Scale nucleation natural precursors: a case study of “micro/nanodust” impurities nature in laboratory aqueous samples obtained from Moscow tap water

• K. Popov¹, M. Oshchepkov^1,2, A. Kovalenko^1,2, A. Redchuk¹, J. Dikareva¹ and I. Pochitalkina²

¹ JSC “Fine Chemicals R&D Centre”, Krasnobogatyrskaya str. 42, b1, Moscow, 107258, Russian Federation
² D. Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9, 125047 Moscow, Russian Federation

Abstract: Recent studies revealed that the bulk scale nucleation has a heterogeneous character with nano/microdust impurities acting as scale templates in aqueous medium. Thus, the scale inhibition phenomenon is associated exactly with nano/microdust surface blockage by antiscalant molecules. Meanwhile, little is known about the nature of dust impurities. Therefore, the present report is focused solely on the study of suspended solid matter occurring in reagent grade water and in some tap water samples by means of particle counter technique, ICP analysis, DLS, SEM and X-ray diffraction. A particle counter was used to demonstrate that foreign solid particles sized over 100 nm are inevitably present in any reagent grade chemicals in amounts from 10² to ≥10⁵ units per 1 ml (from 10⁵ to ≥10⁸ per dm³), including water for ion chromatography (Sigma–Aldrich), KCl (Sigma–Aldrich) and HNO₃ for microelectronics (Avantor Performance Materials Ltd). At the same time, DLS revealed for HNO3 that the microfraction (≥100 nm) registered by a particle counter constitutes less than several per cent of the solid impurities sized below 100 nm. It was found that a common laboratory practice of dust removal via 200 or 220 nm filters provides a substantial decrease in the concentration of microparticles but only slightly affects the fraction below 200 nm, to say nothing of nanoparticles (1 nm ≤ size ≤ 100 nm). Moreover, this operation does not provide even complete removal of the fraction sized over 200 nm. Meanwhile, deionized water demonstrates a significantly lower concentration of solid impurities larger than 100 nm (320 per 1 ml) than distilled water (4300 per 1 ml). A combination of ICP, SEM and X-Ray diffraction analyses of distilled water produced from Moscow tap water indicated that the elemental composition of microparticles includes Si, O, Ca, Fe, and Al. A comparison of microparticle (size >100 nm) content in tap water samples taken in different cities worldwide demonstrates that there is no significant difference between them. The particle concentration ranges from 280 000 (Amsterdam) to 440 000 (Rome) units per 1 ml which is almost within the 20% measurement error. Thus, the problem of micro/nanodust occurrence in distilled/deionized water is common for many laboratories worldwide involved in water treatment studies.

Keywords: water, nucleation, scale formation, nano/micro impurities, particle counter, SEM, DLS, “Micro/Nanodust” removal

Int. J. Corros. Scale Inhib., 2020, 9, no. 3, 1097-1112 PDF (687 K)
doi: 10.17675/2305-6894-2020-9-3-20

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