The characteristics of temperature-responsive ionic liquids on the integrated operational effectiveness of water...

Large amounts of wastewater are produced from semiconductor manufacturing, and the production energy consumption has skyrocketed with its global demand in recent years. Forward osmosis (FO) provides unique merits in reclaiming the wastewater if suitable draw solutes with high water flux, low leakage, and limited energy requirement in regeneration are available. Two lower critical solution temperature-ionic liquids (LCST-ILs), tetrabutylphosphonium trimethylbenzensulfonate ([P₄₄₄₄][TMBS]) and tetrabutylphosphonium maleate ([P₄₄₄₄][Mal]) were synthesized and systematically assessed as recycled draw solutes in FO for the water reclamation from the wastewater of Si-ingot sawing. The water flux of [P₄₄₄₄][TMBS] and [P₄₄₄₄][Mal] was 4.12 and 2.67 LMH in the FO for the authentic sawing wastewater, respectively. The characteristics of relatively higher hydrophobic and the structure configuration ensure the lower thermal-stimulus separation energy (E_ts) of the spent [P₄₄₄₄][Mal] solution and its relative ease in recycling because of the higher regeneration ratio. The more hydrophilic [P₄₄₄₄][TMBS] based draw solution (DS) exhibits higher osmotic pressure, which is beneficial for water filtration but leads to higher E_ts. The estimated energy required for the integrated processes, including FO filtration for the sawing wastewater, thermal separation of draw solute, and the reclaimed water polishing, for the system with [P₄₄₄₄][Mal] as draw solutes is 14.22 kWh m^-3. The value significantly reduced to 1.33 kWh m^-3 if low-grade waste heat (<100 °C) was applied for the thermal separation.