Hafit khireddine - Academia.edu (original) (raw)

Papers by Hafit khireddine

African Journal of Food, Agriculture, Nutrition and Development, 2009

The present work is a part of our scientific project about the valorisation of the common dates g... more The present work is a part of our scientific project about the valorisation of the common dates grown in southern Algeria. The principal aim was to study the drying ability of the fruit pulp with the view to produce food powders, which can easily take the place of many synthetics ingredients (white sugar, colorant like caramel) in many food preparations. The specific structure of the date pulp was also described: presence of two edible constitutive tissues (outside pigmented and inside white) that can influence the technological proprieties (as drying) of the whole fruit. The pigmented and white part weights were significantly different (p ≤ 0.05). Results reveal the preponderance of white part, which can favourably influence the heat processing such as drying since the coloured pulp is already pre-browned compared with the white part. Hot air (60°C) and microwave (MW) (350W) drying kinetics of date (Phoenix dactylifera L.) pulp pieces from Mech-Degla variety were investigated. Colour change (browning) was also analyzed during these drying processes using absorbance measurement at 420nm of the hydro alcoholic extract from pulp pigmented part. The latter has a heterogeneous initial colour in the same fruit. Three shades can be noticed: yellow, beige and brown related to the optic densities (at 420nm) of 0.92, 1.5 and 1.93 respectively. The minimal moisture contents reached by means of MW and hot air drying are about 8 (during 5 min) and 5 % dry basis (during 165 min) respectively. On the other hand, the MW drying could be considered instantaneous but it involves a few scorched spots on pulp pieces what may be due to the non uniformity of the initial date pulp colour or to the inadequacy of the chosen power. In addition, the applied model strongly fit the experimental data for convective air drying (R 2 = 0.995; MRE = 6.71%) compared to MW drying (R 2 = 0.94; MRE = 18.4%)

Environmental science and pollution research international, Jun 20, 2024

Hybrid Advances, Nov 30, 2023

Journal of Sol-Gel Science and Technology, Dec 26, 2023

Materials today communications, Mar 1, 2023

The modification of porosity and surface silanization are efficient methods to improve physicoche... more The modification of porosity and surface silanization are efficient methods to improve physicochemical and biological properties of bioactive glass. For sol-gel-derived glasses, the use of surfactant in the synthesis medium allows to pattern porosity and may significantly impact their in vitro bioactivity. Additionally, surface functionalization by silanization may be a key method for grafting drugs or biomolecules to the glass surface. In this work, we realized a comparative study of the effect of porosity modification and surface silanization on in vitro bioactivity of sol-gel-derived bioactive glasses. The materials characterization by FTIR spectroscopy, XRD analysis, ICP-OES spectroscopy, and SEM-EDS, before and after soaking in SBF, showed that the ordered porosity increases significantly the kinetics of hydroxyl-carbonate apatite formation and induces a control of the mineralization at the glass surface. The results show also that the glass remains bioactive after silanization. The present work shows that porosity structuring both improves the in vitro bioactivity of our glass and increases the silanization rate of the glass surface.

Surface and Interface Analysis

The use of 316L stainless steel as an orthopedic bone plate material or as a substrate for coatin... more The use of 316L stainless steel as an orthopedic bone plate material or as a substrate for coating implies the need to study its properties in a biological medium simulating human body environment. Therefore, the aim of this work is to investigate the microstructural characteristics, corrosion resistance, and mechanical properties of 316L stainless steel in the culture medium and then to check the cytotoxicity of the stainless steel in the presence of human mesenchymal stem cells. The characteristics of the stainless steel were evaluated by studying the microstructure of the samples in untreated state and after soaking in minimum essential medium‐alpha (α‐MEM) for 7 days. The results indicated the formation on the surface of the 316L stainless steel of goethite and deposits composed of Ca and P with porous and amorphous structures, which led to the decrease in the elastic modulus and the hardness of the soaked stainless steel as shown by nanoindentation test. Nevertheless, the hardn...

Journal of physics, Dec 1, 2017

The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer o... more The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer on the morphological and mechanical properties of hydroxyapatite (HAP) bioceramic coatings deposited on 316L stainless steel (316L SS) by sol-gel method in order to improve the properties of hydroxyapatite and expand its clinical application. The addition of TiO2 as sublayer of a hydroxyapatite coating results in changes in surface morphology as well as an increase of the microhardness. The deposition of the inner-layer provides the formation of new types of hydroxyapatite coatings at the same condition of annealing. This represents an advantage for the various applications of the hydroxyapatite bioceramic in the medical field. Classical hardness measurements conducted on the coated systems under the same indentation load (10g) indicated that the microhardness of the HAP coating is improved by the addition of TiO2 inner-layer on the 316L stainless steel substrate. The hardness values obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation are slightly different. This is because nanoindentation is more sensitive to the surface roughness and the influence of defects that could be present into the material. Moreover, nanoindentation is the most useful method to separate the contribution of each layer in the bilayer coatings. In this study, the hardness is comparable with those reported previously for pure HAP ceramics (1.0-5.5 GPa) which are close to the properties of natural teeth.

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Jun 24, 2015

Water Science and Technology, Oct 1, 2019

We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to Ca... more We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to CaO) and phosphoric acid at room temperature without pH control. The powder synthesized was utilized for cadmium removal from aqueous solutions using the batch technique. The effects of solution pH, adsorbent dose; initial Cd 2þ concentration, contact time, and temperatures were examined. Furthermore, the adsorption process revealed a pseudo-second-order reaction model and the Langmuir isotherm is the best-fit model to predict the experimental data and adsorption capacity was found to be 62.5 mg/g. Thermodynamic analysis revealed that because of the negative values of ΔG o and the positive value of ΔH o , the adsorption process was spontaneous and endothermic. Cadmium immobilization occurs through a two step mechanism: rapid ion exchange followed by partial dissolution of hydroxapatite and precipitation of cadmium containing hydroxyapatite.

Defect and Diffusion Forum, Sep 1, 2019

. In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless... more . In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless steel substrates using magnetron sputtering techniques, in order to improve their surface properties. The morphology and structure of the coatings were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performances skills in an SBF solution and the adhesion of these deposits were studied to understand these behaviors. From the results it was shown the TiCrN deposition presents the lowest corrosion resistance in the SBF solution, while TiN deposit is the most resistant to corrosion resistance in the same solutions, but its critical load (Lc3-TiN), is relatively low and has a risk of delamination which can limit its use. On the other hand, the Ti deposit exhibits a high resistance to corrosion and a high passivation (icorr (Ti) = 0.57 µA.cm-2 and Rp (Ti) = 67.98 KW.cm2). The critical load (Lc3-Ti = 43.38 N), the crack propagation resistance (CPRs-Ti = 81.64 N) and the scratch hardness (HSL-Ti = 125.75´1012 Pa) also testify to its high adhesion to the AISI 316L substrate. Thus the Ti deposit has proved to be the most favorable protective coating for AISI 316L stainless steel in SBF solution.

Optical Materials, 2014

High optical quality chirowaveguides have been successfully prepared using a synthesized chiral o... more High optical quality chirowaveguides have been successfully prepared using a synthesized chiral organomodified silane (ORMOSIL) precursor chemically transformed to a pre-condensed active material prior to dip coating. The chemical and physical parameters are optimized to elaborate in a single step dip coating 4.5 lm thick planar chirowaveguides presenting low loss (<1 dB/cm). The refractive index can be adjusted from 1.630 to 1.655 at 543.5 nm by adding tetraethoxysilane (TEOS) in the solution and by increasing the annealing temperature and time. It is shown that only 10% racemization occurs when annealing is conducted under vacuum at temperature lower than 120°C during less than 10 h. Finally, the highest specific optical rotation (OR) obtained is 7°/mm.

Water Science & Technology, 2011

Carbonate hydroxyapatite (CHAP) was synthesized from different precursors; synthetic (CaCO3 and C... more Carbonate hydroxyapatite (CHAP) was synthesized from different precursors; synthetic (CaCO3 and Ca(OH)2) and natural (egg shell before and after calcinations at 900°C) under different conditions and characterized by using TG/DTG analysis, X-ray powder diffraction (XRD) method and Fourier transform infrared (FT-IR) spectroscopy techniques. The results of these analyses indicate that the four powders present the same structure of hydroxyapatite. Furthermore the four powders obtained were used for the retention of lead. The results obtained indicated that all powders present high adsorption capacity for lead, but from environmental and economic views, the hydroxyapatite synthesized from eggshell no calcined (HA2) is most advantageous. The influence of different sorption parameters, such as: initial metal concentration, equilibration time, solution pH and sorbent dosage was studied and discussed.

Water Science and Technology, 2019

We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to Ca... more We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to CaO) and phosphoric acid at room temperature without pH control. The powder synthesized was utilized for cadmium removal from aqueous solutions using the batch technique. The effects of solution pH, adsorbent dose; initial Cd2+ concentration, contact time, and temperatures were examined. Furthermore, the adsorption process revealed a pseudo-second-order reaction model and the Langmuir isotherm is the best-fit model to predict the experimental data and adsorption capacity was found to be 62.5 mg/g. Thermodynamic analysis revealed that because of the negative values of ΔGo and the positive value of ΔHo, the adsorption process was spontaneous and endothermic. Cadmium immobilization occurs through a two step mechanism: rapid ion exchange followed by partial dissolution of hydroxapatite and precipitation of cadmium containing hydroxyapatite.

Materials Science and Engineering: C, 2017

Titania-Hydroxyapatite (TiO 2 /HAP) reinforced coatings are proposed to enhance the bioactivity a... more Titania-Hydroxyapatite (TiO 2 /HAP) reinforced coatings are proposed to enhance the bioactivity and corrosion resistance of 316L stainless steel (316L SS). Herein, spin-and dip-coating sol-gel processes were investigated to construct two kinds of coatings: TiO 2 /HAP composite and TiO 2 /HAP bilayer. Physicochemical characterization highlighted the bioactivity response of the TiO 2 /HAP composite once incubated in physiological conditions for 7 days whereas the TiO 2 /HAP bilayer showed instability and dissolution. Biological analysis revealed a failure in human stem cells adhesion on TiO 2 /HAP bilayer whereas on TiO 2 /HAP composite the presence of polygonal shaped cells, possessing good behaviour attested a good biocompatibility of the composite coating. Finally, TiO 2 /HAP composite with hardness up to 0.6 GPa and elastic modulus up to 18 GPa, showed an increased corrosion resistance of 316L SS. In conclusion, the user-friendly sol-gel processes led to bioactive TiO 2 /HAP composite buildup suitable for biomedical applications.

Journal of Physics: Conference Series, 2017

The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer o... more The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer on the morphological and mechanical properties of hydroxyapatite (HAP) bioceramic coatings deposited on 316L stainless steel (316L SS) by sol-gel method in order to improve the properties of hydroxyapatite and expand its clinical application. The addition of TiO2 as sublayer of a hydroxyapatite coating results in changes in surface morphology as well as an increase of the microhardness. The deposition of the inner-layer provides the formation of new types of hydroxyapatite coatings at the same condition of annealing. This represents an advantage for the various applications of the hydroxyapatite bioceramic in the medical field. Classical hardness measurements conducted on the coated systems under the same indentation load (10g) indicated that the microhardness of the HAP coating is improved by the addition of TiO2 inner-layer on the 316L stainless steel substrate. The hardness values obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation are slightly different. This is because nanoindentation is more sensitive to the surface roughness and the influence of defects that could be present into the material. Moreover, nanoindentation is the most useful method to separate the contribution of each layer in the bilayer coatings. In this study, the hardness is comparable with those reported previously for pure HAP ceramics (1.0-5.5 GPa) which are close to the properties of natural teeth.

Data and Knowledge in a Changing World, 1998

Three-dimensional (3d) frameworks of fast-alkali conductors have promising properties for electro... more Three-dimensional (3d) frameworks of fast-alkali conductors have promising properties for electrochemical sensors. Their conductivity is excellent at room temperature (about 10−4 to 10−3 S.cm−1), very much higher than the conductivity of usual membranes. They are sufficiently stable in water to be proposed as sensitive membranes in ISE devices. The mobile ions, such as sodium or other alkali ions, move through the structure from one site to another by 3d tunnels which are very well calibrated in size. The higher the mobility of an ion, the faster its exchange at the interface with the analyzed solution.

Journal of Materials Science, 2013

ABSTRACT The modification of hydroxyapatite surface by grafting polypyrrole has been investigated... more ABSTRACT The modification of hydroxyapatite surface by grafting polypyrrole has been investigated with two hydroxyapatites (HA) powders. One is natural derived from bovine bone, it was prepared by calcination at 750 °C. The other is synthetic synthesized by the sol–gel method using Ca(NO3)2·4H2O and P2O5. The presence of (C4H3N)n polymeric fragment bound to HA surface was evidenced by infrared analysis. X-ray powder analysis has shown that the apatite structure remains unchanged during the surface modification. The thermogravimetric analysis has shown that the weight loss exhibited by HA increased from 8.7 to 47.8 and from 18.3 to 42.8 wt% for natural hydroxyapatite (NHA)/polypyrrole and synthetic hydroxyapatite (SHA)/polypyrrole, respectively, as the pyrrole solution concentration increased from 5 to 15 wt%. Grafting of polypyrrole on HA surface caused an increase in specific surface area up to 113 m2/g for SHA and up to 107 m2/g for NHA aged in 15 wt% pyrrole solution (HA/15Pyrrole). According to the results found for these two apatites, a mechanism of surface modification was proposed for the formation of N–H hydrogen bonds as the result of a reaction between the C4H5N organic reagent and OH− ions of the HA.

Journal of Hazardous Materials, 2011

A factorial design was employed to evaluate the quantitative removal of zinc from aqueous solutio... more A factorial design was employed to evaluate the quantitative removal of zinc from aqueous solutions on synthesized hydroxyapatite. The experimental factors and their respective levels studied were the initial zinc concentration in solution (35≤C(Zn)≤85 mg/L), adsorbent dosage (4.5≤C(susp)≤9.5 g/L), Ca/P molar ratio (1.667≤Ca/P≤2) and calcination temperature of hydroxyapatite (600≤T(Cal)≤800 °C). The adsorption parameters were analysed statistically by means of variance analysis by using the STATISTICA software. The experimental results and statistical analysis show that increasing in the calcination temperature from 600 to 800 °C decrease the zinc adsorption whereas the increase of adsorbent dosage increases it. Based on the analysis of variance and the factorial design of experiments, adsorbent dosage has a positive effect on the removal of zinc, whereas zinc concentration, Ca/P molar ratio and calcination temperature have a negative effect on this process. The factorial results also demonstrate the existence of statistically significant binary interactions of the experimental factors. The experimental results were fitted to the Langmuir and Freundlich equations to find out adsorption capacities. In most cases, the results indicate that the sorption data fits well in the Freundlich isotherm model. The results of XRD analysis, pH(PZC) and pH(Final) values indicated that ion exchange and dissolution/precipitation mechanisms predominate for the sorption of zinc on our hydroxyapatite.

African Journal of Food, Agriculture, Nutrition and Development, 2009

The present work is a part of our scientific project about the valorisation of the common dates g... more The present work is a part of our scientific project about the valorisation of the common dates grown in southern Algeria. The principal aim was to study the drying ability of the fruit pulp with the view to produce food powders, which can easily take the place of many synthetics ingredients (white sugar, colorant like caramel) in many food preparations. The specific structure of the date pulp was also described: presence of two edible constitutive tissues (outside pigmented and inside white) that can influence the technological proprieties (as drying) of the whole fruit. The pigmented and white part weights were significantly different (p ≤ 0.05). Results reveal the preponderance of white part, which can favourably influence the heat processing such as drying since the coloured pulp is already pre-browned compared with the white part. Hot air (60°C) and microwave (MW) (350W) drying kinetics of date (Phoenix dactylifera L.) pulp pieces from Mech-Degla variety were investigated. Colour change (browning) was also analyzed during these drying processes using absorbance measurement at 420nm of the hydro alcoholic extract from pulp pigmented part. The latter has a heterogeneous initial colour in the same fruit. Three shades can be noticed: yellow, beige and brown related to the optic densities (at 420nm) of 0.92, 1.5 and 1.93 respectively. The minimal moisture contents reached by means of MW and hot air drying are about 8 (during 5 min) and 5 % dry basis (during 165 min) respectively. On the other hand, the MW drying could be considered instantaneous but it involves a few scorched spots on pulp pieces what may be due to the non uniformity of the initial date pulp colour or to the inadequacy of the chosen power. In addition, the applied model strongly fit the experimental data for convective air drying (R 2 = 0.995; MRE = 6.71%) compared to MW drying (R 2 = 0.94; MRE = 18.4%)

Environmental science and pollution research international, Jun 20, 2024

Hybrid Advances, Nov 30, 2023

Journal of Sol-Gel Science and Technology, Dec 26, 2023

Materials today communications, Mar 1, 2023

The modification of porosity and surface silanization are efficient methods to improve physicoche... more The modification of porosity and surface silanization are efficient methods to improve physicochemical and biological properties of bioactive glass. For sol-gel-derived glasses, the use of surfactant in the synthesis medium allows to pattern porosity and may significantly impact their in vitro bioactivity. Additionally, surface functionalization by silanization may be a key method for grafting drugs or biomolecules to the glass surface. In this work, we realized a comparative study of the effect of porosity modification and surface silanization on in vitro bioactivity of sol-gel-derived bioactive glasses. The materials characterization by FTIR spectroscopy, XRD analysis, ICP-OES spectroscopy, and SEM-EDS, before and after soaking in SBF, showed that the ordered porosity increases significantly the kinetics of hydroxyl-carbonate apatite formation and induces a control of the mineralization at the glass surface. The results show also that the glass remains bioactive after silanization. The present work shows that porosity structuring both improves the in vitro bioactivity of our glass and increases the silanization rate of the glass surface.

Surface and Interface Analysis

The use of 316L stainless steel as an orthopedic bone plate material or as a substrate for coatin... more The use of 316L stainless steel as an orthopedic bone plate material or as a substrate for coating implies the need to study its properties in a biological medium simulating human body environment. Therefore, the aim of this work is to investigate the microstructural characteristics, corrosion resistance, and mechanical properties of 316L stainless steel in the culture medium and then to check the cytotoxicity of the stainless steel in the presence of human mesenchymal stem cells. The characteristics of the stainless steel were evaluated by studying the microstructure of the samples in untreated state and after soaking in minimum essential medium‐alpha (α‐MEM) for 7 days. The results indicated the formation on the surface of the 316L stainless steel of goethite and deposits composed of Ca and P with porous and amorphous structures, which led to the decrease in the elastic modulus and the hardness of the soaked stainless steel as shown by nanoindentation test. Nevertheless, the hardn...

Journal of physics, Dec 1, 2017

The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer o... more The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer on the morphological and mechanical properties of hydroxyapatite (HAP) bioceramic coatings deposited on 316L stainless steel (316L SS) by sol-gel method in order to improve the properties of hydroxyapatite and expand its clinical application. The addition of TiO2 as sublayer of a hydroxyapatite coating results in changes in surface morphology as well as an increase of the microhardness. The deposition of the inner-layer provides the formation of new types of hydroxyapatite coatings at the same condition of annealing. This represents an advantage for the various applications of the hydroxyapatite bioceramic in the medical field. Classical hardness measurements conducted on the coated systems under the same indentation load (10g) indicated that the microhardness of the HAP coating is improved by the addition of TiO2 inner-layer on the 316L stainless steel substrate. The hardness values obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation are slightly different. This is because nanoindentation is more sensitive to the surface roughness and the influence of defects that could be present into the material. Moreover, nanoindentation is the most useful method to separate the contribution of each layer in the bilayer coatings. In this study, the hardness is comparable with those reported previously for pure HAP ceramics (1.0-5.5 GPa) which are close to the properties of natural teeth.

Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, Jun 24, 2015

Water Science and Technology, Oct 1, 2019

We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to Ca... more We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to CaO) and phosphoric acid at room temperature without pH control. The powder synthesized was utilized for cadmium removal from aqueous solutions using the batch technique. The effects of solution pH, adsorbent dose; initial Cd 2þ concentration, contact time, and temperatures were examined. Furthermore, the adsorption process revealed a pseudo-second-order reaction model and the Langmuir isotherm is the best-fit model to predict the experimental data and adsorption capacity was found to be 62.5 mg/g. Thermodynamic analysis revealed that because of the negative values of ΔG o and the positive value of ΔH o , the adsorption process was spontaneous and endothermic. Cadmium immobilization occurs through a two step mechanism: rapid ion exchange followed by partial dissolution of hydroxapatite and precipitation of cadmium containing hydroxyapatite.

Defect and Diffusion Forum, Sep 1, 2019

. In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless... more . In the present work several films of Ti, TiN, and TiCrN have been coated on AISI 316L stainless steel substrates using magnetron sputtering techniques, in order to improve their surface properties. The morphology and structure of the coatings were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performances skills in an SBF solution and the adhesion of these deposits were studied to understand these behaviors. From the results it was shown the TiCrN deposition presents the lowest corrosion resistance in the SBF solution, while TiN deposit is the most resistant to corrosion resistance in the same solutions, but its critical load (Lc3-TiN), is relatively low and has a risk of delamination which can limit its use. On the other hand, the Ti deposit exhibits a high resistance to corrosion and a high passivation (icorr (Ti) = 0.57 µA.cm-2 and Rp (Ti) = 67.98 KW.cm2). The critical load (Lc3-Ti = 43.38 N), the crack propagation resistance (CPRs-Ti = 81.64 N) and the scratch hardness (HSL-Ti = 125.75´1012 Pa) also testify to its high adhesion to the AISI 316L substrate. Thus the Ti deposit has proved to be the most favorable protective coating for AISI 316L stainless steel in SBF solution.

Optical Materials, 2014

High optical quality chirowaveguides have been successfully prepared using a synthesized chiral o... more High optical quality chirowaveguides have been successfully prepared using a synthesized chiral organomodified silane (ORMOSIL) precursor chemically transformed to a pre-condensed active material prior to dip coating. The chemical and physical parameters are optimized to elaborate in a single step dip coating 4.5 lm thick planar chirowaveguides presenting low loss (<1 dB/cm). The refractive index can be adjusted from 1.630 to 1.655 at 543.5 nm by adding tetraethoxysilane (TEOS) in the solution and by increasing the annealing temperature and time. It is shown that only 10% racemization occurs when annealing is conducted under vacuum at temperature lower than 120°C during less than 10 h. Finally, the highest specific optical rotation (OR) obtained is 7°/mm.

Water Science & Technology, 2011

Carbonate hydroxyapatite (CHAP) was synthesized from different precursors; synthetic (CaCO3 and C... more Carbonate hydroxyapatite (CHAP) was synthesized from different precursors; synthetic (CaCO3 and Ca(OH)2) and natural (egg shell before and after calcinations at 900°C) under different conditions and characterized by using TG/DTG analysis, X-ray powder diffraction (XRD) method and Fourier transform infrared (FT-IR) spectroscopy techniques. The results of these analyses indicate that the four powders present the same structure of hydroxyapatite. Furthermore the four powders obtained were used for the retention of lead. The results obtained indicated that all powders present high adsorption capacity for lead, but from environmental and economic views, the hydroxyapatite synthesized from eggshell no calcined (HA2) is most advantageous. The influence of different sorption parameters, such as: initial metal concentration, equilibration time, solution pH and sorbent dosage was studied and discussed.

Water Science and Technology, 2019

We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to Ca... more We report the synthesis of hydroxyapatite (HAP) powder from waste mussel shells (decomposed to CaO) and phosphoric acid at room temperature without pH control. The powder synthesized was utilized for cadmium removal from aqueous solutions using the batch technique. The effects of solution pH, adsorbent dose; initial Cd2+ concentration, contact time, and temperatures were examined. Furthermore, the adsorption process revealed a pseudo-second-order reaction model and the Langmuir isotherm is the best-fit model to predict the experimental data and adsorption capacity was found to be 62.5 mg/g. Thermodynamic analysis revealed that because of the negative values of ΔGo and the positive value of ΔHo, the adsorption process was spontaneous and endothermic. Cadmium immobilization occurs through a two step mechanism: rapid ion exchange followed by partial dissolution of hydroxapatite and precipitation of cadmium containing hydroxyapatite.

Materials Science and Engineering: C, 2017

Titania-Hydroxyapatite (TiO 2 /HAP) reinforced coatings are proposed to enhance the bioactivity a... more Titania-Hydroxyapatite (TiO 2 /HAP) reinforced coatings are proposed to enhance the bioactivity and corrosion resistance of 316L stainless steel (316L SS). Herein, spin-and dip-coating sol-gel processes were investigated to construct two kinds of coatings: TiO 2 /HAP composite and TiO 2 /HAP bilayer. Physicochemical characterization highlighted the bioactivity response of the TiO 2 /HAP composite once incubated in physiological conditions for 7 days whereas the TiO 2 /HAP bilayer showed instability and dissolution. Biological analysis revealed a failure in human stem cells adhesion on TiO 2 /HAP bilayer whereas on TiO 2 /HAP composite the presence of polygonal shaped cells, possessing good behaviour attested a good biocompatibility of the composite coating. Finally, TiO 2 /HAP composite with hardness up to 0.6 GPa and elastic modulus up to 18 GPa, showed an increased corrosion resistance of 316L SS. In conclusion, the user-friendly sol-gel processes led to bioactive TiO 2 /HAP composite buildup suitable for biomedical applications.

Journal of Physics: Conference Series, 2017

The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer o... more The aim of this paper is to investigate the effect of the addition of titania (TiO2) innerlayer on the morphological and mechanical properties of hydroxyapatite (HAP) bioceramic coatings deposited on 316L stainless steel (316L SS) by sol-gel method in order to improve the properties of hydroxyapatite and expand its clinical application. The addition of TiO2 as sublayer of a hydroxyapatite coating results in changes in surface morphology as well as an increase of the microhardness. The deposition of the inner-layer provides the formation of new types of hydroxyapatite coatings at the same condition of annealing. This represents an advantage for the various applications of the hydroxyapatite bioceramic in the medical field. Classical hardness measurements conducted on the coated systems under the same indentation load (10g) indicated that the microhardness of the HAP coating is improved by the addition of TiO2 inner-layer on the 316L stainless steel substrate. The hardness values obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation are slightly different. This is because nanoindentation is more sensitive to the surface roughness and the influence of defects that could be present into the material. Moreover, nanoindentation is the most useful method to separate the contribution of each layer in the bilayer coatings. In this study, the hardness is comparable with those reported previously for pure HAP ceramics (1.0-5.5 GPa) which are close to the properties of natural teeth.

Data and Knowledge in a Changing World, 1998

Three-dimensional (3d) frameworks of fast-alkali conductors have promising properties for electro... more Three-dimensional (3d) frameworks of fast-alkali conductors have promising properties for electrochemical sensors. Their conductivity is excellent at room temperature (about 10−4 to 10−3 S.cm−1), very much higher than the conductivity of usual membranes. They are sufficiently stable in water to be proposed as sensitive membranes in ISE devices. The mobile ions, such as sodium or other alkali ions, move through the structure from one site to another by 3d tunnels which are very well calibrated in size. The higher the mobility of an ion, the faster its exchange at the interface with the analyzed solution.

Journal of Materials Science, 2013

ABSTRACT The modification of hydroxyapatite surface by grafting polypyrrole has been investigated... more ABSTRACT The modification of hydroxyapatite surface by grafting polypyrrole has been investigated with two hydroxyapatites (HA) powders. One is natural derived from bovine bone, it was prepared by calcination at 750 °C. The other is synthetic synthesized by the sol–gel method using Ca(NO3)2·4H2O and P2O5. The presence of (C4H3N)n polymeric fragment bound to HA surface was evidenced by infrared analysis. X-ray powder analysis has shown that the apatite structure remains unchanged during the surface modification. The thermogravimetric analysis has shown that the weight loss exhibited by HA increased from 8.7 to 47.8 and from 18.3 to 42.8 wt% for natural hydroxyapatite (NHA)/polypyrrole and synthetic hydroxyapatite (SHA)/polypyrrole, respectively, as the pyrrole solution concentration increased from 5 to 15 wt%. Grafting of polypyrrole on HA surface caused an increase in specific surface area up to 113 m2/g for SHA and up to 107 m2/g for NHA aged in 15 wt% pyrrole solution (HA/15Pyrrole). According to the results found for these two apatites, a mechanism of surface modification was proposed for the formation of N–H hydrogen bonds as the result of a reaction between the C4H5N organic reagent and OH− ions of the HA.

Journal of Hazardous Materials, 2011

A factorial design was employed to evaluate the quantitative removal of zinc from aqueous solutio... more A factorial design was employed to evaluate the quantitative removal of zinc from aqueous solutions on synthesized hydroxyapatite. The experimental factors and their respective levels studied were the initial zinc concentration in solution (35≤C(Zn)≤85 mg/L), adsorbent dosage (4.5≤C(susp)≤9.5 g/L), Ca/P molar ratio (1.667≤Ca/P≤2) and calcination temperature of hydroxyapatite (600≤T(Cal)≤800 °C). The adsorption parameters were analysed statistically by means of variance analysis by using the STATISTICA software. The experimental results and statistical analysis show that increasing in the calcination temperature from 600 to 800 °C decrease the zinc adsorption whereas the increase of adsorbent dosage increases it. Based on the analysis of variance and the factorial design of experiments, adsorbent dosage has a positive effect on the removal of zinc, whereas zinc concentration, Ca/P molar ratio and calcination temperature have a negative effect on this process. The factorial results also demonstrate the existence of statistically significant binary interactions of the experimental factors. The experimental results were fitted to the Langmuir and Freundlich equations to find out adsorption capacities. In most cases, the results indicate that the sorption data fits well in the Freundlich isotherm model. The results of XRD analysis, pH(PZC) and pH(Final) values indicated that ion exchange and dissolution/precipitation mechanisms predominate for the sorption of zinc on our hydroxyapatite.