(41i) Iron Functionalized PVDF-PAA Membrane for Treatment of Processed Water from Oil Industries

Membranes are finding wide applications in water reuse applications to meeting effluent discharge limits. Additional advantages can be obtained if membrane pores (for ex., microfiltration membranes) can be functionalized to provide catalytic activities for organic pollutant degradation. Polyvinylidene difluoride (PVDF) functionalized membranes immobilized with metal oxide nanoparticles provide such a robust system to catalyze the oxidation of a wide variety of organic compounds by using appropriate oxidants. An example application is, degradation of long chain organic acids that are often present in processed water from oil industries accompanied by high TDS.

In this study, commercial microfiltration membranes were functionalized with polyacrylic acid by in situ polymerization. Carboxylic acid groups present in the functionalized membrane was first ion exchanged with sodium followed by ferrous ions. Ferrous ions were eventually oxidized to iron oxide. In-situ generation of iron oxide particle prevented aggregation of this nanoparticles. Functionalized membrane was characterized and evaluated for its catalytic properties.

Oxidants like hydrogen peroxide, persulfate salts can be employed for the oxidation of the contaminants. Hydrogen peroxide is known to generate hydroxyl radicals with have an oxidation potential of 2.6 V and persulfate is known to generate sulfate radicals having an oxidation potential of 2.3 V. However hydrogen peroxide is relatively less stable and is known to be corrosive. Onsite generation of hydrogen peroxide can avoid the issues associated with transportations. Persulfate is relatively more stable, less corrosive and less expensive. In this study, both, Persulfate salts and hydrogen peroxide, were investigated for their effectiveness in catalyzing oxidation reactions.

Solution phase experiments in the presence of ferrous ions (1000 mg/l) and persulfate salt (5000 mg/l) was found to be effective in oxidizing 95% of the organic acids. Iron oxide functionalized membrane with an iron loading of 1.2 mg/lit was observed to oxidize 54% of organic acids in presence of 5000 mg/l potassium persulfate for the residence time of 6 seconds in membrane pores. As processed water from oil industries also contains high TDS of around 150 to 200 thousand mg/l, impact of TDS was also investigated in the study. Functionalized membranes was observed to be an effective platform for immobilizing iron oxide nanoparticle and catalyzing oxidation of organic acids. This project was supported by Nanostone Water Co, NSF KY EPSCoR program, and by NIH-NIEHS-SRC.