Novel draw solutes of iron complexes easier recovery in forward osmosis process

Le Truong Giang,Le Van Nhan,Nguyen Quang Trung,Pham Thi Phuong Thao

doi:10.2166/wrd.2017.150

Le Truong Giang, Le Van Nhan + Show 2 more

Open Access

https://doi.org/10.2166/wrd.2017.150

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Abstract

Abstract Forward osmotic (FO) membrane is a new process for producing fresh water from salt water. The study of draw solute is essential in the development and application of FO technology; draw solution should be good at drawing water and easy at recovery. In this paper, three complex draw solutes such as ammonium iron (II) sulfate, ammonium iron (III) sulfate and ammonium iron (III) citrate with different concentrations were studied. The physical properties such as pH, conductivity and total dissolved solids (TDS) have simultaneously been investigated. The pH of most ammonium complexes was decreased whereas TDS increased with increasing of draw solution concentrations. We found that high water flux of these iron complexes was reported in the range of 8.88–11.24 LMH which was higher than the ammonium bicarbonate draw solution. In addition, more than 90% iron complexes draw solutions were recovered by NF-90 membrane, which plays an important role in the FO process to produce fresh water. This study provides direct evidence for the ability of permeate water from feed solution to draw solution, which shows the potential applications of iron complexes in FO process to produce fresh water from sea-, brackish or river water.

Highlights

Along with the rise in sea levels, the status of salinity is occurring in many countries in the world including Vietnam, which seriously impacts on agricultural production and life in these areas
The Forward osmotic (FO) membrane will not undergo hydrolysis and structure change when it is tested in the draw solutions of the iron complexes, which can ensure the consistent FO performance
These results demonstrated that a series of iron complex draw solutions can be recovered using NF-90 membrane, which plays an important role in the FO process to produce fresh water using iron complexes as draw solutes substitute Ammonium bicarbonate (AB)

Summary

INTRODUCTION

Along with the rise in sea levels, the status of salinity is occurring in many countries in the world including Vietnam, which seriously impacts on agricultural production and life in these areas. Two types of technologies that are widely used around the world for desalination can be broadly classified as either thermal technology or membrane technology These technologies need energy to operate and produce fresh water. Inorganic salts were investigated as draw solutions in the FO process in previous studies due to their low cost and high osmotic pressure potential which creates a high flux (Achilli et al ; Alnaizy et al ). According to Kiriukhin & Collins ( ), the low charge and small hydrated radius of monovalent and divalent ions in the draw solution can result in a high reverse flux of salts, such as 0.6 M NaCl (7.2 GMH), 0.6 M NH4HCO3 (18.2 GMH) when deionized (DI) water was used as the feed solution. Exploration of suitable draw solutes plays an important role in developing the further advancement of FO processing and even commercialization of an FO membrane (Ren & McCutcheon ; Shaffer et al )

METHODS

Experimental setup

RESULTS AND DISCUSSION

CONCLUSIONS