Optimization of Effective Parameters in Fabrication of PVC Flat Sheet Membranes by Response Surface Method for Application in Humic Acid Separation

Hypothesis: 

Considering water quality problems and strict rules established for drinking water treatment, there is an urgent need to use more effective and economical methods to remove natural organic matter from water. Meanwhile, membrane processes are one of the effective methods to remove these pollutants. In this way, in order to prepare a membrane with a high ability to remove pollutants, in the present study, the production and optimization of poly(vinyl chloride) (PVC) membranes with poly(ethylene glycol) (PEG) additives have been carried out.

PVC microporous membranes were prepared by nonsolvent-induced phase separation method. Influential parameters in the membrane fabrication, including the concentration of PVC and PEG and the composition of the coagulation bath were optimized using the response surface methodology (RSM). Meanwhile, tensile strength and porosity were considered as responses.

The obtained results showed that all the membranes had an asymmetric structure with finger like pores. It was also found that the tensile strength of the membranes increased with the increase in PVC concentration. The lowest tensile strength was related to the membrane made of 10.30% (by wt) of PVC, while the membrane made of 18.7 % (by wt) of PVC had the highest tensile strength. In addition, for the optimum membrane in which the concentration of PVC was 17.52% (by wt), the concentration of PEG was 5.87% (by wt) and the volume fraction of ethanol in the coagulation bath was 0.27, the tensile strength and porosity of the membranes were obtained as 5 MPa and 80.57, respectively. Furthermore, in the following, titanium dioxide nanoparticles (TiO2) were used to prepare the composite membrane under the aforementioned optimum conditions. The obtained results showed that the optimum membrane containing 2% (by wt) of nanoparticles had the highest humic acid separation efficiency with a value of 80%.