Techno-Economic Analysis of Bipolar Membranes Electrodialysis for the Hexacyanocobalic Acid Green Conversion

Hexacyanocobalic acid (H3Co(CN)(6)) is an important material utilized in the cyanide complex catalyst, which can be used for ring-opening polymerization of epoxides, cyclic anhydrides, and episulfides. The current method for synthesizing H3Co(CN)(6) involves a chemical synthesis. However, it is impeded by the complex preparation process, extra reagent usage, and the presence of intermediate products. In this work, hexacyanocobalic acid was prepared from potassium hexacyanocobalate by a clean and efficient bipolar membrane electrodialysis (BMED) method. The effects of different feed concentrations, acid-base compartment volume ratios, and membrane stack configurations on H3Co(CN)(6) preparation were investigated. The experimental results show that at the operation voltage of 8 V, feed/base compartment volume ratio of 2:1, and feed concentration of 0.4 mol/L, the concentration of H3Co(CN)(6) approached 0.2 mol/L with a conversion rate of 35.3%. Simultaneously, the K+ concentration in the acid compartment decreased to a low value of 32.1 g/L. The specific energy consumption and current efficiency for the BMED stack are 1.6 kW h/kg of H3Co(CN)(6) and 85.8%, respectively. Economic analysis indicated the total process cost of preparing H3Co(CN)(6) by BMED is 1.1 $/kg. Therefore, this facile strategy provides valuable insight for H3Co(CN)(6) production without the introduction of additional chemicals.

Automated summary

In this study, hexacyanocobalic acid was prepared from potassium hexacyanocobalate using a clean and efficient bipolar membrane electrodialysis (BMED) method. The effects of different factors on the preparation process were investigated. The results showed that under certain conditions, high concentration and conversion rate of hexacyanocobalic acid can be achieved.