Neutral Titanium Dioxide Sol Preparation via Phosphoric Acid
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Solution Overview
Problem
The development of stable, neutral, and transparent photocatalytic titanium dioxide sols is challenging due to the tendency of TiO2 to flocculate at neutral pH and the difficulty in identifying effective steric stabilizers for its small particle size, which affects their stability and photoactivity, and also poses issues with odor and flammability in alkaline forms.
Innovation Solution
Neutralizing alkaline titanium dioxide sols with phosphoric acid to create a stable, transparent, and reactive photocatalytic titanium dioxide sol with a pH range of 8.5 to 9.5, maintaining stability for extended periods and enhancing photoactivity, while reducing odor and flammability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the pH of alkaline titanium dioxide sol is reduced to neutralize it, then odor and flammability are reduced, but the colloidal system agglomerates and becomes unstable
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pH reduction process and using specific neutralizing agents to achieve a final pH range (8.5-9.5) that maintains colloidal stability while eliminating harmful properties. The gradual adjustment of pH parameters prevents agglomeration during neutralization.
Solution Approach 2:
The patent uses intermediary substances such as organic acids (acetic acid, formic acid) or weak inorganic acids (carbonic acid) as mediators during the neutralization process. These intermediaries allow controlled pH reduction without causing the severe agglomeration that would occur with strong acids, thereby maintaining colloidal stability while reducing harmful properties.
2Stability of the object's composition
If alkaline peptizing agents are used to maintain sol stability, then colloidal stability is improved, but strong odor and flammability occur
Solution Approach 1:
The patent changes the chemical nature of peptizing agents from strong alkaline agents (ammonia, NaOH) to organic bases or weak inorganic bases. This parameter change in the chemical composition eliminates odor and flammability while maintaining the ability to peptize and stabilize the titanium dioxide colloidal system.
Solution Approach 2:
The patent employs composite or mixed peptizing systems combining organic bases with other stabilizing agents to achieve both colloidal stability and environmental friendliness. This composite approach allows the system to maintain stability without relying on harmful alkaline substances.
3Object-affected harmful factors
If stable neutral titanium dioxide sols are formed, then environmental friendliness is improved, but photoactivity and stability over time are reduced
Solution Approach 1:
The patent optimizes multiple parameters including pH (maintained at 8.5-9.5), particle size distribution, and peptizing agent concentration to achieve a formulation that simultaneously provides environmental friendliness and high photoactivity. The controlled neutralization process preserves the reactive surface sites necessary for photocatalysis.
Solution Approach 2:
The patent uses organic peptizing agents as intermediaries that not only stabilize the colloidal system but also enhance or preserve photoactivity. These organic molecules interact with the titanium dioxide surface to maintain stability while allowing photocatalytic function, overcoming the typical trade-off between stability and reactivity.
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 resulting sols exhibit improved stability and photoactivity, maintaining transparency and photocatalytic efficiency for over a month, with enhanced NOx removal and antibacterial properties, outperforming commercially available sols in terms of stability and activity.
Implementation Method 1
Neutralizing alkaline titanium dioxide sols with phosphoric acid to create a stable, transparent, and reactive photocatalytic titanium dioxide sol with a pH range of 8.5 to 9.5
Implementation Method 2
The photocatalytic properties of the semiconducting titanium dioxide material result from the promotion of electrons from the valence band to the conduction band under the influence of ultraviolet (UV) and near-UV radiation
Implementation Method 3
the holes oxidize adsorbed water to produce reactive hydroxyl radicals
Implementation Method 4
the electrons reduce adsorbed oxygen to produce superoxide radicals
Implementation Method 5
both of which can degrade NOx and volatile organic compounds (VOCs) in the air
Implementation Method 6
Titanium dioxide colloidal sols have proven to be useful precursor materials for forming such transparent and reactive coatings
Data Source
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AI summary
A method for preparing a neutral, stable and transparent photocatalytic titanium dioxide sol is provided. The method comprises (1) contacting an alkaline titanium dioxide sol with an alkaline peptizing agent to provide a peptized alkaline titanium dioxide sol; (2) neutralizing the peptized alkaline titanium dioxide sol; and (3) obtaining or collecting the neutral, stable and transparent photocatalytic titanium dioxide sol. The titanium dioxide sol is stable and transparent over a range of pH of about 7.0 to about 9.5. The titanium dioxide sol may include crystallites of titanium dioxide having an average particle size of less than about 10 nm with at least 90% of the crystallites being in the anatase form.