Electrodialysis for bleach effluent recycling in kraft pulp production: Simultaneous control of chloride and other non-process elements

In the United States, more than 50 million tons of kraft pulp are produced per year. A strong effort by kraft pulp producers has been under way for se veral years to reduce water use. The in-process recycling of the acidic ble ach effluent carrying metals, transition metals, calcium, and often large a mounts of chloride is still a significant challenge. The simultaneous selec tive removal of chloride, and detrimental cations from the acidic bleach ef fluent of bleached kraft pulp mills by electrodialysis was investigated. Th e laboratory results with actual effluents show that very good removal leve ls can be achieved in an economical process. The chloride removal From acid ic bleach effluent will aid significantly in keeping chloride levels accept able in the recovery cycle.