Simultaneous rejection of chromium(VI) and fluoride [Cr(VI) and F] by nanofiltration: Membranes characterizations and estimations of membrane transport parameters by CFSK model

- To study on the feasibility of NF300 and PN40 nanofiltration membranes for rejection of Cr(VI) and F from binary solution.
- Characterization of NF300 and PN40 membrane with FTIR, SEM, and AFM.
- Rejection of Cr(VI) and F was enhanced with increasing pressure and significant influence by pH of feed solution.
- Membrane transport parameter and mass transfer coefficient was estimated by using CFSK model.
- Experimental observed rejection and true rejection by Cr(VI) and F show good arrangement.

The current work examines the performance of NF300 and PN40 nanofiltration (NF) membranes for simultaneous rejection of Cr(VI) and F.Experimental: results indicate that, Cr(VI) and F percentage of removal was improved with increasing operating pressure and declined with increasing feed concentration. Highest percent rejection of Cr(VI) and F were found 97% and 92% with NF300 and 88% and 82% with PN40 membranes for 5 ppm feed respectively. Maximum removal was found at pH 8 and above with NF300 membrane compared to PN40 membrane. Mass transfer coefficient (MTC) was found 6.88 × 104 cm/s and 5.74 × 104 cm/s and membrane transport parameters (MTPs) such as solute permeability was 4.03 × 105 cm/s and 6.23 × 105 cm/s and reflection coefficient was 0.9688 and 0.9223 using CFSK model for 5 ppm feed of Cr(VI) and F respectively for NF300 membrane. A Good correlation was found in experimental results (observed rejection for Cr(VI) and F was 0.97 and 0.92) and the model predicts results (true rejection for Cr(VI) and F was 0.9731 and 0.9222) for 5 ppm feed of Cr(VI) and F respectively for NF300 membrane.