Electrodialysis for chloride removal from the chemical recovery cycle of a Kraft pulp mill

Abstract

The selective removal of chloride from a solution with high ionic strength containing multiple divalent anions, using electrodialysis with monovalent selective ion-exchange membranes is described. The process is characterized in terms of limiting current density, selectivity, and current efficiency. The correlation between limiting current density, chloride concentration and average fluid velocity is discussed. Using actual electrostatic precipitator dust from the chemical recovery cycle of a Kraft pulp mill the fouling behavior of the membranes was investigated in batch desalination experiments. Long term behavior over nearly 100h was studied. The feed contained organic contamination and a large number of inorganic components at low concentrations. The process performed excellently, despite the fact that no pre-treatments were applied to the feed.