Using diffusion dialysis, acids and alkalis can be selectively separated from metal salts and returned to the production process.
The technology enables the cost-effective recovery of valuable resources while supporting sustainable circular processes.
High Recovery Efficiency | Scalable | Cost-Efficient
Overview fields of application
ACIDS
H2SO4
HCl
H3PO4
HNO3
METALS
Ni
Cu
Fe
Al
BASES
NaOH
KOH
REPRESENTATIVE INDUSTRIES
The following examples highlight industries where Spiraltec’s spiral wound modules are successfully in use.
Anodizing
Steel pickling
Pickling
Copper pickling
Regenerate of ion exchange
Fly ashes recovery
Cleaning of H₂SO₄
Exchange HCl with H₂SO₄
Hemicelluloses
The spiral wound modules are highly versatile and suitable for a wide range of applications. Additional industries can be tested or evaluated upon request.
Designed for maximum process reliability – engineered for economical operation
Maximum separation efficiency = high-performance operation
Highest separation efficiency for metal salts
Highest salt concentration in waste water
Lowest amount of acid in waste water
Continuous operation = stable process conditions
Constant bath conditions in the process through continuous operation
Minimal consumption of input materials combined with high product quality through consistent process control.
Modular system = easy scalability
Thanks to their modular design, the modules are flexibly configurable, easily scalable, and cost-effectively integrated.
Compact design = maximum plant efficiency
With its high-volume density of the membrane surface, the WD Membrane Spiral Module can process considerably more solution than conventional devices within the same space requirement.
The design enables high process availability and minimizes maintenance time.
In an anodizing process, up to 95% of the free acid can be recovered. At the same time, significantly less than 1% of the aluminum is returned to the bath.
BASES RECOVERY
In bases recovery, the WD membrane spiral-wound module achieves a 70% recovery of free bases.
METAL RECOVERY
The recovery of acids or bases using our WD membrane spiral-wound modules can also be advantageously applied in metal recovery processes.
How it works
The World's Only Countercurrent Spiral-Wound Membrane Modules
Diffusion dialysis is a membrane separation process used to recover free acids and bases from electrolytic solutions or to selectively exchange ions within them. Spiraltec GmbH is the only company worldwide offering spiral-wound membrane modules engineered for true countercurrent flow operation — a key advantage for separation efficiency.
How It Works
The separation process is driven by the concentration gradient between two fluids. By operating in countercurrent mode, our spiral-wound modules maximize this gradient across the full length of the membrane, enabling higher recovery rates and more efficient ion exchange than conventional co-current designs.
A Strategic Partnership for Advanced Membrane Technology
Since 2015, Spiraltec has partnered exclusively with FUMATECH BWT GmbH, gaining access to the latest generation of ion-conducting flat membranes. This partnership goes beyond materials supply—FUMATECH BWT GmbH also supports our ongoing R&D, ensuring our diffusion dialysis modules stay at the forefront of membrane innovation.
ACID DIFFUSION DIALYSIS
Acid diffusion dialysis uses an anion exchange membrane to separate two channels. For efficient acid recovery, feed solution (from the process) and deionized water are passed through the channels in countercurrent flow. Because of the positive surface charge of the membrane, acid anions can diffuse through the selective membrane, and are then absorbed by the water. Due to the very small size of the acid cation H+, it is entrained in the anion diffusion, while the much larger positively charged metal ions are retained. The spiral membrane module WD achieves recovery rates of up to 95% of the free acid with metal retention of up to 99%.
CAUSTIC DIFFUSION DIALYSIS
In caustic diffusion dialysis, a cation exchange membrane is used. For efficient caustic recovery, the feed solution and the deionized water are also passed in countercurrent flow. The caustic cations can diffuse through the selective membrane due to its negative surface charge. Due to the small size of the leach anion OH-, it is entrained in the cation diffusion, while larger anions are retained. It has been shown in practice that recovery of caustic solutions with cation exchange membranes works, even though the OH- ions are much larger than the H+ ions that are co-diffused during acid diffusion dialysis. However, the diffusion rates are lower than in acid diffusion dialysis. In caustic recovery, the spiral membrane module WD achieves up to 70% recovery of free caustic with simultaneous salt retention of up to 99%.
From Laboratory Testing to a Reliable Process Solution
Every process is unique. With our diffusion dialysis laboratory testing service, we determine the optimal operating conditions for your specific application – before moving to industrial implementation.
For an initial evaluation, we only require 30 liters of your process stream. Based on these results, we develop a customized diffusion dialysis solution that integrates seamlessly into your existing process.
Greater certainty in system design:
The insights gained provide a reliable basis for the planning and sizing of an industrial diffusion dialysis system.
Application-specific testing:
We test diffusion dialysis under conditions that reflect your individual process requirements.
Reliable process design:
The results provide valuable data for the safe and efficient design of your future industrial-scale system.
With Spiraltec, you receive more than just a membrane solution – you gain an experienced partner who supports you from the initial feasibility study through to industrial implementation.
VERSIONS OF WD MODULE
WD-AR10
Spirale membrane modules for acidrecovery
Two different performance sizes:
WD10 with a flow rate of 5–15 L/h WD20 with a flow rate 10-30 L/h.
Application-specific membrane
Depending on the acid type and concentration, we select the most suitable module.WD-
End sealing: For highly aggressive solutions, the WD Spiral Membrane Module can be supplied with a highly resistant potting.
The right compact system or individual module system for your application:
We offer standardized compact systems as well as flexible modular systems to cover a wide range of application scenarios. Our solutions are designed to integrate efficiently into existing processes and meet diverse industrial requirements.
You are welcome to send us your specific requirements and process data. Based on this information, we will evaluate the technical possibilities and recommend the most suitable system from our portfolio. We will then provide you with a tailored quotation for your application.
The fully automatic supply unit of the DDSU150 series is suitable for operating up to three module systems of the DS10 series or one module system of the DS20 series.
Technical data:
Dimensions: 1200 x 800 x 1200 mm (L x W x H)
Pump capacity: max. 220 l/h
Power supply: L1/N/PE AC 230 V 50 Hz
Operating pressure: max. 4.0 bar
Storage tanks: approx. 65 l per tank
Empty weight: approx. 220 kg
Advantages:
Integrated storage tanks
Optional safety filtration
Stackable with modular system DS10-10
Complete housing made of PP-H
LET'S TALK ABOUT YOUR APPLICATION
Contact
Bastian Mildenberger (Head of Process Development)
Frank Moser (Head of Application Development & Plant Engineering)
Do you have questions about diffusion dialysis or would you like to know whether it’s suitable for your application? Get in touch – we look forward to learning about your requirements and working with you to find the right solution.
