Fabrication of a two-membrane configured electrodialytic methanesulfonic acid generator for ion chromatography.

An electrodialytic methanesulfonic acid (MSA) generator with a two-membrane configuration is described for ion chromatography (IC). It is fabricated by using a stacked anion exchange membrane (sAEM) and a bipolar membrane (BPM) plus stacked sAEMs (BPM-sAEM) to respectively isolate the central eluent channel from two outer regenerant chambers bearing the MSA feed solution. The cation exchange membrane (CEM) side of a BPM is facing the central channel (the cathode direction) and the sAEM is at the cathode side with respect to the anode of the BPM-sAEM side. Under an electric field, the hydronium ion produced at the junction layer of BPM via enhanced water splitting will electromigrate through CEM associated with BPM into the central channel, meanwhile methanesulfonate from the MSA feed solution at the cathode migrates into the central channel to combine with the hydronium ion together to form a solution of MSA. Such a device can produce a gas-free MSA eluent and no gas removal device is required. The produced MSA concentration was highly dependent on the applied current and up to at least 60.5 mM MSA could be produced. The device showed good running stability, as indicated by the retention time of RSD 0.15% and the peak area of RSD 1.7%.