Study On The Preparation Of Fe₃O₄-Chitosan@Biochar And The Treatment Of Oilfield Production Water

In recent years,due to the low production of crude oil,most of China’s oil extraction uses water injection.With the increase in the number of years of oil production,the water content of oilfield produced water has increased year by year.As a result,oilfield produced water has not only increased production but also increased it.Handling difficulty.For a long time,the treatment of oilfield produced water has been the focus of much attention of scientific researchers.Its high COD content and oil are difficult to degrade in organic wastewater.There are many methods for processing oilfield produced water.Among them,the adsorption method is widely used as a simple and efficient method.Nowadays,most of the researches on adsorbents focus on the research of modification and compounding.However,there are still many problems in the use of adsorbents to treat wastewater,such as high cost,large amount,unrecoverable,and easy to produce secondary pollution.It severely restricted the pace of its scientific research.How to make the sorbent retain its high efficiency and achieve recycling?This makes the research and development of magnetic adsorbents very important.Biochar has a wide range of raw materials and has a rich pore structure.Chitosan has a variety of functional groups and is viscous.The preparation method of magnetic nano Fe₃O₄is simple and convenient.It has good magnetic properties.Fe₃O₄compound into an effective compound of organic,inorganic and magnetic materials can not only increase the specific surface area of particles,increase active sites,but also enable rapid magnetic separation and regeneration.In this study,different biochars were prepared from rice stalks at different cracking temperatures,and the optimal cracking temperature of the water produced in the biochar-treated oil field was studied.Magnetic Fe₃O₄magnetic particles were prepared by chemical co-precipitation method,and biochar was loaded with chitosan as the binding agent to synthesize Fe₃O₄-chitosan@biochar composite material.Scanning electron microscope（SEM）was used to observe the ultrafine morphology and structure of the surface,which has a large specific surface area and surface active molecular energy;its specific surface area,pore size,and pore capacity were measured by specific surface and porosimeter（BET）Analyzed and determined with large specific surface area and pore diameter;X-ray diffractometer（XRD）samples were used to analyze the crop phase.It has a multi-faceted crystal structure and good crystallinity.Analysis of its chemical structure and existing functional groups revealed that new functional groups were generated,and the types and number of functional groups increased.The feasibility of Fe₃O₄-chitosan@biochar adsorption on oilfield produced water was studied.The adsorption effect was studied under different p H,dosage,reaction adsorption time,initial concentration,temperature and other conditions.Under the best experimental conditions,the highest removal rate of turbidity of oilfield produced water is98.51%,the highest removal rate of COD is 83.36%,the highest removal rate is 90.67%,the turbidity after adsorption treatment is 0.92NTU,and the COD is 75.5mg/L,the oil content is4.48mg/L,which meets the comprehensive sewage discharge standard.Through the fitting of kinetic and thermodynamic models,it was found that the adsorption process of Fe₃O₄-chitosan@biochar on COD and oil in oilfield produced water is more in line with the quasi-second-order kinetic adsorption model.The process is mainly based on chemical adsorption and physical adsorption.As a supplement,the Langmuir equation and the Freundlich equation can be used to perform a good fit.The process is a combination of single-layer adsorption and multi-layer adsorption.The results show that Fe₃O₄-chitosan@biochar has good adsorption performance for pollutants in oilfield produced water.The Fe₃O₄-chitosan@biochar in the saturated state in the test was desorbed to the regenerated Fe₃O₄-chitosan@biochar,which was used to re-adsorb the produced water from the oil field,and subjected to 6 regeneration degradation tests in the desorption-adsorption-desorption cycle.The research results show that the regenerated Fe₃O₄-chitosan@biochar has stable adsorptivity,and still has a high adsorption effect on COD and oil in the produced water in the oil field,has a high repetition rate,and can be recycled.