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 Na 2 SO 4 into other high-value products (NaOH, H 2 SO 4 , and (NH 4 ) 2 SO 4 ), 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 Na 2 SO 4 using BMEDM was always higher than that from BMED and EDM. Based on the advantages of low investment (132 $) and energy cost (152 $/t Na 2 SO 4 ), EDM was applicable to factories with a low output of Na 2 SO 4 (production capacity <45%), whereas BMED (157.3 $/t Na 2 SO 4 ) and BMED-5 (227.6 $/t Na 2 SO 4 ) were applicable to factories with a high output of Na 2 SO 4 (production capacity >45%) based on high net profits.