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RED PEPPER POWDER COLOR MEASUREMENT BY USING AN INTEGRATING SPHERE … 21. D. Bicanic, E. Westra, J. Seters, S. van Houten, D. Huberts, I. Colic-Baric, J. Cozijnsen and H. Boshoven, J. Phys. IV France, 2005, 125, 807. 22. Gy. Lukács, Szinmérés, Műszaki Könyvkiadó, Budapest, 1982. 23. Chang-Seok Kim, Moon Ki Kim, Byungjo Jung, Bernard Choi, Wim Verkruysse, Myung-Yung Jeong, J. Stuart Nelson, Lasers in Surgery and Medicine 2005, 37, 138. 59
STUDIA UNIVERSITATIS BABEŞ-BOLYAI, CHEMIA, LIV, 3, 2009 MATHEMATICAL MODELING FOR THE CRYSTALLIZATION PROCESS OF HYDROXYAPATITE OBTAINED BY PRECIPITATION IN AQUEOUS SOLUTION VALENTINA R. DEJEU a , BARABÁS RÉKA a , POP ALEXANDRU a , BOGYA ERZSÉBET SÁRA a , PAUL-ŞERBAN AGACHI a ABSTRACT. In the paper are presented the theoretical and experimental results concerning the influence of pH and temperature over the rate of the transformation: beta-whitlockite (beta-tricalcium phosphate) in hydroxyapatite (HAP). From the data of the kinetic studies were calculated the values of the rate constants and activation energies at pH = 8.5 – 12. Based on the obtained values for the activation energies it has been established that the process of transformation of beta-whitlockite in HAP could be described using a combined macrokinetic mechanism: transfer – mass transformation. The mathematical of the process has been elaborated and the numerical values of the constants from the mathematical model were determined. Based on the proposed model process simulations were made and the results show that the obtained values fit well with the experimental data, which confirms the model validation. Keywords: hydroxyapatite, macrokinetic mechanism, mathematical model INTRODUCTION Due to its excellent properties like high biocompatibility, atoxicity and bone integration, HAP was accepted as biomaterial for biomedical purposes since 1920 and nowadays has many applications in medicine [1, 2, 3, 4]. Factors that affect the rate of adsorption of HAP in the human body are mostly determined by its chemical reactivity which depends on many different factors like: composition, particle size, defects, porosity, surface area and crystallinity [5]. On the other hand, these properties are greatly influenced on the route and conditions under which HAP is produced [6, 7]. HAP powder can be prepared in a variety of ways. The reactions could be classified in two categories: a - solid phase reaction b – precipitation a Universitatea Babeş-Bolyai, Facultatea de Chimie şi Inginerie Chimică, Str. Kogălniceanu Nr. 1, RO-400084 Cluj-Napoca, Romania, vdejeu@chem.ubbcluj.ro
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R /(mol m -2 s -1 ) 0.06 0.05 0.04
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ANA-MARIA CORMOS, JOZSEF GASPAR, AN
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Studia Universitatis Babes-Bolyai C
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MELINDA-HAYDEE KOVACS, DUMITRU RIST
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MELINDA-HAYDEE KOVACS, DUMITRU RIST
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STUDIA UNIVERSITATIS BABEŞ-BOLYAI,
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IRON DOPED CARBON AEROGEL AS CATALY
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128 ANDRADA MĂICĂNEANU, HOREA BED
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ANDRADA MĂICĂNEANU, HOREA BEDELEA
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CRISTINA MIHALI, GABRIELA OPREA, EL
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144 CRISTINA MIHALI, GABRIELA OPREA
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146 Interfering ion, J - I - DBS -
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CONCLUSIONS 148 CRISTINA MIHALI, GA
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150 CRISTINA MIHALI, GABRIELA OPREA
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152 D. MIHU, L. VLASE, S. IMRE, C.
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154 Intens. x105 1.5 1.0 0.5 0.0 x1
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D. MIHU, L. VLASE, S. IMRE, C. M. M
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162 A. PETER, M. BAIA, F. TODERAS,
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164 (a) V relative [%] (c) V relati
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A. PETER, M. BAIA, F. TODERAS, M. L
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BIOSORPTION OF PHENOL FROM AQUEOUS
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186 ANDREI ROTARU, MIHAI GOŞA, EUG
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ANDREI ROTARU, MIHAI GOŞA, EUGEN S
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194 OCTAVIAN STAICU, VALENTIN MUNTE
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ln(τ i / s) OCTAVIAN STAICU, VALEN
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204 MARIA ŞTEFAN, IOAN BÂLDEA, RO
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EXPERIMENTAL SECTION 210 MARIA ŞTE
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EQUILIBRIUM STUDY ON ADSORPTION PRO
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STRATEGIES OF HEAVY METAL UPTAKE BY
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CORROSION INHIBITION OF BRONZE BY A
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E / mV vs. SCE POTASSIUM-SELECTIVE
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POTASSIUM-SELECTIVE ELECTRODE BASED
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POTASSIUM-SELECTIVE ELECTRODE BASED
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256 CODRUTA VARODI, DELIA GLIGOR, L
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CODRUTA VARODI, DELIA GLIGOR, LEVEN
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PHARMACOKINETIC INTERACTION BETWEEN
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