Blended Ionic Liquid Draw Material for Forward Osmosis

The patent uses a composite draw solution comprising multiple temperature-sensitive materials (such as combinations of PEG and polysaccharides, or multiple ionic liquids with different LCSTs) to achieve both easy temperature-based separation and reduced residual concentration. The composite formulation allows synergistic effects where each component contributes to different aspects of separation efficiency and residual reduction.

The patent employs materials with specific lower critical solution temperatures (LCSTs) that change phase behavior at controlled temperatures. By selecting materials with appropriate LCST parameters (e.g., PEG 200 with LCST ~20°C, PEG 400 with LCST ~35°C), the system enables complete phase separation at elevated temperatures, reducing residual draw solution concentration below detection limits while maintaining high osmotic pressure during operation.

The patent divides the draw solution into multiple ionic compound components, each with distinct properties (different anions like CH3SO3−, I−, CF3COO−, or different cations with varying alkyl chains). This segmentation allows independent optimization of each component's contribution to osmotic pressure and phase-transition behavior, enabling precise control over separation temperature and residual concentration through compositional adjustments.

The patent designs ionic compounds with multifunctional characteristics where the same base structure (e.g., phosphonium or nitrogen-containing cations) can pair with different anions to achieve multiple functions: maintaining high osmotic pressure, enabling temperature-responsive phase separation, and reducing residual concentration. This universality allows a single ionic liquid platform to address multiple performance requirements simultaneously.