Preparation And Application Of Adsorption Membrane Based On The Assembly Of Tannic Acid And Polymer

The soluble pollutant including dye and heavy metals brought about threats to the environment and living bodies.Meantime,the separation of the pollutants from water was a difficult job.Membrane technology and adsorption are among the effective physical separation technologies.However,the industrial membrane met with a problem of low flux,while the ultrathin membrane,which had high flux was limited by its low mechanical strength.The adsorption required a long resident time.As a result,new materials are still hungered.Based on the problem of membrane and adsorption materials,a new routine was developed by combining the membrane and adsorbent,which was to enable the microfiltration membrane to be able to remove the dye and heavy metal via surface modification.In this paper,the membrane-like materials were prepared by mixing and deposition of tannic acid/polyethylene glycol and tannic acid/chitosan/MOF on polyether sulfone microfiltration membrane.Their effect on removal performance and mechanism for dye and heavy metal.In the first part,the tannic acid(TA),a natural polyphenol and polyethelene glycol(PEG)was assembled via hydrogen bond.The mixture was deposited on PES membrane to obtain a TA/PEG/PES material.SEM revealed that the mixture didn't form a dense membrane on the surface.Instead,it dispersed in the outer and inner surface of the membrane.It allowed dynamic water treatment by filtration under vacuum.The impact of molecular weight of PEG,TA/PEG ratio and the volume of mixture on the performance of material was studied with the removal of Rhodamine B as the standard.The result showed that the total filtrate volume got up to 1300 mL and the optimum flux got up to 4777 L·m-2·h-1·bar-1 with removal above 98.9%when the PEG10000 was employed at the PEG:TA=1:1 and at 20 mL of mixture.The flux was about 100 times of conventional membrane.In the second part,UiO-66 is synthesized with hydrothermal method,and then added to a solution of TA and CS to synthesize TA/CS/MOF composite colloidal particles under pH induction.Experiments are also conducted to study the effects of two factors,the proportion of MOF to CS and the pH of synthetic colloidal particles,on membrane separation performance.When the pH value of synthetic composite colloidal particles is 3.5 and the mass ratio of MOF and CS is 30%,highest retention rate of the adsorption membrane is achieved for methylene blue(cationic dye),acid red(anionic dye)and hexavalent chromium solutions,all above 99%,and the flux is 14.1?32.5 L m-2·h-1·bar-1.Finally,experiments are conducted to compare dynamic adsorption and static adsorption,and it is found that dynamic adsorption is more conducive to membrane separation performance as it takes less time and has higher separation efficiency.