Recent developments in forward osmosis: opportunities and challenges

Recently, forward osmosis (FO) has attracted growing attention in many potential applications such as power generation, desalination, wastewater treatment and food processing. However, there are still several critical challenges, including concentration polarization, membrane fouling, reverse solute diffusion and the need for new membrane development and draw solute design in FO. These challenges are also the current research focus on FO. This paper aims to review the recent developments in FO, focusing on the opportunities and challenges. It begins with discussing the advantages of the FO process over pressure-driven membrane processes. These potential advantages lie in FO's low energy consumption, low fouling propensity, reduced or easy cleaning, low costs, high salt rejection and high water flux. Next, the recent applications of FO, as the outcomes of the above advantages, are described. The key part of this review is a detailed discussion of five critical challenges faced by FO and their relationships. Finally, the future of FO is viewed. This review provides a clear outline for FO-concerned researchers on the recent developments in FO.