A study of a ferric-lactate complex as draw solute in forward osmosis

In forward osmosis (FO), draw solution is a critical problem which restricts the progress and application of FO technology. The study of an optimal draw solution is essential in the application of the FO technology. In this paper, a mild one-pot method was used to synthesize a ferric-lactate (LAFe) complex, which had a good performance of high osmotic pressure, moderate viscosity and high solubility, as a potential draw solute. Then, the properties of the LAFe complex in FO were systematically studied. The water flux was improved to 18.78 ± 1.56 L m−2 h−1 (LMH) at 1 M LAFe, which was 1.8 times than that of 1 M NaCl. And, the reverse salt flux of the 1 M LAFe (1.00 ± 0.09 g m−2 h−1) obviously was diminishing, only 1/4 of the 1 M NaCl. Furthermore, in the application test, 1 M LAFe exhibited the water flux of 7.54 LMH (in the first hour) when the seawater of Huanghai coast was used as the feed solution. The recovery of the LAFe was employed successfully by a nanofiltration method, achieving a high efficiency of 96%.