Preparation Of Magnetic Polyaluminum Silicate Nanocomposite And Study On Its Coagulation Of Produced Water In Oilfields

At present,most of China's oil fields have entered the period of high-water-bearing,and much of oilfield waste water generated during the oil refining process is in urgent need of treatment.Magnetic coagulation is an emerging technology that combines traditional coagulation and magnetic separation technologies.It has become one of the research hotspots in the field of environmental engineering because of its high separation efficiency,high adsorption capacity,and renewable recyclability.In this work,a kind of magnetic nanocomposites,PFeNPs,with the coagulation properties were synthesized with aluminum sulfate,sodium silicate,and FeNPs.Through the coagulation experiment of the water produced in the oilfield,the optimal preparation conditions of PFeNPs were optimized:pH 1.5,(Al)/n(Fe)molar ratio 3.67:1,n(Al)/n(Si)molar ratio 1:2,activation the 5h,aging time 11h,ultrasound time 0.5h.The FT-IR,XRD,Zeta potential,Al-Ferron timed complex colorimetry,and VSM analysis were used to analyze PFeNPs,PSA,and FeNPs prepared under the optimal condition.The results show that the PFeNPs is a nano-sized magnetic polymer with a positive charge,and its surface contains a large number of-OH reactive groups.In addition,it was found that PFeNPs is three-dimensional 'silkworm cocoon'-like inorganic polymer material wrapped by filaments and net-like PSA.The water produced from the oilfield was used to evaluate the coagulation performance of PFeNPs.Four coagulants at the aging time of 4h,9h,11h and 22h were prepared respectively:PFeNPs4,PFeNPs9,PFeNPsll,PFeNPs22,and the coagulation experiment was carried under the conditions of addition of 0.6 g/L and pH of 8,The best removal capacities in terms of turbidity,total organic carbon(TOC)and calcium ions were 96.2%,99.87%,and 98.02%,respectively.Because of the magnetic extrusion and its own gravity,the coagulation of PFeNPs is only 67.23%,which is much lower than the moisture content of the polysilicate aluminum floc 98.29%,and it meets the regular pattrern between aging time and the fractal dimension.In addition,the flocculation mechanisms of the PFeNPs transformed from electrical neutralization to sweep flocculation with increasing aging time.The intensity factor and recovery factor of the flocs formed by electricity neutralization are higher than those formed by sweep flocculation.After large-scale crushing of the floes formed by sweep flocculation,the higher the zeta potential of the floes is,the lower the recovery factor is.The flocculation(PFloc)regenerative study showed that PFloc lost coagulation performance,and PSA can be used as a regenerating solution,can make it exibit active(MPFloc),repeated use 5 times,turbidity,TOC and the removal rate of calcium ions reached 96.8%,78.4%,and 46.5%.Compared PFloc with PFloc by FT-IR,XRD,thermogravimetry,SEM and contact angle analysis,it was found that the active site of PFloc was occupied by contaminants.The active hydroxyl content was only 1.46%far lower than that of MPFloc(6.67%),while MPFloc has a denser PSA envelope than PFloc,and MPFloc has superior dispersion performance in the production of water in the oil field.