神鳥 和彦

The adsorption of myoglobin (MGB) onto various kinds of colloidal synthetic hydroxyapatite [X10(PO4)6(OH)2, noted CaHap, SrHap and CaSrHap for X = Ca, Sr and Ca + Sr, respectively] particles was investigated at 15 °C in a 1 x 10-4 mol dm-3 KCl solution of pH 6.0. The adsorption rate of MGB onto CaHap was comparable to that of lysozyme (LSZ) and was faster than that of bovine serum albumin (BSA). This distinction was explained by the difference in the molecular mass of these proteins (MGB: 17 800 Da, LSZ: 14 600 Da, BSA: 67 200 Da) the diffusion rates of the smaller MGB and LSZ molecules to the CaHap surface are faster than that of the larger BSA. The adsorption isotherms of MGB onto these synthetic hydroxyapatites (Haps) exhibited the Langmuir type and the surface charge of the MGB-covered Haps showed almost constant negative value and was independent of the MGB concentration for all the Haps. The values of the saturated amounts of adsorbed MGB for CaHap were independent of the Ca:PO4 molar ratio of the materials, supporting less importance of an electrostatic interaction between MGB and Haps because MGB molecules are electrostatically neutral at pH 6. It was presumed that MGB molecules are adsorbed onto phosphate ions exposed on ac and bc crystal faces by the van der Waals attractive force without taking advantage of the electrostatic interaction.

The effects of chloride ions on the morphology and structure of hematite particles, produced from a forced hydrolysis reaction of acidic Fe(iii) solution, were investigated. Spherical hematite particles were precipitated under all conditions employed which changed the molar fraction of coordinative Cl- to non-coordinative NO3- ions to Fe(iii) ions in the solutions. The size of the particles was increased with increase in the molar fraction of FeCl3, FeCl3/[FeCl3+Fe(NO3)(3)] (X-FeCl3) although no remarkable change was observed in varying that of HCl, HCl/(HCl+HNO3) (X-HCl). TEM and XRD measurements suggested that the hematite particles formed at X(FeCl3)less than or equal to 0.2 exhibited a single-crystal nature, although those produced at X(FeCl3)greater than or equal to 0.4 are polycrystalline with an enlarged c edge length in a unit cell possessing OH- ions in the lattice. The rate of phase transformation from beta-FeOOH to hematite decreased with increase in X-FeCl3 and was closely related to the crystal lattice distortion. The results obtained were explained by an aggregation mechanism taking into account the difference in the coordination properties of Cl- and NO3- ions to Fe(iii) ions. The hydrolysis reaction of Fe(iii) was slowed in the presence of Cl- by its strong coordination to produce electrically neutral, extremely low molecular weight polynuclear (PN) species, [FeO2/3(OH)(4/3)(H2O)(x)Cl-1/3](p). Therefore, this system gave a large spherical particle through the aggregation of the neutral small PNs with less mutual electrostatic repulsion force. In contrast, NO3- ions exhibited a fast hydrolysis reaction owing to their non-coordinative nature and produced positively charged, high molecular weight PNs, [FeO2/3(OH)(4/3)(H2O)(x)](p)((p/3)+), resulting in less aggregated small hematite particles owing to their repulsion force. This aggregation mechanism was further confirmed by gas adsorption, TEM and addition of NaCl.

The oxidation products of Fe(OH)(2) formed in the presence of Co2+, Cu2+ and Cr3+ were characterized by various means. Co2+ and Cu2+ produced pure Fe3O4 by inhibiting the generation of alpha-FeOOH, whilst Cr3+ promoted the alpha-FeOOH formation and interfered with the Fe3O4 formation. The Fe3O4 particles produced with Co2+ exhibited high Fe2+ content, electrical conductivity and stability to oxidation. Mossbauer spectroscopy demonstrated that the excess Fe2+ replaced for Fe3+ in B-sites of Fe3O4. A small quantity of metal Fe formed in addition to Fe3O4 on adding Co2+. (C) 1999 Elsevier Science Ltd. All rights reserved.

The surface of synthetic calcium hydroxyapatite Ca-10(PO4)(6) (OH)(2) (CaHAP) particles was modified with hexanoic CH3(CH2)(4) COOH (HA) and decanoic CH3(CH2)(8)COOH (DA) acids in hexane and the resulting materials were characterized by various means. XRD pattern, specific surface area, and morphology of the CaHAP particles were essentially not altered by the modification, FTIR and TPD results indicated that HA and DA molecules are hydrogen-bonded to the surface P-OH groups of CaHAP in three adsorption types. The surface of modified particles became hydrophobic. When the modified samples were outgassed at 500 degrees C, HA and DA were removed and the surface P-OH groups were revived. The modified material adsorbed much less H2O and CO2 than the unmodified one. (C) 1999 Academic Press.

Grafting of oleylphosphate (OP) molecules to the surface of calcium hydroxyapatite particles (HAP) was carried out by a coprecipitation method with a Ca(OH)(2)-H3PO4 system in the presence of disodium oleylphosphate (DSOP). All the particles exhibited a single-crystal nature with rod-like shape and were elongated along c-axis from 36 to 122 nm in particle length with an increase in the concentration of DSOP. It was suggested that 0 similar to 84% of the phosphate ions exposed on the ac or be faces of the HAP particles are exchanged with phosphate ions of DSOP molecules directing oleyl groups outward. The hydrophobicity of OP-grafted HAP particles was enhanced with an increase in the DSOP concentration. This high surface hydrophobicity was further confirmed by water adsorption experiments. The materials with the surface oleyl groups adsorbed much less water than the HAP particles produced without DSOP. (C) 1999 Elsevier Science B.V. All rights reserved.

Carbonated barium hydroxyapatite (Ba-10(PO4)(6)(OH)(2-2x)(CO3)(x), X = 0.30-0.57, BaHAP) particles with different Ba/P molar ratios were prepared by a wet method. CO32- ions were incorporated into OH- sites of a BaHAP lattice during the preparation at high solution DH. The obtained BaHAP particles were well crystallized and showed a high thermostability. On elevating the mixing temperature of H3PO4 and Ba(OH)(2) solutions, the mean particle size of BaHAP particles decreased and their specific surface area increased. The amount of CO2 adsorbed irreversibly on BaHAP particles increased with an increase of their Ba/P molar ratio. (C) 1999 Academic Press.

The adsorption of bovine serum albumin (BSA) and lysozyme (LSZ) to oleyl phosphate(OP)-grafted calcium hydroxyapatite (OP-CaHAP) with different degrees of hydrophobicity, ranging the number of surface oleyl group per unit nm(2) (n(o)) from 0 to 2.60, was investigated. The pronounced effects of the hydrophobic moiety of adsorbent on protein adsorption were observed. The saturated amount of adsorbed BSA (n(s)) was increased up to n(o) = 0.6 by an enlargement of hydrophobic interaction between hydrophobic CaHAP particle and proteins. However, n(s) decreased at n(o) greater than or equal to 1.3 by increasing the electrostatic repulsive force between negatively charged BSA and OP-CaHAP particles. On the other hand, the n(s) value of LSZ was continuously increased up to n(o) = 2.0 and saturated by increasing either the hydrophobic interaction or the electrostatic attraction of positively charged LSZ and negatively charged OP-grafted CaHAPs. The BSA adsorption experiment revealed that the effect of positively charged adsorption sites on the exposed ac or bc crystal faces (C-sites) of the CaHAPs is screened by the OP-groups grafted on their particle surfaces. (C) 1999 Academic Press.

Calcium hydroxyapatite (CaHAP) was prepared by homogeneous precipitation from aqueous solutions in the presence of formamide (FA) and Cl- ions. The structures and compositions of the particles formed under various conditions were examined by various methods. The crystal phase and morphology of the particles depended on the concentrations of the reagents, especially FA, in the starting solutions. Spherical, Ca-deficient CaHAP particles with diameters less than 800 mu m were obtained with 3-7 mol/dm(3) FA and consisted of needle-like particles growing in a radial manner. Cl- ions contributed to the crystal growth of these CaHAP particles. (C) 1999 Elsevier Science Ltd.

Colloidal calcium hydroxyapatite (CaHAP) particles were modified with Ni2+, Cu2+, Co2+ and Cr3+ ions by ion-exchange and coprecipitation. The CaHAPs doped with these ions were characterized by various methods including FTIR, XPS, TEM and ICP. The atomic ratio, metal/(Ca + metal), of the surface phase (X-s) of the particles modified with Ni2+ and Cu2+ by coprecipitation was much less than the atomic ratio of the whole particle (X-w), while X-s of the particles modified with Cr3+ approximated to their X-w. In the modification by ion-exchange, X-s was larger than X-w except for the Ni2+-substituted samples where X-s was identical to X-w. The surface P-OH groups were decreased by cation-exchange of the protons of the P-OH groups with Ni2+, Cu2+ and Co2+ in both the modification methods. On the other hand, Cr3+ ions were doped in the surface phase by anion-exchange of the surface phosphate ions with hydrated chromium hydroxide anions. (C) 1998 Elsevier Science B.V. All rights reserved.

The surfaces of calcium hydroxyapatite (CaHAP) particles with different Ca/P atomic ratios, synthesized by the precipitation method, were characterized and the adsorption mechanism of CO2 on CaHAP at 25 degrees C was elucidated mainly by FTIR. The number of surface P-OH groups was maximum at Ca/P = 1.6 while the quantity of irreversibly adsorbed CO2 was minimum at the same Ca/P. This indicates that the surface P-OH groups not only are the reversible adsorption sites for CO2 but also interfere with the irreversible adsorption of CO2. IR bands due to H2O and CO32- appeared on CO2 adsorption and were intensified by increasing the adsorbed amount. The physisorbed CO2 was converted into CO32- ions with the course of time. These results demonstrated that the irreversible adsorption of CO2 progresses via the reaction of CO2 with surface OH-: 2OH(-) + CO2 --> CO32- + H2O.

The effects of metal ions (Cu-II, Ni-II, Co-II and Cr-III) On the morphology and structure of haematite particles, produced from a forced hydrolysis reaction of FeCl3-HCl at various concentrations of metal ions ranging from 0-0.8 in Me/(Fe + Me) atomic ratio (X-Me), were investigated by various means, Spherical and a few double-spherical haematite particles were altered to diamond-shaped particles with increase in the concentration of divalent metal ions accompanied by a reduction of particle size up to X-Me = 0.8. On the other hand, spherical haematite particles with a few double-spherical particles were formed for the system doped with Cr-III at X-Cr less than or equal to 0.04 but no pure haematite particle was produced above this concentration. TEM and XRD suggested that the haematite particles formed at X-Cu less than or equal to 0.4 and X-Cr less than or equal to 0.04 are polycrystalline with an enlarged c edge length in the unit cell, though the diamond-like particles produced at X-Cu greater than or equal to 0.6 exhibited a single-crystal nature. TG and FTIR indicated that the haematite particles produced with metal ions are hydrohaematite and contain OH- ions in the lattice. The rate of phase transformation from beta-FeOOH to haematite was closely related to the crystal lattice distortion and the amounts of the lattice OH- ions which affected the morphology and structure of the haematite particles. Part of the dopants were incorporated into the particles and were concentrated in the particle surface phase.

The surface of synthetic calcium hydroxyapatite Ca-10(PO4)(6)(OH)(2) (CaHAP) particles was treated by repeated modification with hexamethyldisilazane [(CH3)(3)Si](2)NH (HMDS) in hexane and thermal treatment and the surface of the modified CaHAP was characterized by various means, No remarkable change in XRD patterns or in particle shape by the modification was observed. The width of the CaHAP particles gradually increased with repeating the modification. FTIR results indicated that HMDS reacted with surface P-OH groups of CaHAP to yield surface Si-(CH3)(3) groups. The surface of the modified CaHAP was hydrophobic. The surface Si-(CH3)(3) groups turned to three kinds of surface Si-OH groups by treating the modified materials at 500 degrees C in air. These formed surface Si-OH groups and the remaining surface P-OH groups reacted with HMDS by repeating the modification, resulted in the increase of the surface Si atoms. The modified material having surface Si-(CH3)(3) or Si-OH groups adsorbed much less CO2 than the unmodified one, (C) 1998 Academic Press.

The adsorption affinity of bovine serum albumin (BSA) and lysozyme (LSZ) to calcium hydroxyapatite (CaHAP) was evaluated by desorption and two step adsorption methods. These experiments were carried out at 15 degrees C in a 1 x 10(-4) mol dm(-3) KCI solution of pH 6.0. BSA molecules were scarcely desorbed, exhibiting an irreversible adsorption of BSA, though LSZ slightly desorbed. This result supports our previous findings that LSZ adsorbs weakly onto phosphate ions exposed on ac or be faces of CaHAP while BSA adsorbs strongly onto positively charged sites on ac or be faces of CaHAP. The amount of adsorbed LSZ was markedly increased by the pre-adsorption of BSA, where LSZ was adsorbed onto BSA-covered CaHAP. On the other hand, the amount of adsorbed BSA was not changed by the pre-adsorption of LSZ. In both pre-adsorption systems it was confirmed by an HPLC method that no protein molecule pre-adsorbed was desorbed after the post-adsorption procedure. Therefore, it was interpreted that the enhancement of adsorption of positively charged LSZ is induced by an electrostatic attractive force through pre-adsorption of negatively charged BSA molecules with a high coverage. However, since the coverage of LSZ onto CaHAP is considerably low, no stimulation of BSA adsorption occurred on the LSZ-covered surface. The formation of double protein adsorbed layers consisting of pre- and post-adsorbed proteins was proposed. (C) 1998 Elsevier Science B.V. All rights reserved.

Calcium alkyl phosphates (CaAP) synthesized by the reactions of Ca(OH)(2) with hexyl, octyl and decyl phosphates in aqueous systems were characterized by various means. X-ray diffraction patterns of CaAP showed a strong diffraction peak and two weak ones below 2 theta = 15 degrees. The d values of these peaks increased in proportion to the carbon number of the alkyl phosphates. The plate-like CaAP particles prepared using hexyl phosphate give rise to lattice patterns with uniform alternating spacings of about 1.3 and about 2.2 nm. When treated at 700 degrees C in air, CaAP transformed into beta-Ca2P2O7. The molar ratios Ca/P and alkyl groups/P of CaAP approximated to unity. The chemical formula could be shown as ROPO3Ca . 1.7H(2)O. These facts suggest that CaAP is composed of alternating bimolecular layers of alkyl phosphates and a dicalcium phosphate dihydrate (DCPD)-like phase. (C) 1998 Elsevier Science B.V. All rights reserved.

The products of the reactions of ferric oxyhydroxides (alpha-, beta- and gamma-FeOOH) with Ferrous species in O-2-free aqueous systems containing Cl- were characterized by XRD, FTIR and TEM. The reactions using all the FeOOH gave Fe3O4 at 25-100 degrees C and a wide pH range from 3 to 13, accompanying a depletion of FeOOH. The yield of Fe3O4 depended on the molar ratio of OH/Fe(II) in the suspensions, showing a maximum at OH/Fe(II) = 2. The maximum yield of Fe3O4 was in the order of beta-FeOOH > gamma-FeOOH>>alpha-FeOOH. It was revealed that Fe3O4 is formed by the reactions of the dissolved species of Fe(OH)(2) with those of FeOOH. (C) 1998 Elsevier Science Ltd. All rights reserved

The effects of dioxane (DX) on morphology and texture of haematite particles produced from a forced hydrolysis reaction of FeCl3-HCl solution were investigated by TEM, XRD, XFS, FTIR, TG-DTA, N2 and H2O adsorption, and zeta potential measurements. The spherical shape of haematite particles produced below the DX concentration of 10 vol% (diameters: 600-1000 nm) was changed to cubic for particles produced at more than 12 vol% DX (mean edge lengths: 900-1200 nm). The rod-like β-FeOOH particles were precipitated as cubic particles at the DX concentration ≤28 vol%. TEM and XRD suggested that the haematite particles formed in the presence of DX are polycrystalline with an enlarged c dimension in a unit cell. TG and FTIR indicated that the haematite particles produced with DX are hydrohaematite possessing OH- ions in the lattice. The results obtained in the present study revealed that variation of the polarity of the medium with addition of DX is a determining factor of the particle size and shape rather than the interfacial tension of the medium and the particles.

Influences of various kinds of divalent and trivalent metal ions on the formation, sizes, and pore structures of spherical aluminum phosphate particles were investigated. The addition of metal ions dramatically decreased the size of the spherical particles. A remarkable particle size reduction was observed in the systems doped with trivalent Fe3+ ions compared with those doped with divalent Co2+, Zn2+, and Mn2+ ions. Incorporation of Fe3+ ions into the crystal lattice to give solid solutions with a chemical composition of Al(1-x)Fe(x)PO4 . nH(2)O was observed in the systems doped with trivalent Fe3+ ions, though no substitution to yield particles with a chemical composition of AlPO4 . nH(2)O occurred for divalent ions. The divalent metal ions were adsorbed onto primary fine particles to interfere with particle growth. The divalent metal ions residing among the primary particles in secondary spherical aluminum phosphate particles were eliminated by rinsing and produced highly mesoporous materials without altering the particle morphology. A similar mechanism was depicted for particle formation in the presence of Fe3+ ions and incorporation into the crystal structure. The spherical aluminum phosphate particles produced with Co2+ ions exhibited an electrically neutral surface in the aqueous medium, while those formed with Fe3+ ions manifested an acidic surface due to phosphate ions exposed on particle surfaces. (C) 1998 Academic Press.

Barium-strontium hydroxyapatite solid solutions with different molar ratio Ba/(Ba + Sr) were synthesized by a wet method and characterized by various means. The solid solution particles could be prepared at molar ratios ranging from 0 to 1 however, Ba2+ ions were more difficult to be incorporated into hydroxyapatite crystals compared to Sr2+ ions. With increasing Ba2+ content, the particles grew and finally turned into pure rod-shaped barium hydroxyapatite particles with a size of ca. 0.2 x 2 μm. The resulting particles were agglomerates consisted of primary fine particles except for strontium hydroxyapatite. The molar ratios (Ba + Sr)/P of all the particles were larger than the stoichiometric ratio of 1.67, suggesting that CO3 2- ions, OH- ions, and/or H2O molecules substitute for PO4 3- ions in the crystal lattices. The amount of CO2 adsorbed irreversibly on the particles increased with increasing (Ba + Sr)/P except for strontium hydroxyapatite and fitted a curve with a minimum at a cation/P ratio of ca. 1.56 as well as other HAPs.

Colloidal Ca-10(PO4)(6)(OH)(2)(HA) particles doped with Cr3+ ions in different mole ratios (Cr/(Ca + Cr)) = X(Cr) by a coprecipitation method were characterized by ICP, XRD, N-2, adsorption, TEM, EPMA, TG, XPS and FTIR. Ca2+ ions of HA were substituted by Cr3+ ions in one to one at X(Cr) less than or equal to 0.13. The particle size increased with an increase in X(Cr). When doped at X(Cr) greater than or equal to 0.13 irregular particles were formed besides long rectangular particles containing Cr3+ ions less than ca 0.03 in X(Cr). The compositions of these two kinds of particles showed that the long rectangular particles were HA and the irregular particles were hydrated calcium chromium phosphate hydroxide. The growth of HA crystals was strongly promoted by doping Cr3+ ions. (C) 1997 Elsevier Science Ltd.

The size of amorphous spherical aluminum phosphate particles was controlled by using urea and isopropylamine (IPA), and their texture was investigated by various means. The mean particle diameter (D(p)) of the particles decreased with increasing urea concentration due to an acceleration in the precipitation reaction from decomposition of urea at elevated temperatures. The D(p) decreased upon addition of IPA concentrations of up to 6 mol% to Al ions under a constant urea concentration, while D(p) increased above this concentration because IPA produced electrolytes by reacting with HNO3 the electrolytes may reduce the range of Coulombic repulsion between charged primary particles. All the particles adsorbed selectively H2O molecules. IPA does not act as a template but operates as an effective additive for controlling particle size without altering the inner texture of spherical aluminum phosphate particles.

Magnesium-calcium hydroxyapatite (MgCaHAP) solid solutions have been prepared by a wet method from aqueous solutions with different molar ratios, Mg/(Mg+Ca), ranging from 0 to 0.5. The MgCaHAP particles formed were characterized by XRD, FTIR, TEM, ICP, TG-DTA and gas adsorption techniques. The Mg/(Mg+Ca) ratios of the formed MgCaHAP particles were less than those of the starting solutions. With increasing Mg content, the particles became less crystalline and agglomerates of the fine crystals and finally the products were amorphous at Mg/(Mg+Ca)>0.31. The amount of irreversible adsorption of CO2 and CH3OH showed a minimum at a molar ratio (Mg+Ca)/P of ca. 1.56, less than the stoichiometric ratio of 1.67.

The surface structure of mesoporous silica crystals FSM-16 with a narrowly distributed pore size has been studied by FTIR, measurement of SiOH number and adsorption of N-2 and H2O. IR spectra of FSM-16 outgassed at temperatures above 170 degrees C showed a sharp band at 3740 cm(-1) due to free SiOH and a broad shoulder at 3600-3500 cm(-1) due to hydrogen-bonded SiOH. The SiOH number, determined by a weight-loss method, amounted to 3.3 groups nm(-2), which is less than that of mesoporous silica gels. The amount of H2O adsorbed on FSM-16 decreased with calcination above 800 degrees C, owing to the dehydroxylation of SiOH. On treating with alcohol, the number of free SiOH decreased, leading to a decrease in H2O adsorption. The crystallinity of FSM-16 was lowered by pressing. With increasing pressure the specific surface area decreased and the SiOH number increased, up to 9.5 groups nm(-2).

Calcium hydroxyapatites (CaHAP) substituted with Fe3+ ions of different atomic ratios Fe/(Ca+Fe) = X(Fe) from 0 to 0.23 were synthesized and characterized by various methods. The number of Ca2+ ions in CaHAP substituted by one Fe3+ ion was higher than one, implying that the formation of cation vacancies and the protonation of PO43- ions are caused by Fe(III)-substitution. X(Fe) of the surface layer of the particles determined by XPS was less than the total X(Fe). IR spectra of Fe(III)-substituted CaHAP contain a band at 3707 cm(-1) assigned to the surface Fe-OH groups in addition to the surface P-OH bands at 3688, 3677, and 3658 cm(-1). With an increase in X(Fe), the amount of irreversible adsorption of CO2 decreased whilst those of CH3OH and H2O first decreased and then increased. IR results showed that the surface Fe-OH groups act as stronger irreversible adsorption sites for CO2 and CH3OH compared to the surface P-OH groups.

Spherical aluminum phosphate particles with a mean particle diameter of 477 +/- 16 nm, produced from aging of a solution containing Al(NO3)(3), Na2HPO4 and HNO3 at 100 degrees C for 19 h in 20-cm(3) Teflon-lined screw-capped Pyrex test tube without agitation, were characterized by various means. It was revealed from x-ray diffraction measurement and transmission electron microscope observation that amorphous particles are formed by agglomeration of small primary particles. The particles exhibited a high selective adsorption of H2O though they adsorbed small. amount of N-2 and CO2. This characteristic phenomenon was explained by rehydration of Al3+ ions by H2O molecules that were penetrated into the particles.

Calcium hydroxyapatites (CaHAPs), with particle lengths varying from 27 to 103 nm but similar widths of about 15 nm, were synthesized, and the adsorption behavior of bovine serum albumin (BSA) on these synthetic CaHAPs was investigated at pH 6.0 and 15°C. The size of the synthetic CaHAP particles increased on increasing the concentration of H3PO4 in the aging solution. The adsorption isotherms of BSA on CaHAPs were pseudo-Langmuir type. The saturated amounts of adsorbed BSA (ns), which are the plateau values of the adsorption isotherms, increased with an increase in particle length of the CaHAPs. However, no relationship was found between ns and the molar ratio of calcium to phosphorus in CaHAP particles. These results suggest that the particle texture is significant in the adsorption of BSA. The large rod-like particles with flat surfaces are advantageous for the adsorption of negatively charged BSA by the large number of positively charged adsorption sites on the exposed ac or bc crystal faces. © 1995.

Carbonate calcium hydroxyapatites (CAP) containing various amounts of carbonate ions from 0 to 10.1 wt.% were synthesized, and the adsorption behavior of bovine serum albumin (BSA) on these synthetic CAPs was investigated at pH 6.0 and 15 degrees C. The size of the synthetic CAP particles decreased by uptaking CO2-3 ions. The FTIR spectra of CAPs revealed that the CO32- ions are substituted for both OH- and PO43- ions. However, no remarkable difference was detected among the surface properties of these CAPs. The adsorption isotherms of BSA on CAPs were pseudo-Langmuir type. The saturated amounts of adsorbed BSA (n(s)), which is the plateau value of the adsorption isotherms, decreased with an increase in CO32- ion content in CAPs. This fact could be explained by the difference in the particle textures of CAPs, the large rod-like particles with flat surface are advantageous for the adsorption of negatively charged BSA by the large number of positively charged adsorption sites on the exposed ac or be crystal planes. It was considered therefore that the particle texture is significant in the adsorption of BSA. (C) 1995 Academic Press, Inc.

The forced hydrolysis of FeCl3-HCl solution in the presence of surfactants such as sodium dodecyl sulphate (SDS), cetyltrimethyl ammonium chloride (CTAC), polyoxyethylene (20) nonylphenyl ether (NP-20) and po ly(oxyethylene-oxypropylene) (PE-64) has been carried out and the precipitated particles were characterized by various techniques. No effect on the morphology of the precipitates was observed for CTAC and NP-20. The addition of a small amount of PE-64 progressed the particle growth but PE-64 yielded small lemon-shape alpha-Fe2O3 particles at high concentration. On the other hand, the morphological uniformity of alpha-Fe2O3 particles was impaired and they changed to needle- or rod-like alpha-FeOOH particles with increase in the SDS concentration. The alpha-Fe2O3 particles formed with SDS showed a high selective adsorption of H2O and CO2, although alpha-FeOOH particles have no such selectivity. The alpha-FeOOH particles thus prepared exhibited a low porosity on the heat treatment in vacuo.