Problem solving in wastewater during the production of PET (polyethylene terephthalate)

Plastics are produced by polymerization. In addition to temperature, pressure, etc., catalysts are often used in the process.
PET is produced by the reaction of monomers of purified terephthalic acid (a dicarboxylic acid) and ethylene glycol (a di-alcohol) in the presence of a cobalt catalyst. The reaction produces excess EG and other reaction products such as propylene glycol (PG) and tri-ethylene glycol, which are later recovered and recycled. Both substances combine
to form long polymers chains. Water is also formed as a reaction product.
The problem arises from residual cobalt (Co) in the wastewater, which cannot be reduced to a low level by normal processes. In the EU, strict limits apply to heavy metals in wastewater.
The values achieved so far are in the ppm range (mg/l) and are too high to reuse or discharge the water. Required are ppb-level values.
Electrocoagulation (EC), which is already used for the clarification of electroplating wastewater to remove various metal species, has been tested here.
With special electrodes, EC works very selectively and achieves values below 10 ppb for cobalt (Co). At this time, a field trial is taking place in Europe at a well-known PET manufacturer, which is delivering
these values for cobalt.
Cobalt compounds are mainly present as chloride, nitrate or sulfate. These compounds are in turn classified as hazardous to the aquatic
environment because of their solubility and chemical reactions.
There is no maximum value for cobalt in the current drinking water ordinance. The limit values for nickel and the cobalt compounds mentioned above are
used for this.
Bioway has been working for years in the field of wastewater treatment and has a cooperation with a well-known European manufacturer of electro- coagulation-systems.
To this time there is no better method available to reduce the cobalt content in water down to ppb levels.
For more information, please use our e-mail:
contact@biowayconsulting.com.

Bioway Consulting Ltd
Norbert Pautz
C./ Tirant Lo Blanc 4
ES-03750 Pedreguer / Alicante - Spain
Mail: contact@biowayconsulting.com
www.biowayconsulting.com

Bioway Consulting Ltd is the successor of Bioway GmbH - Switzerland. Active in the field of waste-water clearing with methods of electrolysis. Founded
1998 in Germany now over 30 years experience in water treatment.

This release was published on openPR.