Insoluble organic compounds in the Bayer process

During the dissolution of bauxite in a high-temperature (250-255 degreesC) Bayer process, which separates aluminum hydroxide and oxide in the ore from iron oxide and other impurities, a number of insoluble materials are produ ced from organic material entering the refinery with the bauxite. These ins oluble organic materials appear in the waste solids termed "red mud", in th e shell side of the heat exchangers, on sodium oxalate crystals, aluminum h ydroxide gibbsite precipitate, in a precipitation tank scale, and on oxalat e-gibbsite coprecipitation fines. These materials have been analyzed by NMR and pyrolysis GC/MS techniques. The organic material on the bauxite and re d mud were found to differ considerably from each other. The deposits on so dium oxalate released higher concentrations of alkenes and alkanes on pyrol ysis. The results are interpreted using current host-guest concepts of humi c materials and hydrophobicity.