Ultrafiltration behavior of CuO particles synthesized without and with different surfactants using PAN and PES membranes†

Four different CuO particles were synthesized, with no surfactant (CuO/NS) and with three surfactants: Triton X-100 (CuO/TX100), cetyltrimethylammonium bromide (CuO/CTAB) and sodium dodecyl sulfate (CuO/SDS). The filtration behavior of these particles at different concentrations with two UF membranes (PAN and PES), was studied. More than 99% CuO removal was obtained in all experiments, while the membrane fluxes showed variations. At 50 and 100 mg L⁻¹ CuO concentrations, the normalized flux values were either 1.0, indicating no change, or were greater than 1.0, suggesting that the filtration of CuO particles improved the membrane flux. However, at 50 mg L⁻¹, CuO/TX100 showed a significant flux decline for PES by 10%, while at 100 mg L⁻¹ a 15% flux decline was observed for CuO/CTAB with PAN. At lower CuO/NS particle concentrations (<50 mg L⁻¹), PAN showed a much larger flux decline of up to 27%, whereas the PES performance was more stable with a maximum decline of 5%. When the Cu²⁺ mass distribution was studied in the membrane system, the copper mass within the membrane for all types of particles was considerably larger for the PAN membrane than for the PES membrane. FT-IR results confirmed the appearance of new functional groups on PAN after the filtration of CuO/NS, indicating a possible interaction between Cu²⁺ and the membrane.