Acid Cleaning Membrane Reuse Method in Metal Surface Treatment Processes

In metal surface treatment processes, acid cleaning plays a crucial role in removing oxide scales, rust, and surface impurities. However, during prolonged operation, traditional acid solutions gradually accumulate metal ions and impurities, resulting in reduced cleaning efficiency, increased waste liquid generation, and higher treatment costs.

To achieve energy conservation, emission reduction, and resource recycling, membrane separation technology for acid solution reuse has become a key development trend in the surface treatment industry.

An acid cleaning membrane is a special type of membrane material featuring acid resistance and selective ion separation capability, typically designed with nanofiltration (NF) or reverse osmosis (RO) composite structures.

The membrane selectively allows small acid molecules (such as H⁺ and Cl⁻) to pass through while rejecting large metal ions and suspended impurities.

1. Permeate (filtrate) contains reusable acid components.
2. Concentrate (retentate) holds heavy metal ions and impurities for further treatment.

This process effectively separates and purifies acid solutions for continuous reuse in production.

The acid cleaning membrane system is usually integrated with metal pickling lines. A typical reuse process includes the following steps:

1. Acid Solution Collection – Partially used acid from the pickling tank is directed into the recovery system.
2. Pretreatment Stage – Large particles and oil residues are removed through filtration or sedimentation.
3. Membrane Separation – The acid solution passes through the membrane unit, where the permeate is recovered acid and the concentrate contains impurities.
4. Acid Reuse – The recovered acid permeate is returned to the pickling tank to maintain a stable acid concentration and reduce fresh acid consumption.
5. Concentrate Disposal – The concentrate can be further treated to recover valuable metals or neutralized for discharge.

This process achieves an acid recovery rate of 70%–90%, significantly reducing waste acid discharge.

• Reduced Operating Costs – Minimizes acid purchase and waste treatment expenses.
• Improved Cleaning Efficiency – Maintains acid activity and consistent pickling performance.
• Extended Equipment Lifespan – Reduces corrosive impurities and protects tanks and pipelines.
• Environmental Compliance – Decreases waste acid and heavy metal emissions, supporting green manufacturing goals.

Acid cleaning membrane technology has been successfully applied in steel, electroplating, aluminum processing, and automotive parts manufacturing. For example, stainless steel pickling wastewater treated by acid cleaning membranes can achieve about 80% acid recovery and over 95% metal ion removal.

Future development focuses on:

• Enhancing acid and temperature resistance of membrane materials;
• Combining electrodialysis (ED) and membrane hybrid systems;
• Implementing smart monitoring and automatic acid concentration control for improved stability and cost-efficiency.

The adoption of acid cleaning membrane reuse technology marks a shift toward resource recycling and clean production in the metal surface treatment industry. By efficiently recovering and reusing acid from pickling wastewater, enterprises can lower costs while promoting sustainable industrial development.