Application Of Graphene Oxide-TiO₂ Nanocomposite Modified Ultrafiltration Membrane In Water Treatment

The past decades has seen rapid growth in economy growth,however,the following environmental problems and resources overconsumption can't be ignored.As the government improved the drinking water quality standards,wastewater treatment has suffered great pressure to effectively produce clean water with less energy consumption.Traditional wastewater treatment processes can't effectively remove the micro-contaminants,which has been widely detected in many water bodies.Membrane technology,featuring simple process and high efficiency,is one of the most important methods in water treatment.However,its low removal rate of microcontaminants and membrane fouling issue has greatly restricted its application in water treatment.In this study,hydrophilic photocatalyst GOT nanocomposite was introduced into PVDF UF membranes through blending modification and surface coating respectively,and the physicochemical properties,antifouling ability and removal rate to HA and SDZ were evaluated detailed.Besides,xDLVO theory was used to analyze the cause of improved antifouling ability with addition of GOT from a mirco perspective.Results showed that with the addition of GOT,GOT/PVDF hybrid membranes become more hydrophilic and membrane pore structure was also improved towards better rejection rate and antifouling ability.When PVDF addition amount is 21%,membrane shows the least wrinkles morphology on surface and is still casting-able.When GOT's addition amount is 0.1%,membrane possesses a porosity of 84.6%,pore size of 32 nm,contact angle of 55.4°,zeta potential of-19.02 mV,and pure water flux of 80 LMH in dead-end filtration,as well as HA rejection of 82%.SEM mapping shows the membrane is asymmetric in pore structure,and EDS analysis confirms that GOT is uniformly dispersed in membrane bulk.In anti-fouling experiments,relative flux of GOT membrane only drops 25% after 180 min ultrafiltration experiment against 2ppm HA solution.And the fouled membrane shows a slight dark-yellow color,indicating only a small amount of HA molecules attached.In addition,the rejection rate of HA is 73-78%.Besides,xDLVO theory explains the improved antifouling ability from mirco perspective.Results showed that the interfacial free energy between GOT membrane and HA molecules is repulsive so HA is not apt to accumulate in membrane pores or on membrane surface.However,the photocatalytic experiments of GOT/PVDF hybrid membranes has shown little degradation of pollutants although the flux decline is slower.Immobilized GOT on membrane surface by dynamic filtration method and post heat treatment to fabricate GOT/PVDF surface modified membranes.When GOT addition amount is 0.01 g,the membrane possesses a contact angle of 44.3° and pure water flux of 87.5 LMH.The removal rate against HA and relative flux in dark condition is 99% and 0.906;and the values turn to 100% and 1.90 with UV irradiation.For SDZ experiments,the removal rate and relative flux is 98.3% and 1.96 respectively.