Research On Synthesis And Treatment Of Emulsified Oil From Petroleum Wastewater Of Cationic Chitosan-based Flocculant

A large amount of oil-contianing water is produced from the process of petrochemical production and oilfield exploit.And the stable emulsified oil is difficult to remove.It will pose a threat to the social environment and human health if it’s discharged without treatment.Flocculation by adding flocculants to form polymer flocs is a common method for treating emulsified oily wastewater.Commonly used flocculants include inorganic flocculants such as polyaluminum chloride(PAC)and polyferric chloride(PFC)and organic flocculants like acrylamide(AM)and polyacrylamide(PAM),but problems existed including toxicant residual monomers and difficult to biodegrade.Therefore,highly efficient and environmentally friendly materials or technologies should be developed for the separation of oil and water in emulsified oily water,which is beneficial to environmental and economy.In this paper,chitosan(CS),AM and methacrylpropyltrimethylammonium chloride(MAPTAC)were selected as raw materials,2-hydroxy-4 ’-(2-hydroxyethoxy)-2-Methyl phenyl acetone(IR2)was chosen as the photo-initiator,and the two monomers AM and MAPTAC were graft copolymerized with CS by low-pressure ultraviolet method with wavelength 253.7nm and power 24W to obtain a cationic chitosan-based flocculant CS-g-P(AM-MAPTAC).The emulsified diesel water obtained by ultrasonic emulsification was used as simulated wastewater,and flocculants were added for flocculation treatment.In this paper,the effects of photo-initiator concentration,total monomer concentration,ratio of total monomer to CS,monomer mass ratio and illumination time were investigated and the optimized synthesis conditions were obtained;The basic characteristics,molecular structure,surface morphology,thermal stability and particle size distribution of CS-g-P(AM-MAPTAC)were measured:In addition.the effects of the amount of flocculants,pH value,the initial oil concentration and the grafting ratio of flocculant on the oil removal ratio were explored,from which the flocculation mechanism was discussed.Experimental results show that the optimized synthesis conditions are:photo-initiator concentration(mass fraction)0.3%,total monomer concentration(mass fraction)7.5%.ratio of total monomer to CS of 4.monomer mass ratio of 25%with illumination time of 120min.Analysis of infrared spectroscopy(FTIR).nuclear magnetic resonance hydrogen spectroscopy(1H NMR)and X-ray diffraction(XRD)have proved the successful synthesis of the graft copolymer CS-g-P(AM-MAPTAC).The results of scanning electron microscope(SEM)and BET specific surface area show that the surface of CS-g-P(AM-MAPTAC)is uneven with folds,exhibiting a large specific surface area.The solubility test results demonstrate that the solubility of the copolymer after graft modification is significantly improved.From the flocculation results,it’s also found that the CS-g-P(AM-MAPTAC)4 flocculant with the grafting ratio of 338.03%making the best flocculation effect with a dosage of 2mg·L-1,and the oil removal ratio is 95.8%.In a wide range of pH of 6-10,initial oil concentration of 500～2100mg·L-1,CS-g-P(AM-MAPTAC)4 exhibits excellent flocculation performance,and the oil removal ratio is maintained at 93%～97%,showing the feature of wide flocculation window.Compared with CS and commercially available cationic polyacrylamide(CPAM),the dosage of CS-g-P(AM-MAPTAC)is lower and the flocculation performance is more prominent.Besides,it can be found that the good synergy between charge neutralization and adsorption bridging forming large floc and the net catching and sweeping effect further improved the flocculation effect in the process of emulsified oily wastewater treatment.In a word,the graft copolymer CS-g-P(AM-MAPTAC)is a new type of oil-containing wastewater flocculant with wide flocculation window,high efficiency and certain economic and environmental properties with good prospects for development.