Ion Rejection Performance Of Ceramic Microfiltration Membrane Modified By Graphene Oxide

Due to the large pore size of ceramic microfiltration membrane,it can’t be used to separate and remove ions from the solution directly.Our previous studies have found that the conductive ceramic microfiltration membrane has the excellent ion rejection performance under the assisted action of external electric field.In this paper,we firstly prepare the membrane support by the slip-casting method used 5μm Al₂O₃ powder as the main raw materials,and then the support was coated with 1μm and 150 nm Al₂O₃ powder,respectively.Al₂O₃ composite membrane was obtained finally.Graphene oxide was prepared by the improved Hummers method,and the membrane was modified by graphene oxide with the transfer via vacuum method,Combined with the thermal reduction process,the conductivity of the modified membrane was controlled.at the same time,the ion rejection performance of the modified membrane with external electric field assisted was studied.In the paper,we mainly discussed the influence of ball milling time and dosage of dispersant on the dispersion of nano Al₂O₃ powder,the relationship between dosage of stabilizing agent and stability of nano Al₂O₃ slurry,the effect of thermal reduction temperature on conductive property of graphene oxide,the controlling effect of the modification times and the thermal reduction temperature on the conductivity of modified membrane and the influence of modification times,external electric field,thermal reduction temperature,membrane pore size,ion species and ion concentration on the ion rejection performance of the modified membrane,and using laser particle size analyzer,four point probe tester,Raman spectra,SEM,TEM to analyze and characterise the experimental samples.The results show that:When sintering at 1500℃,the rupture strength of the support is 42.35 MPa,its average pore size is about 410 nm,its porosity is about 42.26%,its pure water permeation flux is about 2002.43 l/（m²·h·bar）,Using 10 wt%nano Al₂O₃ powder,adding0.15 wt%Dolapix CE-64 and 3.0 wt%PVA-1799,we can obtain the stable suspension slurry of nano Al₂O₃ powder.When using 1μm and 150 nm Al₂O₃ powder as the main materials,the pore size of ceramic membrane is 120 nm and 80 nm,respectively.With the improved Hummers method,graphene oxide was prepared and its average particle size is about 15 nm.After thermal reduction at 160℃,200℃and 230℃,the conductivity of graphene oxide is 14.497 s/m,100.165 s/m and 124.521 s/m,respectively.Through regulating modification times and thermal reduction temperature,the conductivity of modified ceramic microfiltration membrane is 0.714×10^-83.383×10^-8s/m.Under the different external electric field,we measured the ion rejection performance of the modified membrane for different salt solution,and found that the modified membranes have the different rejection performance for different ions,for cationic rejection rate,Mg²⁺>Ca²⁺>Na⁺;For anionic rejection rate,SO₄^2->Cl^-.When modified three times,thermal reduction at 200℃and under the voltage of 9 V,the average ion rejection rate of modified membrane for 1×10^-3 mol/l MgCl₂ solution is87.44%,at this point,its permeation flux is 1871.57 l/（m²·h·bar）.