Mech-Chem’s Acid Purification Systems utilize a dependable and economical anion membrane technology known as Diffusion Dialysis.

Mech-Chem manufactures a line of Acid Purification Systems that utilize the process of diffusion dialysis to remove dissolved metal impurities from used, spent or waste acid solutions. This produces a clean acid solution that can be reused in production operations.

Diffusion Dialysis is a very effective technology for the recovery and purification of used, spent, or waste acid solutions that contain low levels of dissolved metals and still contain a large fraction of the acids. This membrane technology is used for acid recovery applications such as plating baths, anodizing baths, acid pickling and metal finishing applications.

​With new emphasis on cost reduction and green technologies, these membrane systems are also finding new applications for recovering and purifying spent or waste acid streams in mining applications and battery acid recycling.

In the recovery of acids with diffusion dialysis, an anion exchange membrane acts as a semi-permeable barrier between a flowing water stream and a flowing acid solution that contains the dissolved metals. The anion exchange membrane has fixed positive charges located on its surface. These positive charge locations attract the negatively charged anions in the solution that come in close contact with the anion exchange membrane surface. As a result, the acids in the spent or waste acid solution are attracted to the membrane.

​The metal ions which are larger molecules and positively charged are repelled by the positively charged membrane. This allows the acid molecules to diffuse through the membrane at a much faster rate than the dissolved metals. The result is that the water entering a diffusion dialysis system exits as the recovered acid solution containing most of the acid. The spent or waste acid solution entering the diffusion dialysis exits as an acid depleted solution containing most of the dissolved metals. Normal acid recovery is 80% to 90% with removal of 70% to 90% of the dissolved metals . 

Mech-Chem Associates, Inc.’s Acid Purification Systems are simple to operate, dependable, and economical. Our purification systems use an advanced membrane separation technology known as Diffusion Dialysis to separate, recover, and purify strong acids from spent acid solutions contaminated with dissolved metals. An anion exchange membrane serves as a semi-permeable barrier between a flowing stream of water and a flowing stream of process acid. Through this membrane, the processes of both Diffusion and Dialysis occur. These processes are carried out hundreds of times through the numerous internal channels that are contained in the many layers that make up the centrally-located stack of the Acid Purification System.

This technology is capable of recovering acids from concentrated baths that would have been discarded in the past. The purified acid is returned to the process tank for continued use, while a concentrated metal containing aqueous solution is removed for waste treatment. Typically, 80%-90% of the initial process acid is recovered in one pass through the system with 70%-90% removal of dissolved metals from the process acid.

​The Acid Purification Systems manufactured by Mech-Chem Associates, Inc. are tailored to client’s needs with respect to materials of construction and operating capacity required. The systems range in size from the AP-15, which processes 15 gallons of acid per day, to the AP-1200, which processes up to 1,200, which processes up to 1,200 gallons of acid per day. 

• Up to 90% Reduction in New Acid Purchases
• Increase Acid Bath Life/ Decrease Neutralization Costs
• Maintain Bath Uniformity for Optimum Performance
• Increase Production/ Reduce Downtime
• Reduce Hazardous Waste Disposal Costs 

This Acid Purification Lab unit is designed for testing on small volumes of acid solutions, to provide users with an introduction to the technology, and with initial performance data. Evaluation of the results may lead to further pilot scale testing, or to full-scale installation at the facility.

​Lab units are available for monthly rental, or may be purchased. The Lab units are designed to process between 1/2 to 1 gallon of acid solution, per 24 hours of operation, depending upon the type of concentrations of acids and dissolved metals in solution.