Experimental investigation and comparison of PBI/MWCNT and PSF/MWCNT membranes for recovering water from RO reject of brackish water by FO

Sharan Srinivas Venkatesh; Pandiyarajan Vellaichamy; Sundararajan Thirumalachari; Velraj Ramalingam; Mohan Doraiswamy Raju

doi:10.1016/j.heliyon.2024.e28455

Experimental investigation and comparison of PBI/MWCNT and PSF/MWCNT membranes for recovering water from RO reject of brackish water by FO

Heliyon. 2024 Mar 27;10(7):e28455. doi: 10.1016/j.heliyon.2024.e28455. eCollection 2024 Apr 15.

Authors

Sharan Srinivas Venkatesh¹, Pandiyarajan Vellaichamy¹, Sundararajan Thirumalachari², Velraj Ramalingam³, Mohan Doraiswamy Raju¹

Affiliations

¹ Department of Chemical Engineering, AC Tech, Anna University, Chennai, 600 025, Tamil Nadu, India.
² Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600 036, Tamil Nadu, India.
³ Institute for Energy Studies, Anna University, Chennai, 600 025, Tamil Nadu, India.

Abstract

The performances of polybenzimidazole (PBI) and polysulfone (PSF) membranes for recovering water from reverse osmosis (RO) reject of brackish water through forward osmosis (FO) were assessed and compared. Non-functionalised multi-walled carbon nanotubes (MWCNT) were added to the membrane casting solutions, with concentrations ranging from 0 to 3 wt%. The experiment was conducted for eight samples using RO reject of brackish water as the feed solution (FS) and 2 M analytical grade MgCl₂ as the draw solution (DS). The hydrophilicity, water permeability, salt rejection rate (R_s), water flux (WF) and porosity of the membranes improved with increasing MWCNT content up to 2 wt%. Also, the structural parameter, salt permeability and reverse solute flux decreased. PBI/MWCNT_{2 wt%} exhibited the best performance among the membranes tested compared with porosity of 70 ± 4 %, structural parameter of 0.36 ± 0.2 μm, and R_s of 93.5 %. In contrast with the pristine PBI membrane, an average water flux enhancement of 15 % and 49 % was observed for the FS and DS sides, respectively, for PBI/MWCNT_{2 wt%}. It is evident from the results that including MWCNT improves the performance of both membranes, with better relative performance for PBI membranes than PSF membranes.

Keywords: Forward osmosis; Membranes; Multi-walled carbon nanotubes; Polybenzimidazole; Polysulfone.