Antimony(III) Cement Additive for Hexavalent Chromium Reduction

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Solution Overview

Problem

Current methods for reducing hexavalent chromium in cement, such as using Iron(II) and Tin(II) salts, are inefficient due to oxidation issues and incompatibility with high free lime content, leading to incomplete reduction and adverse effects on cement properties.

Innovation Solution

The use of antimony(III) compounds, specifically antimony(III) oxide, inorganic salts, or organometallic compounds, added in liquid form or suspension to cement before, during, or after grinding, which act as strong reducing agents in alkaline conditions to convert hexavalent chromium to less toxic chromium(III), without being affected by free lime content.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Iron(II) salts are used as reducing agents, then hexavalent chromium can be reduced to chromium(III), but the reducing effect is lost due to oxidation by air and moisture, requiring several times higher dosage than stoichiometric

Engineering Contradiction:
Improvereducing effect stabilityVSAvoidamount of reducing agent required
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent changes the chemical state of the reducing agent from solid powder to liquid form, which prevents oxidation by air and moisture. This parameter change (physical state) maintains the reducing effect stable and eliminates the need for excessive dosages, resolving the contradiction between reliability and quantity required

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent uses a liquid reducing agent that is stable and does not oxidize like traditional solid Iron(II) salts. This allows using the reducing agent efficiently without waste, eliminating the need for continuous replenishment or excessive dosing to compensate for oxidation losses

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

2Productivity

If Tin(II) salts are used as reducing agents, then better reducing performance is achieved with stoichiometric dosages, but Tin(II) is oxidized by air and dismutates to Tin(0) and Tin(IV) before chromium reduction can occur

Engineering Contradiction:
Improvereducing efficiencyVSAvoidreducing effect longevity
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent changes the physical state from solid to liquid, which fundamentally alters the chemical stability. The liquid form prevents the oxidation and dismutation reactions that occur in solid Tin(II) salts when exposed to air, maintaining both high productivity and reliability simultaneously

Inventive Principle:
Principle #35Parameter changes

3Reliability

If stannous salts are used in grinding of clinker with high amount of free lime, then hexavalent chromium reduction is attempted, but stannous hydroxide is formed and quickly oxidized to Tin(IV), requiring increased Tin(II) amount

Engineering Contradiction:
Improvechromium reduction effectivenessVSAvoidTin(II) dosage
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses liquid antimony(III) compounds instead of solid stannous salts. The liquid form combined with antimony(III)'s chemical properties prevents rapid oxidation even in the presence of free lime, maintaining effective chromium reduction at stable dosages without the need for increased amounts

Inventive Principle:
Principle #35Parameter changes

4Reliability

If Iron(II) sulphate is used at high dosages to ensure sufficient reduction, then hexavalent chromium is reduced, but extended setting time occurs in cementitious systems

Engineering Contradiction:
Improvechromium reduction completenessVSAvoidcement setting time
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent changes both the chemical composition (from Iron(II) to antimony(III)) and physical state (to liquid form). This combination achieves complete chromium reduction at lower, controlled dosages that do not interfere with cement setting properties, resolving the contradiction between reduction completeness and setting time

Inventive Principle:
Principle #35Parameter changes

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

Antimony(III) compounds effectively reduce hexavalent chromium to a significant extent, outperforming traditional reducing agents like Iron(II) and Tin(II) salts, especially in cements with high free lime content, while ensuring environmental and safety benefits through liquid form usage.

Implementation Method 1

the antimony(III) is a strong reducing agent in alkaline solution and can effectively reduce chromium(VI) to less toxic and less soluble chromium(III)

Methodology Applied
Scientific EffectRedox reactions: Redox Reactions

Data Source

PatentEP2077979B2Additives and methods for reducing hexavalent chromium in cement
Publication Date: 2016.04.27 MAPEI SPA

AI summary

A method for reducing hexavalent chromium in cement comprising the addition, to said cement, of antimony(lll) compounds as reducing agents.