DESALT ED TEST KIT Operating Manual
- Gu Zhouying
- Mar 26
- 6 min read
Updated: Apr 3
What is Electrodialysis?
Electrodialysis (ED) is an electrochemical separation process used to remove ions from aqueous solutions using ion-exchange membranes and an electric field. It is commonly applied in desalination, wastewater treatment, and the recovery of valuable chemicals.
1.1 Mechanism:
An electric field is applied across a stack of alternating cation-exchange membranes (CEMs) and anion-exchange membranes (AEMs).
Cations (positively charged ions) migrate toward the cathode, passing through CEMs but blocked by AEMs.
Anions (negatively charged ions) migrate toward the anode, passing through AEMs but blocked by CEMs.
This results in the separation of ions, creating a diluted stream (low ion concentration) and a concentrated stream (high ion concentration).
ABOUT DESALT LAB TEST？
2.1. ED LAB TEST EQUIPMENT INTRODUCTION
The DESALT Electrodialysis (ED) Lab Test Equipment is a compact, modular system designed for testing and optimizing ion removal processes. It is ideal for research, pilot studies, and small-scale applications.
Key Features:
Modular Design: Allows easy assembly and customization based on specific testing requirements.
Precision Control: Equipped with adjustable voltage, current, and flow rate settings for accurate experimentation.
Real-Time Monitoring: Includes sensors for pH, conductivity, and temperature to track process performance.
Scalable: Test results can be directly used to design larger-scale ED systems.
2.2. CUSTOMIZE FOR DIFFERENT BRAND MEMBRANE
The DESALT Lab Test Equipment is highly versatile and can be customized to accommodate membranes from various brands. This ensures compatibility with specific project requirements and allows for comparative testing of membrane performance.
Customization Options:
Membrane type (CEM, AEM, bipolar).
Stack configuration (number of cell pairs, flow distribution).
Integration with existing lab setups.
2.3. SCALE UP ACCORDING TO THE TEST RESULT
The DESALT Lab Test Equipment is designed to provide reliable data that can be directly used for scaling up to industrial systems.
Scaling Process:
Test results from the lab equipment are analyzed to determine optimal operating conditions (e.g., voltage, flow rate, membrane type).
These parameters are used to design larger-scale ED or BPED systems with confidence in their performance.
3. How to run the test?
3.1. How to install the equipment
Before starting the test, ensure the following preparations are completed:
ED flow chart (Fig 3.1) is given below for how to connect the equipment:
Equipment Check:
Verify that all components of the DESALT ED/BPED test kit are present and in good condition.
Inspect membranes, pumps, tubing, and electrical connections for any damage or leaks.
Solution Preparation:
Prepare the feed solution (e.g., brackish water, wastewater, or salt solution) according to the test requirements.
Ensure the concentrate and electrode rinse solutions are ready.
Calibration:
Calibrate sensors (e.g., pH, conductivity, temperature) to ensure accurate data collection.
Safety Measures:
Wear appropriate personal protective equipment (PPE) such as gloves and safety goggles.
Ensure the workspace is clean and free of obstacles.
3.2. ED Flow Chart for How to Connect the Equipment
The flow chart below illustrates the steps to connect the DESALT ED Lab Test Equipment:
Feed Solution Tank:
Connect the feed solution tank to the feed pump (P101).
Feed Pump (P101):
Pump the feed solution into the ED stack.
ED Stack:
Connect the feed inlet (SKID IN) to the ED stack.
Connect the dilute outlet (SKID OUT) to the diluent tank.
Connect the concentrate outlet (SKID OUT) to the concentrate tank.
Electrode Rinse Solution:
Connect the electrode rinse solution tank to the electrode rinse pump (P201).
Pump the electrode rinse solution through the electrode compartments.
Power Supply:
Connect the power supply to the ED stack and set the desired voltage/current.
Monitoring:
Use sensors (T10, T20, T30) to monitor temperature, conductivity, and pH during the test.
Return to Tank:
Return the dilute and concentrate streams to their respective tanks for recirculation or disposal.
3.3. POWER-ON OPERATION
Begin by starting the electrode solution pump, followed by the feed liquid pump, acid liquid pump, and alkali liquid pump. The flow rate in the electrode chamber should generally be maintained at 3–4 cm/sec, while the flow rate in the concentrate and dilute channels should be controlled at 4–6 cm/sec. (The typical pressure drop is around 0.3-0.5 bar for a flow velocity of 3-4 cm/sec. The flow (L/hr) can be calculated based on the flow velocity (3-4cm/sec), spacer thickness (0.55mm), spacer effective width, and cell pair numbers).
Adjust the flow rates to ensure the inlet flow and pressure of each feed solution are approximately equal. Circulate each solution for 3–5 minutes to ensure all compartments are filled with liquid and any air bubbles are fully expelled.
Next, connect the positive terminal (red) of the DC power supply to the anode lead of the electro-dialyzer and the negative terminal (black) to the cathode lead. Power the electro-dialyzer using the DC power supply, which can operate in either constant current or constant voltage mode.
Important:
The recommended applied voltage should be maintained at ≤1.0V per repeating unit;
The recommended current density should be maintained at ≤500 A/m2;
For 10 pairs ED stack, the test voltage is 10 pairs * 1V/pair + 5 V (electrolyte room ) = 15V
3.4. POWER-OFF OPERATION
When the treatment reaches the expected results, first gradually reduce the voltage and current of the DC power supply to 0, then turn off the feed pumps, and then replace the feed solutions with deionized water to rinse the membrane stack and equipment components.
3.5. GENERAL MAINTENANCE
If the unit leaks internally or externally, tighten the unit further; if the condition does not improve, the membrane or diaphragm may need to be replaced.
After the experiment, please rinse the feed liquid or electrode liquid in the electro-dialyzer, solution tank, and water pump. If the equipment is not used for a long time, please inject 5% NaCl solution to preserve the electro-dialyzer membranes.
3.6. CLEANING PROCEDURES
If a partial blockage occurs in the electro-dialyzer, indicated by a rise in pressure or a drop in flow rate, the equipment must be cleaned. Cleaning involves both backwashing and chemical cleaning.
Note: Ensure the DC power supply is turned off during all cleaning procedures.
Backwashing Procedure:
Reverse the inlet and outlet water pipes of the desalination and concentration chambers of the electro-dialyzer, so the water flows in the opposite direction to the original configuration. If the electro-dialyzer is partially blocked, backwash it with deionized water for at least 30 minutes.
Chemical Cleaning Procedure (if backwashing is insufficient):
Inorganic Salt Deposits:
Rinse the electro-dialyzer with deionized water.
Inject 1% hydrochloric acid and let it sit for more than 30 minutes.
Rinse thoroughly with clean water.
Repeat the process if necessary, depending on the severity of the blockage.
Organic Pollutants:
Rinse the electro-dialyzer with deionized water.
Inject 1% sodium hydroxide and let it sit for more than 10 minutes.
Rinse thoroughly with clean water.
Repeat the process if necessary, depending on the level of contamination.
Bacterial Growth:
Rinse the electro-dialyzer with deionized water.
Inject clean water containing 20 ppm free chlorine and let it sit for more than 10 minutes.
Rinse thoroughly with clean water.
Repeat the process if necessary, depending on the degree of contamination.
4. How to do data analysis
4.1 Expected test results of ED
Ion Removal Efficiency:
A significant reduction in ion concentration in the dilute stream (e.g., 80-95% removal of target ions like Na⁺, Cl⁻).
A corresponding increase in ion concentration in the concentrate stream.
13% - 18% concentration salt solution.
Energy Consumption:
Measured in kWh/m³ of treated water, typically ranging from 0.5 to 2.5 kWh/m³ depending on feed salinity and operating conditions.
Flow Rates:
Stable flow rates for feed, dilute, and concentrate streams, indicate proper system operation.
pH and Conductivity Changes:
Slight pH variations in the dilute and concentrate streams due to ion migration.
Conductivity decreases in the dilute stream and increases in the concentrate stream.
4.2 What parameters should be recorded during the test?
To ensure accurate analysis, the following parameters should be recorded during the test:
Feed Solution:
Initial ion concentration (e.g., Na⁺, Cl⁻).
Conductivity and pH.
Temperature
Dilute Stream:
Ion concentration
Conductivity and pH.
Temperature
Electrolyte:
Conductivity
pH.
Operating Conditions:
Applied voltage and current.
Flow rates for feed, dilute, and concentrate streams.
Energy Consumption:
Total energy used (kWh/m³).
Comments