PVDF-PDMS Membrane for Light and Bubble-Free Oxygen Transfer
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Solution Overview
Problem
Current membranes used in algae-bacteria symbiotic systems for wastewater treatment lack light permeability, limiting the growth of algae due to insufficient light transmission, and are not optimized for bubble-free aeration, affecting the efficiency of the system.
Innovation Solution
A light- and oxygen-permeable membrane is prepared using polyvinylidene fluoride (PVDF) and polydimethylsiloxane (PDMS) with a specific coating and curing process, allowing for both light and gas permeability, enhancing light transmission and oxygen transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional membranes are used for bubble-free aeration, then oxygen transfer is achieved, but light transmission is blocked, limiting algae growth
Solution Approach 1:
The patent uses a composite membrane structure combining PVDF (providing mechanical strength and porosity for oxygen transfer) and PDMS (providing high light transmission and gas permeability). This composite approach allows simultaneous achievement of bubble-free aeration and light penetration for algae growth
Solution Approach 2:
The PVDF layer is designed with controlled porosity (pore size 0.03-0.08 μm, porosity 30-60%) to enable oxygen transfer through the membrane while maintaining structural integrity. The porous structure allows gas permeability while the PDMS coating ensures light transmission
2Reliability
If membrane aeration is applied to maintain system stability, then oxygen supply is improved, but algae photosynthesis is limited due to light blocking
Solution Approach 1:
The PDMS coating forms a thin film (5-20 μm thickness) on the PVDF support layer. This thin film structure provides sufficient gas permeability for oxygen transfer while being transparent to light, allowing light to penetrate to the algae on the outer surface for photosynthesis
Solution Approach 2:
The membrane has different functional zones: the PVDF support layer provides mechanical strength and porosity for gas transfer, while the PDMS coating layer provides light transmission and gas permeability. Each layer is optimized for its specific function to resolve the contradiction
3Ease of operation
If current membranes are used, then bubble-free aeration is achieved, but light transmission efficiency is insufficient for optimal algae growth
Solution Approach 1:
The patent optimizes key parameters including PDMS coating thickness (5-20 μm), PVDF pore size (0.03-0.08 μm), and PVDF porosity (30-60%) to balance gas permeability and light transmission. These parameter adjustments enable both bubble-free aeration and sufficient light penetration for high algae productivity
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 enables effective light irradiation within the algae-bacteria mixture, improving algae growth and system efficiency by allowing both light and gas transfer, making it suitable for large-scale applications.
Implementation Method 1
PVDF and PDMS are adopted as main raw materials... A PDMS liquid is clear and transparent, and a smooth film formed after curing of the PDMS liquid also has ultra-high optical transparency
Implementation Method 2
In MABRs, oxygen is present in a micro-scale state and does not cause bubbles visible to the naked eyes... The PDMS liquid is filled into pores of a hydrophobic PVDF film
Data Source
AI summary
A method for preparing a light- and oxygen-permeable membrane includes: adding polyvinylidene fluoride (PVDF), an organic solvent, and a pore-forming agent successively to a container, stirring at 60° C. to 80° C. for 5 h to 7 h, and conducting vacuum deaeration to obtain a PVDF casting solution; adding polydimethylsiloxane (PDMS) and a curing agent successively to a container, thoroughly stirring at 20° C. to 25° C., and conducting static deaeration to obtain a PDMS casting solution; blade-coating the PVDF casting solution on a glass plate, rinsing the glass plate in a rinsing tank to remove the organic solvent and the pore-forming agent, and oven-drying the glass plate to obtain an initial membrane; and coating the PDMS casting solution on a back side of the initial membrane, placing the initial membrane at room temperature for 2 h to 4 h, and oven-drying the initial membrane to obtain the light- and oxygen-permeable membrane.