The crystal growth of calcium sulfate dihydrate in the presence of additives

Liu, Sung-Tsuen; Nancollas, G.H.

doi:10.1016/0021-9797(73)90318-4

Cited by 133 publications

(71 citation statements)

References 14 publications

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“…Then ATMP gets adsorbed onto gypsum nuclei, thus blocking the active crystal growth sites [3,5,[10][11][12][13][14][15][16][17][34][35][36][37][38][39]. This theoretical ground has stimulated numerous studies on selection of inhibitors that are better adsorbed onto gypsum, calcite or another scale to form a solid surface [39][40][41][42][43][44].…”

Section: Tentative Mechanism Of Gypsum Scale Formation Inhibition By mentioning

confidence: 99%

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

2018

Int. J. Corros. Scale Inhib.

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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 SiO 2 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 aminotris(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 Ca 2+ and 2 4 SO  for these centers and blocks them. Therefore the number of gypsum growth centers diminishes significantly. Thus the concentration of corresponding CaSO 4 ·2H 2 O 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.

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Section: Tentative Mechanism Of Gypsum Scale Formation Inhibition By mentioning

confidence: 99%

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

2018

Int. J. Corros. Scale Inhib.

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“…En présence de 1 mg.L -1 de PAS, l'analyse Raman (figure 3) montre que le sulfate de calcium, précipité à partir de la solution sous-saturée, cristallise sous les trois variétés ; gypse (CaSO 4 En augmentant la concentration (5 mg.L -1 ), le polyacrylate (PAS) inhibe la formation de l'hémihydrate qui disparaît et oriente la cristallisation vers la forme anhydre comme le montre le spectre présenté sur…”

Section: Effet Du Polyacrylateunclassified

“…Il existe six phases, anhydres ou hydratées, du sulfate de calcium : le gypse (CaSO 4 . 2H 2 O); 2 hémihydrates ( et ) et 3 anhydrites (I, II, III).…”

Section: Introductionunclassified

“…Les polyphosphates et les polyacrylates sont les familles de tartrifuges généralement utilisées à cause de leur susceptibilité à former des liaisons avec les cations (Ca 2+ ) [4][5][6][7]. Ceci leur permet d'être efficace même à faible dose.…”

Section: Introductionunclassified

“…Ceci leur permet d'être efficace même à faible dose. L'effet des polyphosphates et des phosphonates sur la précipitation du gypse a été étudié par Liu et Nancollas [4]. Ils ont montré que ces inhibiteurs ralentissent la vitesse de précipitation à partir de solution sursaturée en sulfate de calcium et augmentent le temps de germination.…”

Section: Introductionunclassified

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Étude de l’effet d’un polyacrylate et d’un polyphosphate sur la morphologie et la minéralogie du sulfate de calcium

et al. 2004

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Abstract. The retarding influence of polyacrylate and polyphosphate on the nucleation of calcium sulphate was investigated. SEM analyses show that these inhibitors didn't only influence the nucleation kinetics but also the precipitate morphology by adsorption onto crystal growth sites. The influence of different concentrations of the additives on the mineralogy of solid precipitated was also examined. Spectroscopy Raman analyses showed that the calcium sulphate can precipitate under different phases, gypsum (CaSO 4 .2H 2 O), hemihydrate (CaSO 4 .1/2H 2 O) and / or anhydride (CaSO 4 ), as function of inhibitors concentrations.

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Sequestrants

2010

Sanitation

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Sequestrants 3 3.1 Defi nitionSequestrants are chemical agents forming water -soluble complexes with metals. The binding process sequesters or inactivates the metal ions and prevents them from reacting with anions that give a low solubility product, such as carbonate, sulfate, and phosphate. Competition is the most important feature of the sequestering reaction. Two types of anions compete for polyvalent cations. The fi rst type (precipitants) cause insolubility, and the second (sequestrants) endeavor to pull the metal out of the precipitated material and keep it soluble. As already mentioned, the result of the competition depends on several variables which depend on the metals involved: concentration, pH, temperature, stability constant, and ionic strength. For this reason, a signifi cant number of molecules with functional groups suitable for forming coordination bonds have been synthesized in addition to the traditional polyphosphates, EDTA, NTA, citrate, and gluconate. The molecular engineers continue to investigate new combinations of functional groups in new structures, aiming at fi nding out new categories of sequestrants and making the already existing classes perform better.The words ' ligand ' and ' chelant ' are used to describe sequestrants, and ' chelation ' and ' complexation ' are adopted as synonyms of sequestration. However, ligand denotes the type of functional group able to form bonds with metals. The term ligand should be used to identify the single coordinating group instead of the whole sequestering molecule. In the same way, chelant should refer to the stoichiometric sequestrants. Sequestrant is intended as a general name defi ning molecules suitable for forming coordination complexes.The primary distinction among sequestrants concerns stoichiometric and threshold behavior.A sequestrant is defi ned to be stoichiometric when, excluding the coordination bonds, it is able to react with a number of positive charges (metals) exactly equal to the sum of its negative valences. When the amount of metal causes this number to be exceeded, all the complexes are inactivated and the sequestrant itself precipitates and contributes to scale. Sanitation: Cleaning and Disinfection in the Food Industry. Mario Stanga

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The crystal growth of calcium sulfate dihydrate in the presence of additives

Cited by 133 publications

References 14 publications

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

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

Étude de l’effet d’un polyacrylate et d’un polyphosphate sur la morphologie et la minéralogie du sulfate de calcium

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