Tree-Like Nanofiltration Membrane for Wastewater Treatment
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Solution Overview
Problem
Existing nanofiltration membranes face challenges in effectively removing organic matters and heavy metal ions from wastewater due to their horizontal structure, which leads to agglomeration, low specific surface area, and slow mass transfer.
Innovation Solution
A novel composite nanofiltration membrane with a tree-like structure is designed, where cellulose fibers act as tree roots, hydroxyapatite nanowire arrays serve as tree trunks, and MOF nanocrystals function as tree leaves, enhancing the specific surface area and mass transfer while integrating ion exchange and high adsorption capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a separation layer is attached to a support layer horizontally, then the membrane structure is simple and easy to manufacture, but it causes agglomeration, low specific surface area, and slow mass transfer
Solution Approach 1:
The patent transforms the traditional horizontal two-dimensional attachment of separation layer to support layer into a vertical three-dimensional tree-like structure. Hydroxyapatite nanowires grow vertically from the support layer, and MOF nanocrystals are deposited on the nanowire surfaces, creating a multi-layered vertical architecture that dramatically increases the specific surface area while maintaining manufacturing feasibility through controlled growth processes
Solution Approach 2:
The patent implements a nested structure where MOF nanocrystals are deposited on the surface of hydroxyapatite nanowires, which themselves are grown on the support layer. This nested arrangement of multiple functional materials at different hierarchical levels maximizes the utilization of space and surface area, allowing each component to contribute its specific function while collectively achieving enhanced performance
2Ease of manufacture
If a separation layer is attached to a support layer horizontally, then the membrane structure is simple, but it results in slow mass transfer
Solution Approach 1:
The vertical tree-like structure creates shortened diffusion paths from the feed side to the permeate side compared to horizontal structures. The vertically oriented nanowires and nanocrystals provide direct channels for mass transfer, reducing resistance and enhancing the rate at which substances pass through the membrane while maintaining structural integrity
Solution Approach 2:
The tree-like structure inherently creates a porous network with interconnected voids between nanowires and nanocrystals. This porous architecture facilitates rapid mass transfer by providing multiple parallel pathways for substance transport, reducing tortuosity and enhancing the overall mass transfer rate while maintaining mechanical stability
3Device complexity
If conventional nanofiltration membranes are used, then the structure is simple, but it is difficult to effectively remove organic matters and heavy metal ions with different properties
Solution Approach 1:
The patent applies local quality by assigning different functional characteristics to different components at specific locations within the membrane structure. Hydroxyapatite nanowires provide ion exchange capacity for heavy metal ions, while MOF nanocrystals offer tailored pore sizes and surface chemistry for organic matter removal. Each component is strategically positioned to optimize its function for specific contaminant types
Solution Approach 2:
The patent creates a composite membrane structure combining cellulose support layer, hydroxyapatite nanowires, and MOF nanocrystals. This multi-material composite approach integrates the advantages of each material: cellulose provides mechanical strength, hydroxyapatite offers ion exchange for metals, and MOF delivers selective adsorption for organics, achieving versatile removal capability across different contaminant classes
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 tree-like structured nanofiltration membrane exhibits a significantly higher interception rate for both positively-charged and negatively-charged dyes and heavy metal ions, outperforming conventional horizontal membranes by improving surface roughness and specific surface area.
Implementation Method 1
the novel composite nanofiltration membrane integrates the ion exchange performance of hydroxyapatite and the high adsorption of MOF nanocrystals, which can allow the efficient removal of organic matters and heavy metal ions in wastewater
Implementation Method 2
the novel composite nanofiltration membrane integrates the ion exchange performance of hydroxyapatite and the high adsorption of MOF nanocrystals, which can allow the efficient removal of organic matters and heavy metal ions in wastewater
Data Source
AI summary
Provided are a preparation method of a nanofiltration membrane with a tree-like structure and use. The preparation method includes: taking a cellulose fiber filter paper as a substrate, and allowing hydroxyapatite nanowire arrays to grow in situ through solvothermal synthesis to obtain a composite filter paper; and repeatedly soaking the composite filter paper in a solution of trimesic acid and iron chloride in ethanol to allow continuous deposition to obtain the nanofiltration membrane with the tree-like structure. The nanofiltration membrane with the tree-like structure of the present application has a larger surface roughness and a larger specific surface area than the conventional nanofiltration membranes, and thus exhibits a very high interception rate (higher than 94%) for anionic/cationic dyes and heavy metal ions Pb2+. Therefore, the nanofiltration membrane with the tree-like structure of the present application has excellent environmental benefits.