Adsorption Characteristics of Non-Adsorbable Nonionic Surfactant, Tx-100, on the Surface of Hydroxyapatite in the Presence of an Anionic Surfactant

Reaction of Ca-deficient hydroxyapatite, HAP-400, with heavy metals, Pb (II), Fe (III), Fe (II), Cu (II), Cd (II), Cr (II), Co (II), Ni (II), and Zn (II) was investigated at 25˚C for 4 h in water, compared with stoichiometric hydroxyapatite HAP-300. From heavy metal consumption and [Ca]/[Metal], which is defined by molar ratio of eluted Ca and consumed heavy metal, the reactions of HAP-400 with the heavy metals except for Pb (II) and Fe (III) proceed via metal-adsorptive substitution mechanism. In the reactions of HAP-400 with Pb (II) and Fe (III), the metals were completely consumed with equivalent elution of Ca, but these reactions proceeded by no simple substitution mechanism to afford Pb (II)-and Fe (III)-bearing HAP-400 with specific structures, namely HAP-400-Pb and HAP-400-Fe.By XRD and FT-IR microspectroscopy, it was found that HAP-400-Pb is constituted of both newly formed lead apatite crystal and the original apatite crystal, and that HAP-400-Fe is constituted of much amorphous FePO 4 phase around the original apatic phase. Therefore, it was concluded that the reactions of HAP-400 with Pb (II) and Fe (III) proceed by the following mechanism: erosion of the apatic structure and formation of a brand-new structure containing metal. This mechanism can be named apatite-erosive substitution mechanism.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

REACTION OF Ca-DEFICIENT HYDROXYAPATITE WITH HEAVY METAL IONS ALONG WITH METAL SUBSTITUTION

Moriguchi

Nakagawa

Kaji

2008

“…Column [1] is water alone , [2] TX or TN, [3]-[8] for an aqueous solution of TX-DP or TN-DP . A concentration of added CaCl2/mM= 0(column [3]), 2(column [4]) , 4(column [5]), 6(column [6]), 8(column [7]), and 10(column [8]). The concentrations of both Triton and DP in the columns [3]-[8] were kept constant at 10mM.…”

Section: Figurementioning

confidence: 99%

Binding Mechanism of Triton X-100 and Triton N to the Surface of Hydroxyapatite in an Aqueous Phase

Oda

Shimabayashi

2005

Self Cite

Water-insoluble dodecylphosphate (DP) was solubilized by a micelle of a nonionic surfactant such as Triton X-100(TX) and Triton N (TN) , f orming a mixed micelle. The mixed micelle was adsorbed by HAP after isomorphous substitution of phosphate group of DP for orthophosphate ion on HAP and electrostatic attractive force between a negative charge of DP and Ca2+ on HAP. As a result, nonadsorbable nonionic surfactant was adsorbed indirectly to HAP together with DP forming hemi-and/or admicelle. In an aqueous solution of CaCl2 , the solution of nonionic surfactant-DP became turbid. DP was selectively captured by Ca2+ , resulting in formation of the Ca-DP precipitate, which was separated from the mixed micelle. However, nonionic surfactant remained in an aqueous phase. Thus, the mixed micelle showed different behavior on the surface of HAP and in an aqueous phase .

“…The surface of HAP also shows affinity for phosphorylated organic compounds. [5][6][7][8] Alkylphosphates (AP), which are esters of alkyl alcohols and phosphoric acid, could be easily adsorbed on the surface of HAP. The adsorption mechanism was of an ion exchange or of an isomorphorus substitution of a surface phosphate ion for a phosphate group of AP.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Adsorption Properties of Hydroxyapatite Surface-Modified by Cetylphosphate

Warabino

Ueno

Hino

et al. 2006

Self Cite

Hydroxyapatite (HAP) was prepared from CaCl 2 , Na 2 HPO 4 and NaOH in an aqueous phase mixed with a chloroform solution of cetylphosphate (CP). The CP was incorporated mainly on the surface of HAP but not to its bulk phase, resulting in formation of a hydrophobic surface. This surface-modified HAP has various characteristic properties different from those of the intact HAP. Some of the examples are as follows; an increase in a contact angle of water droplet, a decrease in a mean diameter of the HAP particle, and increases in the amounts of adsorption of various organic compounds. The aim of this study was of characterization of the surface-modified HAP through determining the adsorption amounts of various organic compounds on the surface. As for the adsorption of a surfactant to the modified HAP, it was concluded that hydrophobic interaction between alkyl chains of a surfactant and those of CP implanted on the surface became more important than hydrophilic interaction between polar/ionic groups of a surfactant and ions exposed on the intact area of the HAP. In the adsorption of bovine serum albumin (BSA), it was denatured by the CP implanted on the surface of the modified HAP (i.e., surface denaturation). Adsorption properties of the surface-modified HAP were quite different from those of the intact HAP.