Two-Stage Electrolysis for Sulfate and Halide Water Separation
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Solution Overview
Problem
Existing methods for treating sulfuric acid waters or waste solutions containing heavy metal cations and high non-carbonate hardness and salinity are inadequate in achieving sulfate reduction, halide ion separation, and introducing buffering capacity, leading to high costs, environmental issues, and non-compliance with quality standards.
Innovation Solution
A two-stage electrochemical process using anion exchange membranes without added carbon dioxide in the first stage, followed by controlled carbon dioxide introduction in subsequent stages, to precipitate cations and separate anions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical neutralization methods are used to treat sulfuric acid waters, then the pH value can be raised and acidity neutralized, but sulfate levels cannot be reduced below approximately 2 g/l and additional soluble ions increase hardness and salinity
Solution Approach 1:
The patent replaces chemical neutralization methods with an electrochemical separation system using electrodialysis cells. This system uses electric fields to drive ion migration through selective membranes, substituting chemical reactions with physical-electrical processes to achieve sulfate separation without adding neutralizing agents that increase salinity
Solution Approach 2:
The patent employs ion-selective membranes (anion-exchange and cation-exchange membranes) as thin film barriers that selectively transport ions based on their charge. These membranes enable precise separation of sulfate anions from the water stream while allowing other ions to pass or be retained according to membrane selectivity, achieving compliance with quality standards
2Manufacturing precision
If electrochemical treatment is applied to separate ions, then sulfate and halide ions can be separated, but electrolysis cell clogging occurs due to precipitate formation
Solution Approach 1:
The patent divides the electrolysis process into multiple sequential stages with different functional objectives. The first stage focuses on ion separation without CO2 addition to avoid clogging, while subsequent stages handle pH adjustment and precipitation. This segmentation allows each stage to optimize for its specific function without compromising the other
Solution Approach 2:
The patent performs ion separation as a preliminary action before pH adjustment and precipitation steps. By separating ions first in a CO2-free environment that prevents clogging, then subsequently adjusting pH and allowing controlled precipitation, the system establishes a sequence where the critical separation function is protected from the clogging risks of later chemical treatment stages
3Stability of the object's composition
If carbon dioxide is introduced during electrolysis to adjust pH, then buffering capacity can be introduced, but electrolysis cell clogging occurs due to precipitate formation
Solution Approach 1:
The patent segments the CO2 introduction into a separate stage that occurs after the ion separation stage is complete. This timing separation ensures that CO2-induced precipitation occurs only after ions have been separated, preventing clogging during the critical separation phase while still achieving pH adjustment and buffering capacity in the final treatment stage
Solution Approach 2:
The patent performs ion separation as a preliminary action before introducing CO2 for pH adjustment. This sequence ensures that the separation membranes remain clear and functional during the separation process, while CO2 is introduced later when precipitation is less likely to cause operational problems
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
Achieves >99.5% separation efficiency for sulfate and halide ions, reduces cation concentrations to trace levels, and avoids electrolysis cell clogging, enabling continuous operation and compliance with environmental regulations.
Implementation Method 1
The at least one cathode compartment and the at least one anode compartment are separated by an anion exchange membrane. Anions present in the at least one cathode compartment are transported through the anion exchange membrane into the at least one anode compartment and separated.
Implementation Method 2
these waters are introduced into a cathode compartment of a first electrolysis cell comprising at least one cathode compartment and at least one anode compartment, where they undergo electrolysis
Implementation Method 3
followed by controlled carbon dioxide introduction in subsequent stages, to precipitate cations and separate anions effectively
Data Source
AI summary
The invention relates to a process for separating anions and cations from acidic waters or waters containing sulfate and/or halide ions. In a first stage, these waters are subjected to electrolysis, and the anions and cations are separated. However, no carbon dioxide is added to these waters before or during the first stage. After electrolysis in the first stage, a further electrolysis is carried out in a second stage, during which anions and cations are separated, and any cations present are hydrolyzed and subsequently precipitated. Carbon dioxide is added to the first solution before, during, and/or after the second stage.