Development of ion-selective nanofiltration (NF) membranes for resource recovery from seawater desalination brine

• Main Author: Toh, Xin Yi
• Other Authors: Wang Rong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Nanofiltration; Resource recovery; Ion-selective
• Online Access: https://hdl.handle.net/10356/177340
• Institution: Nanyang Technological University

Water is becoming increasingly scarce due to urbanisation. The amount of water consumed worldwide has increased six times in the last century [1]. An average person consumes fifteen litres of water daily [2]. The current state of increasing water scarcity is a serious threat to both global socioeconomic development and human existence. Over 96% of the water on the Earth's surface is found in the oceans and is saline [3]. Hence, desalination is needed before the water is suitable for consumption. Over the years, desalination processes have advanced immensely; Reverse osmosis (RO) and membrane distillation (MD) are efficient seawater desalination methods for reducing water constraints. The energy needed to desalinate saltwater has decreased by about 80% since the 1980s [4]. However, during the seawater desalination process, a significant amount of brine with high salinity and hardness is also produced. Desalinated brine has a salinity that is 1.6-2 times greater than seawater [5]. Because of its extreme salinity, the brine requires cautious handling, but its contents also offer an opportunity for recovering precious resources. This study underscores the importance of continued research and development in membrane technology to address the complex challenges of water scarcity and environmental sustainability. This research explores the efficacy of Layer-by-Layer (LBL) nanofiltration (NF) membranes in selectively separating monovalent and divalent ions from desalination brine. LBL membranes exhibit superior selectivity toward divalent and polyvalent ions while allowing permeation of monovalent ions, making them promising candidates for resource recovery applications. The investigation includes an analysis of various fabrication techniques for NF membranes and factors influencing membrane permeability and ion rejection.