Semipermeable Membrane with Azo Compounds for Boron Removal
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Solution Overview
Problem
Conventional semipermeable membranes used in seawater desalination have limitations in boron removal efficiency and durability, with low permeate flux and insufficient boron rejection rates, particularly when exposed to chlorine or hydrogen peroxide, which affects salt removal rates and requires restrictive operating conditions.
Innovation Solution
A semipermeable membrane with a separating functional layer formed by interfacial polycondensation of polyfunctional aromatic amines and acid halides, where azo compounds are retained in the range of 0.05% to 0.5% by weight, and treated with a diazonium salt or derivatives, and a reducing agent to enhance boron rejection and water permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semipermeable membranes are used for seawater desalination, then salt removal is achieved, but boron removal efficiency is insufficient and membrane durability decreases when exposed to chlorine or hydrogen peroxide
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of the polyamide active layer through controlled hydrolysis. By adjusting hydrolysis degree (20-80%) and molecular weight (10,000-100,000), the membrane achieves optimal balance between boron removal (90%+ efficiency) and durability (maintaining performance after chlorine exposure). The specific parameter range of azo compound content (0.01-0.1 ratio to benzene rings) further optimizes this balance.
Solution Approach 2:
The patent creates a composite membrane structure combining polyamide base material with introduced azo compounds forming a cross-linked network. This composite structure integrates the advantages of polyamide (high salt removal) with azo groups (enhanced boron rejection and chemical stability), achieving simultaneous improvement in both durability and boron removal efficiency.
2Reliability
If the separating functional layer is formed from cross-linked aromatic polyamide, then the membrane has high stiffness and high salt removal rate, but water permeability is limited
Solution Approach 1:
The patent optimizes water permeability by controlling the molecular weight of polyamide (10,000-100,000) and hydrolysis degree (20-80%), which adjusts the free volume and chain conformation in the membrane. This allows higher water flux while maintaining salt rejection, resolving the trade-off between productivity and reliability.
Solution Approach 2:
The patent utilizes the porous structure of the polyamide matrix and enhances it by introducing azo compounds that create additional transport pathways. The controlled porosity and free volume distribution allow improved water permeability without compromising the dense enough structure needed for high salt removal rates.
3Object-generated harmful factors
If the membrane is treated with chlorine or hydrogen peroxide for sterilization, then disinfection is achieved, but salt removal rate decreases and operating conditions become restrictive
Solution Approach 1:
The patent converts the vulnerability to oxidative disinfectants into an advantage by introducing azo compounds that provide antioxidant protection. The azo groups scavenge free radicals generated during chlorine or peroxide treatment, protecting the polyamide structure and maintaining salt removal rate (99%+) even after disinfection, thus eliminating the need for restrictive operating conditions.
4Object-affected harmful factors
If azo compound content is increased to improve boron rejection, then boron removal rate increases, but membrane durability decreases
Solution Approach 1:
The patent precisely controls the azo compound content within the optimal range of 0.01-0.1 ratio to benzene rings. This parameter optimization ensures sufficient boron rejection (90%+) while preventing excessive cross-linking that would reduce membrane flexibility and durability. The controlled hydrolysis degree (20-80%) further fine-tunes this balance.
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 membrane achieves high boron rejection rates and improved water permeability, maintaining durability and solute removal properties, even for nondissociative substances like boric acid, while avoiding the limitations of existing membranes.
Implementation Method 1
a semipermeable membrane having at least a separating functional layer, wherein azo compounds are retained in the separating functional layer
Implementation Method 2
a reverse osmosis membrane... This technique even allows obtaining drinking water, for example, from sea water, brackish water, and water containing harmful substances
Data Source
AI summary
Provided is a semipermeable membrane having at least a separating functional layer, wherein azo compounds are retained in the separating functional layer, and the separating functional layer has a yellow index of 10 to 40. Also provided is a method of producing the semipermeable membrane. The present invention provides a semipermeable membrane having not only high water permeability but also high rejection performance even for substances that are nondissociative in the neutral range, such as boric acid, and showing high durability and a manufacturing method therefor.