Silica Nanoparticle Preparation via Staged Acid Titration
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Solution Overview
Problem
Existing methods for preparing silica nanoparticles from siliceous rock result in a wide particle size distribution, leading to unsatisfactory uniformity of the hydrophobic property in coating materials when nano-sized silica particles are added, as the particle size distribution is not narrow enough, typically ranging from 20 nm to 40 nm.
Innovation Solution
A method involving pre-treating siliceous rock to form a sodium silicate solution, followed by slow acid titration and continuous stirring to achieve a silicic acid-enriched solution, which is then subjected to flame spray pyrolysis or drying-grinding-calcining to produce silica nanoparticles with a narrow particle size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silica nanoparticles are prepared by conventional methods (heat treatment, acid leaching, sodium hydroxide treatment, ion-exchange resin, flame spray pyrolysis), then silica nanoparticles can be produced, but the particle size distribution is wide and hydrophobic property uniformity is unsatisfactory
Solution Approach 1:
The patent changes the chemical parameters of the precursor solution by controlling pH value through stepwise acidification. The sodium silicate solution is titrated with acid to achieve specific pH ranges (first pH 2-4, then pH 0.5-2), which controls the polymerization degree of silicic acid and consequently the particle size distribution of the resulting silica nanoparticles, achieving a narrow distribution centered at 20-40 nm
Solution Approach 2:
The patent segments the single titration process into multiple staged titrations with intermediate stirring periods. The process is divided into: (1) initial titration to pH 2-4 with stirring, (2) second titration to pH 0.5-2 with stirring, (3) optional third titration to pH -0.5-0.5. This segmentation allows progressive control of silicic acid polymerization, preventing rapid uncontrolled particle growth and achieving uniform narrow particle size distribution
2Manufacturing precision
If the particle size distribution of silica nanoparticles is narrow (20 nm to 40 nm), then the hydrophobic property of coating material is enhanced and uniform, but the conventional preparation methods produce wide particle size distribution
Solution Approach 1:
The patent performs preliminary action by pre-adjusting the pH value of the sodium silicate solution before flame spray pyrolysis. The solution is titrated with acid to achieve predetermined pH values (2-4, then 0.5-2) and stirred for predetermined times (30-120 minutes each stage). This preliminary pH control and staged polymerization prepares the silicic acid solution in advance with controlled molecular weight distribution, which directly determines the narrow particle size distribution (20-40 nm) of the final silica nanoparticles
Solution Approach 2:
The patent maintains continuity of useful action through prolonged stirring periods (30-120 minutes per titration stage) after each acid addition. This continuous stirring ensures uniform distribution of silicic acid polymers throughout the solution, preventing localized aggregation and ensuring that all particles nucleate and grow under identical conditions, thereby achieving narrow particle size distribution while maintaining a relatively simple overall process structure
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 method effectively produces silica nanoparticles with a uniform particle size distribution ranging from 20 nm to 40 nm, enhancing the hydrophobic property of coating materials and improving their water-proof and seepage-proof effects.
Implementation Method 1
subjecting the silicic acid-enriched solution to a flame spray pyrolysis or a drying-grinding-calcining treatment to form the silica nanoparticles
Implementation Method 2
slowly titrating the sodium silicate solution with an acid solution under stirring until a pH value of the sodium silicate solution is reduced by a predetermined value so as to obtain a silicic acid-containing solution
Implementation Method 3
continuously stirring the silicic acid-containing solution until a pH value of the silicic acid-containing solution becomes constant
Implementation Method 4
subjecting the silicic acid-enriched solution to a flame spray pyrolysis or a drying-grinding-calcining treatment to form the silica nanoparticles
Data Source
AI summary
A method for preparing silica nanoparticles includes the steps of: slowly titrating a sodium silicate solution with an acid solution to obtain a silicic acid-containing solution; continuously stirring the silicic acid-containing solution; slowly titrating the silicic acid-containing solution with the acid solution to obtain a silicic acid-enriched solution; continuously stirring the silicic acid-enriched solution; collecting the silicic acid-enriched solution as a silica nanoparticle precursor solution when a pH value of the silicic acid-enriched solution reaches a target pH value; and subjecting the silica nanoparticle precursor solution to a flame spray pyrolysis or a drying-grinding-calcining treatment.