Barite crystallization in presence of novel fluorescent-tagged antiscalants

• M. Oshchepkov^1,2, K. Popov¹, A. Ryabova³, A. Redchuk¹, S. Tkachenko^1,2, J. Dikareva¹ and E. Koltinova¹

¹ JSC “Fine Chemicals R&D Centre”, Krasnobogatyrskaya str. 42, b. 1, 107258 Moscow, 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, Vavilova str., 38, 119991 Moscow, Russian Federation

Abstract: Formation of barite crystals in a bulk supersaturated aqueous solution at ambient temperature is studied in presence of two novel fluorescent-tagged antiscalants: a bisphosphonate 1-hydroxy-7-(6-methoxy-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)heptane-1,1-diyldi-(phosphonic acid), HEDP-F, and a co-polymer of N-allyl-4-methoxy-1,8-naphtalimide with acrylic acid, PAA-F1 by fluorescent microscopy, scanning electron microscopy (SEM), turbidimetry, dynamic light scattering (DLS) and a particle counter technique. Both scale inhibitors at a 20 mg·dm^–3 dosage are found to be effective in supersaturated BaSO₄ solutions with saturation index (SI) 10 at 25°C (0.001 mol·dm^–3). Herewith PAA-F1 reveals a higher efficacy than HEDP-F. At the same time a dramatic impact of foreign background “nanodust” particles on antiscalant efficacy is detected and interpreted in terms of barite nucleation. It is demonstrated, that barite nucleation takes place exclusively on “nanodust” particles as a bulk heterogeneous process. Thus an antiscalant molecule acts not so much as barite nuclei surface modifiers, but as the modifiers of “nanodust” particles. It is shown that inter alia the lower efficacy of HEDP-F relative to PAA-F1 is associated with insoluble barium salts formation by the former reagent (tentatively by Ba₂HEDP-F·nH₂O or BaH₂HEDP-F·mH₂O). Thus an efficacy evaluation may be strongly affected by the way of antiscalant introduction into the system. Being initially added to the barium brine both antisclants demonstrate greater difference in barite scale inhibition, than in the case of the sulfate brine. Both fluorescent-tagged reagents reveal perfectly an antiscalant location on barite crystals. Despite expectations they cover BaSO₄ crystal surface uniformly, and indicate no special concentration of antiscalant on crystal’s kinks, edges etc. Thus the scale inhibitors affect rather the primary nucleation step of barite solid phase formation than the secondary one (macro-crystal growth phase).

Keywords: barite, fluorescence, fluorescent-tagged antiscalants, fluorescent microscopy, turbidimetry, dynamic light scattering, scale inhibition mechanism, polyacrylate, bisphosphonate

Int. J. Corros. Scale Inhib., 2019, 8, no. 4, 998-1021 PDF (1 482 K)
doi: 10.17675/2305-6894-2019-8-4-12

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