Ag/SiO2@cTiO2 Core-Shell Photocatalyst for Nitrate Removal
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Solution Overview
Problem
Current photocatalytic materials for nitrate removal in water face challenges such as low reductive removal efficiency, poor selectivity, and instability, especially in high-concentration nitrate solutions and complex systems like high-salinity brine, due to issues with titanium dioxide-based catalysts and the reactivity of silver in the presence of chloride ions.
Innovation Solution
A core-shell structured Ag/SiO2@cTiO2 photocatalytic material is developed, where silver nanoparticles are stabilized within silicon dioxide microspheres, wrapped with an amorphous titanium dioxide shell that crystallizes to form an anatase structure, enhancing electron separation and stability through surface plasmon resonance and light scattering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If titanium dioxide-based photocatalysts are used for nitrate removal, then photocatalytic activity is achieved, but reductive removal efficiency and nitrogen selectivity are low
Solution Approach 1:
The patent uses a core-shell structured composite material Ag/SiO2@cTiO2, where silver nanoparticles are embedded in a silicon dioxide matrix and coated with a thin titanium dioxide shell. This composite structure combines the plasmonic properties of Ag, the stability of SiO2, and the photocatalytic activity of TiO2, achieving both high removal efficiency and nitrogen selectivity simultaneously
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where different materials are positioned in specific locations: Ag nanoparticles in the core for plasmonic enhancement, SiO2 matrix for structural stability, and a thin TiO2 shell on the surface for selective photocatalytic reaction. This spatial differentiation of material properties optimizes both efficiency and selectivity
2Productivity
If modified titanium dioxide photocatalysts are used, then nitrate removal effect is prominent, but stability in recycling is poor
Solution Approach 1:
The patent employs a thin SiO2 shell enclosing the Ag nanoparticles, providing mechanical protection and structural stability. The SiO2 matrix acts as a flexible yet rigid framework that maintains the photocatalyst's integrity during recycling, preventing particle aggregation and material leaching while preserving photocatalytic activity
Solution Approach 2:
The composite Ag/SiO2@cTiO2 structure enhances stability through the robust SiO2 matrix that protects the soft Ag nanoparticles from oxidation and aggregation during repeated use, while the thin TiO2 shell maintains photocatalytic functionality across multiple recycling cycles
3Productivity
If silver is added to enhance photocatalytic activity, then reduction efficiency improves, but silver reacts with chloride ions to produce silver chloride and becomes inactive
Solution Approach 1:
The patent introduces SiO2 as an intermediary material that physically separates and protects the Ag nanoparticles from direct contact with chloride ions in the solution. The SiO2 matrix acts as a protective barrier, allowing Ag to maintain its plasmonic properties and photocatalytic activity without reacting with Cl- to form inactive AgCl
Solution Approach 2:
The SiO2 matrix forms a protective shell around the Ag nanoparticles, creating a physical barrier that prevents chloride ions from reaching and reacting with the silver surface, thereby maintaining reduction efficiency in the presence of chloride
4Productivity
If complex modification processes are applied to improve photocatalytic performance, then removal efficiency increases, but preparation process becomes extremely cumbersome
Solution Approach 1:
The patent uses a one-pot solvothermal synthesis method where all components (Ag nanoparticles, SiO2 matrix, and TiO2 shell) are assembled simultaneously in a single reaction step. The preliminary preparation of Ag nanoparticle solution and controlled hydrolysis of TEOS during the solvothermal process enable straightforward formation of the core-shell structure without multiple complex modification steps
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 Ag/SiO2@cTiO2 material achieves high nitrate reduction activity and selectivity, maintaining stability even in the presence of chloride ions, effectively removing high-concentration nitrates and demonstrating improved photocatalytic performance compared to traditional titanium dioxide-based catalysts.
Implementation Method 1
enhancing electron separation and stability through surface plasmon resonance
Implementation Method 2
wrapped with an amorphous titanium dioxide shell that crystallizes to form an anatase structure
Implementation Method 3
enhancing electron separation and stability through surface plasmon resonance and light scattering effects
Implementation Method 4
adding a sodium borohydride solution dropwise to a resulting mixed solution at room temperature, and vigorously stirring to obtain a yellow-brown silver nanoparticle sol solution
Implementation Method 5
adding a small amount of tetraethyl orthosilicate (TEOS) dropwise to a mixed solution of water, ammonia water, and isopropyl alcohol (IPA), vigorously stirring a resulting mixture in a water bath to continue a reaction to obtain a silicon dioxide (SiO2) seed
Data Source
AI summary
A photocatalytic material for efficient photocatalytic removal of a high-concentration nitrate, and a preparation method and use thereof are disclosed. The preparation method includes the following steps: step 1: preparation of a citrate-stabilized silver nanoparticle; step 2: synthesis and functionalization modification of SiO2 step 3: preparation of Ag/SiO2; and step 4: preparation of an Ag/SiO2@cTiO2 core-shell structure. The photocatalytic material prepared by the present disclosure has high reduction catalytic activity and can quickly remove a high-concentration nitrate and achieve high nitrogen selectivity. In addition, due to protection of a titanium dioxide shell, the photocatalytic material has excellent stability and can remove a high-concentration nitrate in water when the nitrate coexists with a high-concentration chloride ion.