| Human daily production and life will produce a large amount of oily wastewater,and the discharge of untreated oily wastewater will cause serious harm to the water environment,thereby threatening human health.Therefore,oil-water separation technology is of great significance.In recent years,functional materials with special wettability have been applied to various fields such as self-cleaning,anti-icing,printing,water collection,liquid transfer,oil/water separation,etc.,and special wetting materials have been rapidly developed.Among them,super-hydrophilic underwater super-oleophobic materials are the new research hotspots of current special wettability materials.It is known from the theory of wetting that the super-hydrophilic surface in air can also exhibit super-oleophobic properties under water.Based on this theory,two super-hydrophilic underwater super-oleophobic quartz sand materials were prepared by simple solution immersion method,and some oil-water separation studies were carried out.The details are as follows:(1)Preparation of super-hydrophilic underwater super-oleophobic quartz sand filter material by chitosan modification method.The results of SEM scanning electron microscopy showed that the surface of the unmodified quartz sand filter material was covered with an organic film.After XPS photoelectron spectroscopy analysis,not only the content of C element in the surface modified chitosan quartz sand filter material increased,but also a characteristic peak of N1 s,indicating that chitosan has been bound to the surface of quartz sand filter material.The FTIR infrared spectrum analysis indicated that some of the NH2 on the chitosan reacted with the alcohol group of pentanediol to produce C=N bond.The CH2 OH of chitosan reacted with the silanol on the surface of quartz sand to produce two water and CO-Si key.By measuring the underwater oil contact angle of the quartz sand particles before and after the modification,it is found that the underwater oil contact angle of the non-surface-modified quartz sand filter material is 129.8°,and the water of the chitosan-modified quartz sand filter material is obtained.The oil contact angle is 153.2°,which indicates that the modification method has obvious improvement on the underwater super-oleophobicity of the quartz sand filter material,and reaches the level of underwater super-lipophilic.(2)Preparation of super-hydrophilic underwater super-oleophobic quartz sand filter material by potato powder modification method.By utilizing the adhesion ability of water-based polyurethane,the potato waste residue adheres to the surface of the quartz sand filter material,and the nano structure constructed by it changes the roughness of the surface of the quartz sand,thereby increasing the underwater oleophobic capacity of the modified quartz sand.SEM scanning electron microscopy results show that the surface of potato powder modified quartz sand filter material is coated with an organic film,and a large number of micron-scale microstructures are attached.It should be water-based polyurethane adhesively adhered to nano-silica and activated potato powder in quartz.The surface of the sand filter produces a micron-scale roughness that provides sufficient roughness for the quartz sand filter to provide hydrophilicity.XPS photoelectron spectroscopy analysis showed that the surface of N-element of water-based polyurethane appeared on the surface of potato powder modified quartz sand filter material,and the content of C and O on the surface of potato powder modified quartz sand filter material increased significantly,indicating that potato residue was successfully attached.On the surface of the quartz sand filter.By FTIR infrared spectroscopy,most of the hemicellulose and lignin in the low-temperature alkali-activated potato powder were removed,and no new groups were introduced,indicating that the modification mechanism is that the aqueous polyurethane acts as an adhesive.The quartz sand and potato powder modifier are well adhered together.The underwater oil contact angle of the obtained potato powder modified quartz sand filter material was measured to be 152.4°,which reached the level of underwater super-oleophobic.(3)Through the penetration experiment,it is shown that the two surface-modified quartz sands penetrate water faster in the air than the non-surface-modified quartz sand,which indicates that the hydrophilicity is improved.In addition,after water wetting,the speed of the two surface-modified quartz sands is slower than that of the non-surface-modified quartz sand,which indicates that the underwater oleophobicity is improved.The super-hydrophilic underwater super-oleophobic properties of the modified filter media are described qualitatively.(4)Through the filtration experiment of oily wastewater,chitosan has good removal ability for oily wastewater.Compared with unmodified quartz sand,the removal rate of oily wastewater is nearly doubled.Potato powder modified quartz sand has a slightly better removal ability of oily wastewater than unmodified quartz sand,but the increase is limited.(5)Through the filtration experiment of the oil-water mixture,it can be seen that for the oil and rapeseed oil,it can be seen that the two surface-modified quartz sands have a relatively high removal rate after filtering the 1:20 volume ratio mixed oil.Compared with unmodified quartz sand,the oil-water separation ability of the two surface-modified quartz sands has been greatly improved.For n-hexane,the surface-modified quartz sand removal effect is also improved compared to the unmodified quartz sand.(6)Through a series of stability tests,it is shown that even in some extreme environments,the oil contact angle of the modified quartz sand under water is larger than that of the unmodified quartz sand.Specifically,even in the strong acid environment of chitosan-modified quartz sand with poor acid resistance,the underwater oil contact angle is as high as 136.5°,which is much higher than that of unmodified quartz sand.The oil contact angle is 129.8°. |
PDF Full Text Request