Polymer-Embedded Reducing Agents for Cement Chromium Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for reducing hexavalent chromium in cements, such as using iron(II) sulphate, tin(II) sulphate, and antimony trioxide, pose health and environmental risks due to their toxicity and potential for dust release during handling and use, and lack effective encapsulation methods to prevent abrasion-induced dust release.
Innovation Solution
Embedding a suitable reducing agent, like antimony trioxide, in a polymer matrix with high solubility in alkaline conditions and mechanical resistance, using extrusion technology to create granules that prevent dust release and ensure controlled particle size distribution, allowing safe handling and effective reduction of hexavalent chromium in cements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If reducing agents like iron(II) sulphate, tin(II) sulphate, or antimony trioxide are added during cement grinding or storage, then hexavalent chromium is reduced to trivalent chromium, but dust release during handling poses health risks to operators
Solution Approach 1:
The reducing agent particles are encapsulated within polymer capsules, creating a nested structure where the active ingredient is contained inside a protective shell. This prevents dust release during handling while maintaining the reducing agent's effectiveness in converting Cr(VI) to Cr(III) when released in the cement matrix.
Solution Approach 2:
A polymer shell is formed around the reducing agent particles to create a protective barrier. The shell prevents dust release during handling and storage, while being designed to degrade or release the reducing agent under the alkaline conditions of cement hydration, thus eliminating harmful dust exposure while maintaining chemical effectiveness.
2Object-generated harmful factors
If antimony trioxide is dispersed in a liquid carrier, then dust release is eliminated, but the liquid additive cannot be used during cement bagging due to mixing difficulties
Solution Approach 1:
The reducing agent is transformed from a liquid dispersion into solid polymer-embedded particles. This parameter change in physical state allows the additive to be easily handled as a powder during bagging operations, eliminating the mixing difficulties associated with liquid carriers while maintaining the benefit of reduced dust release through polymer encapsulation.
3Ease of operation
If antimony trioxide is used in powder form, then it can be used during cement bagging, but it is considered a suspected carcinogen by inhalation
Solution Approach 1:
The antimony trioxide powder is nested within polymer capsules, creating a hierarchical structure that maintains the powder form for easy handling during bagging operations while preventing inhalation exposure. The polymer shell acts as a protective barrier that releases the active ingredient only under cement hydration conditions.
Solution Approach 2:
A polymer shell encapsulates the antimony trioxide particles, creating a protective barrier that prevents inhalation of the carcinogenic powder during handling. The shell is designed to degrade or release the reducing agent under alkaline conditions, thus eliminating inhalation risks while maintaining handling flexibility.
4Object-affected harmful factors
If tin sulphate or tin chloride are used as reducing agents, then hexavalent chromium is reduced effectively, but severe burns can occur upon contact with skin or eyes
Solution Approach 1:
A polymer shell is formed around the tin sulphate or tin chloride particles to create a protective barrier that prevents direct contact with skin and eyes, thus eliminating the risk of severe burns. The shell is designed to degrade under alkaline conditions, releasing the reducing agent only when needed in the cement matrix.
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 polymer-embedded reducing agents maintain efficacy in reducing hexavalent chromium while eliminating environmental and health risks associated with dust release, ensuring safe handling and controlled release in alkaline environments, thus meeting the European Community's soluble chromate level requirements.
Implementation Method 1
Cr(VI) is chemically reduced to Cr(III) that is less toxic and precipitates in the alkaline conditions commonly found during the hydration of cement
Implementation Method 2
polymers suitable for use in the method according to the invention are characterized by good solubility in alkaline conditions
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3
AI summary
A method is described for reducing hexavalent chromium in common cements and cement based materials comprising the addition, to said cements, of a suitable reducing agent embedded in a polymer matrix consisting of polyvinyl acetate (PVA), polyvinyl alcohol (PVOH), polyglycolic acid (PGA), polyglycolic acid/lactic acid copolymers (PGA/PLA), polyacrylic acid (PAA), maleic polyanhydride (PMA), acrylic or methacrylic acid/acrylic ester/styrene copolymers, acrylic or methacrylic acid/maleic anhydride copolymers, ethylene/maleic anhydride copolymers, polyester/maleic anhydride copolymers, ethylene oxide/polyethylene oxide copolymers.