Weak-Acid Leaching for Metal Recovery from Industrial Byproducts
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Solution Overview
Problem
Conventional acid leaching processes for extracting metals from industrial waste residues are costly due to high acid consumption and generate significant carbon emissions, and the separation of leached components is complex, while silica gels formed during leaching have poor filterability and flow properties.
Innovation Solution
The use of a weak acid for leaching, combined with controlled pH variations in sequential reaction chambers, reduces acid consumption and carbon emissions, and produces suitable pozzolanic materials and concentrated streams of valuable metals, using electrochemical systems to regenerate acids and bases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong acid is used for leaching to extract metals from industrial waste residues, then metal extraction efficiency is improved, but acid consumption increases and separation complexity increases
Solution Approach 1:
The patent changes the chemical parameter of the leaching agent from strong acid to weak acid (such as acetic acid, citric acid, or lactic acid). This parameter change reduces acid consumption while maintaining effective metal extraction, as weak acids selectively dissolve metal oxides without excessive acid consumption and generate fewer harmful byproducts.
Solution Approach 2:
The patent applies selective leaching where the weak acid targets specific metal oxides (such as calcium, magnesium, and other valuable metals) while leaving other components (like silica and alumina) relatively unaffected. This local quality approach allows efficient extraction of desired metals with reduced acid consumption and simplified separation of leached components.
2Productivity
If strong acid is used for leaching to extract metals from industrial waste residues, then metal extraction efficiency is improved, but separation complexity increases
Solution Approach 1:
The patent applies selective leaching where the weak acid targets specific metal oxides (such as calcium, magnesium, and other valuable metals) while leaving other components (like silica and alumina) relatively unaffected. This local quality approach allows efficient extraction of desired metals with reduced acid consumption and simplified separation of leached components.
3Productivity
If carbon dioxide or carbonates are used to precipitate calcium carbonate and magnesium carbonate, then alkali metal extraction is improved, but carbon emissions increase
Solution Approach 1:
The patent converts the harmful effect of carbon emissions into a beneficial process by using carbonated brine (a byproduct of the electrolysis process) to precipitate calcium and magnesium as carbonates. This approach utilizes what would otherwise be a waste stream, reducing the need for external carbon sources and minimizing additional carbon emissions while maintaining effective alkali metal extraction.
Solution Approach 2:
The system uses its own byproduct (carbonated brine from electrolysis) to perform the precipitation function, making the process self-sufficient. The carbonated brine generated during acid regeneration is directly used for calcium and magnesium precipitation, eliminating the need for external carbon dioxide sources and reducing overall carbon emissions.
4Area of stationary object
If silica gels are formed during leaching, then surface area is improved, but filterability and flow properties worsen
Solution Approach 1:
The patent changes the pH parameter during the leaching process to control silica gel formation. By maintaining specific pH ranges and using weak acids, the process minimizes excessive silica gel precipitation while preserving beneficial surface area characteristics. This parameter control prevents the formation of problematic silica gels that would otherwise impair filterability and flow properties.
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
This approach decreases acid usage, lowers environmental impact, and generates high-value metal products like magnesium hydroxide and iron oxides, improving the economic viability and environmental sustainability of the process.
Implementation Method 1
supplying a feedstock material comprising an alkaline earth metal and an weak acid to a first reaction chamber to form a first process stream comprising an alkaline earth metal salt
Implementation Method 2
supplying the first process stream and hydroxide containing base to one or more additional reaction chambers to form one or more precipitated oxide or hydroxide products
Implementation Method 3
using electrochemical systems to regenerate acids and bases
Data Source
AI summary
Disclosed herein are acid-base leaching methods and systems. Specifically, the systems and methods can include reacting a feed material comprising at least two metals selected from the group consisting of iron, magnesium, and calcium with a weak acid to produce a first leachate comprising ions of the at least two metals and an insoluble product; reacting the first leachate with a base to produce a first solid product comprising a first metal and a second leachate comprising ions of a second metal different from the first metal; and reacting the second leachate with the base to produce a second solid product comprising the second metal and a third leachate.