Preparation And Application Of Magnetic Cationic Polyaluminum Silicate Composite Coagulant

With the rapid development of China's industrial level,the amount of industrial wastewater is gradually increasing,the composition of wastewater is becoming more and more complex,and the difficulty of treatment continues to increase.Facing the serious shortage of fresh water available per capita in China,it is urgent to further improve the efficiency of harmless treatment of industrial wastewater.Coagulation has always been one of the most efficient methods of treating produced water,but the existing coagulant has problems such as large addition amount,low treatment efficiency,and difficulty in adapting to the increasingly complicated wastewater environment etc.Therefore,it is of great significance to develop a multi-functional and high-efficiency composite coagulant for the efficient treatment of industrial wastewater and the protection of freshwater resources.Based on the traditional polysilicate,this paper designed and developed a high-efficiency composite magnetic coagulant(GSPSA-MNPs)with adsorption efficiency by introduced magnetic particles to increase the magnetic properties,cationic quaternary ammonium salt to increase charge,cyclodextrinto increase adsorbability of the product.In the first part of the thesis,the magnetic cationic polyaluminum silicate composite coagulant——GSPSA-MNPs,was prepared by using self-made polyaluminum silicate(PSA),cyclodextrin polymer(GEPCD)and purchased nanometer ferroferric oxide(MNPs)as raw materials,and made the magnetic polyaluminum silicate(PMNPs)and cationic polyaluminum silicate(GSPSA)by the way.Optimized the preparation material ratio and parameters by bentonite simulated wastewater:activation pH isl.5 and time is 5h,mass fraction of SiO2 is 1.8%,Si/Al=1:1.8,aging time is 10h;?-CD/SA/GTA=1:3:3,reaction temperature is 70?,GEPCD/PSA/MNPs=4:3:l,modified temperature is 20? and time is 30min.And characterized and analyzed GSPSA-MNPs by FT-IR,XRD,SEM and Zeta potential detection.The results showed that GSPSA-MNPs were(Si-O-Fe)chemically bonded nanoscale magnetic polymers with a certain positive charge,the main shape is spherical structure with a diameter of about 60nm,and the surface contains a large number of-OH reactive groups and cavity structures.In the second part of the thesis,bentonite and p-Nph simulated wastewater were treated by PSA,PMNPs,GSPSA and GSPSA-MNPs.The results showed that MNPs increased the settling speed of flocs and cyclodextrin enhanced the adsorption performance of samples,which made GSPSA-MNPs have better turbidity and phenol removal ability than PSA,and the treatment efficiency was improved.In order to compare the difference between synthetic composite coagulants and composite coagulants,PSA-CPAM60 and PMNPs-CPAM40 were synthesized by the combination of PSA,PMNPs and CPAM,and treated the same bentonite and p-Nph simulated wastewater.It was found that the highest turbidity and p-Nph removal rate reached 96.02%and 12.36%.However,the turbidity removal effect is still not as good as GSPSA-MNPs;the remove rate of p-Nph is far less than GSPSA-MNPs,which reflected the better adsorption function of GSPSA-MNPs again.In the third part of the thesis,the pH value,dosage and settling time of the three composite coagulants in the treatment of actual oilfield wastewater were optimized by RSM.Under the optimal conditions,the turbidity removal rates of the three composite coagulants were 96.22%,94.25%and 94.31%,respectively;the removal rates of TOC were 96.54%,85.32%and 92.14%,respectively;the removal rates of Ca2+ were 86.95%,89.32%,and 82.24%,respectively.Meanwhile,the average moisture content of the flocs produced by the three were 71.1%,80.2%,and 87.26%,respectively,and the water content of flocs obtained by GSPSA-MNPs is much lower than that of conventional flocs.After treatment,the pollution indexes of produced water are greatly reduced,and the water quality is much better thant before,which showed that it is feasible to treat oilfield produced water with GSPSA-MNPs.