Synthesis and characterization of cobalt-molybdenum oxides catalysts supported on magnesium phosphates.

International audienceIn this work, magnesium phosphates named MgP were synthesized by copptn. from an aq. soln. contg. Mg(NO3)2.6H2O and H3PO4 (85%) with addn. of an 0.4 M NaOH soln. until pH 9. The solids Co-Mo/MgP were synthesized by the dry-impregnation method, with loadings ranging from 4 to 12 wt.% of MoO3 with a Co/Mo at. ratio fixed at 0.5. The solids obtained were then characterized by X-ray diffraction (XRD), thermogravimetric anal. (TGA), DTA, IR spectroscopy (IR); and their sp. surface area were detd. using gas adsorption measurements of nitrogen

Influence of tungsten on the anatase-rutile phase transition of sol-gel synthesized TiO2 and on its activity in the photocatalytic degradation of pesticides

International audienceIn the present study, titanium dioxide and tungsten-modified titanium dioxide photocatalysts were synthesizedby sol–gel method. Structural and morphological characterization has been carried out by using X-ray powderdiffraction (XRD), FT-IR spectroscopy, BET surface area and transmission electron microscopy (TEM)coupled to the energy dispersive spectroscopy (EDX). The adsorption and photocatalytic performances wereinvestigated using two chlorophenoxy herbicides; 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP) as models of organic pollutants in water. The obtained results showthat addition of tungsten to the sol-gel preparation of TiO2 delayed the conversion of anatase to rutile phase.Further increase in tungsten loading apparently stabilized the anatase phase from transformation into inactiverutile. It is also found that, tungsten doped TiO2 exhibited a remarkable enhancement of the photocatalyticactivity compared with the unmodified TiO2 for the photodegradation of the two selected organochlorinesherbicides

Catalytic wet air oxidation of high BPA concentration over iron-based catalyst supported on orthophosphate

Abstract The catalytic performance of Fe supported on nickel phosphate (NiP) was evaluated for the removal of bisphenol A (BPA) by catalytic wet air oxidation (CWAO) at 140 °C and 25 bar of pure oxygen pressure. The prepared NiP and Fe/NiP materials were fully characterized by XRD, N₂-physisorption, H₂-TPR, TEM, and ICP analysis. Iron (Fe/NiP) impregnation of NiP support enhanced the BPA removal efficiency from 37.0 to 99.6% when CWAO was performed. This catalyst was highly stable given the operating conditions of acidic medium, high temperature, and high pressure. The Fe/NiP catalyst showed an outstanding catalytic activity for oxidation of BPA, achieving almost complete removal of BPA in 180 min at a concentration of 300 mg/L, using 4 g/L of Fe/NiP. No iron leaching was detected after the CWAO of BPA. The stability of Fe/NiP was performed over three consecutive cycles, noting that BPA conversion was not affected and iron leaching was negligible. Therefore, this catalyst (Fe/NiP) could be considered as an innocuous and effective long-lasting catalyst for the oxidation of harmful organic molecules

Hydrothermal carbonization of Argan nut shell:functional mesoporous carbon with excellent performance in the adsorption of bisphenol A and diuron

Abstract Hydrochar derived from Argan nut shell (ANS) was synthesized and applied to remove bisphenol A (BPA) and diuron. The results indicated that the hydrochar prepared at 200 °C (HTC@ANS-200) possessed a higher specific surface area (42 m²/g) than hydrochar (HTC@ANS-180) prepared at 180 °C (17 m²/g). The hydrochars exhibited spherical particles, which are rich in functional groups. The HTC@ANS-200 exhibited high adsorption efficiency, of about 92% of the BPA removal and 95% of diuron removal. The maximum Langmuir adsorption capacities of HTC@ANS-200 at room temperature were 1162.79 mg/for Bisphenol A and 833.33 mg/g for diuron (higher than most reported adsorbents). The adsorption process was spontaneous (− ΔG°) and exothermic (− ΔH°). Excellent reusability was reclaimed after five cycles, the removal efficiency showed a weak decrease of 4% for BPA and 1% for diuron. The analysis of Fourier transforms infrared spectrometry demonstrated that the aromatic C=C and OH played major roles in the adsorption mechanisms of BPA and diuron in this study. The high adsorption capacity was attributed to the beneficial porosity (The pore size of HTC@ANS-200 bigger than the size of BPA and diuron molecule) and surface functional groups. BPA and diuron adsorption occurred also via multiple adsorption mechanisms, including pore filling, π–π interactions, and hydrogen bonding interactions on HTC@ANS-200

Toward new benchmark adsorbents:preparation and characterization of activated carbon from argan nut shell for bisphenol A removal

Abstract The use of argan nut shell as a precursor for producing activated carbon was investigated in this work. Two activated carbons AC-HP and AC-Na were prepared from argan nut shell by chemical activation method using phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH), respectively. Textural, morphological, and surface chemistry characteristics were studied by nitrogen physisorption, TGA, SEM, TXRF, FTIR, XRD, and by determining the pHPZC of the AC-HP. The adsorption experiments revealed that AC-HP was more efficient in adsorption of BPA due to high specific surface area (1372 m²/g) compared to AC-Na (798 m²/g). The obtained adsorption data of BPA on AC-HP correlated well with the pseudo-second-order model and the Langmuir isotherm (Qmax = 1250 mg/g at 293 K). The thermodynamic parameters (ΔG° < 0, ΔH° < 0, and ΔS° < 0) indicate that adsorption of BPA on AC-HP was spontaneous and exothermic in nature. The regeneration of AC-HP showed excellent results after 5 cycles (95–93%). This work does not only provide a potential way to use argan nut shell but also represents a sustainable approach to synthesize AC-HP, which might be an ideal material for various applications (energy storage, catalysis, and environmental remediation)

Steam activation of waste biomass:highly microporous carbon, optimization of bisphenol A, and diuron adsorption by response surface methodology

Abstract Highly microporous carbons were prepared from argan nut shell (ANS) using steam activation method. The carbons prepared (ANS@H2O-30, ANS@H2O-90, and ANS@H2O-120) were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared, nitrogen adsorption, total X-ray fluorescence, and temperature-programmed desorption (TPD). The ANS@H2O-120 was found to have a high surface area of 2853 m²/g. The adsorption of bisphenol A and diuron on ANS@H2O-120 was investigated. The isotherm data were fitted using Langmuir and Freundlich models. Langmuir isotherm model presented the best fit to the experimental data suggesting micropore filling of ANS@H2O-120. The ANS@H2O-120 adsorbent demonstrated high monolayer adsorption capacity of 1408 and 1087 mg/g for bisphenol A and diuron, respectively. The efficiency of the adsorption was linked to the porous structure and to the availability of the surface adsorption sites on ANS@H2O-120. Response surface method was used to optimize the removal efficiency of bisphenol A and diuron on ANS@H2O-120 from aqueous solution

Catalytic abatement of dichloromethane over transition metal oxide catalysts:thermodynamic modelling and experimental studies

Abstract Dichloromethane (DCM) is a noxious chemical that is widely used in industry. The current work focuses on the catalytic abatement of DCM from industrial effluents to minimize its harmful effects to the environment and human wellbeing. Three transition metal oxide catalysts (V, Cu and Mn) supported on γ-Al₂O₃ were synthetized for total oxidation of DCM in presence of steam. Thermodynamic modelling was used to reveal information related to the stability of the used transition metal oxides in the abatement conditions. The results showed that with 10 wt-% CuO and 10 wt-% V₂O₅ containing catalysts 100% conversion of DCM together with 90% HCl yield and insignificant by-product formation can be achieved at temperature around 500 °C. According to modelling, V₂O₅ should be stable at the conditions of DCM oxidation, while CuO would be more stable at higher temperature level (decomposition of CuCl₂ starts at 300 °C). MnCl₂ remains stable until 800 °C, which leads to deactivation of MnO₂ catalyst. Presence of steam inhibits the poisoning of the materials by chlorine based on thermodynamic calculation. XRF analysis supports the results of thermodynamic modelling — used MnO₂ and CuO catalysts contain chlorine, which was not detected in case of V₂O₅/Al₂O₃. CuO/γ-Al₂O₃ seems to be a good alternative to noble metal catalysts for the total oxidation of dichloromethane when used in the presence of steam and the temperatures above 300 °C to minimize Cl-poisoning. The outcomes of this study showed that the prepared metal oxides are promising catalysts to minimize pollution caused by chlorinated volatile organic compounds

Total oxidation of dichloromethane over silica modified alumina catalysts washcoated on ceramic monoliths

Abstract Silica modified alumina was used in this study for coating of a cordierite monolith substrate with two different channel densities. The performance of the prepared monolith catalysts was evaluated in catalytic total oxidation of dichloromethane before and after Pt impregnation. The characteristics similar to the powder form catalysts were kept rather successfully after washcoating the monolith as evidenced by electron microscopy (FESEM) and N2 physisorption. A dichloromethane (DCM) conversion of higher than 80% at 500 °C was reached over all the catalysts with 200 cpsi. The maximum conversion was obtained with the catalyst containing 10 mol % of silica. The total amount of major byproducts (CO, CH3Cl and CH2O) were slightly decreased by increasing the silica loading, and remarkably after Pt impregnation. After impregnation of Pt, the HCl yields were increased for two samples with the higher loading of silica (10 and 15 mol %) and reached the maximum when silica loading was 10%. Even though Pt impregnation did not significantly affect the DCM conversion, it improved the selectivity. Comparison between the two substrates (200 and 600 cpsi) evidenced that the key parameters of the monolith influencing the DCM oxidation are low value of open fraction area, hydraulic diameter, thermal integrity factor and high value of mechanical integrity factor and geometric surface area

Comparative study on the support properties in the total oxidation of dichloromethane over Pt catalysts

Abstract The aim of this work was to study the influence of the support oxide properties on the total oxidation of dichloromethane in moist conditions. The support materials γ-Al2O3, TiO2, CeO2 and MgO were synthesized by a sol-gel method followed by wet impregnation of Pt and characterized by different physico-chemical techniques. The conversion of DCM was higher than 90% at 500 °C over impregnated and non-impregnated Al2O3, TiO2 and CeO2, even at high GHSV. CO, CH3Cl and CH2O were the major by-products observed and their amounts decreased after Pt impregnation. The CH3Cl formation was higher when Lewis acid sites were present while the existence of Brønsted sites promoted the CH2O formation. The complete conversion of DCM was achieved at around 450 °C over the Al2O3 and Pt/Al2O3 and at 500 °C for Pt/TiO2. These two catalysts exhibited the highest total acidities among the materials tested. The activity of Pt/Al2O3 remained the same also after 55 h of testing, however, increase in Pt particle size and decrease in acidity were observed. Pt/CeO2 while being less active showed smallest amount of by-product formation during the whole temperature range used in light-off tests. This is most probably due to its easy reduction ability. The textural parameters of the supports did not appear to be the key parameters when considering the activity and selectivity of the catalysts