ISSN 2305-6894

DLS study of a phosphonate induced gypsum scale inhibition mechanism using indifferent nanodispersions as the standards for light scattering intensity comparison

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

Abstract: The dynamic light scattering (DLS) special technique is used to study the bulk supersaturated gypsum aqueous solutions during the induction period in 0.2 mol·dm–3 NaCl at pH 9 and 25°C. It is based on the standard SiO2 nanoparticles (Ludox TM40) injection into the supersaturated gypsum solution. These nanoparticles act as an internal indifferent light scattering intensity reference and provide a semiquantitative measurement of a relative gypsum particles content in a blank solution and in the system treated with amino¬tris(methylenephosphonic acid), ATMP. It is found that ATMP sufficiently reduces the number of gypsum nuclei, spontaneously formed in the supersaturated solutions. In a parallel way the chemical forms of antiscalant in the experimental systems have been modeled. A tentative nonconventional mechanism of scale inhibition is proposed. It assumes that the active crystal formation centers already exist in any analytical grade aqueous solution in the form of solid nanoimpurities with a size ranging from one to several hundred nm. The ATMP antiscalant competes with Ca2+ and for these centers and blocks them. Therefore the number of gypsum growth centers diminishes significantly. Thus the concentration of corresponding CaSO4·2H2O particles gets reduced at least 10-fold. The collision rate of such particles decreases 100-fold. This explains both induction time prolongation by ATMP and sub-stoichiometry of its efficacy.

Int. J. Corros. Scale Inhib., , 1, 9-24 PDF (1 669 K)
doi: 10.17675/2305-6894-2018-7-1-2

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