Langmuir-Hinshelwood Kinetic Model Research Articles

Studies of Clinoptilolite-Rich Zeolitic Tuffs from Different Regions and Their Activity in Photodegradation of Methylene Blue

The present study focuses on clinoptilolite (CLI)-rich natural zeolitic tuffs and their photocatalytic activity in the degradation of cationic organic dyes. CLI from different regions was tested in the photocatalytic degradation of methylene blue (MB) as a model cationic dye. The photocatalytic tests were performed at room temperature and atmospheric pressure under visible light irradiation. For all the CLI samples, the highest activity was observed at pH = 6. Total MB degradation varied between 70 and 91% (C0 = 10 mg dm–3, 0.2 g dm–3 of photocatalyst, during 300 min). It is suggested that the presence of Fe species in the studied tuffs is responsible for the photocatalytic activity. The activity increases linearly with the Fe content in the tuffs. The MB photodegradation follows the Langmuir–Hinshelwood kinetic model. The recyclability tests showed good stability and efficiency of the photocatalyst. The degradation rate decreased from 91 to 69% during three reaction cycles, indicating a promising potential of natural zeolites in the treatment of textile industry wastewater.

Preparation of a surface modified fly ash-based geopolymer for removal of an anionic dye: Parameters and adsorption mechanism

Geopolymers have been recently studied as environmentally friendly and low-cost adsorbents especially for the removal of cationic species in wastewater treatment mainly because of their negative surface charge at spontaneous pH conditions. Although there are very few recent studies conducted with different geopolymer composites on anionic dyes, high cost, difficulty of the composite preparation and most importantly the necessity of very low pH values limit their usage. Hence, in this study, a simple and low-cost surface modification with CTAB was applied to a previously prepared fly ash-based geopolymer (GEO) for the removal of anionic Acid Blue 185 (AB185) without the need of strongly acidic conditions. Within this scope, the effects of CTAB dosage (1–5% by weight of GEO), adsorbent dosage (0.5–3.0 g L−1) and initial dye concentration (10–50 mg L−1) were studied as a function of retention time (5–300 min). For 40 min, the removal efficiency of AB185 substantially increased from 0.29 up to 79.36% for the respective GEO and its modified product with 4% CTAB (MGEO4). The efficiency increased with the adsorbent (MGEO4) dosage of up to 2.0 g L−1 at which 89.20% was obtained for 300 min. However, a little decrease was observed down to 81.10% for 3.0 g L−1. The efficiency values of 98.19 and 89.20% were obtained for the initial AB185 concentrations of 10 and 50 mg L−1, respectively. The Langmuir-Hinshelwood kinetic model is highly correlated with the experimental results. The high adsorption capacity attained in a very short time suggests that the main mechanism is based on physical adsorption via the electrostatic attraction between MGEO4 and AB185. Overall results have indicated that the CTAB-modified fly ash-based geopolymer can be effectively used for the adsorption of AB185.

Kinetics of fatty acid ketonization in liquid phase with anatase and rutile TiO2 catalysts

Catalytic ketonization of carboxylic acids is promising for the synthesis of renewable products. Despite its potential, fatty acid ketonization and its kinetics in the liquid phase are less investigated. This work encompasses kinetic evaluation of two TiO2 catalysts (anatase and rutile) for C-C coupling of C12-C18 fatty acids in inert dodecane solvent. The rutile catalyst, with higher Lewis acid density, showed higher intrinsic activity and more favorable activation energy barriers. Unfortunately, this material suffers from stronger product inhibition by ketone, water and carbon dioxide compared to anatase. Langmuir-Hinshelwood kinetic models were developed and validated against the experimental data, supporting that C-C coupling of adsorbed species is rate determining in the ketonization mechanism. The Lewis acid site density and distance between active Ti species at the surface were invoked to explain the activity patterns. The impacts of substrate chain length, solvent and liquid phase purging on the ketonization kinetics were investigated, showcasing potential for future improvements.

Photocatalytic degradation of methylene blue using ZnO supported on wood waste-derived activated carbon (ZnO/AC)

This study reports the preparation of ZnO supported on wood waste-derived activated carbon (ZnO/AC) and its activity towards photocatalytic degradation of methylene blue (MB). The removal of MB is imperative owing to its toxic impacts on the receiving water bodies. Thus, finding treatment techniques with criteria of efficient, cost-effective, and environmentally benign is highly needed. ZnO/AC has been synthesized by the incipient wetness impregnation method and was characterized using XRD, FTIR, PL, and UV–Vis-NIR. Characterization analysis revealed the successful impregnation of ZnO onto the AC. The best photocatalytic degradation of MB using ZnO/AC was achieved at 180 min, adsorbent dosage of 3 g/L, and pH 8. Complete MB degradation was attained at lower initial MB concentrations (10 – 50 mg/L) and slightly decreased at higher initial MB concentration (100 mg/L). The experimental data fitted well with the pseudo-first-order Langmuir-Hinshelwood kinetic model with a correlation coefficient (R2) greater than 0.995. The results revealed that the synthesized ZnO/AC exhibited remarkable photocatalytic activity towards the degradation of MB.

Design of S-scheme 3D nickel molybdate/AgBr nanocomposites: Tuning of the electronic band structure towards efficient interfacial photoinduced charge separation and remarkable photocatalytic activity

We reported the facile synthesis of new S-scheme 3D NiMoO4/AgBr nanocomposites photocatalysts and their promising photoactivity for the methylene blue degradation. For efficient separation and transfer of charge carriers, heterojunction construction is desirable. The nickel molybdate heterostructured photocatalysts were fabricated by using facile template free hydrothermal and precipitation methods. The α-phase has doubly ionized vacancies and the β-phase has singly ionized vacancies, which makes the structures promising materials for photocatalytic applications. The fabricated photocatalysts were fully characterized. Photocurrent-time experiments, PL spectroscopy, and EIS were applied for charge carrier transfer, recombination and resistance investigations. Optical behavior of samples was analyzed by DRS technique and Tauc method and effect of different parameters on photoactivity was evaluated. The photocatalytic activity of NiMoO4/AgBr nanocomposite was larger than that of bare NiMoO4 and AgBr. Based on quenching method, it can be concluded that holes and hydroxyl radicals were the main active species and according to Langmuir-Hinshelwood kinetics model, the reaction obeyed the pseudo first order kinetics. High photocatalytic activity was related to the synergistic effect induced by formation of 3D NiMoO4/AgBr nanostructures. Active site on the surface of 3D NiMoO4/AgBr structure, high surface area, band structure and efficient charge separation and transfer through the NiMoO4/AgBr, are other effective factors on photodegradation. No morphology and structure changes observed after 4 consecutive cycle which concluded that the nanocomposites are chemically stable and can be used for practical cases.

Photocatalytic process augmented with micro/nano bubble aeration for enhanced degradation of synthetic dyes in wastewater

This research combines TiO2 nanopowder photocatalyst (TNP) with micro/nano bubble aeration (MNBA) to enhance the dye degradation of the photocatalytic process treating synthetic dye wastewater. The experimental synthetic dyes were indigo carmine (IC) and reactive black 5 (RB5). The dye degradation performance of the photocatalytic process without MNBA (TNP ​+ ​UVA) and with MNBA (TNP ​+ ​UVA ​+ ​MNBA) under various initial dye concentrations were evaluated. The results showed that, given the initial IC and RB5 dye concentrations of 2 ​μM, the degradation efficiency of TNP ​+ ​UVA and TNP ​+ ​UVA ​+ ​MNBA were 100%. With higher dye concentrations (4–10 ​μM), the degradation efficiency of TNP ​+ ​UVA and TNP ​+ ​UVA ​+ ​MNBA were between 84.05-98.20% and 90.64–100%. The kinetics of the photodegradation reaction of both dyes were described by the Langmuir-Hinshelwood kinetic model. The pseudo first order degradation rate constants of the photocatalytic process with MNBA were 1.44 and 1.66 times higher than those without MNBA for IC and RB5.

Syngas production by carbon dioxide reforming of methane over Pt/Al2O3 and Pt/ZrO2-SiO2 catalysts

Carbon dioxide reforming of methane (CDRM) is an effective way for syngas production. In this work, two laboratory-made Pt-based catalysts Pt/Al2O3 and Pt/ZrO2-SiO2 (Pt content = 0.5%) were used for the CDRM process in a fixed-bed reactor. The effects of changing space time (0.08–0.167 g-h/L) on CH4 and CO2 conversions and syngas ratio and yield were studied in the 773–1073 K range in an integral reactor. At 1073 K, the effects of CO2/CH4 ratio in the feed (0.5–2 mol/mol) and time-on-stream (up to 10 h) were investigated. For an equimolar feed of CH4 and CO2, the conversions of CH4 (72.6 and 70.6%) over Pt/Al2O3 and Pt/ZrO2-SiO2 catalysts at T = 1073 K and space time = 0.167 g-h/L were comparable; the corresponding CO2 conversion values were 77.6 and 74.8%. The kinetics of CDRM was studied between 848 and 898 K in a differential reactor and the data were analyzed using the power-law and Langmuir-Hinshelwood kinetic models.

Photocatalytic degradation kinetics of cationic and anionic dyes using Au–ZnO nanorods: Role of pH for selective and simultaneous degradation of binary dye mixtures

Photocatalysis with ecofriendly and low cost materials is attractive for degradation of organic pollutants without aid of strong reagents. In this regard, Au nanoparticle decorated ZnO nanorods (Au–ZnO) with good crystalline quality was synthesized by cost-effective and scalable hydrothermal method followed by photo-reduction of Au salt. This study addresses variation of photocatalytic degradation kinetics of different nature of dyes with various scavengers and pH conditions. Further, the process versatility is demonstrated by selective or simultaneous degradation of binary dye mixtures with optimized parameters. From Langmuir-Hinshelwood kinetic model, dye concentration range for first order limiting case was determined, and further validated from measured surface area of photocatalyst and change in dye absorbance before irradiation. Better adsorption with faster degradation exhibited by Methylene Blue (MB) dye showed efficient mineralization, revealed from chemical oxygen demand measurements. In Au–ZnO photocatalysis, generation of hydroxyl radical and its significant role in dye degradation was demonstrated using different scavengers. Variation of dye adsorption with pH dependent surface charge characteristics of photocatalyst resulted about one order higher degradation rate constant of MB at high pH. Strong pH dependent MB degradation is shown to be useful for its selective or simultaneous degradation with other dyes. Results of this study are useful for designing photo-reactors and these nanoparticles are efficient for degradation of different dyes, their combinations and industrial effluents under low power UV lamp for treatment different organic pollutants.

Cinética de la esterificación de éteres de glicol con ácido acético para la obtención de acetatos de éteres de glicol

Glycol ether acetates are solvents of great industrial interest due to their low water solubility and slow evaporation rate. In the present work, the kinetics of esterification of glycol ethers with acetic acid to obtain glycol ether acetates was studied. Different synthesis conditions were evaluated, such as reaction temperature, catalyst type, catalyst loading and molar ratio between reactants. Uncatalyzed, catalyzed under homogeneous conditions with pTSA and under heterogeneous conditions with Amberlyst 15 were carried out. Second order kinetic model for the homogeneous system and Langmuir-Hinshelwood kinetic model for the heterogeneous system were proposed and the fit to the experimental data was performed to estimate the reaction rate constants. It was found that the maximum in reaction conversion depends mostly on the ratio between reactants, while temperature, catalyst type and catalyst loading have a significant effect on the reaction rate. Models’ predictions are in good agreement with the experimental data and the values of the reaction rate constants are consistent with values reported in other studies.

Fundamental reaction kinetics of high-pressure reductive amination of polyalkylene glycol

This study investigates reaction kinetics of high-pressure amination of polyalkylene glycol (PAG) to polyetheramine (PEA). The reductive amination of PAG was carried out depending on the NH3 amount, reaction temperature, reaction pressure, and H2O content in a batch reactor to understand the effect of these factors on activity and selectivity toward the primary amine. Contrary to the fact that the amination step is a zero-order reaction and dehydrogenation of alcohol to ketone is the rate-limiting step in the reductive amination of alcohol, the amount of NH3 significantly affected the reaction rate. The increased amount of NH3 enhanced the activity and selectivity for PEA, in contrast with the results reported in prior studies. A Langmuir-Hinshelwood kinetic model was established to reflect the effect of the NH3 amount, and kinetic parameters such as the rate constant and activation energy were obtained at a high pressure around 150 bar. It was also found that the absence of NH3 caused the reverse reaction of PEA to the secondary amine in the presence of H2. The fundamental kinetic analysis provides a competitive synthesis route for improving the activity and selectivity toward the primary amine.

Methane steam reforming reaction in solid oxide fuel cells: Influence of electrochemical reaction and anode thickness

The influence of operation temperature, inlet gas composition, current density and the anode thickness on the methane steam reforming reaction over nickel yttria-stabilized zirconia anodes was experimentally studied in solid oxide fuel cells. The experimental results were analyzed using data fitting in Power-Law and Langmuir–Hinshelwood kinetic models. Similar trends of dependence of methane and steam partial pressures were observed in both models. The methane reaction order is positive. Negative influence of steam partial pressure on the methane steam reforming reaction rate are found. The electrochemical reaction and anode thickness affect the reforming kinetics parameters. The anodes thickness shows particular influences on the steam reaction order, and the activation energy when a current is produced. The model evaluation suggests that the two models are comparable and the extra parameters within the Langmuir–Hinshelwood kinetic model are contributing to the lower mean absolute percentage error and higher coefficient of determination R 2 . • Current promotes the methane steam reforming reaction rate. • Anode thickness influences the fitted activation energy. • More experimental data is helpful in getting a reliable rate expression. • Importance of studying effect of mass-transfer on the global MSR kinetics.

Photocatalytic Degradation of Ethylbenzene in Aqueous Solutions by ZnFe2O4 Nanoparticles Supported on the Copper Slag: Optimization, Kinetics and Thermodynamics Studies

ZnFe2O4/Copper slag (CS) which is an environmentally friendly and cost-effective catalyst was produced by co-precipitation methods and a thermal process. The synthesized catalyst was characterized by XRD, SEM, EDX and BET surface area analysis. The X-rays diffraction pattern confirmed that the crystal structure of ZnFe2O4 after stabilization on CS zeolite has not changed. The SEM images showed that, despite their varying sizes, the particles all have the same shape. Photocatalytic activity of the catalyst was tested for the degradation of ethylbenzene (EB) in water by UV + H2O2 method in the reverse-flow packed bed photo reactor. The process optimization and modeling were performed using the full factorial method. The initial concentration of EB = 30 ppm, pH = 9 and initial H2O2 concentration = 15 ppm were the best conditions. Under ideal process conditions, the removal efficiency of EB was greater than 99.5%. The validity of the Langmuir-Hinshelwood kinetics model was confirmed using EB photocatalytic degradation experimental results. The values of 〖∆H〗^⫲and 〖∆S〗^⫲ for the photocatalytic degradation of EB by ZnFe2O4/CS catalyst in the UV+H2O2 process were calculated based on the transition state theory and gave 1.67 kJ mol-1 and -263.057 J K-1 mol-1 respectively.

The Influence of Hydrodearomatisation Reaction Kinetics on the Modelling of Sulphur and Aromatics Removal from Diesel Fuel in an Industrial Hydrotreating Process

Over the years, the hydrotreating process has been considerably improved in order to facilitate the production of environmentally friendly diesel fuels by reducing sulphur and aromatics concentrations, as mandated by contemporary emissions regulations. In this study, different kinetic models for the hydrodearomatisation reaction and the influence of reaction rate on performance of the industrial trickle bed reactor for hydrotreating of gas oil and light cycle oil fractions were analysed. The impact on reactor temperature, catalyst wetting efficiency, and conversion of sulphur and aromatics were determined. The results of simulations were compared with experimental data from an industrial test run and the best model for the observed process is proposed. Reactor performance and overall efficiency of the process is strongly dependent on the kinetics of hydrodearomatisaton with respect to aromatics conversion but even more so with respect to the temperature increase in the reactor, which affects all key catalytic reaction parameters, catalyst wetting efficiency, and thus the sulphur conversion. Based on the obtained simulation results, it could be concluded that reactor performance is strongly dependent on the hydrodearomatisation reaction. The best predictions of outlet temperature as well as sulphur and aromatic conversion (deviation from the experimental value 0.87 K, 0.01% and 2.57%, respectively) are achieved with the Langmuir–Hinshelwood kinetic model proposed by Owusu-Boakye.

Photoelectrochemical performance of tubewall‐separated titanium dioxide nanotube array photoelectrode

AbstractTitanium dioxide nanotube array (TiO2 NTA) grown on titanium substrate has been fabricated as active photoelectrode for organic compound degradation. TiO2 NTA shows the tubewall‐separated nanotube arrangement and anatase crystal structure. Transient photocurrent of 1.86 mA and open‐circuit photovoltage of 0.26 V are determined to keep stable level under ultraviolet (UV) light irradiation, indicating its high photoelectrochemical activity. The cathodic polarization process causes more feasible electron transfer than the equilibrium process and anodic polarization process, which is consistent with the declining current response at an increasing positive potential. The photocatalytic activity of TiO2 NTA is fully evaluated through UV light‐induced photocatalysis and photoelectrocatalysis degradation of organic dye X‐3B as a reactant pollutant. The pseudo‐first‐order reaction rate constant is enhanced from 0.00346 min−1 for photocatalysis to 0.00521 min−1 for photoelectrocatalysis using Langmuir–Hinshelwood kinetic model of heterogeneous catalysis. The tubewall‐separated nanotube structure could induce photoelectron directional transport and provide extra interspace for reactant organic molecule diffusion at accessible surface area. The positive potential applied on TiO2 NTA could further promote photoelectron–hole pair separation. Two strategies of photoelectron generation and photoelectron–hole separation are accordingly adopted to improve its electro‐assisted photocatalytic activity. Therefore, the tubewall‐separated TiO2 NTA could present the promising photoelectrocatalysis application.

Sonocatalytic degradation of amoxicillin from aquaculture effluent by zinc oxide nanoparticles

In this study, zinc oxide nanoparticles (nano-ZnO) was effectively synthesised by precipitation method to catalyse the ultrasound degradation of amoxicillin aquaculture effluent. The nanoparticles at different calcination temperatures were characterised by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and Brunauer, Emmett and Teller (BET) surface area determination. Characterisation results indicated that Zn existed as different compounds at different temperature, besides, pure zincite (ZnO) was obtained at 500 °C having a BET surface area of 8.39 m2/g. The degradation experiments indicated that the ultrasound/H2O2 system with nano-ZnO was more effective for amoxicillin degradation than they were independently. The ultrasound/H2O2 system with nano-ZnO could be described by the Langmuir-Hinshelwood kinetic model. The addition of H2O2 and nano-ZnO to the ultrasound reactor enhanced the degradation of amoxicillin from 46.87% up to 98.9%. The recyclability and stability of nano-ZnO also showed that the catalytic activity of nano-ZnO during ultrasound degradation of amoxicillin was not lost up to five cycles. Thus, the application of ultrasound in the presence of H2O2 and nano-ZnO is favorable and effective for the remediation of aquaculture effluent.

Adsorption and Photocatalytic Activity of Nano-magnetic Materials Fe3O4@C@TiO2-AgBr-Ag for Rhodamine B

Background: TiO2 nanoparticles possess adsorption capacity and photocatalytic activity, and are thus fitted for removal of dyes from water. However, TiO2 nanoparticles are difficult to separate from the bulk solution due to high loss. Moreover, TiO2 can only use light with a wavelength of less than 387.5 nm, so the utilization efficiency of solar energy is very low. The present work prepared Fe3O4@C@TiO2-AgBr-Ag composites to overcome the shortcomings of TiO2. Objective: Adsorptive and photocatalytic performance of nano-magnetic materials Fe3O4@C@TiO2- AgBr-Ag. Methods: Fe3O4@C@TiO2 and Fe3O4@C@TiO2-AgBr-Ag magnetic nanocomposites were prepared by the sol-gel method. Their structure was characterized. Performances of Fe3O4@C@TiO2 and Fe3O4@C@TiO2-AgBr-Ag for removing Rh B were thoroughly investigated and compared. Langmuir– Hinshelwood kinetic model was applied to analyze the heterogeneous processes of adsorption and photodegradation. Results: Removal experiments were carried out with Rhodamine B as the subject. The effects of contacting time, pH, subject concentration, and doses of photocatalyst on the removal performance were studied. The removal of Rh B by Fe3O4@C@TiO2 and Fe3O4@C@TiO2-AgBr-Ag involved both adsorption and photodegradation, and the photocatalytic activity of Fe3O4@C@TiO2-AgBr-Ag was much higher than that of Fe3O4@C@TiO2. The optimum removal conditions were determined. Under the optimal conditions, the removal rate of Rhodamine B with Fe3O4@C@TiO2 was 77.8%, and the removal rate of Rhodamine B with Fe3O4@C@TiO2- AgBr-Ag was 87.3%. Conclusion: The coupling of the nanostructured metal Ag to the outer surface of TiO2 could effectively increase photocatalytic efficiency under visible light. The photocatalysts could be separated from bulk solutions by using a magnet and be easily recycled. The removal reaction kinetics fitted with the first-order model.

Improved photocatalytic oxidation performance of gaseous acetaldehyde by ternary g-C3N4/Ag-TiO2 composites under visible light

In the process of photocatalytic oxidation (PCO), titanium dioxide (TiO2) shows excellent capabilities. However, when TiO2 is used to remove volatile organic compounds (VOCs), there are some drawbacks including weak adsorption of gaseous contaminants, insufficient utilization of sunlight, and rapid recombination of photogenerated carriers. Herein, a TiO2-based ternary heterogeneous photocatalyst, g-C3N4/Ag-TiO2, was successfully fabricated to photodegrade gaseous acetaldehyde (one of the representatives of oxygenated VOCs) under visible light. Among the various samples, the g-C3N4/50 wt% Ag-TiO2 exhibited an excellent photocatalytic activity, which was 5.8 times of bare TiO2. The mineralization efficiency of acetaldehyde was also increased by 3.7 times compared to bare TiO2. The substantial improvement in the PCO performance of the ternary system can be associated with the good adsorption to acetaldehyde gas and light-harvesting capability, as well as improved charge separation process. The application of Langmuir-Hinshelwood kinetic model suggested that relative humidity played a significant role in the VOCs degradation. Also, the photodegradation of gaseous acetaldehyde primarily occurred on the catalysts surface. Based on several characterizations, i.e., UV–vis spectroscopy, photoluminescence spectrum, photocurrent spectroscopy and electron spin-resonance test, a suitable degradation mechanism is proposed. This study provides a novel ternary photocatalyst with improved photocatalytic performance and stability, which can be used for the low-concentration VOCs abatement in the indoor environment.

Kinetic modeling and reaction pathways for thermo-catalytic conversion of carbon dioxide and methane to hydrogen-rich syngas over alpha-alumina supported cobalt catalyst

This study investigates the kinetic modeling and reaction pathway for the thermo-catalytic conversion of methane (CH4) and Carbon dioxide (CO2) over alpha-alumina supported cobalt catalyst. Rate data was obtained from the thermo-catalytic reaction at a temperature range of 923–1023 K and varying CH4 and CO2 partial pressure (5–50 kPa). The rate data was significantly influenced by the changes in the reaction temperature as well as the CH4 and CO2 partial pressure. To estimate the kinetic parameters, the rate data were fitted with five Langmuir-Hinshelwood kinetic models. The discrimination of the kinetic models using different parameters revealed that the Langmuir-Hinshelwood kinetic model with the assumption of CH4 being associatively adsorbed on a single and CO2 being dissociative adsorbed with bimolecular surface reaction best described the rate data. The analysis of the kinetic model using a non-linear regression solver results in activation energies of 15.88 kJ/mol, 36.78 kJ/mol, 65.51 kJ/mol, and 41.08 kJ/mol for CH4 consumption, CO2 consumption, H2 production, and CO production, respectively. The thermo-catalytic reaction was influenced by carbon as indicated by the rate of carbon deposition which was mainly caused by methane cracking. The reaction pathway for the thermo-catalytic conversion of the CH4 and CO2 over the alpha-alumina supported cobalt catalyst can best be described as by CH4 associative adsorption on the alpha-alumina supported cobalt catalyst single site and CO2 dissociative adsorption with bimolecular surface reaction.

Heterogeneous UV-Switchable Au nanoparticles decorated tungstophosphoric acid/TiO2 for efficient photocatalytic degradation process

In the present study, gold nanoparticles were locally well-decorated on the surface of TiO2 using the tungstophosphoric acid (HPW), as UV-switchable reducing intermediate linkers. The prepared Au NPs/HPW/TiO2 nanostructure was characterized using FTIR, XRD, EDS, SEM and TEM, which confirmed the successful attachment of quasi-spherical Au NPs in the range of 20–30 nm on the surface of HPW modified TiO2. Also, the FTIR results show that the Au NPs were binded to TiO2 through the terminal the oxygen atoms HPW. The photocatalytic performance of prepared nanostructures was assessed in degradation of nitrobenzene. The nitrobenzene photodegradation kinetic study revealed that it well followed the Langmuir–Hinshelwood kinetic model with the apparent rate constant of 0.001 min−1 using anatase TiO2, 0.0004 min−1 using HPW, 0.0014 using HPW/TiO2, while it was obtained 0.0065 min−1 using Au NPs@HPW/TiO2 nanostructure. It shows that the photocatalytic rate of the prepared nanocomposites increased by 6.5- and 4.6-fold compared to photoactivity of anatase TiO2 and HPW/TiO2 respectively. Also, the photocatalytic mechanism of process was proposed. Moreover, the reusability study confirmed that its photocatalytic activity still remained high after three cycles.

Ruthenium-Imine catalyzed KBH4 hydrolysis as an efficient hydrogen production system

The present study focused on the increasing of hydrogen evolution through hydrolysis of potassium borohydride in the presence of Ruthenium complex catalyst. It is the first time to use the Ru-Imine complex catalyst in KBH4 hydrolysis reaction to hydrogen evolution. The new Ru complex was synthesized from the tetradentate Imine ligand namely 4,4′-methylenebis (2,6-diethyl)aniline-3,5-di-tert-butylsalisylaldimine and Ru salt under the inert atmosphere. Ru-Imine complex was fully characterized by Elemental Analysis, Infrared Spectroscopy, Scanning Electron Microscope, X-Ray Diffraction Analysis, Brunauer-Emmett-Teller Surface Area Analysis and Transmission Electron Microscopy. By the synthesized Ru-Imine complex catalyst, the potassium borohydride hydrolysis reaction resulted in a lower energy barrier with 20,826 kJ/mol activation energy (Ea) for nth order kinetic model and 18,045 kJ/mol for Langmuir-Hinshelwood (L-H) kinetic model. According to the results Ru-complex was highly active and stable catalyst in KBH4 hydrolysis reaction to hydrogen evolution with 45,466 mL H2/gcat.min and 76,815 mL H2/gcat.min hydrogen generation rates at 30 °C and 50 °C respectively. Moreover Ru-Imine complex catalyst displayed 100% stability even at fifth recycle.