A new insight into the mechanism of the scale inhibition: DLS study of gypsum nucleation in presence of phosphonates using nanosilver dispersion as an internal light scattering intensity reference

Insight into the Mechanisms of Scale Inhibition: A Case Study of a Task‐Specific Fluorescent‐Tagged Scale Inhibitor Location on Gypsum Crystals

“…Meanwhile, the number of HEDP‐F molecules exceeds the number of solid suspended particles by several orders of magnitude. Thus at the moment the brine mixture is prepared, the supersaturated gypsum solution contains at pH 5 to 6 the species: “free” [Ca] 2+ , [SO 4 2− ], [CaHhedp‐F] − , [H 3 hedp‐F] − , [H 2 hedp‐F] 2− ions, and a neutral complex [Ca 2 hedp‐F]°. Tentatively the phosphonate species “block” the surface of solid suspended particles (gypsum crystallization centers) from calcium and sulfate ions, and do not let CaSO 4 ⋅ 2H 2 O crystals to form.…”

“…Indeed the logK CaL values, measured at 25 °C and ionic strength 0.1 mol ⋅ dm −3 , are estimated as 6.4 (HEDP, R=methyl); 6.13 (AHPP, R= ethylamine), 5.80 (DMAHPP, R=2‐dimethylaminoethyl), 6.48 (MHPP, R= morpholinoethyl) . Thus, the stability constants estimated critically by IUPAC for HEDP, represent a good approximation also for HEDP‐F speciation, used in a present study.…”

“…Indeed, we have observed such a decrease provided by amino‐tris(methylenephosphonic acid) via DLS technique . Recently we got the new confirmation of these results by DLS for three phosphonates . Notably, as far as HEDP−F is added initially to the sulfate brine, then it isolates all heterogeneous impurities in it before the brines get mixed.…”

“…As far as we know, this is the first communication on the visualization of an antiscalant location during the scale formation. Our results on the gypsum crystals are in a perfect agreement with independent dynamic light scattering studies of gypsum supersaturated solutions ,…”

“…All the brines and antiscalant solutions were clarified before use by 0.045 μm Millipore Nylon filters to remove dust, and then by 0.020 Whatman inorganic membrane filter Anotop 10 Plus. However, the solid tiny impurities with a size ranging from 100 to 500 nm were still present in solutions and were detected by a particle counter (SLS‐1100) after filtration in amounts around 4000 to 5000 particles per 1 ml as it was also reported elsewhere . Thus the gypsum crystals formation was likely to pass rather the heterogeneous nucleation stage, than the homogeneous one.…”