Bench Scale Analysis of Bipolar Membrane Electrodialysis for Treatment of the HAC Decants at the CIBA-GEIGY Newport Pigment Plant
Creators: name: Kissell, Jeffrey Robert
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 1995

description: One of the wastes generated during the production of Quinacridone organic pigments at the Ciba-Geigy Newport, Delaware production facility, consists of approximately 50% acetate ion on a weight basis and lesser amounts of succinate, methanol and other constituents. The waste is commonly refereed to as the "HAc decants". The decants, which are currently discharged to the municipal wastewater treatment plant, represent a significant BOD loading. Ciba is currently investigating options for reducing BOD discharge as part of a plant waste minimization program. One option is to try recovering the acetic acid using a novel bipolar membrane electrodialysis process. This bench scale study was the first part of a larger project intended to assess the feasibility of using bipolar electrodialysis, herein referred to as BED, to treat the HAc decants. The process under study is a two compartment system manufactured by the Aqualytics division of The Graver Company, which until very recently was Aquatech Systems, a division of Allied Signal Inc. Using BED, an acid salt waste is separated into two components, an acid component and a base component, both of which may be recyclable. This application of bipolar electrodialysis is intended for recycling acetic acid, a raw material in the Quinacridone production process. Pretreatment of the waste was necessary to prevent damage to the stack membranes that might be caused by calcium and Dowtherm, which are components of the waste. Dowtherm is a mixture of biphenyl andl diphenyl ether. Pretreatment options under study were filtration and carbon adsorption. The waste was diluted to prevent precipitation of sodium acetate and to provide water for water splitting", and ion exchange was used to remove calcium prior to electrodialysis. A four cell stack was leased from Aqualytics, and a system was built to operate the stack. Ten runs were performed using the bench scale BED unit; five using pure solutions of sodium and acetate, and five using pretreated HAc decants. Based upon the results presented in this report, estimates were made for the membrane area and power consumption required for scale-up at the most efficient conditions. Recommendations for study at the pilot scale, are also made in the report. The conclusions from the study were: Membrane filtration followed by the use of carbon adsorption appears to provide effective removal of Dowtherm. • The application of the BED technology to the HAc decants appears to be an efficient and effective method for recovery of the HAc decants, capable of nearly 85% current efficiency and 99% conversion of sodium acetate to acetic acid. • Based on limited testing, the pretreated HAc decants appear to be compatible with the membranes used in the BED unit. It may be possible to achieve acetic acid concentrations of 40% in a full-scale system, but concentrations this high were not achieved with the experimental unit.