Bipolar membrane electrodialysis of Na₂CO₃ and industrial green liquor for producing NaOH: A sustainable solution for pulp and paper industries

Industrial waste with high salinity cannot be drained into waterways due to tightened environmental regulations. Bipolar membrane electrodialysis (BPED) is getting more attraction not only to treat water flows but also to produce valuable commodities. The BPED technique has various advantages in terms of product purity, control over product concentration, having no by-products, low
environmental impact, and low energy consumption. In this short paper, we emphasize a comparative study in two different configurations for the treatment of green liquor (a waste solution of NaOH, Na₂S and Na₂CO₃ from pulp mills) with BPED to produce NaOH. The best results are obtained in a five-compartment setup where the capture of H₂S formed from green liquor is possible, followed by the capture of CO₂. This work also indicates that BPED technology is a sustainable solution to treat carbonate-rich waste, which will facilitate the current need to control greenhouse emissions.