Thermally Responsive Ionic Liquid Draw Solute for Forward Osmosis

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Solution Overview

Problem

Current forward osmosis desalination technologies face challenges due to the lack of suitable draw solutes that balance high osmotic pressure with ease of regeneration, leading to high energy consumption and membrane fouling, which is not lower than that of reverse osmosis processes.

Innovation Solution

The use of thermally responsive ionic liquids or compounds as draw solutes, which undergo phase separation at a lower critical solution temperature, allowing for energy-efficient regeneration using solar or industrial waste heat, reducing the hydraulic pressure needed for water recovery and minimizing energy consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional draw solutes (inorganic salts, organic salts, polyelectrolytes, glucose) are used to generate high osmotic pressure, then water permeation is achieved, but energy consumption increases due to high hydraulic pressure needed for regeneration

Engineering Contradiction:

Improveenergy consumptionVSAvoidease of regeneration

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The invention changes the physical-chemical parameters of the draw solute by using thermally responsive ionic liquids that undergo phase separation at specific temperatures (LCST/UCST). This temperature-dependent parameter change enables low-energy regeneration through phase separation instead of high-pressure filtration, directly resolving the energy consumption vs. regeneration ease contradiction

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention exploits phase transition phenomena (liquid-liquid phase separation at LCST or solid-liquid phase separation at UCST) of thermally responsive ionic liquids to separate draw solute from water. This phase transition mechanism replaces energy-intensive high-pressure filtration with low-energy thermal processing, achieving both high osmotic pressure and ease of regeneration

Inventive Principle:

Principle #36Phase transitions

2Productivity

If reverse osmosis is used for seawater desalination, then water production is achieved, but membrane fouling and high pressure requirements occur

Engineering Contradiction:

Improvewater productionVSAvoidmembrane fouling

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The invention replaces the mechanical high-pressure filtration system of reverse osmosis with a thermally driven phase separation system. Forward osmosis uses osmotic pressure (no hydraulic pressure needed) for water permeation, and regeneration uses thermal phase separation instead of mechanical filtration, eliminating membrane fouling while maintaining water production capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If magnetically responsive nanoparticles are used as draw solutes, then separation is enabled, but osmotic pressure decreases and nanoparticle agglomeration occurs

Engineering Contradiction:

Improveseparation capabilityVSAvoidosmotic pressure

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention changes the response mechanism from magnetic field (nanoparticles) to thermal field (thermally responsive ionic liquids). The thermal response maintains high osmotic pressure because the ionic liquid molecules remain dissolved and functional until the phase separation temperature is reached, avoiding the osmotic pressure loss and agglomeration problems of magnetic nanoparticles

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly reduces energy consumption in forward osmosis desalination to 23% of current reverse osmosis levels, enabling efficient desalination of high-salinity water with improved water quality and reduced membrane fouling.

Implementation Method 1

some of these draw solutes have a lower critical solution temperature (LCST) of around 40° C., making it convenient to scavenge inexpensive or free solar heat and industrial waste heat

Methodology Applied

Scientific EffectPhase separation: Phase Change

Implementation Method 2

The water permeation in FO is an energy-input-free process driven by the osmotic pressure difference of draw solution and feed solution

Methodology Applied

Scientific EffectOsmosis: Osmosis

Data Source

PatentUS11241655B2Draw solute for a forward osmosis process

Publication Date: 2022.02.08 NANYANG TECH UNIV

AI summary

A draw solute for a forward osmosis process, the draw solute comprising: a thermally responsive ionic compound having at least one of: a lower critical solution temperature (LCST) and an upper critical solution temperature (UCST), the draw solute being regeneratable from a diluted aqueous draw solution after forward osmosis via one of: liquid-liquid phase separation and solid-liquid phase separation, the draw solute being regeneratable when the diluted aqueous draw solution is at a temperature selected from one of: above the LCST and below the UCST.