چكيده به لاتين
In this study, a novel ultrafiltration polyacrylonitrile (PAN) mixed
matrix membranes (MMMs), containing goethite nanoparticles (GNP) were fabricated for Cu(II) ion adsorptive removal from aqueous solutions. First, nanospherical goethite nanoparticles, with a diameter up to 60 nm, were synthesized and analyzed. The next step was the fabrication and evaluation of a matrix membrane. The optimum conditions for the fabrication and evaluation of membranes were determined using response surface methodology (RSM) based on Box-Behnken design (BBD). This was including two independent set of design of experiments; in which the first one was the fabrication variables and their effect on the metal ion removal and pure water permeability under constant operating conditions (feed concentration of 20 ppm, pH equal to 4.5 to 5, and pressure of 1 bar), and the second one was study of the effect of operational conditions on the membrane separation property.
The variables evaluated in the first design of experiment included polyacrylonitrile concentration (15-18%), polyvinylpyrrolidone additive amount (1.3-1.5%), and the loading percent of nanoparticles (0.1-0.5 wt%). The variables evaluated in the second design of experiment were feed ion concentrations (20-200 ppm) and pH (range of 2-5) as well as the operating pressure (1-3 bar). The optimum conditions for the first experiment at which the maximum ion removal and the maximum water permeability were achieved was 15%, 1.3% and 1.0% for polyacrylonitrile, poly (vinylpyrrolidone) and GNP loading, respectively, at which, the highest Cu(II) removal was 49.1% and the maximum pure water flux was 285 L/m2 h bar. These values confirmed the accordance of the experiments and the predicted values by the model which were 47.6% and 268 L/m2 h bar, respectively.
For the second experiment, the optimum conditions, at which the maximum ion removal was achieved, were the feed concentration of 20 ppm, the feed pH of 4.5, and the operating pressure of 1 bar. These conditions were objective to the initial feed conditions in the first design of experiment. The predicted value for the optimal membrane removal in the second design of the experiment was 45.022% which was fairly close to 49.1%, i.e., the value obtained from the experiments. The results of absorption studies by polyacrylonitrile/ goethite nanocomposite demonstrate that the absorption of Cu(II) ions by the membrane increases with the goethite nanoparticles loading percent. In addition, the removal of Pb(II) metal ions was evaluated by the optimal membrane with the initial feed conditions of 20 ppm, and pH of 6 at operating pressure 1 bar. For Pb(II) the obtained ion removal was 43%. In this study, the membrane with GNP = 0.5%, PAN = 16.5% and PVP = 1.1% was fabricated and it was estimated that the metal ion removal and flux of the membrane were about 90% and 150 L/m2 h bar respectively.
