Researchers at Da-Yeh University (大葉大學) in Changhua County have recently made a breakthrough in recycling CD and DVD discs by using a leaching technique that can clean all the coating from the discs in a few minutes without damaging them.
The technique, involving alcohol and nitric acid leaching and supersonic cleaning, won a gold medal at this year’s Taipei International Invention Show and Technomart late last month.
The technique, which has been granted patent rights by the Intellectual Property Office, was developed by a masters’ degree graduate in the Department of Environmental Engineering under the guidance of professor Lee Ching-hua (李清華).
Lee said the two sides of each disc have to be separated and then soaked in alcohol for a minute, before being moved to a supersonic washing machine to get rid of the memory dye and ink.
The DVD discs are then placed in a nitric acid bath and afterwards in another supersonic cleaner to remove the protective coating and metal reflective layers.
The second leaching is followed by a water wash, which leaves clean, transparent polycarbonate discs.
CD discs can be cleaned the same way, but the processing period is even shorter as they do not have two sides that need to be separated first, Lee said.
Lee said used CD and DVD discs are sold at about NT$15 per kilogram on average, but recycled discs that have been cleaned by means of Yang’s technique could fetch NT$45 per kilogram.
About 60 million discs are thrown away each year in Taiwan.