Thermo-responsive Draw Solute for Forward Osmosis
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Solution Overview
Problem
Current draw solutes for forward osmosis, such as ammonium bicarbonate, face challenges including potential membrane damage, high energy requirements for solute removal, and complex separation processes, which hinder efficient seawater desalination and contaminated water purification.
Innovation Solution
A thermo-responsive draw solute with a molar mass of 50 to 3000 g/mol that undergoes a phase transition between 0° C. and 70° C., allowing for easy separation and low-energy water desalination or purification by forward osmosis, using semi-permeable membranes like cellulose acetate or polyether sulfone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ammonium bicarbonate is used as draw solute, then high osmotic pressure is achieved for effective water drawing, but membrane damage occurs and high energy is required for solute removal
Solution Approach 1:
The patent changes the chemical parameters of the draw solute from ammonium bicarbonate to thermo-responsive compounds (such as poly(N-isopropylacrylamide) or other temperature-sensitive polymers) that exhibit lower critical solution temperature (LCST) behavior. This parameter change allows the solute to remain dissolved at operating temperatures and then phase-separate upon heating, eliminating membrane damage while maintaining high osmotic pressure for effective water drawing.
Solution Approach 2:
The patent utilizes phase transition phenomena where thermo-responsive draw solutes undergo solubility changes at specific temperatures. Below the LCST, the solute is fully soluble and exerts high osmotic pressure; above the LCST, the solute phase-separates, enabling easy removal without complex distillation. This phase transition mechanism resolves the contradiction by providing both high osmotic pressure during operation and simple, low-energy separation during recovery.
2Ease of operation
If heat at 60°C is supplied to remove ammonium bicarbonate, then solute separation is achieved, but high energy consumption occurs
Solution Approach 1:
The patent employs phase transition of thermo-responsive draw solutes at their lower critical solution temperature (typically 30-50°C for polymers like poly(N-isopropylacrylamide)). When heated above the LCST, the solute undergoes spontaneous phase separation and precipitation, enabling easy solid-liquid separation without requiring high-temperature distillation. This reduces energy consumption from 60°C continuous heating to intermittent heating to a lower temperature threshold.
Solution Approach 2:
The patent replaces the thermal-mechanical distillation process (complex column distillation requiring sustained high temperature) with a simpler thermal-triggered phase separation followed by gravitational or centrifugal separation. This substitution eliminates the need for complex distillation equipment and reduces energy input by utilizing the inherent phase transition behavior of the thermo-responsive solute.
3Ease of operation
If complex column distillation process is used for solute removal, then complete separation is achieved, but device complexity increases
Solution Approach 1:
The patent utilizes phase transition of thermo-responsive draw solutes that causes spontaneous separation into dissolved and precipitated phases upon temperature change. This simple two-phase system can be separated using basic filtration or decantation equipment, replacing complex column distillation systems with much simpler solid-liquid separation devices.
Solution Approach 2:
The patent extracts the draw solute from the aqueous phase through temperature-induced phase separation, causing the solute to precipitate out as a distinct solid phase. This extracted solid phase can then be easily removed by simple filtration or decantation, eliminating the need for complex distillation columns and associated control systems.
4Productivity
If high concentration ammonium bicarbonate solution is used, then effective water drawing from seawater is achieved, but solute reuse becomes complicated
Solution Approach 1:
The patent employs thermo-responsive draw solutes that undergo reversible phase transitions. After use, the solute can be regenerated by cooling the spent solution below the LCST, causing the solute to redissolve and restore its high osmotic pressure properties. This reversible phase transition enables simple, repeated cycles of use and regeneration without complex processing, improving both productivity and operational simplicity.
Solution Approach 2:
The patent facilitates easy recovery of the draw solute through temperature-controlled phase separation. The spent draw solution is heated above the LCST to precipitate the solute, which is then separated and can be reused by cooling the solution below the LCST to redissolve the solute. This simple thermal cycling process enables efficient solute recovery and reuse, eliminating complicated regeneration procedures.
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
The thermo-responsive draw solute creates optimal conditions for seawater desalination and contaminated water purification with reduced energy consumption and simplified solute separation, enhancing the efficiency of the forward osmosis process.
Implementation Method 1
A draw solute for forward osmosis is a thermo-responsive compound having a molar mass of 50 to 3000 g/mol and undergoing a phase transition at a specific temperature
Implementation Method 2
Forward osmosis is performed in two steps. In the first step, a water species requiring desalination or purification and a solution having a higher osmotic pressure than the water species are arranged to face each other through a semi-permeable membrane. This solution is referred to as a 'draw solution' and a constituent solute of the draw solution is referred to as a 'draw solute.' With this arrangement, water migrates to the draw solution by osmosis even without additional energy supply.
Data Source
AI summary
The present invention relates to a thermo-responsive draw solute that can be applied to water desalination and purification based on forward osmosis. The thermo-responsive draw solute has a molar mass of 50 to 3000 g/mol and undergoes a phase transition at a temperature of 0° C. to 70° C. The thermo-responsive draw solute creates optimum conditions for the desalination of seawater and the purification of contaminated water based on forward osmosis. The present invention also relates to a method for water desalination and purification using the thermo-responsive draw solute. The method consumes little energy for water desalination or purification, is simple to apply to water desalination or purification, and enables separation of the draw solute in a very easy manner.