Tin(II) Complex Adjuvant for Chromium Reduction
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Solution Overview
Problem
Current adjuvants for reducing Cr(VI) ions in hydraulic binders are unstable in aqueous solutions, prone to oxidation, and lose effectiveness over time, requiring precise dosing and being corrosive, which complicates their use and storage, especially in alkaline environments, and fail to maintain chromium (VI) levels below the regulatory threshold of 2 ppm.
Innovation Solution
A stable aqueous solution of a tin(II) complex with a carboxylic acid or its salt, such as gluconic acid, is used to reduce Cr(VI) ions to Cr(III), which is stable across a wide pH range, non-corrosive, and maintains effectiveness over time, allowing for the preparation of materials with chromium (VI) content below 2 ppm without altering the properties of the treated materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Fe(II) sulfate is used as a chromium(VI) reducing agent, then chromium (VI) content is reduced, but the adjuvant loses effectiveness quickly due to oxidation of Fe(II) ions in contact with air and requires precise dosing equipment
Solution Approach 1:
The patent changes the chemical form of the reducing agent from simple Fe(II) sulfate to a complexed form where Fe(II) is coordinated with ligands (such as EDTA, citric acid, or tartaric acid). This parameter change in molecular structure protects the Fe(II) ions from oxidation by air, maintaining their reducing effectiveness throughout storage and extending the duration of action from hours to months.
2Stability of the object's composition
If tin(II) ions are used in very acidic pH conditions to maintain stability, then the adjuvant remains stable, but expensive corrosive-resistant equipment is required
Solution Approach 1:
The patent changes the pH parameter from very acidic (pH < 2) to near-neutral or slightly alkaline conditions (pH 6-9) by using complexing agents that stabilize tin(II) ions through coordination chemistry. This allows the adjuvant to maintain stability without requiring corrosive-resistant equipment, as the complexed tin(II) remains stable in a much wider pH range.
3Stability of the object's composition
If powder form adjuvants are used to maintain stability, then oxidation is reduced, but precise dosing becomes delicate and requires specific equipment
Solution Approach 1:
The patent changes the physical state parameter from solid powder to liquid solution form. The adjuvant is provided as an aqueous solution containing complexed Fe(II) or tin(II) ions, which maintains stability against oxidation while allowing for easy and precise dosing using standard liquid measurement equipment. The solution form eliminates the need for specialized powder handling and dosing equipment.
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 solution provides a stable and effective means to reduce chromium (VI) content in hydraulic binders to below 2 ppm, meeting regulatory requirements, while being non-corrosive and maintaining stability across various pH levels, ensuring long-term effectiveness and compatibility with existing manufacturing processes.
Implementation Method 1
The invention relates to the use of an adjuvant for reducing Cr(VI) ions to Cr(III)... compositions containing Fe(II) sulfate can be used as a chromium(VI) reducing agent... Tin(II) ions tend to oxidize to tin(IV), which reduces the effectiveness of the adjuvant
Data Source
AI summary
The invention concerns an adjuvant for reducing chromium (VI) ions into chromium (III) comprising a tin (II) complex and a carboxylic acid or one of its salts, as well as a method for preparing same. The invention also concerns a method for preparing a material with reduced chromium (VI) content. The invention further concerns the use of said adjuvant for reducing chromium (VI) ions into chromium (III).