Browsing by Author "Trari, M."

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Characterization and application of the hetero-system LaCoO3/ZnO for degradation of Orange II under solar light
(Springer, 2023) Ouatizerga, A.; Rekhila, G.; Mirad, S.; Trari, M.
LaCoO3 elaborated by nitrate route was characterized physically and electrochemically to be applied in the Orange II (OII) oxidation upon solar light. The X-ray difraction (XRD), SEM analysis and electrical conductivity were undertaken. The difractogram showed that the single phase is completed at 850 °C and the oxide crystallizes in a distorted perovskite structure. The peak at 643 cm−1 in the attenuated total refection (ATR) spectrum confrmed the purity of the phase. The forbidden band (1.35 eV), determined from the difuse refectance, is assigned to Co3+: d-d transition in a low spin confguration (3d6 , E5/2) in conformity with the black color of the oxide. The feld-dependent magnetization was measured at 300 K in the range±25 kOe, and the perovskite exhibits a low magnetism with a saturation magnetization (0.28 emu/g) confrming the low spin state Co3+. The thermal variation of the conductivity is characteristic of non-degenerate behavior and a hole mobility of 10−2 cm2 V−1 s −1 and an activation energy of 0.11 eV. The latter is diferent from that obtained from the thermo-power, a signature of a conduction mechanism by small polaron hopping. LaCoO3 is chemically stable above pH 5; an exchange current density of 40 μA cm−2, a polarization resistance of 1.92 kΩ cm2 and a corrosion potential of 0.99 VSCE were obtained at pH~ 7 (Na2SO4, 0.1 M). Curiously and unlike the perovskites, the variation of the inverse of the square of the capacitance as a function of potential (C−2−E) indicates p type behavior with a fat band potential of 0.30 VSCE and holes density of 1.97× 1017 cm−3. The conduction band (−0.94 VSCE), made up of Co3+: 3d orbital, enables the formation of the radical O2 •−, and as application, the oxide was successfully experimented for the oxidation of OII upon solar irradiation. The hetero-junction p-LaCoO3/n-ZnO enhances considerably the photo-activity, due to the facile transfer of electrons with an abatement of 86% at neutral pH. The oxidation follows a frst-order kinetic with a half photocatalytic life of 23 min
Enhancement of photocatalytic reduction of Cr(VI) using hetero-system NiAl2O4/ZnO under visible light
(Aljest, 2019) Bouallouche Née Saadi, Rachida; Kebir, M.; Nasrallah, N.; Hachemi, M.; Amrane, A.; Trari, M.
Hexavalent chromium Cr(VI) is well known to be a toxic and non-biodegradable contaminant and can cause significant environmental damage if it is not eliminate from wastewater. However, it can be reduced to Cr(III), which is less toxic by photocatalysis process using the heterosystem NiAl2O4/ZnO. NiAl2O4 prepared by nitrate method crystalize in a spinel structure and was characterized, by XRD, FTIR, and SEM techniques. NiAl2O4 acts as electrons pump and the electron transfer to chromate is mediated via ZnO. Under the optimized conditions, the percentage of Cr(VI) reduction was 62 % for 20 mg/L, NiAl2O4/ZnO ratio (1/1) at pH~3.7 and under visible light. An improvement up to 72% was obtained when the reaction occurs in a Rishton reactor with six bleds after 6 h illumination. It is therefore concluded that the Cr(VI) photocatalytic reduction followed a pseudo first order kinetic model, in agreement with the Langmuir–Hinshelwood mechanism. This work revealed that the NiAl2O4/ZnO heterosystem exhibits a better photocatalytic efficiency for the photoreduction of Cr(VI) mainly due to the good separation of electron-hole pairs (e-/h+) in this combination.
Influence of pretreatment on the properties of α-Fe2O3 and the effect on photocatalytic degradation of methylene blue under visible light
(IWA Publishing, 2020) Mokhtari, S.; Dokhan, N.; Omeiri, S.; Berkane, B.; Trari, M.
The hematite (α-Fe 2 O 3 ) nanostructures were synthesized by thermal oxidation of metal at 500 C under atmospheric pressure. We studied the effect of the electrochemical pretreatment of the substrate before calcinations and its impact on the morphology, crystalline structure, lattice microstructural, and optical properties of α-Fe 2 O . Uniform nanosheets were observed on the sample surface after calcination; their dimension and morphology were accentuated by the pretreatment, as conﬁrmed by the SEM images. The characteristics of the nanostructures, analyzed by X-ray diffraction (XRD), revealed a rhombohedral symmetry with the space group R-3c and lattice constants: a ¼ 0.5034 nm and c ¼ 1.375 nm. The average crystallite size and strain, determined from the Williamson-Hall (W-H) plot, showed substantial variations after the substrate pretreatment. The Raman spectroscopy conﬁrmed the changes in the crystal properties of the hematite submitted to pretreatment. The diffuse reﬂectance allowed to evaluate the optical gap which lies between 1.2 and 1.97 eV, induced by the electrochemical processing. The photocatalytic activity of α-Fe 3 ﬁlms was assessed by the degradation of methylene blue (MB) under LED light; 15% enhancement of the degradation for the pretreated specimens was noticed
Kinetic and equilibrium studies of cobalt adsorption on apricot stone activated carbon
(Elsevier, 2014) Abbas, Moussa; Kaddour, S.; Trari, M.
The activated carbon from apricot stone with H3PO4 and its ability to remove Co2+ are reported. The FTIR spectroscopy brings insights on interactions between the functional groups of the carbon and Co2+. Adsorption studies are carried in batch mode by varying the initial Co2+ concentration and pH. A comparison of two kinetic models on the overall adsorption rate shows that the system is described by the pseudo-second-order kinetic model. The Freundlich model fits the data with a monolayer adsorption capacity of 111.11 mg/g at pH 9. The enthalpy and free energy indicate an endothermic and not spontaneous process
Mass-transfer processes in the adsorption of crystal violet by activated carbon derived from pomegranate peels: Kinetics and thermodynamic studies
(SAGE Publications, 2020) Abbas, Moussa; Harrache, Zahia; Harrache, Zahia; Trari, M.
This study investigates the potential use of activated carbon, prepared from pomegranate peels, as an adsorbent activated using H3PO4 and its ability to remove crystal violet from an aqueous solution. The adsorbent was characterized by the Brunauer–Emmett–Teller method (specific surface area: 51.0674 m2 g−1) and point of zero charge (pHPZC = 5.2). However, some examined factors were found to have significant impacts on the adsorption capacity of activated carbon derived from pomegranate peels such as the initial dye concentration (5–15 mg L−1), solution pH (2–14), adsorbent dose (1–8 g L−1), agitation speed (100–700 r/min), and temperature (298–338 K). The best adsorption capacity was found at pH 11 with an adsorbent dose of 1 g L−1, an agitation speed at 400 r/min, and a contact time of 45 min. The adsorption mechanism of crystal violet onto activated carbon derived from pomegranate peels was studied using the pseudo-first-order, pseudo-second-order, Elovich, and Webber–Morris diffusion models. The adsorption kinetics were found to rather follow a pseudo-second order kinetic model with a determination coefficient (R2) of 0.999. The equilibrium adsorption data for crystal violet adsorbed onto activated carbon derived from pomegranate peels were analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation with qmax capacities of 23.26 and 76.92 mg g−1 at 27°C and 32°C, respectively. The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters like the free energy, enthalpy, and entropy to predict the nature of adsorption process. The negative values ΔG0 (−5.221 to −1.571 kJ mol−1) and ΔH0 (−86.141 kJ mol−1) indicate that the overall adsorption is spontaneous and exothermic with a physisorption process. The adsorbent derived from pomegranate peels was found to be very effective and suitable for the removal of reactive dyes from aqueous solutions, due to its availability, low-cost preparation, and good adsorption capacity
Methane steam reforming on supported nickel based catalysts. effect of oxide ZrO2, La2O3 and nickel composition
(2013) Belhadi, A.; Trari, M.; Rabia, C.; Cherifi, Ouiza
The catalytic properties of Ni (4 and 10 wt%) supported on both La2O3 and ZrO2 were investigated for the methane steam reforming reaction between 475°C and 700°C at atmospheric pressure. The catalysts were prepared by the im- pregnation method and characterized by several techniques (atomic absorption, BET method, X-ray diffraction and TG-TPO). The catalytic activity of Ni/support systems strongly depends on both of the nature and physico-chemical properties of the support. No deactivation was observed in catalytic systems, whatever the reaction temperature indicat- ing high stability of the catalyst
Photochemical conversion of CO2 into methyl alcohol using SiC micropowder under UV light
(2017) Azzouz, F.; Kaci, S.; Bozetine, I.; Keffous, A.; Trari, M.; Belhousse, S.; Aissiou-Bouanik, S.
In our study, microparticles SiC powder was investigated as a catalyst for CO2 photoreduction into methanol under UV light. The photochemical conversion of methanol was studied as function of time of exposition, the concentration and the grain size of the catalyst. The selectivity of the used catalyst to promote methanol formation was noticed. It was noticed also that the grain size and concentration have a great impact on the photochemical conversion of CO2 to methanol. The best yield of methanol was achieved when a concentration of 0.75 M of SiC powder of 17 m grain size and an exposure time to UV light of 2 h where assured. Maximum molar concentration of methanol achieved was under UV irradiation of 365 nm. Therefore, the catalytic property of silicon carbide has proved its efficiency in the photochemical conversion of CO2 into alcohol thus far under UV light
Photoelectrochemical characterization of nano-crednerite AgMnO2 synthesized by Auto-Ignition : a novel Pphotocatalyst for H2 evolution
(Springer, 2022) Koriche, N.; Brahimi, R.; Bellal, B.; Trari, M.
AgMnO2 nanocrystallites (31 nm) were prepared by sol-gel auto-ignition at 400°C in air. The crednerite characterized by X-ray diffraction (XRD) showed a single phase, crystallizing in a monoclinic unit cell (SG: C2/m). The refinement was made by isotypy with CuMnO2. The oxide is a narrow band-gap semiconductor with an indirect transition at 1.43 eV. The electrical conduction occurs predominantly by small polaron hopping between mixed valences Ag2+/+ in the (a, b) planes with an activation energy of 0.35 eV. The density of holes (NA = 2 × 1015 cm–3) and their mobility (μh = 0.8 × 10–4 m–2 V–1 s–1) indicate a conduction being thermally activated. The oxygen insertion in the layered crystal lattice induces p-type conductivity, a fact confirmed by the electrochemical measurements. The flat band potential (Efb = –0.04 V) indicates a cationic character of both valence and conduction bands deriving mostly from Ag+ 4d-orbital. The electrochemical impedance spectroscopy shows the predominance of the bulk contribution followed by diffusion of O2– species. The energetic band diagram of AgMnO2 established from the photoelectrochemical study, predicts a spontaneous hydrogen formation; a rate evolution of 39 µmol g–1 min–1 and a power conversion of 0.37% were obtained under visible light irradiation (27 mW cm–2)
Physical properties of the delafossite CuCoO2 synthesized by co-precipitation /hydrothermal route
(Elsevier, 2021) Bouakaz, H.; Abbas, Moussa; Brahimi, R.; Trari, M.
CuCoO2 crystallizing in the delafossite structure was prepared by co-precipitation/hydrothermal method at low temperature (~ 150 °C). It is stable in air up to ~400 °C beyond which it turns into the spinel. The oxide has a direct optical transition attributed to the crystal field splitting of Cu+, linearly coordinated. It exhibits p-type behavior due to O2− insertion in the layered lattice. Such property is corroborated by a cathodic photocurrent in the intensity-potential (J – E) plot and a negative slope of the capacitance potential (C−2– E) plot. The latter traced in NaOH (0.01 M) electrolyte, exhibits a straight line from which a flat band potential of +0.411 V and a hole density of 6.9 × 1023 m−3 were extracted. An exchange current density of 7.36 μA cm−2and a polarizarion resistance (6.69 kΩ cm2), derived from the semi-logarithmic curve (log(J) – E), indicate a good electrochemical stability with a medium hysteresis loop and a low H2-over potential. The anisotropy of the 2 D dimensional crystal structure allows reversible oxygen insertion in the (0 0 n) planes evidenced from the (J – E) profiles. The Electrochemical Impedance Spectroscopy (EIS) measurements give two well-distinguished depressive semicircles in the dark. The diameter of the semicircle at high frequencies (1.49 kΩ cm2) decreases down to (1.28 kΩ cm2) under irradiation, a behavior typical of a non-degenerate semi conductivity of CuCoO2
Physical properties of the perovskite SrTiO3−δ synthetized by chemical route
(Springer, 2023) Merrad, S.; Abbas, M.; Brahimi, R.; Bellal, B.; Trari, M.
The perovskite SrTiO3−δ elaborated by chemical route was characterised by physical and electrochemical methods. The oxide crystallizes in a cubic structure with a lattice parameter of 3.907(5) Å and a crystallite dimension of 71 nm. The morphology visualized by the SEM-EDX analysis shows spherical grains with a mean size of 0.2 μm, formed by agglomeration of crystallites. The diffuse reflectance gave a gap (Eg) of 3.21 eV, ascribed to the charge transfer O2−: 2p → Ti4+: 3d. The thermal variation of the conductivity (σ) obeys an exponential law {σ = σoexp-0.27 eV/T} assigned to low hopping polarons. The electrochemical characterization was undertaken in Na2SO4 solution (10− 1 M) and the n-type character demonstrated from the capacitance measurement and cyclic voltammetry under UV-irradiation, is due to oxygen deficiency. A flat band potential (Efb) of − 0.31 VSCE was determined with a depletion width extended up to ~ 4 μm, advantageous for the formation of electron / hole (e− / h+) pairs. The electrochemical stability against photocorrosion was also shown from the semi-logarithmic plot (log J–E). As application, the Congo Red a diazo dye (CR) is successfully oxidized under UV light on SrTiO3−δ; an abatement of 63% was reached. According to the scavengers mechanism, hydroxyl •OH is the main specie responsible for the CR oxidation. The discoloration follows a pseudo-first-order kinetic with a half-life of 189 min
Preparation and physical properties of the layered niobate Cu0.5Nb3O8 : application to photocatalytic hydrogen evolution
(Elsevier, 2015) Belmokhtar, N.; Brahim, R.; Nedjar, R.; Trari, M.
Semiconducting and electrochemical properties of the spinel FeCo2O4 synthetized by co-precipitation. Application to H2 production under visible light
(Elsevier, 2023) Bouakaz, H.; Abbas, Moussa; Benallal, S.; Brahimi, R.; Trari, M.
FeCo2O4 elaborated by co-precipitation was characterized photo-electrochemically for the first time in order to assess its performance for the hydrogen production. The X-ray diffraction revealed a single phase crystallizing in the spinel structure with a lattice constant of 8.1075 Å and a crystallite size of 35 nm. The UV–Visible diffuse reflectance of the black product exhibits an absorption above 650 nm and a direct optical transition at 1.53 eV was determined, assigned to the crystal field splitting of Co3+: 3d orbital hexa-coordinated. The transport properties indicated semi-conducting properties of FeCo2O4, the positive thermo-power (S300k = 666 μV K−1) demonstrated that holes are majority charge carriers. The Electrochemical Impedance Spectroscopy (EIS) realized in Na2SO4 (0.1 M) electrolyte showed two semicircles at high and intermediate frequencies, characteristic of the charge transfer and grain boundaries respectively. The first diameter (1249 Ω cm2) decreases under visible light down to 742 Ω cm2, thus supporting the semiconducting behavior and no inhibiting effect is observed due to the appearance of the photo-effect. The inverse of the square of the capacitance as a function of the potential (C−2 – E) exhibits a line, negatively slopped, characteristic of p-type behavior with a hole concentration of 21.9 × 1020 cm−3. The conduction band (−0.76 VSCE), made up of Co3+: 3d orbital is more cathodic than the H2-level leading to a spontaneous H2 evolution under visible irradiation (29 mW cm−2) with a liberation rate of 0.58 μmol H2/h−1/g. FeCo2O4 an showed excellent chemical stability after its reuse for the H2 production, as evidenced by X-ray diffraction
Study of Congo Red removal from aqueous solution by using the deficient perovskite SrTiO3-δ under solar light
(Elsevier, 2022) Merrad, S.; Abbas, Moussa; Brahimi, R.; Trari, M.
The deficient perovskite SrTiO3-δ (STO) synthesized by nitrate route was identified by X-ray diffraction (XRD) and characterised by BET analysis, Attenuated Total Reflectance (ATR) and X-ray photoelectron spectroscopy (XPS). The latter enables us to determine the valence states of Sr2+, Ti4+ and O2−. A band gap of 3.32 eV was determined from the diffuse reflectance, assigned to the charge transfer O2−: 2p → Ti4+: 4s and white coloration of STO. The conduction band (−0.60 VSCE) and the valence band (2.72 VSCE) derived respectively from O2−: 2p and Ti4+: 4s orbitals are within the gap region of STO, thus generating O2·− and ·OH radicals responsible for the photo oxidation of Congo Red (CR), a hazardous dye. The photo-catalytic efficiency of STO was confirmed by the CR adsorption and degradation under solar light. Various physical parameters like the catalyst dose, dye concentration, initial pH, irradiation source and inhibitory effect of anions were studied. The synergetic effect of the electron injection from Congo Red into the STO-conduction band was confirmed by the electrochemical measurements through the photocurrent-potential plots and contribute to the photoactivity. An abatement of 62% and 97% are obtained under UV light and solar irradiation respectively
Synthesis, characterization and application of tetragonal BaTiO3-δ in adsorption and photocatalysis of congo red
(Elsevier, 2023) Merrad, S.; Abbas, Moussa; Brahimi, R.; Bellal, B.; Trari, M.
The synthesis by a simple approach of the deficient Barium Titanate BaTiO3-δ (BTO) crystallizing in a perovskite structure is reported along with the physicochemical properties. Thermal analysis (TG/DSC) was performed to elucidate the synthesis process. The X-ray diffraction (XRD), BET analysis, scanning electron microscopy (SEM-EDS) and electrochemistry were investigated. The catalyst revealed a single phase with a tetragonal symmetry obtained by treatment at 650 °C. The direct band gap (3.34 eV), obtained from diffuse reflectance spectroscopy (DRS), is assigned to the charge transfer O2-: 2p-Ti4+: 3d. The electrical characterization indicated a non-degenerate conductivity due to oxygen vacancies with an activation energy of 0.33 eV. The capacitance measurements indicated n-type behavior with a flat band potential (Efb) of − 0.43 V and a carrier concentration (ND) of 3.90 1018 cm−3. The photocatalytic process was elucidated by the electrical impedance spectroscopy (EIS). The performance of BTO was assessed by a combination of the adsorption of Congo Red (CR) followed by its degradation under UV light. The photodegradation kinetic was well fitted by a pseudo-first-order model with an abatement of 50% and 91% under UV and solar lights respectively. Different scavengers were used to evaluate the reaction mechanism and the radicals O2•- are the main reactive species of the CR oxidation. Four regeneration cycles demonstrated the catalyst stability. A degradation mechanism was established based on the scavengers effect