Composite Membrane Boron Rejection via Functionalized Polyamide
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Solution Overview
Problem
Reverse osmosis membrane desalination processes struggle to achieve high boron rejection rates, particularly for uncharged boric acid, which is challenging due to its small size and similarity to water molecules, leading to difficulties in producing permeate that meets application requirements without additional treatment steps, increasing costs.
Innovation Solution
The use of composite membranes comprising moieties derived from aromatic sulfonyl halides, heteroaromatic sulfonyl halides, and other halides, along with interfacial polymerization to form polyamide membranes, which are treated with specific agents like 4-nitrobenzenesulfonyl chloride or 1,3-benzenedisulfonyl chloride to enhance boron rejection and maintain or improve salt rejection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RO membranes are used, then salt rejection is efficient (up to 99.7%), but boron rejection is poor (below 90%) due to the small size of boric acid molecules
Solution Approach 1:
The patent applies local quality by introducing specific functional groups (sulfonyl, carbonyl, hydroxyl) at particular locations within the membrane's barrier layer to create selective interaction sites for boric acid molecules. This localized chemical modification enables enhanced boron rejection without requiring complete redesign of the entire membrane structure, thus improving reliability while controlling device complexity.
Solution Approach 2:
The patent employs composite materials by combining traditional polyamide matrix with specific functional moieties (sulfonyl halides, carbonyl compounds, hydroxyl groups) to create a heterogeneous barrier layer. This composite structure leverages the base membrane's salt rejection capability while the added functional groups provide selective boron interaction sites, achieving high boron rejection (≥90%) without proportionally increasing overall membrane complexity.
2Reliability
If additional treatment steps are added to reduce boron concentration, then boron rejection improves, but process complexity and costs increase substantially
Solution Approach 1:
The patent applies preliminary action by incorporating boron-selective functional groups directly into the membrane structure during manufacturing, rather than adding treatment steps after water passes through the membrane. This pre-configured chemical environment within the membrane enables high boron rejection (reducing concentration to below 0.5 mg/L) in a single RO stage, eliminating the need for subsequent treatment processes and reducing overall system complexity.
Solution Approach 2:
The patent achieves multi-functionality by designing the barrier layer to simultaneously perform salt rejection (traditional RO function) and boron removal (specialized function) through integrated chemical interactions. The functional groups interact with both ionic species and uncharged boric acid molecules, allowing a single membrane to replace what would traditionally require multiple treatment stages, thus improving boron concentration reduction while avoiding increased process complexity.
3Reliability
If membrane pressure is increased to improve separation, then salt removal efficiency improves, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the membrane barrier layer (introducing sulfonyl, carbonyl, and hydroxyl functional groups) to enhance selective interaction with boron species. This chemical parameter modification enables effective boron rejection through molecular-level interactions rather than relying solely on high mechanical pressure, thereby improving removal efficiency while reducing the energy input required for separation.
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 method achieves boron rejection of at least 90% in a single step, preferably 95% or more, while maintaining high salt rejection, reducing boron concentration in seawater or brackish water to below 0.5 mg/L, thus addressing the limitations of existing RO membrane technologies.
Implementation Method 1
Reverse osmosis is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure
Implementation Method 2
The membrane here is semipermeable, meaning it allows the passage of solvent but not of solute
Data Source
AI summary
Improved methods for reducing boron concentration in seawater or brackish water, while simultaneously maintaining or improving the salt rejection of membrane and flow performance of polyamide reverse osmosis (RO) membranes include contacting the water with a composite membrane comprising moieties derived from an aromatic sulfonyl halide, a heteroaromatic sulfonyl halide, a sulfinyl halide; a sulfenyl halide; a sulfuryl halide; a phosphoryl halide; a phosphonyl halide; a phosphinyl halide; a thiophosphoryl halide; a thiophosphonyl halide, an isocyanate, a urea, a cyanate, an aromatic carbonyl halide, an epoxide or a mixture thereof.