Bipolar Exchange Membrane BPM

Bipolar membranes (BPMs) Property

Bipolar electrodialysis membranes (BM) are specialized ion-exchange membranes composed of two functional groups layers,Bipolar membranes are used in bipolar electrodialysis processes to enhance the separation of ions,the BPED membranes can convert the salts into their corresponding acids and bases. They are unique because they are designed not just to transport ions, but to split water into protons and hydroxide ions because there is the bipolar layer in the middle of the membrane, the bipolar layer is also called catalytic layer whihc can generate hydrogen ions (H⁺) and hydroxide ions (OH⁻).
Generally, the bipolar electrodialysis membrane are formed by two combined ion exchange membranes: Cation-Exchange Membranes (CEMs) and Anion-Exchange Membranes (AEMs). In electrodialysis applications and under the current, these membranes allow for co-ions to pass through while stopping the counter ions.Our BPM is not a composite of a cation exchange layer (CEL) and an anion exchange layer (AEL) bonded together, our BPM is one whole membrane by chemical reaction to advoid the delamination in the operation.
CEL (Cation-Exchange Layer): The layer containing negatively charged groups (e.g., sulfonic acid) that allows cations (H+) to pass through.
AEL (Anion-Exchange Layer): The layer containing positively charged groups (e.g., quaternary ammonium) that allows anions (OH-) to pass through.
Interfacial Layer (IL): Also called the Bipolar Junction, this is the thin region where the two layers meet and where water dissociation occurs.
Water Dissociation Catalyst: Additives placed at the interface to lower the energy required to split water.

Operational Principles

Water Splitting (Dissociation): The core process where
Reverse Bias: The standard operating mode where the CEL faces the cathode and the AEL faces the anode to drive water splitting.
Forward Bias: A mode where ions are driven into the membrane to form water (used in some fuel cell applications).
Second Wien Effect: The physical phenomenon where a high electric field at the junction accelerates the rate of water dissociation.
pH Gradient: The ability of the membrane to maintain different pH environments (e.g., acidic on one side and alkaline on the other) simultaneously.
Three chambers(triplet chambers) or two chambers are available,the repeating unit of BPED is consists of a sequence of three channels(or two channels) separated by three ion-exchange membranes or two of them: anion membrane(AEM), cation membrane(CEM), and bipolar membrane (BPM).

Performance Metrics

Water Splitting Overpotential: The extra voltage required to trigger the water-splitting reaction; lower is better for energy efficiency.
Ion-Exchange Capacity (IEC): A measure of the density of active charged groups within the membrane layers.
Permselectivity: The ability of the membrane to allow specific ions to pass while blocking others (co-ions).
Area Resistance: The electrical resistance of the membrane, which dictates how much energy is lost as heat.

Applications

EDBM (Electrodialysis with Bipolar Membranes): A process used to convert salt solutions into acids and bases: under the electric potential between the two electrodes, the water dissociation reaction takes place in the interlayer of the bipolar membrane, resulting in the production of protons and hydroxide ions.Under the electric field, the ions are driven to opposite sides of the BPM based on their charge, as a result, the acidic and alkaline solutions are generated in the chambers.
Salt Splitting: The industrial process of recovering valuable chemicals from waste salts.
CO2 Electrolysis: Using BPMs to manage pH and improve the efficiency of converting carbon dioxide into fuels.
ZLD (Zero Liquid Discharge): Environmental systems that use BPMs to recycle industrial wastewater into reusable chemicals.
Water Treatment: Used for desalination, pH adjustment, and removing salts from wastewater.
In lithium recovery, Bipolar Membrane Electrodialysis (BMED) is a game-changer because it allows for the direct conversion of lithium salts into high-purity Lithium Hydroxide (LiOH), which is the preferred chemical for high-performance electric vehicle (EV) batteries.

Membrane size

40*20cm per piece
80*40cm per piece
110*55cm per piece
120*60cm per piece
other size

Practical Example 1:

A factory produces sodium sulfate (Na2SO4) waste. Using BMED, they can recycle this waste back into Sulfuric Acid (H2SO4) and Sodium Hydroxide (NaOH) to reuse in their own production line.

Practical Example 2:

in the Battery Recycling,BMED is now being used to treat the "Black Mass" from recycled batteries, recovering lithium from Li2SO4 wastewater generated during the smelting/leaching process.