Finishers’ Think Tank
Solutions to this issue's "Think Tank" questions were provided by industry experts through 
AESF's technical specialists.

Originally Published in:

PLATING AND SURFACE FINISHING
Journal of the American Electroplaters and Surface Finishers Society

May 1990

Chromic Acid in Rinsewater

Question:
Can chromic acid be removed from rinsewater following a cleaning operation?

Answer:
A report from AESF Research Project #40 published in P&SF in October 1978 included detailed 
operation data from five plants on two recovery systems for chromic acid from rinsewater waste. 
One used vacuum evaporation after a cation ion exchanger to remove metallic impurities. The 
other used a triple-bed ion exchange system that included a cation ion exchanger to start, 
followed by two anion exchangers. Recovery of chromic acid ranged from 84 to 93 percent. 
Payback for the installed capital equipment ranged from 5 months to 2 years. By using the cation 
ion exchanger units and deionized water for evaporation makeup, contaminants were kept below 
harmful levels. Other ion exchange systems have been designed and adopted for efficient 
chromic acid recovery since Project #40 was undertaken. For example, a reciprocating ion 
exchange flow system used in more than 50 plants was described by C.J. Brown in a paper 
published in the Proceedings of the AESF Continuous Plating Symposium. Suppliers of ion 
exchange equipment should be able to provide detailed information.