Introduction of our products

Phosphoric Acid Recovery Equipment

For polishing in the aluminum surface processing, chemical polishing mainly using phosphoric acid or electrochemical polishing is performed. However, loss of the polishing solution as a result of bringing it out to the rinsing tank and processing cost for rinsing water were obstacles to the reduction of the surface processing cost.

In recent years, to prevent eutrophication by flowing of phosphorus-containing wastewater into rivers, lakes and marshes, there is a need for the reduction of loads in phosphorus-containing wastewater.

More than 25 years ago, we started “researches on pollution control by recovering and recycling phosphoric acid from the waste liquid by phosphoric acid chemical polishing and wastewater after cleaning” in cooperation with Japan Aluminium Products Association, and established a phosphoric acid recovery technology.

Outline

Phosphoric acid recovery equipment

A diluted recovered phosphating solution with low aluminum concentration is obtained by flowing a waste liquid (part of high-concentration electrolytic solution for electrochemical polishing at the same time) from the primary rinsing water tank after chemical polishing into the adsorption tank and adsorbing dissolved aluminum in the waste liquid using ion-exchange resin.

This diluted recovered phosphating solution is vacuum-concentrated in the vacuum evaporator up to the concentration used as a chemical polishing solution to make a concentrated solution which can be returned to the polishing bath.

Aluminum adsorbed on ion-exchange resin in the adsorption tank is desorbed by sulfuric acid and discharged as an aluminum sulfate solution.

Features

  • Since 80 to 90% of phosphoric acid is recovered, the amount of the polishing solution used for replenishment is reduced significantly.
    As this method removes only the aluminum content from the waste liquid, the other useful components in the polishing solution are recovered to some extent.
    Because phosphoric acid loads in wastewater treatment are reduced significantly, it is possible to significantly reduce the amount of chemicals used for wastewater treatment and the sludge generation amount.
    The phosphoric acid concentration is controlled according to the specific gravity of the solution and elevation of the boiling point, which results in simplification of liquid control which requires frequent analysis.
    As only sulfuric acid is used for regenerating ion-exchange resin, unnecessary components are not mixed in the recovered solution, having no influence on surface processing.
    Since ion-exchange resin does not undergo deterioration and damage excessively, replenishment of ion-exchange resin can be minimized.
    The vacuum evaporation tank is made of glass lining and a vacuum concentration method is used, thus, there are no problems on corrosion resistance.

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