Calcium sulfate dihydrate (gypsum) scale inhibition by PAA, PAPEMP, and PAA/PAPEMP blend

The kinetics of calcium sulfate dihydrate (CaSO 4 ·2H 2 O, gypsum) scale formation on heated metal surface from aqueous solution has been studied by a highly reproducible technique. It has been observed that gypsum growth takes place directly on heated metal surface without any bulk or spontaneous precipitation in the supersaturated solution. A variety of maleic acid based polymers with different functional groups have been examined for their inhibitory effect on gypsum growth. The results indicate that amount of gypsum scale formed on heated metal surface is strongly affected by polymer dosage and the functional groups present in the polymer. Scanning electron microscopic investigations of the gypsum crystals grown in the presence of anionic polymeric additives show that structures of these crystals are highly modified. Results on the performance of various surfactants and biocides are presented.

Section: Homopolymerssupporting

confidence: 91%

Kinetic and morphological investigation of calcium sulfate dihydrate (gypsum) scale formation on heat exchanger surfaces in the presence of inhibitors

Amjad

2017

“…twofold increase in %D value. It is worth noting that a trend in PA concentration vs. %D profiles similar to that observed in the present study has been reported for iron oxide and clay [3,5].…”

Section: Performance Of Synthetic Polymerssupporting

confidence: 89%

“…The effectiveness of polymers as dispersants for clay, calcium phosphate, silica, magnesium silicate, and iron oxide has been investigated by several researchers. Results of these studies reveal that polymers containing different functional groups i.e., carboxyl, sulfonic, amide, ester, etc., exhibit good to excellent dispersancy activity [3,4,5]. Dubin [6] in his study on the evaluation of polyphosphates, phosphonates, and homopolymers of acrylic acid, maleic acid, and acrylic/maleic acid-based copolymers as dispersants for iron oxide showed that copolymers performed better than polyphosphates and phosphonates.…”

Section: Introductionmentioning

confidence: 99%

Comparative evaluation of biopolymers and synthetic polymers as hydroxyapatite dispersants for industrial water systems

Amjad¹,

Kweik²,

Bickett³

2015

Self Cite

The dispersion of hydroxyapatite, Ca 5 (PO 4 ) 3 OH, HAP, by a variety of biopolymers and synthetic polymers of different composition and ionic charge has been investigated. The dispersion data show that polymer effectiveness as HAP dispersant strongly depends upon polymer architecture. Results also reveal that synthetic polymers perform better than biopolymers. It has been found that anionic, non-ionic, amphoteric, and cationic surfactants are ineffective as HAP dispersants. Additionally, it has also been observed that cationic surfactant and cationic polymer exhibit antagonistic effect on the performance of anionic polymeric dispersants.

“…A widely used technique for controlling scale deposition is an application of chemical inhibitors [2,[5][6][7][8]. Commonly used commercial antiscalants are represented mostly by three chemical families: polyphosphates, organophosphonates and organic polyelectrolytes (polyacrylates (PA), and polycarboxysulfonates (PCS)).…”

Section: Introductionmentioning

confidence: 99%

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

2018

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.