Cr(VI) Reducing Mixture Using Iron Silicate and Ferrous Sulphate

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Solution Overview

Problem

Current reducing agents for hexavalent chromium in cement, such as tin sulphate and ferrous sulphate, face challenges including high cost and logistical issues due to low Fe(II) content in iron sulphate by-products, making them non-competitive in distant markets and requiring high dosages, which increases costs.

Innovation Solution

A mixture combining iron sulphate monohydrate with iron silicate from copper production and acidity neutralizing agents like dolomite or limestone, which increases the Fe(II) content and reduces the need for dolomite, enhancing the reducing capacity and stability of the final product.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferrous sulphate is used as a reducing agent for Cr(VI) in cement, then the reduction effectiveness is improved, but the logistical cost increases due to low Fe(II) content in by-products requiring high dosages

Engineering Contradiction:

Improvereduction effectivenessVSAvoiddosage of reducing agent

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent combines iron sulphate monohydrate (providing Fe(II) for reduction) with iron silicate from copper production (providing additional Fe(II) and structural stability) and acidity neutralizing agents (dolomite or limestone). This composite mixture achieves up to 17% Fe(II) content, significantly higher than conventional ferrous sulphate by-products, thereby reducing the required dosage while maintaining reduction effectiveness.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the chemical composition parameters of the reducing agent by incorporating iron silicate and acidity neutralizing agents alongside iron sulphate monohydrate. This parameter modification increases the Fe(II) content from typical low levels in by-products to up to 17%, directly addressing the dosage issue while preserving reduction capability.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If iron sulphate by-products with low Fe(II) content are used, then the cost is reduced, but the logistical competitiveness in distant markets deteriorates due to high dosages required

Engineering Contradiction:

ImprovecostVSAvoidlogistical competitiveness

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

By creating a composite reducing mixture that incorporates iron silicate (an industrial by-product from copper production) alongside iron sulphate monohydrate, the invention increases the Fe(II) content to up to 17%. This allows the product to remain cost-effective (utilizing industrial by-products) while improving logistical competitiveness through reduced dosage requirements in distant markets.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention utilizes industrial by-products (iron silicate from copper production and iron sulphate monohydrate from titanium dioxide production) as raw materials, allowing the system to serve itself by converting waste streams into a high-value reducing agent with superior Fe(II) content, thereby reducing manufacturing costs while improving market competitiveness.

Inventive Principle:

Principle #25Self-service

3Reliability

If the dosage of reducing agent is increased to compensate for low Fe(II) content, then the reduction of Cr(VI) is maintained, but the operational cost increases

Engineering Contradiction:

Improvereduction of Cr(VI)VSAvoidoperational cost

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The composite reducing mixture containing iron sulphate monohydrate, iron silicate, and acidity neutralizing agents achieves up to 17% Fe(II) content, maintaining reliable Cr(VI) reduction while reducing the required dosage and thereby lowering operational costs associated with transportation, handling, and application of the reducing agent.

Inventive Principle:

Principle #40Composite materials

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 new mixture achieves a higher Fe(II) content of up to 17%, improving competitiveness and reducing logistical and operational costs, while effectively converting hexavalent chromium to trivalent chromium, meeting regulatory standards with lower dosages.

Implementation Method 1

The hexavalent chromium in cement can be reduced to trivalent chromium, a substance that is harmless to the skin, using elements with a reducing action. The reduction reaction that occurs when ferrous sulfate is used as a chemical reducer is as follows: CrO4 2-

Methodology Applied

Scientific EffectRedox reactions: Redox Reactions

Implementation Method 2

a mixture combining iron sulphate monohydrate with iron silicate from copper production and acidity neutralizing agents like dolomite or limestone

Methodology Applied

Scientific EffectNeutralization reaction: Chemical Bonding

Data Source

PatentEP4159701A1Mixture for reducing cr(VI) contained in cement to cr(III)

Publication Date: 2023.04.05 ADITIVOS DEL CEMENTO SL

Figure 1~2

AI summary

The reducing mixture of Cr (VI) contained in cements is a mixture of two industrial by-products:on the one hand, filter cake of ferrous sulphate (Filter Salt), as a residue of the manufacture of TiO2 and, on the other, slag of iron silicate from the production of electrolytic copper, to which is added a natural aggregate in a small proportion which acts as a neutralizer of the acidity of the ferrous sulphate (dolomite, calcite and/or slaked lime).