In Situ-generated Yttrium-based Nanoparticle/Polyethersulfone Composite Adsorptive Membranes: Membrane Formation Mechanism And Removal Of Fluoride From Drink Water

In this study,the in situ-generated yttrium-based nanoparticle composite adsorptive membrane was prepared by generating nanoparticle in the membrane matrix,combining the nanoparticle with membrane matrix in a molecular level,which effectively solved the agglomeration and weak compatibility of traditional nanoparticles hybrid membrane,The membrane formation condition and membrane formation mechanism has been investigated.In view of the excessive fluoride in drink water,the fluoride adsorption performance also been studied.The following conclusions can be drawn:（1）The most content of nanoparticle M10-2 membrane is prepared under 0.5M NaOH coagulation bath,10%precursor content,30s air exposure duration,and 12h reaction time.The Y（CO₃）_0.5（OH）₂ nanoparticles in situ generated and distributes uniformly in the membrane matrix without agglomeration.The nanoparticles have good compatibility between membrane matrix.membrane hydrophilicity,thermal stability,porosity and water flux has been improved by the in situ-generated yttrium-based nanoparticle.（2）In the membrane formation process,with the increase of precursor content in the casting solution,the viscosity also increases,which reduces the thermal stability of the casting solution.The precursor content from 2%-8%takes 2–3.5 s to finish the phase inversion process,while 10%content finishes the phase inversion process about 6 s,the demixing process changes from instantaneous demixing to delayed demixing.The composition of coagulation bath（NaOH concentration）increases,which also slows down the phase inversion process,eventually leads to reduction of pore structure on surface of M10-2,inhibits the formation of finger-like macro-voids in the cross section,and produces more tear pores and irregular macro-voids,so the membrane structure can be controlled by adjusting the composition of casting solution and coagulation bath.（3）The adsorption of fluoride experiments carry on pH 7,the maximum adsorption capacity is 50.96mg/g,the adsorption reaction reaches equilibrium within 24 hours.In the filtration experiment,the adsorption capacity is up to 5.99mg/g,a total volume of 1770 bed volume of permeate was produced,the first 115bv permeate is below the maximum contaminant level（MCL,1.5mg/L）,In the presence of coexisting substances,the membrane still shows good performance of fluoride adsorption.In the long-term operation process,there is no leakage of yttrium,and the membrane structure after filtration is not damaged,which indicates that the membrane prepared by this method has good performance of fluoride adsorption and stable application property.