Evaluation of parameters affecting the colloidal destabilization of spent vegetable tannin liquor

The overall objective of this investigation was to develop a chemical method for treating spent vegetable tannin liquor. Vegetable tannin wastes are plagued by a multitude of undesirable characteristics, principal of which is a color problem. Historically, chemical coagulation processes have been successful in reducing color associated with industrial wastes.

The coagulants tested were aluminum sulfate and polyelectrolytes. In addition, the pH and the time interval between aluminum ion and polyelegtrolyte addition were studied. Considerable difficulty was encountered in obtaining a waste product of uniform characteristics over an extended period. This problem was solved by storing a large quantity of waste of typical properties at temperatures near zero degrees centigrade.