Research On Efficiency Of The Forward Osmosis With Anionic Polyacrylamide As The Draw Solution In Polymer Flooding Oil Produced Water Treatment And Membrane Fouling

In response to the high cost of the membrane treatment with polymer flooding oil produced water（PW）such as ultrafiltration,nanofiltration,and reverse osmosis,which is due to the high energy consumption,serious membrane pollution,and associated membrane material loss and frequent replacement,a forward osmosis（FO）process with untraditional draw solutes is exployed to treat PW,which can effectively remove pollutants and minerals in PW.The FO method has received widespread attention due to the unique driving force of the substance passing through the membrane,which differs from the membrane processes driven by external pressure.However,the high energy consumption of Na Cl and other inorganic salt draw solution regeneration and membrane fouling problems have become the limiting bottlenecks which restrict the application of this technology.The paper is based on the issues,and gives the full role play of the drawing solution convenience and re-application without regeneration factors,it adopts anionic polyacrylamide（APAM）as the draw solutes to treat PW,studies the influnence of the pollutant factors on membrane permeability and rejection efficiency,indirectly reflects the dynamic change process of the membrane fouling layers by water flux,analyzes the differences of morphology,composition and structure in the membrane fouling layers in different membrane materials,points out the limiting factor for the formation of the membrane complex layer,proposes the method of membrane cleaning and the formulation of medicament.It Provides theoretical guidance and potential research directions for the further advancement of the pilot-scale application of the FO treatment of PW technology,and the preparation of anti-PW-fouling FO membranes.Firstly,it analyses the feasibility of APAM as the draw solutes to treat PW with the FO,then studies the single effect of the component of the pollutants in PW,synergistic effects of two components and the combined effects of the pollutants in PW on the permeability and rejection efficiency of HTI-CTA membranes,evaluates the treatment efficiency of the FO in the treatment of PW.The results show that APAM can be used as the draw solutes in the FO for the treatment of PW;the increase of the concentration of a single component of crude oil and Sodium dodecyl benzene sulfonate（SDBS）aggravate the degradation of membrane permeability,the synergistic effect of SDBS and crude oil on the membrane permeability attenuation is not only lower than the effect superposition of the two alone but also less than the crude oil alone.The synergistic effect of Ca²⁺and APAM on the permeability attenuation is stronger than that of Na⁺and APAM.The process can effectively remove pollutants and minerals in PW.The HTI-CTA membrane has excellent and stable retention performance for APAM and crude oil,with rejection rates of 99.95%and 99.85%,respectively,and the increase in crude oil concentration increases the rejection rate of metal cations,with more significant increases in K⁺and Ca²⁺scenarios.Secondly,with HTI-CTA and AQP-TFC membranes as the research objects,the water flux attenuation changes of the two membranes as the indicators indirectly reflect the dynamic change process of the membrane fouling layer.The results show that in the scenarios of crude oil components,the water flux attenuation of AQP-TFC membrane is similar to that of HTI-CTA membrane.Compared with the APAM-solute scenarios,the sharp attenuation period in the Na Cl-solute scenario is delayed and longer.In the APAM component scenarios,the attenuation variation of HTI-CTA water flux in the first section is like a straight line and the attenuation rate is relatively large,the second section is like a convex arc and the attenuation rate gradually increases;the attenuation variation of AQP-TFC membrane water flux is approximate to a straight line,too.The attenuation rate grows larger,it is like the second section of HTI-CTA water flux curve.In the multi-component interaction scenarios,AQP-TFC membrane performs more stable,but the average flux is lower,about half of the HTI-CTA,the average flux of AQP-TFC membrane is higher,but decays faster.It compares the morphology,roughness,element difference,functional group difference,etc.of the membrane fouling layer formed in the six scenarios by using SEM,AFM,XPS,FTIR,and analyzes the differences in the fouling layers.It is shown that APAM,Ca²⁺,Na⁺addition have the effect on hindering the combination of C element and the membranes,and promoting the combination of N element and the membranes.The effect is more obvious in the HTI-CTA than in the AQP-TFC.The binding capacity of the membranes to Ca²⁺is higher than to Na⁺,and the binding capacity of the HTI-CTA with Ca²⁺is stronger than the one of AQP-TFC with Ca²⁺.Through the comparative analysis of XPS and FTIR results,it is found that the carboxyl groups on APAM are connected to the carboxyl groups on the surface of the FO membrane through complexing and bridging with Ca²⁺,which increases the strength of the connection between APAM and the membrane surface,and gradually forms an APAM-Ca²⁺bonding layer,which hinders the crude oil from being further adsorbed on the membrane surface.The number of crude oil molecules hindered by APAM bonding layer in HTI-CTA is much greater than that in AQP-TFC.The hindering effect of the membrane carboxyl-Ca²⁺-APAM carboxyl complex layer on the surface of HTI-CTA membrane is greater than that of AQP-TFC.It is proved by hypothesis that the number of carboxyl groups per unit area is the limiting factor for the formation of APAM-Ca²⁺complex layer.Finally,it proposes the HTI-CTA and AQP-TFC membrane cleaning agent formulations and cleaning methods for the PW treatment based on the formation mechanism of membrane fouling and the component structure of the fouling layer by the orthogonal experimental method.And the combination of cleaning formulas for HTI-CTA and AQP-TFC membrane are:Na Cl O 0.2%,SDBS 0.2%,EDTA-2Na0.08%,membrane surface flow rate 8 cm/s;Na OH 0.2%,SDBS 0.2%,EDTA-2Na0.08%,membrane surface flow rate 12 cm/s.And they can restore more than 96%and95%of the membrane water flux respectively.