Fluorescent-tagged antiscalants as a tool of homogeneous membrane scaling mitigation and inhibition mechanism investigation in electrodialysis processing of solutions prone to calcium sulfate precipitation

• V. Gil¹, M. Porozhnyy¹, M. Oshchepkov², O. Rybalkina¹, A. Ryabova³, M. Trukhina⁴, S. Tkachenko² and K. Popov⁴

¹ Kuban State University, 149 Stavropolskaya Str., 350040 Krasnodar, Russian Federation
² Mendeleev University of Chemical Technology of Russia, Miusskaya Sq. 9, 125047 Moscow, Russian Federation
³ Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov Str., 38, 119991 Moscow, Russian Federation
⁴ JSC “Fine Chemicals R&D Centre”, Krasnobogatyrskaya, Str. 42, b1, 107258 Moscow, Russian Federation

Abstract: The application of antiscalants (ASs) is a widely used method for scale inhibition in various water treatment technologies, being economically sound and rather simple in terms of technical implementation. However, despite its advantages, this method has not found wide application in electrodialysis. This study focuses on reducing the scaling of homogeneous cation-exchange membrane by using fluorescent antiscalants in the electrodialysis processing of solutions prone to calcium sulfate precipitation. Two novel antiscalants are tested: 1,8-naphthalimide-based bisphosphonate (HEDP-F) and fluorescein-tagged polyacrylate (PAA-F2). It is shown that the studied antiscalants themselves do not cause any significant change in the transport properties of the cation-exchange membrane CSE (Astom, Japan) under the conditions of an applied electric current. Chronopotentiometry and scanning electron microscopy results reveal significant antiscaling effectiveness for both scale inhibitors at sub-stoichiometric concentrations. PAA-F2 is found to be more efficient than HEDP-F, completely preventing any deposition on the membrane surface during the three-hour electrodialysis experiment. Fluorescence microscopy reveals that under the conditions of an applied electric field, HEDP-F forms a distinct phase and does not interact with the deposit structure, as it was detected previously in absence of electric current. Apparently, the mechanism of its activity primarily involves blocking impurities that function as crystallization centers of precipitate. It is suggested that PAA-F2 blocks solid impurities more efficiently than HEDP-F, since it is a polymeric AS.

Keywords: electrodialysis, scaling, scale inhibition, fluorescent-tagged antiscalants, antiscalant visualization, chronopotentiometry, fluorescence microscopy, calcium sulfate, polyacrylate, bisphosphonate

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 1668-1687
doi: 10.17675/2305-6894-2023-12-4-14

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