The Fabrication Of GOT/PVDF Modified Membrane And Its Application In Water Treatment

With the development of living standards,quality requirements for drinking water are also higher.Ultrafiltration is considered as an effective and environmentally friendly water treatment technology,for its ability to reject suspended substances,colloid,microorganism,and organic matter,without removing minerals from water.However,membrane fouling restricts the further application of this technology.In this study,a layer of graphene oxide-TiO₂（GOT）nanoparticles（NPs）was immobilized on the surface of a commercial poly（vinylidene fluoride）（PVDF）membrane to fabricate a GOT/PVDF modified membrane.The acrylic acid（AA）concentration,GOT concentration,and the temperature of hot-press treatment were experimentally obtained as 20 wt.%,0.10 wt.%,and 70℃,respectively,to attain better performance of the modified membrane based on pure water flux（PWF）and contact angle（CA）.A commercial PVDF membrane was dipped in GOT coating solution of 20 wt.%AA and 0.10 wt.%GOT NPs,then treated at 70℃for 4 hours,and lastly irradiated under ultraviolet（UV）light for 20 min,to fabricate a GOT/PVDF modified membrane.The modified membrane was characterized by Scanning Electron Microscope（SEM）,Atomic Force Microscope（AFM）,and Liquid-Liquid Porometer（LLP）for its surficial microstructure,roughness and porosity.Also the removal performance of different pollutants by the modified membrane was studied.Results showed that the modified membrane,compared with the commercial one,attained increased surficial roughness（from 58.0 nm to 75.3 nm）,decreased pore size（from 115±5 nm to 50±2 nm）,decreased CA（from 64.7±2.3°to 35.5±1.7°）,and decreased PWF(from 688.8±13.4 L·（m²·h）^-1 to 336.3±18.7L·（m²·h）^-1).The modified membrane also showed 100%bacterial removal,and 70%HA removal,which increased to 90%in presence of bacteria.The GOT/PVDF modified membranes were checked on changes of membrane flux and HA removal during the“filtration-backwashing-filtration-backwashing-filtration”cycle,to study the influence of two times of cleaning and three times of 90 min ultrafiltration on their performance.The HA fouled membranes were washed by pure water,then irradiated by UV light,sunlight,and visible light,respectively,and lastly checked for flux recovery rate（FFR）.Contact angles were measured before and after the modified membranes were treated by acid solution,basic solution,and sonication,respectively,to evaluate their stability.Results showed that the modified membranes remained good PWF and HA removal,even after two times of cleaning and three times of 90 min ultrafiltration.Results also showed that the modified membranes attained 71.5%FFR after washed by pure water,indicating high ratio of reversible membrane fouling.The water washed membranes attained over 80%FRR after irradiated by UV light,sunlight,and visible light,respectively,indicating their good self-cleaning ability under all types of light irradiation.Also,the modified membranes showed great stability when treated with acid solution or sonication,while they behaved less stable when treated with base solution.Overall,a novel antifouling and visible light responding GOT/PVDF modified membrane was successfully fabricated and applied for removal of typical pollutants,which broadens the application of photo-catalytic ultrafiltration membranes.