| Poor permeability and membrane fouling caused by the strong affinity between the membrane and foulants, such as organic pollutants and microbial products in the water, has limited the large-scale engineering applications of polymeric ultrafiltration membranes in water treatment. In this study, inorganic materials with hollow structure were incorporated into polymeric membranes to prepare novel inorganic-organic composite ultrafiltration membranes. The structure and performance of the membranes were investigated systematically. In detail, hollow mesoporous silica spheres (HMSS) and hollow porous zirconia spheres (HZO) were added to polyethersulfone (PES) respectively. Then, non-solvent induced phase separation process was used to prepare uniform HMSS/PES and HZO/PES membranes.Surface properties of the as-prepared membranes were measured by the X-ray photoelectron spectrometer and drop shape analysis system. The cross-sections were observed by a scanning electron microscope. The filtration and anti-fouling properties were evaluated by a home-made cross-flow filtration apparatus. The main contents were shown as follows:1) HMSS were successfully prepared with uniform size and good dispersion in a Stober solution. The mean diameter and shell thickness of them were 650 nm and 80 nun respectively. Different concentrations of HMSS were incorporated into PES to prepare HMSS/PES composite membranes, and the effects of HMSS addition on membrane structure and properties were investigated systematically. It can be found that HMSS addition affected the exchanging rate, leading to the macrovoids’ formation and then suppression. The contact angle of composite membrane with 1.5% HMSS was 68.3°, a 13° decline as compared to the pure PES membrane, indicating a significant improvement of the surface hydrophilicity. The pure water flux of the composite membrane increased 4 times and the rejection decreased only a little. The introduction of hydrophilic HMSS can also improve the anti-fouling performance of membrane. Flux recovery ratio after two cycles filtration of bovine serum albumin (BSA) increased, from 54.6% for the pure PES membrane to 76.7% for composite membrane with 1.5% HMSS. In addition, the effect of hollow structure on membrane performances was also investigated, and it was found that HMSS had an advantage over mesoporous silica spheres (MSS) in improving the ultrafiltration properties of PES membrane.2) HZO were successfully prepared via hard-template method. The mean diameter and shell thickness of them were 430 nm and 50 nm respectively. A series of HZO/PES composite UF membranes were prepared with different contents of HZO. Through measurements like contact angle, pure water flux, rejection and so on, it can be found that the advancing contact angle of the HZO/PES composite membrane decreased 20° as compared to the pure PES membrane and the surface hydrophilicity was improved dramatically. The pure water flux of the composite membrane was almost 3.7 times that of the pure PES membrane. After two cycles BSA solution fouling process, flux recovery ratio of the composite membrane increased 20.7%, indicating that incorporating HZO was an effective way to improve the anti-fouling property of PES membrane. Furthermore, the optimized HZO/PES composite membrane was used to treat lead in water with low concentration. The static adsorption experiment showed that pH and co-existent cations were of great significance on adsorption property. Adsorption kinetics and the adsorption isotherm suggested that the adsorption process of lead on composite membrane might be chemisorptions and monolayer adsorption respectively. Furthermore, the dynamic adsorption experiment indicated that when the composite membrane was used to treat water containing 0.1 mg/L lead, it can yield a total volume of treated water of 224 L/m2 with lead concentration below the threshold limited by sanitary standard for drinking water. |
PDF Full Text Request