Characteristics of phosphate adsorption on ferric hydroxide synthesized from a Fe<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript> aqueous solution discharged from a hydrometallurgical process

Ferric hydroxide adsorbent was prepared by a chemical treatment process with H₂O₂, NaOH, and aeration from a Fe₂(SO₄)₃ aqueous solution as a side product discharged from the hydrometallurgical process used to extract neodymium. The ferric hydroxide was used as an adsorbent to prevent eutrophication in water. At the time of synthesis, the most important process variable is the pH condition, which, in this experiment, was changed from pH 3 to 13. The cost of synthesizing ferric hydroxide was sharply reduced by using ferric sulfate, which is considered a side product of the aforementioned hydrometallurgical process, as a starting material, and an adsorbent with high adsorption ability was prepared by controlling the pH level. Microstructural characterization of the synthesized ferric hydroxide revealed particles with a specific surface area of 194.2 m²/g and an average pore diameter of 2.66 nm at pH 6 and 298 K. A column-type packed-bed adsorption experiment was conducted under the following conditions: a flow rate of 0.567 BV/min (3.2 mL/min), 298 K, and atmospheric pressure. The results of the adsorption performance test indicated that the adsorption efficiency of phosphate at concentrations of 10 ppm was 100% at a flow rate of 0.567 BV/min within a contact time of 2 min, and the maximum adsorption capacity for phosphate ions was 65 mg/g.     

Hydrothermal synthesis of mesoporous TiO<Subscript>2</Subscript> nanotubes and their adsorption affinity toward Basic Violet 2

Hydrothermal method was used to synthesize TiO₂ nanotubes (TNTs), which are considered as a novel adsorbent with high surface area and adsorption capacity. Different methods including X-ray diffraction (XRD), transmission electron microscope (TEM) and Brunauer–Emmett–Teller (BET) analysis were used to investigate and identify synthesized TNTs. The adsorption capacity of TNTs was investigated with regard to removing Basic Violet 2 (BV2) as a model organic pollutant from aqueous solution. The mean outer, inner diameter and thickness of the TNTs were found to be approximately 9, 4 and 2.5 nm, respectively. BET–BJH method was used for measuring specific surface area and pore volume of the TNTs which turned out to be 200.38 m² g^?1 and 0.44 cm³ g^?1, respectively. The results of the study indicated synthesized TNTs may be considered as efficient and effective adsorbent for removing BV2 (75.63%) from aqueous solution. The impact of the operational variables, i.e. initial BV2 concentration (2–20 mg L^?1), dosage of adsorbent (0.01–0.6 g), and pH (2–8) in relation to the adsorption capacity of BV2 onto TNTs were investigated. The experimental results of the study were meticulously taken into consideration for discussing and analyzing the adsorption isotherms and kinetics. It was found that the collected experimental data regarding the kinetic and isotherm examinations were compatible and well-matched with the pseudo-first order kinetic model and Langmuir isotherm model (R ²?=?0.9634).     

Modification of Cu/Zn/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalyst by Activated Carbon Based Metal Organic Frameworks as Precursor for Hydrogen Production

In this study, Cu/Zn/Al₂O₃-AC (AC?=?activated carbon) catalyst was synthesized and evaluated for dimethoxymethane (DMM) reformation to hydrogen. The Cu/Zn/Al₂O₃-AC catalyst was prepared using high surface area metal organic frameworks (MOFs) consisting of Cu₃(BTC)₂ (MOF-199) and Zn₄O(BDC)₃ (MOF-5) for Cu(II) and Zn(II) sources respectively, as precursors while γ-Al₂O₃ was applied as support. The synthesized catalyst was investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller analysis (BET), Temperature programmed desorption (NH₃-TPD) and Energy-dispersive X-ray spectroscopy (EDX) techniques. Complete DMM conversion was observed over Cu/Zn/Al₂O₃-AC catalyst (Cu:Zn:Al mole ratio of 6:3:2) under atmospheric pressure, T?=?533 K, GHSV?=?20 NL h^?1 g_cat^?1, N₂/H₂O/DMM?=?24/5/1 volume percent (vol%) with hydrogen productivity of 12.8 L H₂ h^?1 g_cat^?1 and 64% hydrogen concentration. Application of MOFs as precursors and modified activated carbon as an acidic component provided the catalyst with the porous structure and high specific surface area for the hydrolysis of DMM, subsequently, high selectivity and productivity of hydrogen was obtained.     

Effect of CeO<Subscript>2</Subscript>-addition sequence on the performance of CeO<Subscript>2</Subscript>-modified Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in autothermal reforming of iso-octane

Two types of CeO₂-modified Ni/Al₂O₃ catalysts were prepared by a consecutive impregnation method with different sequences in the impregnation of Ni and CeO₂, and their performance in autothermal reforming (ATR) of isooctane was investigated. Catalysts prepared by adding CeO₂ prior to the addition of Ni, Ni/CeO₂-Al₂O₃, produced larger amounts of hydrogen than those obtained using catalysts prepared by adding the two components in an opposite sequence, Ni-CeO₂/Al₂O₃. The results of H₂ chemisorption and temperature-programmed reduction revealed that added CeO₂ increased the dispersion of the Ni species on Al₂O₃ and suppressed the formation of NiAl₂O₄ in the catalyst such that large amounts of Ni species were present as NiO, the active species for the ATR. The elemental and thermogravimetric analyses of deactivated catalysts indicated that Ni/CeO₂-Al₂O₃, which showed a longer lifetime than Ni-CeO₂/Al₂O₃, contained lesser amounts and different types of coke on the surface.     

Highly efficient removal of phenol from aqueous solutions using graphene oxide/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite membrane

To achieve superior separation performance in the phenol aqueous solutions treatment, a novel graphene oxide/Al₂O₃ composite membrane was prepared by a spin coating process. The microstructure measurement shows that the composite membrane has a multilayer structure and graphene oxide has been tightly coated on the surface of the Al₂O₃ membrane interlayer homogeneously. During the treatment of phenol aqueous solutions, the permeation flux and phenol rejection of the composite membrane were investigated. The results show the permeation flux of the membrane is about 1.153 L m^?2 h^?1 bar^?1 and the phenol rejection of the membrane increases to 99.9% when the phenol concentration is 0.01 g L^?1. The high phenol rejection of the composite membrane is mainly attributed to the physical sieving, the solution–diffusion effect and the hydrophobic nature of graphene oxide. All these results indicate the GO/Al₂O₃ composite membrane is a suitable material for the removal of phenol from aqueous solutions in environmental pollution management.     

Synthesis and properties of the composite ceramics from nanocrystalline Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-30% Y<Subscript>0.1</Subscript>Zr<Subscript>0.9</Subscript>O<Subscript>2</Subscript> prepared from a water-alcohol solution

The hydrogel of the mixed oxide Al₂O₃-30% Y_0.1Zr_0.9O₂ was prepared by precipitation of ammonia from a water-alcohol mixture (1 : 5). The Al₂O₃-30% Y_0.1Zr_0.9O₂ compound thus synthesized was characterized using differential scanning calorimetry, transmission electron microscopy, and the BET adsorption method. The obtained sample consisted of spherical particles with an average size of 16–20 nm and a specific surface area of 167 m²/g. The Al₂O₃-30% Y_0.1Zr_0.9O₂ powder was pressed at 300 MPa and then calcinated at 1600°C for 2 h in air. The topographic and structural features of the prepared ceramics were determined using atomic force microscopy and X-ray electron probe microanalysis. The porosity, the Vickers microhardness, and the tensile strength were determined by mercury porometry.     

Synthesis of MIL-101@g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> nanocomposite for enhanced adsorption capacity towards CO<Subscript>2</Subscript>

MIL-101@g-C₃N₄ nanocomposite was prepared by solvothermal synthesis and used for CO₂ adsorption. The parent materials (MIL-101 and g-C₃N₄) and the MIL-101@g-C₃N₄ were characterized by X-ray diffraction, argon adsorption/desorption, Fourier transform infrared spectroscopy, thermal analysis (TG/DTA), transmission electronic microscopy, and Energy-dispersive X-ray spectroscopy. The results confirmed the formation of well-defined MIL-101@g-C₃N₄ with interesting surface area and pore volume. Furthermore, both MIL-101 and MIL-101@g-C₃N₄ were accomplished in carbon dioxide capture at different temperatures (280, 288, 273 and 298 K) at lower pressure. The adsorption isotherms show that the nanocomposite has a good CO₂ adsorption affinity compared to MIL-101. The best adsorption capacity is about 1.6 mmol g^?1 obtained for the nanocomposite material which is two times higher than that of MIL-101, indicating strong interactions between CO₂ and MIL-101@g-C₃N₄. This difference in efficacy is mainly due to the presence of the amine groups dispersed in the nanocomposite. Finally, we have developed a simple route for the preparation of an effective and new adsorbent for the removal of CO₂, which can be used as an excellent candidate for gas storage, catalysis, and adsorption.     

Enhanced cyclic stability of CO<Subscript>2</Subscript> adsorption capacity of CaO-based sorbents using La<Subscript>2</Subscript>O<Subscript>3</Subscript> or Ca<Subscript>12</Subscript>Al<Subscript>14</Subscript>O<Subscript>33</Subscript> as additives

To improve the stability of CaO adsorption capacity for CO₂ capture during multiple carbonation/calcination cycles, modified CaO-based sorbents were synthesized by sol-gel-combustion-synthesis (SGCS) method and wet physical mixing method, respectively, to overcome the problem of loss-in-capacity of CaO-based sorbents. The cyclic CaO adsorption capacity of the sorbents as well as the effect of the addition of La₂O₃ or Ca₁₂Al₁₄O₃₃ was investigated in a fixed-bed reactor. The transient phase change and microstructure were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FSEM), respectively. The experimental results indicate that La₂O₃ played an active role in the carbonation/calcination reactions. When the sorbents were made by wet physical mixing method, CaO/Ca₁₂Al₁₄O₃₃ was much better than CaO/La₂O₃ in cyclic CO₂ capture performance. When the sorbents were made by SGCS method, the synthetic CaO/La₂O₃ sorbent provided the best performance of a carbonation conversion of up to 93% and an adsorption capacity of up to 0.58 g-CO₂/g-sorbent after 11 cycles.     

Combustion synthesis of some compounds in the Li<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system

At least four compounds, viz. LiAlO₂, LiAl₅O₈, Li₅AlO₄ and Li₂Al₄O₇, are known in the Li₂O-Al₂O₃ system. These compounds are important for several technological applications. Combustion synthesis of these compounds using urea as a fuel was attempted. LiAlO₂ and LiAl₅O₈ could be successfully prepared by choosing the starting materials in required stoichiometric ratios. Li₂Al₄O₇ was not obtained as a pure phase; γ-LiAlO₂ was formed as an impurity phase. Li₅AlO₄ could not be prepared by combustion process. Some phosphors based on these aluminates could also be prepared. Activation of these aluminates with Fe³⁺, Mn⁴⁺, Cu⁺, etc. was successfully achieved. Excitation and emission spectra for LiAl₅O₈: Fe³⁺, LiAl₅O₈: Mn²⁺, and Li₂Al₄O₇: Cu⁺ are reported.     

Ni-Co bimetallic catalyst for CH<Subscript>4</Subscript> reforming with CO<Subscript>2</Subscript>

A co-precipitation method was employed to prepare Ni/Al₂O₃-ZrO₂, Co/Al₂ O₃-ZrO₂ and Ni-Co/Al₂O₃-ZrO₂ catalysts. Their properties were characterized by N₂ adsorption (BET), thermogravimetric analysis (TGA), temperature-programmed reduction (TPR), temperature-programmed desorption (CO₂-TPD), and temperature-programmed surface reaction (CH₄-TPSR and CO₂-TPSR). Ni-Co/Al₂O₃-ZrO₂ bimetallic catalyst has good performance in the reduction of active components Ni, Co and CO₂ adsorption. Compared with mono-metallic catalyst, bimetallic catalyst could provide more active sites and CO₂ adsorption sites (C + CO₂ = 2CO) for the methane-reforming reaction, and a more appropriate force formed between active components and composite support (SMSI) for the catalytic reaction. According to the CH₄-CO₂-TPSR, there were 80.9% and 81.5% higher CH₄ and CO₂ conversion over Ni-Co/Al₂O₃-ZrO₂ catalyst, and its better resistance to carbon deposition, less than 0.5% of coke after 4 h reaction, was found by TGA. The high activity and excellent anti-coking of the Ni-Co/Al₂O₃-ZrO₂ catalyst were closely related to the synergy between Ni and Co active metal, the strong metal-support interaction and the use of composite support.     

Study of electrochemical properties and the charge/discharge mechanism for Li<Subscript>4</Subscript>Mn<Subscript>5</Subscript>O<Subscript>12</Subscript>/MnO<Subscript>2</Subscript>-AC hybrid supercapacitor

Spinel Li₄Mn₅O₁₂ was prepared by a sol–gel method. The manganese oxide and activated carbon composite (MnO₂-AC) were prepared by a method in which KMnO₄ was reduced by activated carbon (AC). The products were characterized by XRD and FTIR. The hybrid supercapacitor was fabricated with Li₄Mn₅O₁₂ and MnO₂-AC, which were used as materials of the two electrodes. The pseudocapacitance performance of the Li₄Mn₅O₁₂/MnO₂-AC hybrid supercapacitor was studied in various aqueous electrolytes. Electrochemical properties of the Li₄Mn₅O₁₂/MnO₂-AC hybrid supercapacitor were studied by using cyclic voltammetry, electrochemical impedance measurement, and galvanostatic charge/discharge tests. The results show that the hybrid supercapacitor has electrochemical capacitance performance. The charge/discharge test showed that the specific capacitance of 51.3 F g⁻¹ was obtained within potential range of 0–1.3 V at a charge/discharge current density of 100 mA g⁻¹ in 1 mol L⁻¹ Li₂SO₄ solution. The charge/discharge mechanism of Li₄Mn₅O₁₂ and MnO₂-AC was discussed.     

Facile synthesis of imprinted submicroparticles blend polyvinylidene fluoride membranes at ambient temperature for selective adsorption of methyl <Emphasis Type="Italic">p</Emphasis>-hydroxybenzoate

We developed a simple phase inversion technique to prepare molecularly imprinted membrane (MIM) at room temperature for membrane selective adsorption and separation of methyl p-hydroxybenzoate (M4HB). The prepared SMIP-MIM was characterized by SEM, FT-IR, TGA. Compared with non-imprinted membrane (NIM_1-5) adsorbent, SMIP-MIM_1-5 adsorbent with high specific surface area and showed higher binding capacity, faster kinetic and better selectively adsorption capacity for M4HB. The maximum isotherm adsorption capacity for M4HB of SMIP-MIM₄ was 3.519mg·g^?1, and the experimental data was well fitted to the slips model by multiple analysis. The maximum kinetic adsorption capacity and equilibrium adsorption time for SMIP-MIM₄ were 1.335mg·g^?1 and 160 min, respectively. The mechanism for dynamic adsorption of M4HB onto SMIP-MIM₄ was found to follow pseudo-first-order model and pseudo-second-order model. Additionally, the permeability separation factor of SMIP-MIM₄ for M4HB compared to a structural analogues methyl 2-hydroxybenzoate (M2HB) could reach 2.847. The adsorption capacity of SMIP-MIM₄ for M4HB and M2HB was 0.549mg·cm^?2 and 1.563mg·cm^?2, respectively. The adsorption behavior of M4HB through SMIP-MIM₄ followed the retarded permeation mechanism.     

Reductive amination of ethanol to ethylamines over Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

Ni(x)/Al₂O₃ (x=wt%) catalysts with Ni loadings of 5–25 wt% were prepared via a wet impregnation method on an γ-Al₂O₃ support and subsequently applied in the reductive amination of ethanol to ethylamines. Among the various catalysts prepared, Ni(10)/Al₂O₃ exhibited the highest metal dispersion and the smallest Ni particle size, resulting in the highest catalytic performance. To reveal the effects of reaction parameters, a reductive amination process was performed by varying the reaction temperature (T), weight hourly space velocity (WHSV), and NH₃ and H₂ partial pressures in the reactions. In addition, on/off experiments for NH₃ and H₂ were also carried out. In the absence of NH₃ in the reactant stream, the ethanol conversion and selectivities towards the different ethylamine products were significantly reduced, while the selectivity to ethylene was dominant due to the dehydration of ethanol. In contrast, in the absence of H₂, the selectivity to acetonitrile significantly increased due to dehydrogenation of the imine intermediate. Although a small amount of catalyst deactivation was observed in the conversion of ethanol up to 10 h on stream due to the formation of nickel nitride, the Ni(10)/Al₂O₃ catalyst exhibited stable catalytic performance over 90 h under the optimized reaction conditions (i.e., T=190 °C, WHSV=0.9 h^?1, and EtOH/NH₃/H₂ molar ratio=1/1/6).     

Application of ZnO and TiO<Subscript>2</Subscript> nanoparticles coated onto montmorillonite in the presence of H<Subscript>2</Subscript>O<Subscript>2</Subscript> for efficient removal of cephalexin from aqueous solutions

This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO₂ (TiO₂/GLM) in the presence of H₂O₂. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔG ^o and ΔH ^o revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO₂/GLM, respectively. Temkin constant (B _T ) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.     

Investigation of Characterization and Mechanical Performances of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and SiC Reinforced PA6 Hybrid Composites

In this study, the influence of different weight percentages of alumina oxide (Al₂O₃) and silicon carbide (SiC) reinforcement on the mechanical properties of Polyamide (PA6) composite is investigated. Test specimens of pure PA6, 85 wt% PA6 + 10 wt% Al₂O₃ + 5 wt% SiC and 85 wt% PA6 +10 wt% SiC + 5 wt% Al₂O₃ are prepared using an injection molding machine. To investigate the mechanical behaviors tensile test, impact test, flexural test, and hardness test were conducted in accordance with ASTM standards. Experimental results indicated that the mechanical properties, such as tensile, impact, hardness, and flexural strength were considerably higher than the pure PA6. The tensile fracture morphology and the characterization of PA6 hybrid composites were observed by scanning electron microscope and Fourier transform infrared spectroscopic method. Further, thermogravimetric analysis confirms the thermal stability of PA6 hybrid composites. The reinforcing effects of Al₂O₃ and SiC on the mechanical properties of PA6 hybrid composites were compared and interpreted in this paper. Improved mechanical and thermal characteristics were observed by the addition of small amount of Al₂O₃ and SiC simultaneously reinforced with the pure PA6.     

CO<Subscript>2</Subscript> methanation and co-methanation of CO and CO<Subscript>2</Subscript> over Mn-promoted Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

A series of Mn-promoted 15 wt-% Ni/Al₂O₃ catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al₂O₃ catalysts for CO₂ methanation and the comethanation of CO and CO₂ in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO₂ adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al₂O₃ catalysts had improved CO₂ methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO₂ conversion was achieved with the 1.71Mn-Ni/Al₂O₃ catalyst. The co-methanation tests on the 1.71Mn-Ni/Al₂O₃ catalyst indicated that adding Mn markedly enhanced the CO₂ methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO₂ methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.

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Influence of Magnetic Nanoparticles on Surface Changes in CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>/Nerium Oleander Leaf Waste Activated Carbon Nanocomposite for Water Treatment

The paper reports on the successful use of the nano crystalline cobalt ferrite doped Nerium oleander leaf waste activated carbon (CoFe₂O₄/NOAC) synthesized by an urea assisted auto combustion technique to assess accurate kinetics and equilibrium parameters regarding the investigation of adsorption. The specific features of nano composite were investigated by various analytical techniques such as Scanning electron microscope with EDAX, powder X-ray diffraction study, BET surface area analysis, TG and DSC, Vibrating Sample Magnetometer. The BET analysis indicates that CoFe₂O₄ nano particles embedded in NOAC have increased the pore diameter for better adsorption. TG and DSC show the thermal stability of composite. The VSM study shows the Ferro magnetic behavior of nano composite which revealed that CoFe₂O₄/NOAC could be separated and retrieved easily by an external magnet after adsorption of AV49. The efficiency of adsorption of AV49 from aqueous solution was investigated through a series of batch experiments by using CoFe₂O₄/NOAC. The batch adsorption experiments showed the efficient removal on CoFe₂O₄/NOAC under optimum conditions such as pH 6.5, contact time-55 min and adsorbent dosage-50 mg. Adsorption kinetics—Pseudo first order and second order, Isotherms—Langmuir and Freundlich have been adapted to analyze the adsorption capacity. The results showed that the adsorption followed the pseudo second order kinetics and Langmuir isotherm equation is the best to describe the adsorption process. According to the thermodynamic study, it was very effective at higher temperatures also. The thermodynamic parameters ?G^o, ?H^o and ?S^o were also evaluated for this adsorption.     

Regeneration of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h^?1 for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h^?1, the regeneration conversion can reach nearly to 90%.     

Adsorption and kinetic studies of methylene blue on modified HUSY zeolite and an amorphous mixture of γ-alumina and silica

ABSTRACT

Our work focuses on the study of the adsorption of methylene blue (MB) on adsorbents based on zeolite HUSY and (γAl₂O₃-SiO₂). To optimize the process of removing MB onto Ni/Co USY, different parameters were studied such as contact time, initial pH, initial dye concentration, zero charge’s point, and adsorbent dosage. The adsorption isotherm follows the Langmuir model. The maximum adsorption capacities of MB were 59.88 mg g^?1 for Ni/Co USY and 43.86 mg g^?1 for Ni/Co (γAl-Si) at 298°K. The thermodynamic parameters and activation energy’s values obtained suggested that the adsorption was a physical process, spontaneous, and endothermic in nature. MB adsorption on Ni/Co USY may occur via electrostatic interaction, hydrogen bonding, and Lewis acid–base interaction.     

Oxidative reforming of methane on structured Ni-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/cordierite catalysts

The catalytic properties of Ni/Al₂O₃ composites supported on ceramic cordierite honeycomb monoliths in oxidative methane reforming are reported. The prereduced catalyst has been tested in a flow reactor using reaction mixtures of the following compositions: in methane oxidation, 2–6% CH₄, 2–9% O₂, Ar; in carbon dioxide and oxidative carbon dioxide reforming of methane, 2–6% CH₄, 6–12% CO₂, and 0–4% O₂, and Ar. Physicochemical studies include the monitoring of the formation and oxidation of carbon, the strength of the Ni-O bond, and the phase composition of the catalyst. The structured Ni-Al₂O₃ catalysts are much more productive in the carbon dioxide reforming of methane than conventional granular catalysts. The catalysts performance is made more stable by regulating the acid-base properties of their surface via the introduction of alkali metal (Na, K) oxides to retard the coking of the surface. Rare-earth metal oxides with a low redox potential (La₂O₃, CeO₂) enhance the activity and stability of Ni-Al₂O₃/cordierite catalysts in the deep and partial oxidation and carbon dioxide reforming of methane. The carbon dioxide reforming of methane on the (NiO + La₂O₃ + Al₂O₃)/cordierite catalyst can be intensified by adding oxygen to the gas feed. This reduces the temperature necessary to reach a high methane conversion and does not exert any significant effect on the selectivity with respect to H₂.