Application of response surface methodology in analysis and evaluation of ultrafiltration process

The ubiquitous natural organic matter humic acid and the PVC hollow-fiber ultrafiltration membrane were used in the ultrafiltration study. The evaluation parameters were humic acid removal rate and water transport coefficient, and solution pH, ion concentration and initial filtration flux were selected as the influencing factors. The response surface methodology with three factors five levels central composite design experiment was applied to investigate the relationships between evaluation parameters and influence factors, and the corresponding quadratic regression equations were established. Results indicated that the significant effects of the influencing factors on humic acid removal rate were: solution pH>ion concentration>initial filtration flux, the significant effects of the influencing factors on water transport coefficient were: solution pH =initial filtration flux>ion concentration; the Adj. R² level and P-level of quadratic regression equations for humic acid removal rate and water transport coefficient were 77.10%, 88.12% and 0.001504, 0.0001, respectively, which were good analysis and evaluation of the process of ultrafiltration.