Constant composition study of crystal growth of dicalcium phosphate dihydrate. The influence of polyphosphates, phosphonates, and phytate

Abstract

The influence of inhibitors of varying functional groups on the crystal growth of calcium phosphate dihydrate (CaHP04.2H20, DCPD) on DCPD seed crystals at pH 6.00,37"C, has been studied using the constant composition technique. The inhibitors studied include: (a) polyphosphate (sodium pyrophosphate, sodium hexametaphosphate, SHMP), (b) phosphonates (nitrilotris(methy1ene phosphonic acid), NTMP; I-hydroxyethylidene-1,l-diphosphonic acid, HEDP; ethylenediaminetetra (methylene phosphonic acid), ETMP; hexamethylenediaminetetra(methy1ene phosphonic acid), HMDP); and (c) myoinositol hexaphosphoric acid (phytic acid). The effect of these inhibitors on the growth kinetics have been studied at several inhibitor concentrations. The retarding effect of these inhibitors is discussed in relation to calcium-inhibitor complex formation on the DCPD seed crystals and the structural features of the inhibitor molecules. The fit of the Langmuir adsorption to experimental data supports a mechanism of inhibition through molecular adsorption of the inhibitor ions on the surface of growing crystals. Based upon the kinetic data, the overall order of inhibitors effectiveness is ETMP > HMDP > phytic acid > hexametaphosphate > HEDP > pyrophosphate ZAHID AMJAD. Can. J. Chem. 66, 2181 (1988. OpCrant a un pH de 6,0, i une tempkrature de 37°C et utilisant la technique de la composition constante, on a CtudiC l'influence des inhibiteurs portant divers groupements fonctionnels sur la croissance cristaux de phosphate de calcium dihydrate (CaHP04.2H20, DCPD) sur des cristaux de DCPD ensemences. Les inhibiteurs examinks comportent; (a) des polyphosphates (pyrophosphate de sodium, hexamCtaphosphate de sodium, HMPS), (b) des phosphonates (nitrilotris(acide methylkne phosphonique), NTMP; acide hydroxy-1 tthylidkne diphosphonique-1,1, HEDP; Cthyl&nediaminetCtra(acide mCthylkne phosphonique), HMDP; et (c) l'acide hexaphosphorique du myoinositol (acide phytique). On a CtudiC l'effet de ces inhibiteurs sur la cinCtique de la croissance i plusieurs concentrations d'inhibiteurs. On discute de l'effet retardant de ces inhibiteurs en

Factors Influencing Additive Interactions with Calcium Hydrogenphosphate Dihydrate Crystals

“…On the other hand, HATP has four functional phosphate groups and therefore acts as stronger inhibitor. This is in accordance with the results of related studies on the effectiveness of polyphosphates as crystallization inhibitors. ,, In both cases, however, the interactions were not strong enough to enable the additives to penetrate the water bilayer exposed on the (010) face.…”

“…Hexaammonium tetrapolyphosphate is a known crystal growth inhibitor and is commercially used in the prevention of scale formation on heat exchanger surfaces in industrial water systems. Phytate, myoinositol hexaphosphate, is also a potent crystal growth inhibitor, , found in nature in cereals and cells. It may be involved in calcium metabolism .…”

Influence of Organic Phosphonates on Hydroxyapatite Crystal Growth Kinetics

“…It is interesting to note that kinetic studies of the growth of DCPD, calcium carbonate, and calcium oxalate in the presence of EDTMP, HEDP, and AMP gave quite different results. For example, the orders of phosphonate effectiveness were HEDP > HDTMP > EDTMP > AMP, EDTMP > HDTMP > AMP > HEDP, and EDTMP > HDTMP > HEDP for calcium carbonate, DCPD, and calcium oxalate monohydrate growth inhibition, respectively.…”

Iron oxide dispersants for industrial water systems: types, performance, and selection criteria

“…It is worth noting that whereas phosphonates i.e., AMP, HEDP, PBTC, PAPEMP show poor performance as iron oxide dispersants, these additives have been known to show good to excellent inhibitory efficacy for various scaling systems i.e., CaCO 3 , CaHPO 4 ·2H 2 O, CaSO 4 ·2H 2 O, etc. [7][8][9]. Based on the data presented in Figure 5, phosphonates as iron oxide dispersants may be ranked as follow: PAPEMP > HEDP ~ AMP ~ PBTC > HPA.…”