Arsenic Sequestration Glass Composition
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Solution Overview
Problem
Current methods for sequestrating arsenic oxides, such as the formation of ferric arsenate or vitrification, are costly, inefficient, and face challenges like high iron consumption, interference from other ions, and volatilization issues, resulting in suboptimal arsenic retention and environmental concerns.
Innovation Solution
A method involving the formation of an insoluble and stable glass composition with a specific oxide ratio, using manganese dioxide as an oxidizing agent to convert arsenious oxide to arsenic oxide, which is then stabilized with calcium hydroxide, allowing for the incorporation of up to 20% arsenic oxide into a glass structure without significant volatilization, using recycled glass to reduce costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferric arsenate formation is used to sequester arsenic, then arsenic retention is improved, but iron consumption and cost increase significantly
Solution Approach 1:
The invention changes the chemical composition parameters by using calcium oxide instead of iron salts, and adjusts the pH range to 9-13 (optimal 10-12) to optimize the precipitation reaction conditions for calcium arsenate formation, thereby achieving effective arsenic retention without excessive iron consumption
Solution Approach 2:
The invention replaces expensive ferric salts with cheaper calcium oxide as the precipitating agent. Calcium oxide is more cost-effective and readily available, reducing the overall treatment cost while maintaining effective arsenic sequestration through calcium arsenate formation
2Reliability
If scorodite formation is used to sequester arsenic, then arsenic solubility is reduced, but operational complexity and cost increase
Solution Approach 1:
The invention changes the pH parameter range to 9-13 (optimal 10-12), which is more alkaline than traditional scorodite formation, simplifying the operational conditions and reducing the need for precise pH control while achieving effective arsenic precipitation as calcium arsenate with low solubility
3Reliability
If vitrification is used to sequester arsenic, then arsenic permanence is improved, but volatilization and glass quality deteriorate
Solution Approach 1:
The invention extracts arsenic from the volatilization risk by precipitating it as solid calcium arsenate before glass formation. This separates the arsenic sequestration step from the high-temperature vitrification process, eliminating volatilization issues while maintaining permanence through the insoluble calcium arsenate precipitate
Solution Approach 2:
The invention performs preliminary precipitation of arsenic as calcium arsenate at low temperature before the glass formation process. This preliminary action removes arsenic from the system in a stable, non-volatile form, preventing volatilization during subsequent high-temperature treatment and improving both glass quality and arsenic permanence
4Quantity of substance
If traditional glass formation is used with arsenic, then arsenic incorporation is limited, but glass solubility and stability are compromised
Solution Approach 1:
The invention extracts arsenic from the glass matrix by precipitating it as solid calcium arsenate before glass formation. This removes arsenic from the glass composition entirely, allowing the glass to maintain its low solubility and high stability while still incorporating the arsenic in a separate, stable solid phase
Solution Approach 2:
The invention creates a composite system consisting of glass beads containing embedded calcium arsenate precipitate. This composite structure allows the glass to maintain its inherent low solubility while the insoluble calcium arsenate provides stable arsenic containment, achieving both high arsenic capacity and excellent stability
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 method effectively sequesters arsenic in a glass form that is insoluble and environmentally stable, with over 95% arsenic retention and minimal leaching, addressing the limitations of previous techniques by providing a cost-effective and efficient arsenic disposal solution.
Implementation Method 1
forming an insoluble and stable glass incorporating a fully oxidized form of arsenic generated by oxidation of an initial lower oxide of arsenic
Implementation Method 2
stabilization by calcium salt formation
Implementation Method 3
The method effectively sequesters arsenic in a glass form that is insoluble and environmentally stable
Data Source
AI summary
A method for sequestrating arsenic oxides, comprising forming an insoluble and stable glass incorporating a fully oxidized form of arsenic generated by oxidation of an initial lower oxide of arsenic and stabilization by calcium salt formation. The glass composition for sequestration of arsenic comprises from 50 to 75% silica; from 0.5 to 3% Al2O3; from 1 to 15% MnO; from 5 to 15% CaO; from 1 to 20% As2O5 and from 8 to 14% Na2O, less than four percent of iron oxides, magnesium oxide and other oxides.