Cooperative Adsorption of Nonionic and Anionic Surfactants to the Surface of Hydroxyapatite in an Aqueous Phase

Abstract

Adsorption of polyethyleneglycol mono-p-isooctylphenylether(TX-100) on hydroxyapatite(HAP) was accelerated in the presence of sodium dodecylsulfate(SDS). This is because TX-100 was captured into hemimicelle/ admicelle of SDS formed on the surface of HAP. The adsorption amount on and affinity to HAP of TX-100 increased with the adsorption amount of SDS, forming the mixed micelle on the surface. Sodium dodecylbenzenesulfonate (SDBS) was also adsorbed on HAP in the same manner as that of SDS. However, polyoxyethylene(23) laurylether(C12n23) was little adsorbed by itself and scarcely accelerated the adsorption of SDBS. Anionic surfactants such as SDS and SDBS were adsorbed directly on the surface, while nonionic surfactants such as TX-100 and C12n23 required hydrophobic area to be adsorbed on the surface. The hydrophobic patch on the surface should be formed after the adsorption of the anionic surfactant on H.A.P. The roles of hydrophobic interaction and cooperative adsorption in the adsorption of nonionic surfactants were discussed.

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

“…The result was the latter. The surface tension increased from that in the absence of Ca2+(column [3]) asymptotically to that shown with the column [2] with an increase in a concentration of the added Ca2+ , i.e., in a series of the columns [3]-[8]. This result is showing that the surface tension approaches that in the…”

“…Open and closed columns show the data for TX and TN , respectively. 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. absence of both Ca2+ and DP(=the column [2]). Therefore, it was concluded that DP was selectively pulled out of the mixed micelle and precipitated as the Ca2+ salt of DR Thus, it was concluded that the mixed micelle exhibits different behavior on the surface of HAP (i.e., casting anchor of the DP at the Ca2+ -site and the site for anion exchange on the surface) and in an aqueous solution of CaCl2 (i .e., pulling out of the precipitate of Ca-DP).…”

“…The surface tension of an aqueous solu`tion of nonionic surfactant-DP-CaCl2 was measured, of which results are shown in FIGURE 4. We could expect that if the precipitate contains both the nonionic surfactant and DP, the surface tension should increase with the amount of the precipitate and be located between nonionic surfactant (column [2]) and water(column [1]). If the DP selectively precipitates as a salt of Ca-DP, the surface tension should be between that of nonionic surfactant-DP(column [3]) and nonionic surfactant(column [2]).…”