TiO2 Nanofiltration Membranes via Molecular Layer Deposition
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Solution Overview
Problem
Current ceramic nanofiltration membranes, particularly TiO2, face challenges in precisely controlling pore sizes and membrane thickness, and the sol-gel method requires strict hydrolysis control, limiting their efficiency and scalability for water purification.
Innovation Solution
Molecular layer deposition (MLD) is used to fabricate TiO2 nanofiltration membranes by reacting titanium precursor gases with anodic aluminum oxide substrates, allowing for precise control of coating thickness and pore sizes, and subsequent calcination to form defect-free, dense titanium oxide membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sol-gel method is used to prepare TiO2 nanofiltration membranes, then chemical stability and mechanical strength are improved, but manufacturing precision and ease of operation deteriorate due to strict hydrolysis control requirements
Solution Approach 1:
The patent replaces the conventional sol-gel wet chemical method with a vapor-phase deposition process. Titanium precursor and alkoxide precursor gases are deposited onto the AAO support through vapor-phase reactions, eliminating the need for liquid sol-gel processing and strict hydrolysis control. This substitution of mechanical/chemical processing method resolves the contradiction by maintaining TiO2 membrane reliability while dramatically improving ease of manufacture.
Solution Approach 2:
The patent changes the processing parameters from liquid-phase sol-gel conditions to vapor-phase deposition conditions. By controlling gas flow rates, deposition temperature, and precursor ratios in the vapor phase, the method achieves precise control over membrane composition and pore structure without the complications of sol-gel hydrolysis control, thus resolving the contradiction between reliability and ease of manufacture.
2Reliability
If sol-gel method is used to prepare TiO2 nanofiltration membranes, then chemical stability is improved, but manufacturing precision deteriorates due to difficulty in controlling pore sizes and membrane thickness
Solution Approach 1:
The vapor-phase deposition process replaces the sol-gel method, enabling precise control of film thickness through deposition time and precursor flow rates. The pore size is precisely controlled by selecting AAO supports with specific pore dimensions and controlling the vapor-phase reaction conditions, achieving manufacturing precision that was difficult to obtain with sol-gel processing.
Solution Approach 2:
The patent uses pre-formed AAO supports with precisely controlled pore structures as the base layer. By depositing TiO2 onto these pre-prepared supports with known pore sizes and thicknesses, the method inherits the manufacturing precision of the AAO fabrication process while adding the chemical stability of TiO2, thus resolving the contradiction between reliability and manufacturing precision.
3Reliability
If sol-gel method is used to prepare TiO2 nanofiltration membranes, then chemical stability is improved, but productivity deteriorates due to complex processing conditions
Solution Approach 1:
The vapor-phase deposition process replaces the multi-step sol-gel method, eliminating the need for careful control of hydrolysis, condensation, and drying conditions. The simplified vapor-phase process reduces processing time and complexity, thereby improving productivity while maintaining the chemical stability advantage of TiO2 membranes.
Solution Approach 2:
The patent extracts and eliminates the complex hydrolysis and condensation control steps from the membrane preparation process by using vapor-phase deposition. By taking out these problematic intermediate steps and directly forming the TiO2 layer through vapor-phase reactions, the method improves productivity while preserving the chemical stability of the final TiO2 product.
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 MLD method achieves high water flux and rejection rates for contaminants, with TiO2 nanofiltration membranes demonstrating a pure water flux of 48 L m−2·h−1·bar−1 and 96% rejection of Methylene blue, while offering precise control over membrane composition and scalability.
Implementation Method 1
supplying a titanium precursor gas into a reaction chamber, where the titanium precursor gas reacts with a base support of an anodic aluminum oxide
Implementation Method 2
an alkoxide precursor gas is supplied into a reaction chamber such that the alkoxide precursor gas reacts to with the titanium on the base support to form a hybrid titanium alkoxide
Implementation Method 3
the base support is heated to remove the organic component to leave titanium oxide on the surface of the base support
Implementation Method 4
The reaction chamber is then evacuated to remove any unreacted titanium precursor gas
Data Source
AI summary
Methods are provided for preparing TiO2 nanofiltration membranes for water purification are provided. The method can include supplying a titanium precursor gas into a reaction chamber, where the titanium precursor gas reacts with a base support of an anodic aluminum oxide, and the base support of an anodic aluminum oxide has a surface defining a plurality of pores therein. The reaction chamber can then be evacuated to remove any unreacted titanium precursor gas, and an alkoxide precursor gas can be supplied into a reaction chamber such that the alkoxide precursor gas reacts to with the titanium on the base support to form a hybrid titanium alkoxide. Thereafter, the base support cab be heated to remove the organic component to leave titanium oxide on the surface of the base support.