A study of carbonate-rich brines from Sua Pan to characterize organic contaminants in the soda ash process

• Main Author: Joseph, Manjusha
• Format: Others
• Language: English
• Published: Rhodes University 2001
• Subjects: Sua Pan Soda Ash Project > Botswana; Sodium carbonate > Research; Biotic communities; Organic compounds
• Online Access: http://hdl.handle.net/10962/d1004091

Botswana Ash (Pty) Ltd which is situated in Sua Pan, north east Bostwana, is one of Africa's largest suppliers of salt and soda ash. For a number of years, the company has been experiencing problems which have resulted in the final soda ash product being contaminated and discoloured. The problems experienced at Sua Pan have been reported also to occur in other salt works all over the world. It has been suggested that contamination in many salt works could be possibly be due to the microbial activity by halophilic algae and bacteria that grow in the solar ponds. This study was undertaken to investigate the nature of the contaminating organic compounds present in the brine, to identify the compounds, and to establish how these components vary during the various stages of the soda ash processing. For this study, two sets of brine samples were used; the first set was collected before the summer rains and the second set was collected after the summer rains. Solid bicarbonate and soda ash samples were also used. Extractions, desalting, UV and HPLC analysis and oxidative biotransformations using four enzymes, were used for developing profiles and characterizing the brine components. From these studies, we were able to confirm that the components of the brine are organic in nature. A thorough study of one of the compounds isolated,from solid bicarbonate and soda ash was conducted using UV, HPLC, IR, NMR, HPLC-MS, GC-MS and TLC. The results of these analyses, show that the. isolated compound was benzyl butyl phthalate which is generally regarded to be humic in nature. This compound was found to be present in all the brine samples collected after the summer rains including the well brine, suggesting this compound occurs naturally and is not formed during the processing.