Hydrogel-Coated Reverse Osmosis Membrane Resists Fouling
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Solution Overview
Problem
Reverse osmosis membranes suffer from fouling due to their microscopically rough surface texture, leading to reduced water permeation rates and productivity, with existing coatings either reducing flux or failing to maintain salt rejection performance.
Innovation Solution
A hydrophilic, crosslinked polyvinylpyrrolidone coating is applied to the membrane surface, which is cured in place to form a hydrogel layer that is adherent and resistant to fouling, without significantly altering the membrane's flux or salt rejection capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating is applied to the membrane surface to prevent fouling, then fouling resistance is improved, but flux is reduced
Solution Approach 1:
The patent applies a hydrogel coating with specific physical and chemical parameters (hydrophilicity, crosslinking degree, porosity) that create a fouling-resistant surface while maintaining water permeability. The hydrogel's unique parameter combination allows it to repel organic and inorganic foulants without significantly impeding water flux, thus resolving the contradiction between fouling resistance and productivity
Solution Approach 2:
The patent creates a composite membrane structure by combining the base membrane material with a hydrogel coating layer. This composite structure integrates the selective permeability of the base membrane with the fouling-resistant properties of the hydrogel, achieving both high flux and excellent fouling resistance that neither component could achieve alone
2Reliability
If the membrane surface is modified to reduce fouling, then fouling resistance is improved, but salt rejection performance deteriorates
Solution Approach 1:
The hydrogel coating is applied as a thin surface layer that modifies only the outermost membrane surface properties. This localized modification provides fouling resistance at the surface while preserving the bulk membrane's salt rejection capabilities, thus resolving the contradiction between fouling resistance and salt rejection performance
Solution Approach 2:
The hydrogel coating parameters (thickness, crosslinking density, hydrophilicity) are optimized to provide fouling resistance without compromising the underlying membrane's selective transport properties. The coating thickness is controlled to be sufficient for fouling protection but thin enough to maintain salt rejection, resolving the contradiction between these two performance aspects
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 hydrogel coating effectively prevents fouling by contaminants while maintaining the membrane's initial flux and salt rejection performance, even under fouling conditions, and facilitates complete foulant removal during cleaning.
Implementation Method 1
A reverse osmosis membrane is coated with a hydrophilic, non-crosslinked polymer that is water soluble, the polymer being subsequently crosslinked
Implementation Method 2
a hydrogel coating that is adherent to the reverse osmosis membrane
Implementation Method 3
a hydrophilic, crosslinked polyvinylpyrrolidone coating is applied to the membrane surface, which is cured in place to form a hydrogel layer that is adherent and resistant to fouling
Implementation Method 4
Reverse osmosis is widely used to treat water containing dissolved solutes, principally dissolved salts. Treatment is carried out by causing a pressurized stream of water to flow across the feed side of a membrane. Pressure in excess of the osmotic pressure of the feed solution is applied on the feed side, and under this pressure driving force, water molecules pass through the membrane preferentially.
Implementation Method 5
Almost all reverse osmosis membranes are currently made by interfacial polymerization. In this method, an aqueous solution of a water-soluble monomer, such as a diamine, is deposited in the pores of a microporous support membrane. The amine-loaded support is contacted with a water-immiscible organic solution containing a reactant, such as a triacyl chloride in a hydrocarbon solvent. The amine and acyl chloride react at the interface of the two immiscible solutions to form an ultrathin crosslinked polyamide membrane layer.
Data Source
AI summary
A reverse osmosis membrane is disclosed that has a hydrogel disposed on its surface, wherein the hydrogel is formed from a crosslinked polyvinylpyrrolidone or a copolymer of vinyl pyrrolidone. The hydrogel-coated membrane resists fouling by feed water contaminants. The permeate flux rate and salt rejection of the underlying membrane are not negatively affected by the hydrogel coating.