Research On The Draw Solution And Membrane Property In Forward Osmosis

In forward osmosis (FO) process, the driving force is osmoticpressure difference among the FO membrane. Compared with thetraditional membrane separation process, there are some advantages inFO process, such as low operate pressure, low energy consumption, highrecovery, high rejection of contaminants, lower membrane foulingpropensity and environmental pollution. Thus, it possesses broodprospects. In FO, the key technologies are selectivity membrane and drawsolutions.In this research, the FO performance, draw solution selection, FO-NFhybrid process for brackish water desalination and nanofiltration fordivalent inorganic salt recovery were studied. The effects of operationconditions on the water flux and reverse salt flux in the FO process, the suitable draw solution, the performance of FO-NF hybrid process anddivalent inorganic salt recovery were known.The results shows that,1, When the draw solution (DS) is against the active layer, the waterfluxes with flow directions are related to the DS concentration. With theincreasing of the DS concentration, the increasing rate of reverse salt fluxof CTA-2membrane remains constant. While the feed water (FW) isagainst the active layer, the flow directions have no effect on the waterflux and reverse flux.2, Divalent inorganic salts are good draw solute for high osmoticpressure, stable and recovered by NF easily.3, a dual NF process can produce permeate water with TDS lowerthan500mg/L at a low operate pressure. At the same concentration, theNa2SO4draw solution has a better NF performance.4, the simulate results of ROSA design software shows that a dual NFprocess for divalent inorganic salt recovery is a low operate pressure andlow energy consumption process. And it is the basis for the FO-NF hybrid process.