Carbon Nitride Modified Reverse Osmosis Membrane
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Solution Overview
Problem
Conventional seawater desalination reverse osmosis membranes have low boron removal rates and water flux, failing to meet the requirements of China's drinking water standards and exhibiting suboptimal permeability.
Innovation Solution
The method involves interfacial polymerization on a reverse osmosis base membrane, introducing a carbon nitride solution with excellent dispersibility into the polyamide layer, enhancing both water flux and boron removal performance by adjusting the membrane's hydrophilicity, roughness, and pore structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reverse osmosis membranes are used, then the membrane structure is simple and easy to manufacture, but the boron removal rate is less than 60% and water flux is low
Solution Approach 1:
The patent applies composite materials by combining carbon nitride (g-C3N4) nanoparticles with polyamide to form a composite reverse osmosis membrane. The carbon nitride particles are dispersed in the polyamide matrix during interfacial polymerization, creating a composite structure that leverages the hydrophilic properties and boron rejection capabilities of carbon nitride while maintaining the selective transport characteristics of polyamide, thereby achieving boron removal rates exceeding 90% along with enhanced water flux
Solution Approach 2:
The patent applies local quality by modifying only the active layer of the reverse osmosis membrane through interfacial polymerization with carbon nitride incorporation. The carbon nitride is specifically introduced into the polyamide active layer where it directly interacts with boron ions and water molecules, while the support layer remains unchanged. This localized modification approach targets the specific region needed for boron removal enhancement without complicating the entire membrane structure
2Productivity
If the membrane hydrophilicity and pore structure are optimized for high water flux, then permeability improves, but boron removal performance deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically optimizing multiple parameters including carbon nitride concentration (0.1-1.0 g/L), m-phenylenediamine concentration (0.1-1.0%), trimesoyl chloride concentration (0.1-0.5%), and reaction time (0.5-2 minutes). These parameter adjustments enable simultaneous optimization of water flux and boron removal rate by controlling the formation of the polyamide-carbon nitride composite structure, achieving both high permeability and high boron rejection
3Manufacturing precision
If carbon-based materials are introduced to improve boron removal and water flux, then membrane performance improves, but the preparation process complexity increases
Solution Approach 1:
The patent applies merging by combining the carbon nitride dispersion step with the interfacial polymerization process. The carbon nitride particles are pre-dispersed in the aqueous phase containing m-phenylenediamine and sodium hydroxide, then both phases are mixed to initiate simultaneous polymerization and carbon nitride incorporation. This merged approach integrates multiple functions (dispersion, polymerization, composite formation) into a single operation, reducing process complexity compared to separate steps
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 approach results in a seawater desalination reverse osmosis membrane with improved water flux and boron removal rates, achieving pure water flux of up to 2.03 L/m²/h/bar and simulated seawater flux of 0.80 L/m²/h/bar, with a desalination rate of 98.14% and boron removal rate of 82.46%, surpassing unmodified membranes.
Implementation Method 1
reverse osmosis is currently the most commonly used seawater desalination technology
Implementation Method 2
Carbon-based materials can adjust the hydrophilicity, roughness and interlayer structure of the membrane surface due to their rich functional groups
Implementation Method 3
immersing a reverse osmotic basement membrane into the aqueous solution obtained by the step (2), and then removing the immersed reverse osmotic basement membrane, rolling dry surface solution with a rubber roller, then immersing into the organic liquid phase obtained in step (3) for interfacial polymerization
Data Source
AI summary
A method for creating a seawater desalination reverse osmosis membrane that excels in both water flux and boron removal. The method utilizes the abundant and reactive amino groups of carbon nitride in an interfacial polymerization reaction to enhance the membrane's structure. The unique pore and interlayer structure of carbon nitride is employed to modify the membrane's hydrophilicity, roughness, and interlayer structure, thereby boosting its water flux and boron removal capabilities. Additionally, the carbon nitride solution demonstrates exceptional dispersion properties. Its hydrophilic amino groups react with the organic phase monomer trimesoyl chloride during polymerization, ensuring an even distribution in the polyamide layer without any agglomeration. The evenly dispersed m-phenylenediamine and carbon nitride solution, along with sodium hydroxide in the aqueous phase, quicken the acylation reaction rate. This not only ensures more uniform participation of carbon nitride in the reaction but also further enhances the membrane's water flux and boron removal efficiency.