Graphene quantum dot-added thin-film composite membrane with advanced nanofibrous support for forward osmosis

Abstract

Highlights: What are the main findings? The current study establishes that banyan tree leaf-derived B-GQD-incorporated thin-film composite membranes with a SBS NFM substrate show an enhanced FO performance regarding water flux, salt rejection, and chlorine re-sistance ability. What is the implication of the main finding? The membranes developed in the current study have great prospective applications in wastewater treatment, water purification, and desalination. GQD synthesis from banyan tree leaves was conducted by employing a simple hydrothermal technique. No organic solvent or reducing agent was utilized in this GQD synthesis. The GQDs were incorporated in a TFC membrane for the FO process. The TFC membrane’s support was fabricated by the SBS process. The 0.050-B-GQD/PA TFNC membrane demonstrated excellent FO performance and chlorine resistance. Forward osmosis (FO) technology for desalination has been extensively studied due to its immense benefits over conventionally used reverse osmosis. However, there are some challenges in this process such as a high reverse solute flux (RSF), low water flux, and poor chlorine resistance that must be properly addressed. These challenges in the FO process can be resolved through proper membrane design. This study describes the fabrication of thin-film composite (TFC) membranes with polyethersulfone solution blown-spun (SBS) nanofiber support and an incorporated selective layer of graphene quantum dots (GQDs). This is the first study to sustainably develop GQDs from banyan tree leaves for water treatment and to examine the chlorine resistance of a TFC FO membrane with SBS nanofiber support. Successful GQD formation was confirmed with different characterizations. The performance of the GQD-TFC-FO membrane was studied in terms of flux, long-term stability, and chlorine resistance. It was observed that the membrane with 0.05 wt.% of B-GQDs exhibited increased surface smoothness, hydrophilicity, water flux, salt rejection, and chlorine resistance, along with a low RSF and reduced solute flux compared with that of neat TFC membranes. The improvement can be attributed to the presence of GQDs in the polyamide layer and the utilization of SBS nanofibrous support in the TFC membrane. A simulation study was also carried out to validate the experimental data. The developed membrane has great potential in desalination and water treatment applications.