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Questions and Answers
What is one of the primary uses of electrodialysis?
What is one of the primary uses of electrodialysis?
Electroflocculation involves the binding of pollutants to soluble oxides.
Electroflocculation involves the binding of pollutants to soluble oxides.
False
Name one application of metal recovery processes.
Name one application of metal recovery processes.
Recovery of batteries
Electrodialysis is useful for producing high purity _____ and regenerating acids/bases.
Electrodialysis is useful for producing high purity _____ and regenerating acids/bases.
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Match each process with its description:
Match each process with its description:
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Which of the following is not a common method of electrochemical separation processes?
Which of the following is not a common method of electrochemical separation processes?
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Al3+ and Fe3+ are commonly used as coagulants in electrochemical separation processes.
Al3+ and Fe3+ are commonly used as coagulants in electrochemical separation processes.
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What role do flocculants play in the separation process?
What role do flocculants play in the separation process?
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In electrocoagulation, the charge of suspended particles is shielded by __________ ions produced at a sacrificial anode.
In electrocoagulation, the charge of suspended particles is shielded by __________ ions produced at a sacrificial anode.
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Match the terms related to coagulation and flocculation with their appropriate descriptions:
Match the terms related to coagulation and flocculation with their appropriate descriptions:
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Study Notes
Environmental Electrochemistry: Lesson 1 - Separation Processes
- This document is for student use only within the "Environmental Electrochemistry" course. Copying, distribution, or disclosure is prohibited.
Electrochemical Separation Processes
- Electroflocculation
- Electrolysis
- Electrodialysis
- Electro-electrodialysis
Coagulation/Flocculation
- Coagulant: Typically a trivalent ion (e.g., Al³⁺, Fe³⁺) that neutralizes the charge of suspended particles.
- Flocculant: A polymer that aggregates particles into settleable flocs. Can be inorganic (e.g., bentonite, silica) or organic (e.g., polymers, electrolytes).
Electrocoagulation
- A process where suspended particles' charges are shielded by trivalent ions.
- These ions are created at a sacrificial anode.
- Some particles float to the surface, while heavier ones sink.
- Pollutant binding to insoluble oxides makes them non-leachable, suitable for landfills.
Electrolysis (Metal Electrodeposition)
-
Applications: Metal recovery from:
- Surface treatments processes (e.g., metal pickling)
- Exhausted electrodeposition baths
- Galvanic processes
- Water used for washing galvanic plants
- Battery recovery (e.g., Pb, Cd)
- Other industrial waste streams (e.g., tan industry)
Electrodialysis
- A useful technology for:
- Desalination/concentration
- High-purity water production
- Acid/base regeneration
- Metal recovery
- Wastewater treatment (separating ionic species like amino acids, organic acids)
- Chemical intermediate production
Membranes
- Functional groups (cationic or anionic) in membranes determine ion passage, with ions able to pass through being called counter-ions.
- Permselectivity: Preferential permeation of certain ionic species quantified by the ratio of transported charge to total charge passed through the membrane.
- Solvent Transport: Measured as moles of solvent transported across the membrane per mole of electrons.
Other Important Membrane Properties
- Chemical stability
- Thermal and mechanical stability
- Resistivity (typically expressed as R•S=p•L in Ω cm²)
- Solvents absorbed: membrane swelling
- Electrolyte uptake
Electrodialysis (Diagrammed)
- A diagram shows the flow of cations and anions across the membrane.
Other Electrodialysis Processes
- Recovery of non-electrolytes (neutral or zwitterions) – Double exchange reactions: from MX + NY to MY + NX
EED - Electro-Electrodialysis
- Utilizes ion exchange membranes and faradaic reactions (electron transfer).
- Typical example: salt recovery in acid/base.
- Transport of H⁺ and OH⁻ impacts current efficiency and energy consumption.
- Three compartments are involved, and the process involves moving ions and water.
2 Compartment EED
- Cationic membrane: Base recovery
- Anionic membrane: Acid recovery
Multicell EED
- Uses bipolar electrodes.
- Uses hydrogen evolution cathodes.
- Uses oxygen reduction cathodes.
- Membrane design improves efficiency for ion transfer.
Electrodialysis with Bipolar Membranes (EDBM)
- Bipolar membranes facilitate unidirectional ion transport.
- They're used in multiple-cell electrolytic systems to promote greater efficiency in processes such as saltwater treatment or acid/base production.
Example: HCl Electrolysis
- A diagram shows the electrolysis of HCl, including ion flow and the production of chlorine gas at the anode.
Possible Future Uses
- Catalyst recovery
- Heavy metal treatment (e.g., Chromium(VI))
- Natural product extraction
- Enantioselective separation
Reversed Electrodialysis
- Uses salinity gradients to generate electricity, transforming osmotic pressure into an electrical potential.
- Design similar to electrodialysis, with examples such as seawater and freshwater.
- The challenge lies in the low conductivity of freshwater.
SGP-RE Unit (Diagrammed)
- This diagram shows a system for utilizing a saline gradient pressure-reverse electrodialysis unit to extract energy from salty water.
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Description
Explore the key concepts of electrochemical separation processes in this lesson focused on Environmental Electrochemistry. Understand methods such as electrocoagulation, electroflocculation, and electrolysis, and their applications in removing pollutants from water. This quiz will test your knowledge of these crucial environmental techniques.
