Thermal-Depression Regeneration of Forward (Direct) Osmosis Desalination Technique

Abstract

Forward osmosis (FO) desalination is exhibited utilizing dimethyl ether (DME) as a fresh draw solute, integrated with a thermal-depression regeneration (TDR) system that employs low-grade heat for draw recovery. Unlike traditional reverse osmosis (RO) which needs high hydraulic pressure and is susceptible to membrane fouling, FO is driven by osmotic pressure gradients and therefore operates at low pressure, greatly reducing fouling risk and energy use. DME displays high osmotic activity in water (osmotic pressures up to 4 MPa, 2.1 MPa at 7 wt% DME), appropriate to extract water from seawater feeds. FO experiments attained steady water fluxes of 2–3 L·m⁻²·h⁻¹ (LMH) utilizing a polyamide membrane with a brackish feed, confirming good membrane compatibility and sturdy performance. The volatile DME draw solution is efficiently regenerated by controlled depressurization with moderate thermal input, lever aging DME’s low boiling point to separate it from water without extensive post-treatment. The ending of 99% of the DME is recovered and recycled, with any permeating DME outgassing for capture, developing in trivial solute carryover to the product water. By utilizing low-grade thermal energy for regeneration, the incorporated FO–TDR approach functions with minimal electrical input and accomplishes a specific energy consumption as low as 0.46 kWh per cubic meter of drinking hwater produced. This DME-driven FO system focuses FO’s advantages RO such as lower fouling propensity and decreased energy demand—while achieving high water flux with slight draw solute leakage. These consequences underline FO’s potential as a main technology for energy-efficient desalination, with the likelihood for hybrid or modular integration into sustainable desalination technology systems.