Comparison of bipolar membrane electrodialysis, electrodialysis metathesis, and bipolar membrane electrodialysis multifunction for the conversion of waste Na2SO4: Process performance and economic analysis

To convert Na₂SO₄ into other high-value products (NaOH, H₂SO₄, and (NH₄)₂SO₄), three types of cell configurations of electrodialysis (ED) were applied (three-compartment bipolar membrane ED (BMED), four-compartment ED metathesis (EDM) and five-compartment bipolar membrane ED multifunction (BMEDM)) and parameters such as average voltage variation, removal ratio of salt, product concentration, conversion rate, ion flux, and energy consumption were calculated and compared. The experimental results and calculations indicated that the overall performance of BMEDM was inferior to that of BMED and EDM. An industrial model was established, which indicated that the net profit from converting Na₂SO₄ using BMEDM was always higher than that from BMED and EDM. Based on the advantages of low investment (132 $) and energy cost (152 $/t Na₂SO₄), EDM was applicable to factories with a low output of Na₂SO₄ (production capacity <45%), whereas BMED (157.3 $/t Na₂SO₄) and BMED-5 (227.6 $/t Na₂SO₄) were applicable to factories with a high output of Na₂SO₄ (production capacity >45%) based on high net profits.