Herein, we report the optimization of Pb(II) ions removal from soil by electrokinetic remediation, using the response surface methodology (RSM) based on central composite design (CCD) describing ...individual and interactive effects of three chosen variables: the current intensity (I), electrolyte concentration (C) and remediation time (t). Sulfuric acid was selected as the electrolyte medium. The physicochemical properties of the soil were well characterized. The electrokinetic remediation (EKR) experiments were performed in galvanostatic mode, at constant current intensity. The lead Pb(II) content was measured using the atomic absorption spectrophotometer (AAS). Designing and modeling of the experimental runs were done using the Design Expert software. The results establish that the quadratic polynomial model matches the experimental data between the removal efficiency (η %) and the influencing factors. The obtained p-values (<0.05) through ANOVA analysis reveal a significant term, suggesting that the model was satisfactory. The significance of influencing factors increases is in that order: I < C (H
2
SO
4
) < t; increasing the remediation time translates into higher removal efficiencies. The statistical optimization strategy used in this study was successful in attaining the maximal lead removal of 86.79% using current intensity of 0.05 A, H
2
SO
4
concentration of 0.05 M, and remediation time of 24 h 38 min. Ultimately, besides the great potential of the electrokinetic remediation for efficient removal of Pb(II) species, the RSM-based CCD is a promising and valuable tool for modeling and optimizing their elimination from contaminated soils.
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•Physicochemical properties of iron doped ZrO2 are studied by different techniques.•Total photoreduction of Cr(VI) is achieved in 90 min with 50 mol% Fe-ZrO2/TiO2 hetero-system.•The ...photoreduction of Cr(VI) fit adequately the Langmuir-Hinshelwood model.•The detailed photoreduction mechanism of Cr(VI) has been discussed.
In this work, we are interested by the photocatalytic activity under sunlight irradiation of Fe-doped ZrO2 prepared by co-precipitation. The structural and photophysical properties of the catalysts have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), BET method and UV–Vis diffuse reflectance. The results show that Fe-doped ZrO2 exhibits higher photocatalytic activity than that of both ZrO2 and commercial TiO2 P25. The best photocatalytic activity is obtained with the 50 mol% Fe-content calcined at 600 °C/ 3 h. A total photoreduction of Cr(VI) is achieved within 90 min under solar light with the new hetero-junction Fe-ZrO2/TiO2. The kinetic of Cr(VI) photoreduction is well described by the Langmuir-Hinshelwood (LH) model which obeys to pseudo-first-order kinetics with a rate constant of 0.031 min−1. On the basis of the energy band positions of the hetero-junction Fe-ZrO2/TiO2, the detailed reaction mechanism of reduction of inorganic pollutant has been discussed.
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•New hetero-system La2NiO4/ZnO was used for methyl orange degradation under solar irradiation.•The heterojunction La2NiO4/ZnO was prepared by the impregnation method.•The mechanism ...for the enhanced photocatalytic performance is investigated.
Complete photocatalytic degradation of methyl orange (MO) was obtained in 60 min on the II-type hetero-system La2NiO4/ZnO, prepared by an impregnation method. The band gap of La2NiO4 and ZnO are 1.87 and 3.10 eV, respectively, with a direct optical transition. The position of the conduction and the valence band in the energy diagram confirms the formation of the II-type hetero-junction, thus facilitating the photo-degradation of MO. The kinetics of MO degradation obeys to the first order apparent reaction with a rate constant of 0.022 min−1. The reutilization of the hetero-system was studied with high removal efficiency after three photocatalysis runs.
Summary
The physiopathology of idiopathic achalasia is still unknown. The description of circulating antimyenteric autoantibodies (CAA), directed against enteric neurons in sera of patients, suggests ...an autoimmune process. Recent data showed controversies according to the existence and the significance of CAA.
The aims of this study were to investigate whether CAA are detected in Tunisian patients with idiopathic achalasia and to look for associated clinical or manometrical factors with CAA positivity. Twenty‐seven patients with idiopathic achalasia and 57 healthy controls were prospectively studied. CAA were assessed by indirect immunofluorescence on intestinal monkey tissue sections. Western blot on primate cerebellum protein extract and dot technique with highly purified recombinant neuronal antigens (Hu, Ri, and Yo) were further used to analyze target antigens of CAA. CAA were significantly increased in achalasia patients compared with controls when considering nuclear or cytoplasmic fluorescence patterns. (33% vs. 12%, P = 0.03 and 48% vs. 23%, P = 0.001 respectively). By immunoblot analysis, CAA did not target neuronal antigens, however 52/53 and 49 kDa bands were consistently detected. CAA positivity was not correlated to specific clinical features. The results are along with previous studies demonstrating high CAA prevalence in achalasia patients. When reviewing technical protocols and interpretation criteria, several discrepancies which could explain controversies between studies were noted.
NiBi2O4 was synthesized by sol gel method using citric acid as a complexing reagent. The formed gel was dried and calcined for 9 h at three temperature steps (400, 600, 800 °C) to get a single phase ...with the spinel structure. The as-prepared NiBi2O4 was characterized by X-ray diffraction, FT-IR spectroscopy, and UV–vis diffuse reflectance. The optical band gap (Eg =1.76 eV) was obtained from optical absorption spectroscopy. The thermal variation electrical conductivity, measured in the range (300–473 K), is characteristic of semiconductor, with a conduction mechanism by low polaron hopping and activation energy of 0.2 eV. As application, the methylene blue (MB) was successfully oxidized upon solar light. A removal conversion of 40 % was obtained after 2 h at room temperature. The total photo-oxidation of MB (30 mg/L) was obtained on the new hetero-junction NiBi2O4/ZnO at natural pH in less than 2 h. A photocatalytic degradation mechanism occurred through (electron-hole) pairs generation and the redox reactions taking place on the NiBi2O4/ZnO surface of MB are proposed to explain the high activity under solar light irradiation. The degradation kinetics followed a first order with an apparent constant rate of 0.15 h-1.
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•NiFe2O4 was prepared by sol gel auto-combustion method using glycine as fuel.•New heterosystem p-NiFe2O4/n-TiO2 was used for Congo red dye degradation under solar irradiation.•The ...degradation of Congo red (20 mg/L) is quasi total after 180 min.•Kinetic data was well fitted by pseudo-second order model.
This work is dedicated to the investigation of NiFe2O4, prepared by sol gel auto-combustion method using glycine as fuel, to degrade a hazardous dye (Congo red) under sunlight irradiation. TiO2-NiFe2O4 Z‐scheme has constructed via solid dispersion technique to improve the photoactivity by decreasing the recombination of electron/hole (e−/h+) pairs. The photocatalysts are characterized by X-ray diffraction, Fourier Transform infrared spectroscopy and Scanning electronic microscopy with integrated EDX. The optical characterization indicates a direct transition of NiFe2O4 with the band gap (Eg) of 1.64 eV, and an indirect transition for TiO2 (Eg = 3.21 eV). Electrochemical characterization is used to determine the flat band potential (Efb) using the Mott-Schottky plot of the interfacial capacitance, which confirmed the p and n type behavior of NiFe2O4 (Efb = +0.05 VSCE) and TiO2 (Efb = +0.31 VSCE), respectively. Electrochemical impedance spectroscopy (EIS) shows that NiFe2O4 has a low charge transfer resistance (950 Ω cm2) smaller than that of TiO2. The kinetics of Congo red adsorption is well fitted by a pseudo-second order model. The photodegradation tests confirm that p-NiFe2O4/n-TiO2 hetero-structure facilitates the charge separation of photogenerated electrons and holes by reducing the recombination of (e−/h+) pairs. This increases the overall efficiency of the photocatalytic process, which reaches 97 % of Congo red oxidation after 180 min for the composition (p-NiFe2O4/n-TiO2 (0.75/0.25)).
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•Co3O4 was synthesized by sol-gel route.•Hetero-junction Co3O4/AgI was used as photocatalyst for fast green FCF.•Excited electrons from Co3O4-CB (-1.06 VSCE) are injected into AgI-CB ...(-0.90 VSCE).•The oxidation follows a first-order model with a half catalytic life of 41 min.
This work examines the heterogeneous advanced oxidation for the photodegradation of fast green FCF a recalcitrant dye on the novel hetero-junction Co3O4/AgI. The spinel Co3O4 synthesized by sol-gel route was characterized by thermal analysis (TG), FTIR, XRD, SEM, BET, diffuse reflectance and photo-electrochemically; AgI was synthesized by precipitation. Electrons in Co3O4-CB (-1.06 VSCE) excited by sunlight are injected into AgI-CB (-0.90 VSCE). The hetero-junction p-Co3O4/n-AgI brings important changes in the photo-catalytic properties, thus facilitating the rapid transfer of electron-hole (e−/h+) pairs and significantly improving the photoactivity. Some physical parameters like the pH, photocatalyst dose, CFC concentration as a function of illumination time have been studied. After 90 min, 20 mg/L of fast green FCF disappeared under optimal conditions (pH ∼8, 25 °C, p-Co3O4/n-AgI (Wt. %: 1/1) at a dose of 1 mg/mL) upon natural sunlight. The photodegradation kinetic of fast green FCF, measured spectrophotometrically and by total organic carbon (TOC) showed that the oxidation follows a first-order model with a half catalytic life of 41 min.
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•CoMn2O4 was synthetized by co-precipitation method.•CoMn2O4 exhibits p-type conduction with an activation energy of 0.18 eV.•CoMn2O4 was tested as photo-catalyst in the hydrogen ...photo-evolution under soft experimental conditions.•An evolution rate of 0.175 μmol mg−1 min−1 of H2 was obtained.
CoMn2O4 synthetized by co-precipitation, was successfully tested as photo-catalyst in the H2 photo-evolution under soft experimental conditions. The single phase CoMn2O4 was confirmed by X-ray diffraction (XRD), FTIR spectroscopy and SEM analysis. The black oxide exhibits a good activity in the visible range with a forbidden band (Eg) of 1.61 eV. The latter is obtained from the diffuse reflectance spectrum and assigned to d-d transition of the normal spinel. The BET analysis of CoMn2O4 gave a specific surface area of 24 m2/g. The electrical and photo-electrochemical properties have also been studied; the flat band potential is determined from the capacitance measurement (Efb = 0.17 VSCE). According to the chrono-amperometry curve, CoMn2O4 exhibits p-type conduction with an activation energy of 0.18 eV relative to the Arrhenius-type law. The product turns out to be photo-electrochemically active under visible light, CoMn2O4-CB (-0.88 VSCE) offers the possibility of spontaneous H2-generation under soft conditions {pH ∼ 13, 50 °C, S2O3-2 = 0.025 mol/L, dose CoMn2O4 = 1.25 mg/mL}. An evolution rate of 0.175 μmol mg−1 min−1 of H2 was obtained with a quantum efficiency of 1.47% under a radiation flux of 19 mW cm−2 (1.38 × 1019 photons s−1).
The Pr2NiO4/SnO2 heterojunction with a mass ratio equal to unity was tested with success for the hydrogen production under visible light irradiation. Pr2NiO4, prepared by nitrate route, crystallizes ...in a tetragonal symmetry with K2NiF4 type structure. The physical, electrical and photo-electrochemical characterizations are correlated to show the feasibility of Pr2NiO4 for the hydrogen formation under visible light. The enhanced hydrogen production activity is due to electron injection of activated conduction band Pr2NiO4-CB (−1.53 VSCE) into SnO2-CB (−0.87 VSCE) which acts as an electron pump, resulting in better water reduction. The band gap of the semiconductor Pr2NiO4 is 1.81 eV with a direct optical transition. Pr2NiO4 acquired p type conductivity, due to oxygen insertion in the layered lattice with an activation energy of 0.09 eV. The flat band potential (Efb, 0.18 VSCE), very close to the photocurrent onset potential (0.13 VSCE) and the density of the holes (NA, 1.85 1020 cm−3) were obtained from the Mott-Schottky characteristic. H2 production rate of 24.3 μmol g−1 min−1 is obtained with a quantum yield of 1.45% within 30 min under optimal conditions (1 mg of catalyst/mL, pH ~12 and 50 °C) in presence of S2O2−3 as hole scavenger under visible light flux of 29 mW cm−2.
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•New hetero-system Pr2NiO4/SnO2 was used for H2 production.•Pr2NiO4 crystallizes in a K2NiF4-type structure with space Bmab.•The optical band gap of Pr2NiO4 is directly allowed with a value of 1.81 eV.•The insertion of oxygen into the layered crystal lattice induces p-conductivity.•The photocurrent and Mott-Schottky characterizations indicate p-type conductivity.
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•CoCr2O4 was prepared by co-precipitation method.•CoCr2O4 was used for Congo red dye degradation under solar irradiation.•CoCr2O4 has a direct transition and a band gap (Eg) of ...1.74 eV.•The degradation of Congo red (15 mg/L) is quasi total after 180 min.•The mechanism and the potential band diagram are suggested.
The aim of this study was to examine the potential of CoCr2O4, produced by co-precipitation method to degrade the hazardous dye Congo red (CR) when exposed to solar light irradiation. The as-prepared spinel was characterized by X-ray diffraction, attenuated total reflectance-Fourier transform, BET, X-ray photoelectron spectroscopy, scanning electron-microscopy with integrated EDX, and UV–Vis Diffuse Reflectance Spectroscopy. The experimental tests found that CoCr2O4 has a direct transition with a band gap (Eg) of 1.74 eV. Curiously, the normal spinel crystallizing in a cubic symmetry exhibits n-type conduction and to confirm such type behavior of CoCr2O4, electrochemical characterization was undertaken to determine the flat band potential using the Mott-Schottky plot of the interfacial capacitance. The pseudo-second order model was used to fit the kinetic data of CR adsorption. The results of the photodegradation tests showed that n- CoCr2O4 nanoparticles facilitated the separation of photogenerated electrons/holes (e-/h+) pairs by decreasing the recombination process. This increased the overall efficiency of the photocatalytic process, up to be 94% in oxidizing the CR molecules after 180 min with a low catalyst dose of 0.2 g/L. A reaction mechanism is suggested based on a potential band diagram to explain the photocatalytic degradation of the dye onto CoCr2O4 surface.
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