| A lot of oily wastewater will be produced in the process of industrial production and life.Oily wastewater has caused serious pollution to the environment and posed a serious threat to the living environment of human beings.Deep bed filtration is a common method for deep treatment of oily wastewater.In the filtration unit,oil,water and filter media surface coexist in the filter bed.For hydrophobic and oleophilic filter media,when oil drops migrate to the surface of the filter media,they will adhere to the surface of the filter media and be removed becuase they are subjected to the affinity of the filter media surface.Obviously,the more hydrophobic and lipophilic the filter media is,the easier the oil drops will adhere to the surface of the filter media and the higher the removal efficiency will be.However,for hydrophilic and oleophobic filter media,when the oil drop is close to the surface of the filter media,it will remain spherical due to its oleophobic effect,and it is not easy to flow away from the pores with smaller particle size than the oil drop,so it may also have a high removal efficiency.In addition,in terms of head loss,the more hydrophobic the filter media is,the greater the head loss will be,and vice versa.Therefore,improving the hydrophobicity of the filter media surface can improve the oil removal efficiency of the filter bed,but will increase the head loss of filtration;On the contrary,if the hydrophilic surface of the filter media is improved,the head loss will be reduced.In recent years,great progress has been made in the research of special wettable surfaces in the field of materials,and it has been widely studied in the field of oil-water separation.The special wettability surfaces used for oil-water separation mainly include superhydrophobic and superoleophilic surface and superhydrophilic and underwater superoleophobic surfaces.However,there is little research on the special wettability filter media in the aspect of hard particle filter media filtration.For this reason,this paper studies the preparation and oil removal performance of superhydrophobic superoleophilic,superhydrophilic and underwater superoleophobic quartz sand filter media,and studies the filtration performance of mixed filter media with two different wettability filter media.(1)Tridecane acid and octadecyl trichlorosilane is grafted to the surface of quartz sand filter media by dip-coating method,but no rough structure structured.water contact angle of quartz sand filter media is 134.2°,and the quartz sand filter media has become high hydrophobic surface.By the dip-coating method,three(hydroxymethyl)aminomethane and octadecyl trichlorosilane composite were grafted to the surface of quartz sand filter media.At the same time,to enhance the hydrophobicity of filter media,ZnO nano particles structured rough micro/nano structure.The apparent contact angle of water ot the prepared quartz sand filter media above 150°,oil apparent contact at 0°,the superhydrophobic and superoleophilic quartz sand filter media obtained.The filter media has strong mechanical wear resistance and harshed environmental resistance.(2)Chitosan crosslinked with glutaraldehyde,again through the chemical reaction they are grafted to the surface of quartz sand filter media,and silica nanoparticles structure coarse structure,the superhydrophilic and underwater superoleophobic quartz sand filter media prepared with the underwater oil contact Angle is 152.1±1.20.The chitosan-coated superhydrophilic and underwater superoleophobic quartz sand filter media has certain durability,alkali resistance,mechanical wear resistance and air exposure resistance.Potato residue with NaOH and ultrasonic activation,coated on the surface of the quartz sand filter media using waterborne polyurethane.The as prepared of the underwater oil contact Angle of is 151.7±1.3°.The potato residue-coated superhydrophilic and underwater superoleophobic quartz sand filter media has certain durability,alkali resistance,mechanical wear resistance and air exposure resistance.Because potato residue is a waste,it has good practicability and low cost.(3)As prepared superhydrophobic and superoleophilic quartz sand filter media for water adhesive capacity was only about 2%of the pristine quartz sand filter media,the oil and rapeseed oil adhesive capacities is increased by 54%and 45%than the pristine quartz sand filter media,respectively,for the adhesive capacity of different organic reagent for 5?20 times of pristine quartz sand filter media.Superhydrophobic and superoleophilic quartz sand filter media can remove 99.65%and 96.46%of engine oil and rapeseed oil emulsion wastewater,respectively,and the separation efficiency of oil and water mixture is greater than 92.8%,with good oil-water separation performance.(4)Compared with the pristine quartz sand filter,the two kinds of superhydrophilic and underwater superoleophobic quartz sand filter media can improve the oil removal efficiency of emulsified oil wastewater to a certain extent and the separation efficiency of oil-water mixture to a large extent.The permeability coefficient of water increased by 11%?19%,and that of oil decreased by 6%?8%.Excellent oil-water separation performance and low head loss provide a new scheme for oil-water separation of superhydrophilic and underwater superoleophobic quartz sand filter media.(5)As for the mixed quartz sand filter media with pristine and superhydrophobic and superoleophilic quartz sand filter media,the relation between their apparent contact Angle of water and proportion x of superhydrophobic and superoleophilic quartz sand filter media is as follows:cos?=1/1.33x+0.53-1.41 As for head loss H0 in clean mixed filter bed,its contact Angle with water in mixed filter bed is:H0=180 v/g(1-e)2/e3 1/(?d)2Lv·(0.021?2.75+0.96) This indicates that the hydrophobicity of the filter media increases the head loss.(6)The mixed filter bed not only increases the oil removal efficiency,but also reduces the head loss.For the quality factors of oily wastewater treatment,the single filter media of pristine quartz sand is far less than the mixed filter media.For mixed filter media,the larger the particle size,the stronger the hydrophobicity and the higher the quality factor.In conclusion,four kinds of quartz sand filter media with special wettability were prepared for the first time,and their properties and oil removal properties were studied.Wettability,head loss and oil removal performance of mixed filter bed were studied for the first time. |
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