The textile industry produces large volumes of wastewater that requires appropriate treatment before being released into the environment. Research globally has focused on advanced desalination technologies to augment the limited freshwater resources. Forward osmosis (FO) technology has gained substantial interest as a possible lower-energy desalination technology. However, challenges such as the availability of effective draw solutions (DS) have limited its implementation. This study evaluated alternative feed water resources and assessed the potential of dye solutions as DS. The aim is to dilute a concentrated dye DS to a target concentration for direct dye-batch use, thereby reclaiming water resources. The measured osmotic pressure (OP) of the alternative feed solutions (synthetic brackish water; syntethic seawater; seawater from the Atlantic and Indian Oceans; and wastewater from two textile factories) were 414, 2 761, 2 580, 2 614; 1 716 and 7 822 kPa, respectively. Three basic dyes (Maxilon Turquoise, Red and Blue) and three reactive dyes (Carmine, Olive Green and Black) were selected based on common use in the South African textile industry. The dye samples were prepared without and with lt at different concentrations and different dye-to-salt mass ratios ranging from 1:10 to 1:60. The OP trends for the basic dyes followed Blue >> Red > Turquoise and for the reactive dyes Black >> Olive > Carmine. The overall OP trend was Black > Olive > Carmine > Blue > Red > Turquoise. The OP at different dye concentrations and different dye-to-salt ratios was mostly influenced by the dye chemistry and molecular weight (Mw) rather than the type of dye, i.e., reactive vs basic.The OP trend for the dye-to-salt ratios was 1:60 > 1:50 > 1:40 > 1:30 > 1:20 > 1:10. For both the basic and reactive dyes a linear relationship exists between OP and dye concentration; as well as between OP and Mw. The dye DS exhibited larger OP compared to that of the FS evaluated, thus rendering them suitable DS.

Reactive Black 5 and Basic Blue 41 GRL dyeing solutions (dye-to-salt mixture in a 1:10 dye-to-salt mass ratio) were investigated as draw solutions (DS) in a forward osmosis (FO) system with a biomimetic membrane. Synthetic seawater (SSW) and textile wastewater (TWW1 and TWW2) were evaluated as feed solutions (FS) for water reclamation. Reactive Black 5 and Basic Blue 41 GRL were diluted from 0.02 M to concentrations of 0.002 and 0.004 M, respectively. With Reactive Black 5 as DS and SSW as FS, an initial flux of 20.24 L/m2 h and water recovery of 75% was achieved. Using TWW1 and TWW2, initial water fluxes of 19.51 and 13.43 L/m2 h were achieved, respectively, with a 30% water recovery. Using Basic Blue 41 GRL, initial water fluxes of 18.72, 15.13 and 13.42 L/m2 h were achieved with SSW, TWW1, and TWW2 as FS with water recoveries of 50%, 20% and 20%, respectively. The average reverse solute fluxes for Reactive Black 5 and Basic Blue 41 GRL were 0.06 to 0.34 g/m2 h, respectively. Diluted dyeing solutions were produced, with simultaneous water reclamation from SSW and TWW resulting in similar or higher water fluxes and lower reverse solute fluxes compared with other commercially available membranes.