Temperature-Sensitive Draw Compounds for Forward Osmosis
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Solution Overview
Problem
Current fluid purification technologies, particularly in forward osmosis, face challenges with draw compounds that lack high flux, stability, and efficient regeneration, often resulting in low water flux and high reverse solute diffusion, which are not environmentally friendly and require high energy consumption.
Innovation Solution
The development of temperature-sensitive draw compounds with linear or branched structures, such as ethylene oxide-propylene oxide copolymers, that undergo phase separation upon heating, allowing for efficient solvent separation and regeneration, reducing reverse solute diffusion, and maintaining stability across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional draw compounds are used in forward osmosis, then the purification process can be implemented, but water flux is low and reverse solute diffusion is high
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of draw compounds to include temperature-sensitive properties. The draw solute is designed to undergo phase separation at specific temperatures, changing its physical state from dissolved to precipitated form. This parameter change enables the system to achieve high water flux during operation while preventing reverse solute diffusion through temperature-controlled phase separation.
Solution Approach 2:
The patent utilizes phase transitions as the core mechanism for resolving the contradiction. The draw solute exhibits temperature-dependent solubility, transitioning from a dissolved state during forward osmosis (enabling high water flux) to a precipitated state during regeneration (preventing reverse diffusion). This phase transition allows the system to dynamically control solute behavior to optimize both water flux and minimize reverse solute diffusion.
2Productivity
If draw compounds with high osmotic pressure are used to increase water flux, then purification efficiency improves, but energy consumption increases
Solution Approach 1:
The patent uses phase transitions to resolve the energy consumption contradiction. During forward osmosis, the draw solute remains in dissolved form to maintain high osmotic pressure and drive water flux. During regeneration, temperature-induced phase separation precipitates the solute, releasing osmotic pressure without requiring high-energy processes. This natural phase transition enables efficient energy utilization throughout the cycle.
Solution Approach 2:
The temperature-sensitive draw solute performs self-service by automatically undergoing phase separation at predetermined temperatures during regeneration. This self-triggered mechanism eliminates the need for external control systems or additional energy input to initiate solute precipitation, allowing the system to recover draw solute with minimal energy consumption while maintaining high purification efficiency during operation.
3Ease of manufacture
If conventional draw solutes are used, then the process can operate, but regeneration is difficult and draw solute loss occurs
Solution Approach 1:
The patent applies phase transitions to enable easy regeneration and prevent draw solute loss. The temperature-sensitive draw solute automatically precipitates from the permeate stream when exposed to temperatures above its cloud point, allowing for simple gravitational or centrifugal separation. This phase transition mechanism enables complete draw solute recovery without complex regeneration equipment, eliminating draw solute loss and simplifying the regeneration process.
Solution Approach 2:
The patent uses extraction by selectively removing the draw solute from the permeate stream through temperature-induced phase separation. The precipitated draw solute can be easily separated and recovered, while the purified water is extracted as the product stream. This selective extraction approach enables efficient draw solute regeneration and minimizes substance loss, addressing the regeneration difficulty and draw solute loss problems.
4Device complexity
If non-temperature-sensitive draw compounds are used, then the process is simpler, but regeneration requires high energy input and is less efficient
Solution Approach 1:
The patent applies parameter changes by incorporating temperature-sensitive properties into the draw solute chemistry. This modification enables the system to use mild temperature changes during regeneration instead of high-energy processes. The predetermined cloud point temperature of the draw solute allows for efficient regeneration at low energy input, resolving the contradiction between process complexity and regeneration energy requirements.
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 enhances water flux and reduces reverse solute diffusion, achieving efficient and cost-effective fluid purification while being environmentally friendly, utilizing waste heat for energy and minimizing residual draw compound in the solvent stream.
Implementation Method 1
temperature-sensitive draw compounds with linear or branched structures, such as ethylene oxide-propylene oxide copolymers, that undergo phase separation upon heating
Implementation Method 2
the solvent is transported through a semipermeable membrane from the feed side to the draw side of the membrane. A draw solution having an osmotic pressure greater than that of the feed solution is provided to the draw side of the membrane
Data Source
AI summary
Draw compounds and draw solutions comprising said draw compounds for use in forward osmosis solvent purification systems. The draw compound may be a linear random, sequential, or block molecular chain consisting of at least one oxide monomer or diol monomer and have a temperature-dependent affinity with a feed solvent. The draw compound may further include a first terminal group and a second terminal group, at least one of the first terminal group and the second terminal group selected from the group consisting of a hydroxyl group, an amine group, a carboxylic group, an allyl group, and a C1 to C14 substituted and unsubstituted alky group. The draw compound may also be a branched random, sequential, or block molecular chain consisting of at least one oxide monomer or diol monomer.