| The ?-Al2O3/?-Al2O3 hollow fiber NF composite membrane was successfully prepared by coating ?-AlOOH sol on ?-Al2O3 support hollow fiber membrane with a mean pore size of 230 nm.The membrane was characterized by SEM,pore size distribution,dynamic contact angle,permeance and retention.Effects of soaking time and coating times on?-Al2O3/?-Al2O3 hollow fiber NF composite membrane were investigated in this study which led to optimal membrane preparation conditions.And effects of operation parameters including operating pressure,concentration and pH of feed solution on permeation flux and retention of membrane were studied.Meanwhile,solvents resistance,long time stability and retention of dyes were investigated.The results were as follows:Firstly,?-Al2O3 hollow fiber membranes as supports were prepared by phase inversion and sintering process.Boehmite sol with colloidals diameters ranging in 40?450 nm was prepared by hydrolyzed alumina isopropyl(Al(OC3H7)3)with excess H2O.Then?-Al2O3/?-Al2O3 hollow fiber NF composite membrane was successfully prepared by coating?-AlOOH sol on ?-Al2O3 support hollow fiber membrane,followed by a sintering process at 750? with a dwelling time of 2 h and a heating rate at 1?/min,respectively.After sintering process,aluminum was load on the substrate and separation layers were obtained with the nano-pores.The effects of soaking time and coating times on membrane structure and performance were examined,and the results indicated that with longer soaking time and more coating times,the thickness of separation layers increased,mean pore size and pure water flux decreased and retention increased gradually.The optimal membrane with separation layer of 2.6?m and mean pore size of 1.7 nm was prepared by soaking 30 s and coating 2 times,which demonstrated a pure water flux as high as 17.4 L·m-2·h-1·bar-1 with relative high retention rate of PEG 2000(85.5%),AlCl3(90.9%)and CaCl2(84.1%).Secondly,retention rates to different salts of ?-Al2O3/?-Al2O3 hollow fiber NF composite membrane were studied and the retention rates follow the order of FeCl3>AICl3>MgCl2>CaCl2>NaCl>NH4C1>MgSO4>Na2SO4,which is a typical sequence for the positive charged nanofiltration membranes.Meanwhile,the effects of operation parameters including operation pressure,concentration and pH of feed solution on membrane performance and retention rate were investigated.The results showed that the permeation flux and salts retention rate would increase with operation pressure increasing;on the contrary,the permeation flux and retention rate decreased with feed concentration increasing;the pH in feed solution had little influence on membrane permeation flux while retention rate of cations increased with pH decreasing.Finally,solvent resistance,long time stability and retention of various dyes of?-Al2O3/?-Al2O3 hollow fiber NF composite membrane were investigated.The results indicated that this ?-Al2O3/?-Al2O3 hollow fiber NF composite membrane possessed excellent solvent resistance and good stability in long time test.Meanwhile,the membrane was used to deal with Victoria blue B and crystal violet dye wastewater,which showed retention rate of 98.2%and 96.3%respectively. |
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