Preparation And Performance Assessment Of PVDF-DCOIT Composite Hollow Fiber Membrane

Membrane separation technology has been developed rapidly in the field of wastewater treatment in recent years.However,biological macromolecules,inorganic salts and activated sludges could cause serious membrane fouling,which is the largest bottleneck for large-scale industrialization of membrane technology in wastewater treatment.In this paper,PVDF-DCOIT composite hollow fiber membrane was prepared by regarding PVDF material as the research object and utilizing organic bactericide DCOIT as the additive,which was simpler in process and lower in cost so as to improve its antifouling property and commercial application.Firstly,the traditional NIPS was to fabricate the modified membrane without affecting bactericidal activity of DCOIT by blended PVDF with DCOIT and supplemented hydrophilic modifiers such as PVP and propanetriol.Compared with PVDF membrane,the modified membrane had better permeability reflected by the contact angle?63.35°?,the pure water flux(393.86 L·m^-2·h^-1·bar^-1),porosity?84.68%?and average pore size?0.54?m?.Besides,SEM and AFM were measured to verify that DCOIT was homogenously blended in the matrix and the modified film had smoother film surface and full finger-like pore structure,which indicated the improved morphology,structure and permeability of the modified membrane.Secondly,antifouling properties of the modified membrane in natural organic matters and activated sludges were studied by dead-end filtration tests.In the solution of bovine serum protein,sodium alginate and humic acid,compared with the unmodified membrane,membrane fouling of the modified membrane was reduced by 26%,19%and 74%.In the experiment for anaerobic sludges,flux recovery of the modified membrane could reach 81.4%,69.9%and 63.6%after three hydraulic cleaning.While flux recovery of the unmodified membrane were only 73.7%,50.5%and 45.7%.The total flux recovery the modified one was improved by 39%,which showed that it has excellent fouling-resistance of organic pollution and microbial pollution.Finally,after 44 days of long-term operation in MBRs,transmembrane pressure of the modified membrane was about 44.1%slower than that of the unmodified membrane,and the contents of EPS and SMP was also lower in the modified membrane reactor which was conducive to effectively alleviate adhesion of the microbial fouling on membrane surface.Meanwhile,the COD removal of both reactors was over 91%,but the modified membrane was slightly lower than the non-modified one in terms of methane generation activity and MLVSS,indicating that the release of DCOIT inhibited microbial activity in MBRs,but the effect was subtle.In conclusion,PVDF-DCOIT composite hollow fiber membrane has certain application prospect in wastewater treatment considering its excellent antifouling and permeability.