membranes for water treatment processes

Membranes for Electrodialysis with bipolar Membranes (EDBM)

Membranes for EDBM applications are typically used to produce and concentrate acids and bases. Examples are recovery of lithium (as lithium oxide) or salt splitting of sodium sulfate into sodium hydroxide and sulfuric acid, e.g. in the paper industry.

In this process, the FBM-type bipolar membrane generates H+ and OH- ions via water splitting. The corresponding anions for acid production (e.g., sulfate or chloride) and cations for base production (e.g., sodium or potassium) are provided from a salt solution via selective anion-exchange membranes (e.g. FAB) and cation-exchange membranes (e.g. FKL).

In this way, salts like lithium sulfate or sodium sulfate are converted into sulfuric acid and LiOH or NaOH.

Other organic or inorganic salts can be treated in the same way to produce corresponding acid and base.

Typical properties: Membranes for EDBM

Note:
(1) Measured in 0,5 M NaCl solution @25°C

Membranes for Elektrodialysis (ED)

Membranes for Electrodialysis are used for the desalination and/or concentration of saline water or salt solutions.

The Electrodialysis process is based on alternating arrangement of cation-exchange and anion-exchange membranes within a two-circuit system. The ion concentration in the dilute stream is reduced, the ions migrate into the concentrate chambers, producing both a desalinated and a concentrated solution. The process can be operated as well as electrodialysis reversal (EDR). In this specific mode of operation, the polarity of the electrodes and the dilute and concentrate chambers are reversed at regular intervals.

Typical applications of Electrodialysis is the desalination of process water in the food and beverage industry or other industries that use saline solutions.

Typical properties: Membranes for Electrodialysis (ED)

Note:
(1) Measured in 0,5 M NaCl-solution @25°C

Membranes for Diffusiondialysis (DD)

Membranes for diffusion dialysis are used for the recovery and concentration of acids and bases.

Two membranes are available for acid dialysis: the FAD membrane for standard applications and the FAPQ membrane for applications that require improved oxidation resistance.

All membranes can be applied in flat-sheet or spiral-wound modules.

Typical properties: Membranes for Diffusion Dialysis (DD)

Note:
(1)FAD membranes have limited oxidation stability against oxidants like free chlorine, H2O2, HNO3..; FAPQ membranes have a superior stability and can be applied for solutions containing HF.

Membranes for Electrodeionization (EDI) and Electro-Coat (E-Coat)

The Electrodeionization process is used to produce pure water and ultrapure water with a resistivity of up to 18 MΩ cm.

In Electro-coat (electro-deposition), the paint is applied to the component using an electric field.

Typically, thicker, micro-heterogeneous membranes with high mechanical stability are used for these applications. These membranes can be used in both spiral-wound and flat-sheet membrane modules.

Typical properties: Membranes for EDI and Electro-Coat

Note:
(1) Measured in 0,5 M NaCl-solution @25°C

Membranes for Capacitive Deionization (CDI) and Electrodialysis Reversal (EDR)

Membranes used for CDI and EDR applications are typically thin-film types that offer high energy efficiency in ion removal. Due to their high selectivity, these membranes are technologically well-suited for processes requiring strict limits on residual ion concentrations.

Typical properties: Membranes for CDI and EDR

Note:
(1) Measured in 0,5 M NaCl-solution @25°C