Boron transport through polyamide-based thin film composite forward osmosis membranes Winny Fam a , Sherub Phuntsho a , Jong Hwa Lee b , Jaeweon Cho c , Ho Kyong Shon a, ⁎ a School of Civil and Environmental Engineering, University of Technology, Sydney (UTS), Post Box 129, Broadway, NSW 2007, Australia b R&D Institute/Filter R&D Team 2, WoongJin Chemical Co., Ltd., KANC 906-10, Iui-dong, Yeongtong-gu, Suwon-si, Republic of Korea c Department of Civil and Environmental Engineering, Yonsei University, Yonsei-ro 50, Seodaemun-gu, Seoul 120-749, Republic of Korea HIGHLIGHTS • Reverse solute flux (RSF) and CP phenomenon govern boron transports in FO process. • Monovalent draw solute with higher RSF has lower boron rejection. • Pressure retarded osmosis (PRO) mode of operation results in lower boron rejection. • Boron removal significantly improved at higher feed solution and pH. abstract article info Article history: Received 19 May 2013 Received in revised form 7 November 2013 Accepted 11 February 2014 Available online 5 March 2014 Keywords: Forward osmosis Boron transport Desalination Thin film composite membrane The boron transport in forward osmosis (FO) process using thin film composite (TFC) membranes has been investigated. Two common fertilizers were used as draw solutes and a model seawater as the feed. The in- fluence of several physical and chemical operating conditions on boron solute flux and boron rejection rates was investigated. The examined factors include draw solution types, membrane orientation, feed and draw solution concentrations, boron feed concentration, crossflow rate, and feed solution pH. The key mecha- nisms that govern boron transports are reverse draw solute flux and internal concentration polarization ex- perienced by the membrane during the FO process. Results show that the use of draw solute with small hydrated radius could improve boron rejection hindered by the higher reverse diffusion of draw solutes. The osmotic process operated in the pressure retarded osmosis (PRO) mode results in lower boron rejec- tion. However, the most effective boron removal was achieved by operating the feed solution at high pH (pH = 11) because boron in the solution contains larger-size borate species, and thus increases boron rejec- tion rate up to 94% by electrostatic repulsion. This study mainly focused on the performance of TFC mem- brane in boron removal. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The scarcity of fresh water for domestic, agricultural, and industrial uses has become a critical issue. Membrane technology such as reverse osmosis (RO) provides an immediate solution to meeting water shortages but such technologies come at the expense of high energy consumption, which limits its implementation in many parts of the world. Thus, other process technology is necessary to meet the water quality while utilizing a reasonable amount of energy. Forward osmosis (FO) process has recently obtained increasing attention because of its promising potential for various applications. It is a process driven by intrinsic osmotic pressure difference be- tween two solutions of two different concentrations; hence, the energy requirement is significantly lower compared to RO where a very high hydraulic energy is required. However, water permeating in the FO process only dilutes the draw solution to a certain degree as the final product. Therefore, additional separation and recovery process or a hybrid system that combines FO technology with another process such as membrane distillation [1], nanofiltration [2], or RO [3] is required to produce water with desired quality. When the resulting diluted draw solution can be used directly, such as in the case of water desalination for fertigation use [4–6], FO process offers a signifi- cant advantage over RO because additional separation process and draw solution recovery can be eliminated. Membrane-based desalination process efficiency is highly depen- dent on membrane performance, which is indicated using solute flux and rejection rate particularly for sodium chloride solute. Another solute commonly found in a natural water source that has drawn at- tention from some water research is boron [7,8]. Boron, usually Desalination 340 (2014) 11–17 ⁎ Corresponding author. E-mail address: Hokyong.Shon-1@uts.edu.au (H.K. Shon). http://dx.doi.org/10.1016/j.desal.2014.02.010 0011-9164/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal