Puroxys: Diffusion Dialysis (DD) Acid Recycling Technology

Exergy’s Diffusion Dialysis (DD) is a state-of-the-art technology that uses ion exchange membranes to recycle used or spent industrial acids. The membranes are installed in single or multiple stacks that are supported in a plate and frame structure. This technology provides an efficient, sustainable solution for acid management by separating free acid from metal contaminants.​

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A key feature of the DD system is Exergy’s patent-pending "one-piece" spacer technology. This design allows for rapid and efficient mass transfer and utilizes natural gravity flow to achieve separation. By using gravity to maintain constant flow rates to the membrane stack, the system achieves high recovery rates while minimizing mechanical complexity.​

 

The DD system delivers consistent results through counter-current streams of spent acid and deionized water alternating through the cells. This robust process recycles 80–95% of spent acid and rejects up to 95% of metals, allowing process baths to be used indefinitely without the need for disposal. Designed for longevity, the chemical-resistant membranes typically last between three to five years.

Features

• Recycles 80–95% of used or spent acid 

• Rejects metals up to 95%, allowing baths to be used without need for disposal 

• Lowers energy requirements in anodizing baths by half 

• Fully automatic and continuous operation 

• Chemical resistant membranes last up to five years for typical applications 

• Acid feed filtration included for system protection 

• Modular, skid-mounted designs for easy installation

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Applications

• Maintenance and recycling of HNO3​/HF for etching baths used in stainless steel processing.

• Reclamation of H2​SO4​ and HCl in etching steel.

• Reclamation of H2​SO4​ in anodizing processes.

• Regeneration of battery acids.

• Recovery of H2​SO4​/HNO3​ and H2​SO4​/HCl for etching non-ferrous metals.

• Elimination of the need for concentrated acid waste treatment and disposal