS@CAM can not only separate different types of emulsions,but also maintain good separation rate and oil resistance after repeated separation.In addition,the modified membrane maintains good separation ability even in corrosive solution,which improves the versatility and practicability of the modified membrane in environmental remediation and wastewater purification.