Recent Advance on Draw Solutes Development in Forward Osmosis

Abstract

In recent years, membrane technologies have been developed to address water shortage and energy crisis. Forward osmosis (FO), as an emerging membrane-based water treatment technology, employs an extremely concentrated draw solution (DS) to draw water pass through the semi-permeable membrane from a feed solution. DS as a critical material in FO process plays a key role in determining separation performance and energy cost. Most of existing DSs after FO still require a regeneration step making its return to initial state. Therefore, selecting suitable DS with low reverse solute, high flux, and easy regeneration is critical for improving FO energy efficiency. Numerous novel DSs with improved performance and lower regeneration cost have been developed. However, none reviews reported the categories of DS based on the energy used for recovery up to now, leading to the lack of enough awareness of energy consumption in DS regeneration. This review will give a comprehensive overview on the existing DSs based on the types of energy utilized for DS regeneration. DS categories based on different types of energy used for DS recovery, mainly including direct use based, chemical energy based, waste heat based, electric energy based, magnetic field energy based, and solar energy based are proposed. The respective benefits and detriments of the majority of DS are addressed respectively according to the current reported literatures. Finally, future directions of energy applied to DS recovery are also discussed.

Controlled synthesis and osmotic properties of ionosilica nanoparticles

“…We were particularly inspired by the successful use of ionic liquids as DS [40][41][42]. Hydrophilic nanoparticles were intensively studied as draw solutes in FO in the recent past due to advantages such as easy separation and regeneration via ultrafiltration (UF), and low generated back-flux during the FO process [43][44][45][46]. The ease of separation opens the route towards the regeneration of the nanoparticles and therefore towards the design of closed osmosis-regeneration processes.…”

Forward Osmosis as Concentration Process: Review of Opportunities and Challenges

“…An ideal draw solution must have the following characteristics: allowing for high water flux, minimal reverse draw solute flux, no toxicity, reasonably low cost, easy and low-cost recovery and compatible with feed purpose (facing the draw salt diffusion risk). Numerous studies reported various draw solutions and draw recovery processes ( Table 6 ; [ 26 , 256 , 257 ]). Draw selection in the context of concentration will involve the specific consideration of the following elements: Osmotic pressure should be in line with the required concentration level and the initial osmotic pressure of the feed solution to be treated.…”

Special Issue on “Novel Membrane Technologies for Traditional Industrial Processes”

“…DS regeneration step will consume energy, which renders the necessity to find methods that could reduce energy consumption. Long et al conducted a review analyzing the types of energy applied in DS regeneration [15]. Some DS (e.g., natural sugar, fertilizer) can be directly used without recovery, constituting the most effective way of saving energy.…”