| The illegal discharge of oily wastewater and the frequent occurrence of oil spills in people's daily production and life have not only caused serious ecological crisis and economic loss,but also have huge safety risks to human health.Therefore,exploring a continuous and efficient oil-water separation technology has been the focus of research at home and abroad.In recent years,the application of special wettable materials in the field of oil-water separation has attracted more and more attention due to its unique advantages.Therefore,many researchers focus on the research and development of special wettable oil-water separation materials.Also,they have developed many valuable special wettable oil-water separation materials.It has always been the direction of researchers'efforts that how to effectively combine the opposite special wetting materials to achieve continuous,high-volume,high-efficiency separation of oil-water mixtures and the treatment of difficult-to-treat oily wastewater with a high degree of emulsification.Hence,two treatment methods are designed for oil-water mixture and emulsified oily wastewater using two quartz sand filter media with relatively special wettability.The details are as follows:(1)Separation of oil-water mixture.A two-way continuous oil-water separation device is designed.Its structure is roughly two horizontal filter columns filled with two particulate filter materials with relatively special wettability,and the two filter columns share a liquid inlet cavity.When the oil-water mixture is separated,the two phases(oil phase and water phase)in the mixture can flow through one selective filtration column,but not through the other,so as to achieve continuous and efficient separation of the oil-water mixture.The experimental results of the separation performance of oil-water separation device for different oil-water mixed liquids show that the separation efficiency of the five oil-water mixtures(petroleum ether,engine oil,diesel,cyclohexane,and dichloromethane)are all above 99.4%.In addition,the permeability coefficients of the five oil-water mixed liquids are affected by the properties of the liquid(such as density and viscosity),and their corresponding permeability coefficients also vary greatly.For example,the minimum viscosity of petroleum ether corresponds to a maximum permeability coefficient of 13.13 m/h.Because the oil viscosity is too high,about 350 times that of petroleum ether,the permeability coefficient is very small,only 0.034±0.001 m/h.The results of continuous light/heavy oil-water separation experiments showed that two kinds of light/heavy oil-water mixtures(diesel is light oil and dichloromethane is heavy oil)were continuously separated into 45L of oil-water mixture.The oil-water separation efficiency is greater than 99.4%.Both diesel oil and dichloromethane penetrated the super-hydrophilic column twice.The superoleophilic column was penetrated by water 3 times.And the dichloromethane/water mixture was penetrated 1 time.After backwashing,the separation efficiency of the oil-water separation device can be restored to 99.4%.The experimental results of the filter media particle size on the oil-water separation device show that the filter media particle size is proportional to the permeability coefficient and inversely proportional to the separation efficiency.But the larger the particle size,the greater the risk of lyophobic invasion.For example,when the equivalent particle size is 0.25mm,oil invasion occurs only when the amount of separation on the hydrophilic side is 15 L.When the equivalent particle size is 0.99 mm,oil intrusion occurs when the amount of separation on the hydrophilic side is only 0.5 L.The experimental results of the influence of the length of the filter column on the performance of the oil-water separation device show that an increase in the length of the filter column will improve the efficiency of oil-water separation and reduce the risk of lyophobic invasion.However,an increase in the length of the filter column will lead to a decrease in the water output rate.Therefore,through analysis of experimental data,it is recommended that the equivalent particle size of the filter material be controlled at about 0.6 mm and the filter column length is controlled at 10 cm.This oil-water separation device can achieve continuous,efficient and large-scale oil-water separation.(2)Treatment of oily wastewater.By constructing a mixed filter bed with six ratios of super-hydrophilic underwater super-oleophobic filter material and super-hydrophobic super-oleophilic filter material(super-hydrophilic filter material accounts for 0%,20%,40%,60%,80%And 100%,respectively)to filt oily wastewater.Two methods were used to measure the wettability of the mixed filter bed using the capillary rise method and the direct measurement method of the contact angle meter.Then,after linearly fitting the measurement results of the two methods,the R~2 is 0.9969,indicating that the two test results are accurate and credible.Secondly,the wettability of the mixed filter column and the ratio of its content of super-hydrophilic underwater superoleophobic filter material are fitted with a quadratic curve R~2 is 0.9992,and it is found that the wettability of the filter material and the proportion of super-hydrophilic filter material are The reason for the conic relationship needs further study.It can be known from the experiment of the influence of the filtration rate on the degreasing performance of the mixed filter bed that the size of the filtration rate has a great influence on the degreasing rate of the mixed filter bed.This is because after the flow rate increases,the shear force of the water flow in the pores of the filter material increases,making the possibility of tiny oil beads in the water attached to the surface of the superoleophilic filter material lower,resulting in a lower oil removal rate in the effluent.In addition,the increase of the filtration rate also directly leads to the increase of the head loss.Through data analysis,it is found that the special wettability surface and the filtration rate will also have a coupling effect on the liquid flow resistance.In addition,the filtration rate has a significant effect on the quality factor.The smaller the filtration rate,the greater the quality factor.It shows that the effect of filtration rate on the permeability coefficient is less than the effect on the oil removal efficiency.The experimental results of the influence of filter particle size on the degreasing performance of mixed filter beds show that the oil removal efficiency is basically inversely proportional to the filter particle size,that is,the smaller the filter particle size,the higher the corresponding oil removal efficiency.The permeability coefficient increases with the increase of the particle size of the filter material.This is because a larger particle size has a larger pore radius and a stronger water conductivity.This shows that in terms of permeability coefficient,particle size and wettability do not have a coupling effect.In addition,the influence of filter particle size on quality factor is not obvious.The experimental results of the influence of the height of the filter bed on the degreasing performance of the mixed filter bed show that under the same conditions,the height of the filter bed is directly proportional to the oil removal rate.That is,the greater the height of the filter bed,the greater the corresponding oil removal rate.In addition,because the permeability coefficient has nothing to do with the height of the filter bed,in terms of the permeability coefficient,there is no coupling effect between bed depth and wettability.The depth of the filter bed has a significant effect on the quality factor.The smaller the bed depth,the larger the quality factor.The head loss of the filter bed is directly proportional to the bed depth,but in the initial stage of filtration,the upper part of the filter bed mainly plays a filtering role,and the oil removal efficiency of the filter bed does not increase proportionally with the bed depth.In conclusion,the separation of oil-water mixture and the removal of oily wastewater can be effectively realized by two different combinations of opposite special wettability filter media,which provides a new scheme for practical application in the field of oil-water separation. |
PDF Full Text Request