Electrolyte Cr(VI) Removal Using Fe(II) Ion Exchange
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Solution Overview
Problem
Existing methods for removing Cr(VI) ions from aqueous electrolyte solutions in electrochemical machining either lead to the accumulation of foreign ions, such as sulfate ions, or result in undesirable degradation products, necessitating frequent solution renewal and process fluctuations.
Innovation Solution
The method involves adding Fe(II) ions from an aqueous salt solution that has been treated with an ion exchange resin, preventing the introduction of counterions and allowing for continuous reduction of Cr(VI) to Cr(III) ions, which can then be precipitated out of the solution using an ion exchange resin, enabling continuous operation without foreign ion contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Fe(II) sulfate solution is used for reduction of Cr(VI) ions, then Cr(VI) is effectively reduced to Cr(III), but sulfate ions accumulate in the electrolyte solution causing process fluctuations
Solution Approach 1:
The patent extracts only the necessary component (Fe(II) ions) from the conventional Fe(II) sulfate solution by using an ion exchange resin to selectively release Fe(II) ions while retaining sulfate ions on the resin. This allows the reduction reaction to proceed without introducing harmful sulfate ions into the electrolyte solution.
Solution Approach 2:
The ion exchange resin acts as an intermediary between the Fe(II) sulfate solution and the electrolyte. It selectively releases Fe(II) ions into the electrolyte while retaining sulfate ions, thereby mediating the reduction process without allowing contaminant ions to enter the electrolyte system.
2Loss of substance
If ascorbic acid is used for reduction of Cr(VI) to Cr(III), then no foreign ions are introduced, but degradation products remain in the electrolyte causing secondary reactions
Solution Approach 1:
The patent uses a disposable or regenerable ion exchange resin that can be replaced or regenerated when exhausted. This allows continuous operation without accumulating degradation products, as the resin can be regenerated by washing with acid to restore Fe(II) ions and remove accumulated contaminants.
3Reliability
If batchwise processing with iron(II) sulfate is used, then Cr(VI) reduction is achieved, but frequent electrolyte renewal is required due to sulfate accumulation
Solution Approach 1:
The patent enables continuous operation by using an ion exchange resin that can continuously release Fe(II) ions into the flowing electrolyte without requiring batch processing or frequent interruptions for electrolyte renewal. The resin maintains a steady supply of reducing agents while retaining sulfate ions.
Solution Approach 2:
The patent recovers and retains sulfate ions on the ion exchange resin while discarding them from the electrolyte system. The resin is periodically regenerated by washing with acid to restore Fe(II) ions, allowing continuous operation without sulfate accumulation in the electrolyte.
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 effectively reduces Cr(VI) ion concentrations by over 50% and allows for continuous operation without introducing foreign ions, maintaining electrolyte quality and reducing process fluctuations.
Implementation Method 1
reduction of the Cr(VI) ions to Cr(III) ions by addition of an aqueous solution comprising Fe(II) ions
Implementation Method 2
adding Fe(II) ions from an aqueous salt solution which had previously been brought into contact with an ion exchange resin loaded with Fe(II) ions
Implementation Method 3
Accumulating metal hydroxide precipitate can be subsequently removed from the electrolyte solution thus treated
Data Source
AI summary
The invention relates to a method for removing Cr(VI) ions from an aqueous electrolyte solution, particularly an electrolyte solution for electrochemical metal machining, which comprises the reduction of Cr(VI) to Cr(III) with Fe(II) ions. The Fe(II) ions are added to the electrolyte solution in the form of an aqueous salt solution which has been brought into contact with an ion exchange resin loaded with Fe(II) ions. The invention further relates to a device (1) for electrochemical machining of a workpiece (2) by means of an aqueous electrolyte solution (6), which has an ion exchanger (11) which has been loaded with an ion exchange resin charged with Fe(II) ions.