Photocatalytic degradation of ketorolac tromethamine (KTC) drug in aqueous phase using prepared Ag-doped ZnO microplates

In this study, Ag-doped ZnO microplates were prepared via precipitation technique and further characterized by FESEM, EDS, XRD, FTIR, TGA, XPS, UV-DRS and RT-PL techniques. The outcomes indicated that Ag+ ions were well incorporated into ZnO lattice leading to the absorption of ZnO in visible region as well as effective charge separation. The photocatalytic experiments showed that Ag-doped ZnO microplates show higher catalytic activity (91%) than bare ZnO (71%) for the degradation of KTC drug under solar illumination. The photocatalytic degradation of KTC drug over Ag doped ZnO microplates obeyed pseudo first-order kinetics model. Also, the role of active species was examined by the addition of several scavengers in the photocatalytic degradation system. The results indicated that h+, •OHs, 1O2 and •OH were considered as prime reactive species in photocatalytic degradation process

Palladium-bismuth intermetallic and surface-poisoned catalysts for the semi-hydrogenation of 2-methyl-3-butyn-2-ol

The effects of poisoning of Pd catalysts with Bi and annealing in a polyol (ethylene glycol) were studied on the semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY). An increase in the Pd:Bi ratio from 7 to 1 in the Bi-poisoned catalysts decreased the hydrogenation activity due to blocking of active sites, but increased maximum alkene yield from 91.5% for the Pd catalyst to 94–96% for all Bi-poisoned Pd catalysts, by decreasing the adsorption energy of alkene molecules and suppressing the formation of β-hydride phase. Annealing of the catalysts induced the formation of intermetallic phases and decreased its activity due to sintering of the catalytic particles and low activity of intermetallic compounds. Langmuir–Hinshelwood kinetic modelling of the experimental data showed that poisoning of Pd with Bi changed the relative adsorption constants of organic species suggesting ligand effects at high Bi content

Ultrasound- and microwave-assisted preparation of lead-free palladium catalysts: effects on the kinetics of diphenylacetylene semi-hydrogenation

The effect of environmentally benign enabling technologies such as ultrasound and microwaves on the preparation of the lead-free Pd catalyst has been studied. A one-pot method of the catalyst preparation using ultrasound-assisted dispersion of palladium acetate in the presence of the surfactant/capping agent and boehmite support produced the catalyst containing Pd nanoparticles and reduced the number of pores larger than 4 nm in the boehmite support. This catalyst demonstrated higher activity and selectivity. The comparison of kinetic parameters for diphenylacetylene hydrogenation showed that the catalyst obtained by using the one-pot method was seven times as active as a commercial Lindlar catalyst and selectivity towards Z-stilbene was high. Our work also illustrated that highly selective Pd/boehmite catalysts can be prepared through ultrasound-assisted dispersion and microwave-assisted reduction in water under hydrogen pressure without any surfactant

Low temperature plasma-catalytic NOx synthesis in a packed DBD reactor: effect of support materials and supported active metal oxides

The direct synthesis of NOx from N2 and O2 by non-thermal plasma at an atmospheric pressure and low temperature is presented, which is considered to be an attractive option for replacement of the Haber-Bosch process. In this study, the direct synthesis of NOx was studied by packing different catalyst support materials in a dielectric barrier discharge (DBD) reactor. The support materials and their particle sizes both had a significant effect on the concentration of NOx. This is attributed to different surface areas, relative dielectric constants and particles shapes. The nitrogen could be fixed at substantially lowered temperatures by employing non-thermal plasma-catalytic DBD reactor, which can be used as an alternative technology for low temperature synthesis. The γ-Al2O3 with smallest particles size of 250–160 μm, gave the highest concentration of NOx and the lowest specific energy consumption of all the tested materials and particle sizes. The NOx concentration of 5700 ppm was reached at the highest residence time of 0.4 s and an N2/O2 feed ratio of 1 was found to be the most optimum for NOx production. In order to intensify the NOx production in plasma, a series of metal oxide catalysts supported on γ-Al2O3 were tested in a packed DBD reactor. A 5% WO3/γ-Al2O3 catalyst increased the NOx concentration further by about 10% compared to γ-Al2O3, while oxidation catalysts such as Co3O4 and PbO provided a minor (∼5%) improvement. These data suggest that oxygen activation plays a minor role in plasma catalytic nitrogen fixation under the studied conditions with the main role ascribed to the generation of microdischarges on sharp edges of large-surface area plasma catalysts. However, when the loading of active metal oxides was increased to 10%, NO selectivity decreased, suggesting possibility of thermal oxidation of NO to NO2 through reaction with surface oxygen species

Ultrasound-assisted selective hydrogenation of C-5 acetylene alcohols with Lindlar catalysts

The selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) was performed in the presence of Lindlar catalyst, comparing conventional stirring with sonication at different frequencies of 40, 380 and 850 kHz. Under conventional stirring, the reaction rates were limited by intrinsic kinetics, while in the case of sonication, the reaction rates were 50–90% slower. However, the apparent reaction rates were found to be significantly frequency dependent with the highest rate observed at 40 kHz. The original and the recovered catalysts after the hydrogenation reaction were compared using bulk elemental analysis, powder X-ray diffraction and scanning and transmission electron microscopy coupled with energy-dispersive X-ray analysis. The studies showed that sonication led to the frequency-dependent fracturing of polycrystalline support particles with the highest impact caused by 40 kHz sonication, while monocrystals were undamaged. In contrast, the leaching of Pd/Pb particles did not depend on the frequency, which suggests that sonication removed only loosely-bound catalyst particles.Financial support from the European Commission for the MAPSYN project is greatly acknowledged (MAPSYN.eu No. CP-IP 309376)

Visible light photoactivity of Polypropylene coated Nano-TiO2 for dyes degradation in water

The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation

The Reduction of Alkynes over Pd-based Catalyst Materials-A Pathway to Chemical Synthesis

Many reactions, including selective hydrogenation of alkynes, take place on solid surfaces. These reactions are vital in many areas of industry including the manufacture of polymers and fine chemicals such as vitamins, fragrances, and drugs. The choice of a catalyst is a trade-off between activity, selectivity and costs. Palladium-based heterogeneous catalysts are traditionally used for these processes as they provide the activation of hydrogen at room temperatures and offers reasonable selectivity, but these catalysts have a number of practical drawbacks. This review discusses recent research work in the selective hydrogenation of alkynes on palladium-based catalysts, emphasises the mechanism and catalytic materials and important applications including alkyne removal from gas-phase alkene precursors for polymer synthesis and liquid phase selective hydrogenation for the synthesis of fine chemicals. Langmuir-Hinshelwood reaction kinetic models, reaction intermediates, formation of carbonaceous layer, the nature of active sites and the effects of reversible and irreversible adsorbates over Pd surface are discussed as well as the factors affecting catalyst activity and selectivity and how these can be optimised in synthetic protocols for these reactions

Nanoparticulate Pd-Sn Compounds Supported on Metal Oxides: Synthesis, Material and Catalytic Properties

The manufacture of chemicals requires innovation at the catalyst frontier so that processes can be developed with higher energy efficiency and increased facility of separation and recovery of products. Catalysts with high selectivity and activity control the overall efficiency of a process by avoiding unwanted side-reactions and increasing the conversion per unit time. Although processes catalysed by homogeneous catalysts have the advantage of offering better control and understanding of the reaction mechanism, their frequent dependence on expensive metals which are difficult to recover, often precludes their employment in large-scale applications. Heterogeneously catalysed reactions on the other hand, are not associated with problems regarding recycling and reuse of catalyst, contamination of products or intermediates. This work reports the synthesis, characterization and testing of Pd-Sn nanoalloy catalyst in the selective hydrogenation of 2-methyl-3-butyn-2-ol. Our results show that the Pd-Sn nanoalloy, of composition Pd2.8Sn, supported on ZnO (Pd2.8Sn/ZnO), offers very high activity and selectivity in the semi-hydrogenation of 2-methyl-3-butyn-2-ol to 2-methyl-3-buten-2-ol in the liquid phase. Under identical reaction conditions, Pd2.8Sn/ZnO shows activity, both turnover frequency and activity normalized by Pd content, significantly higher than Pd/CaCO3 (the Lindlar catalyst), with TOF of 137.6 s−1 compared to 79.2 s−1 for Pd/CaCO3 with approximately equal selectivity. The preparation of Pd2.8Sn/ZnO is achieved using a one-pot polyol procedure with the addition of a capping agent (polyvinylpyrrolidone) to control the particle size distribution. TEM shows nanoparticles evenly dispersed on the support, with a size distribution of 4.06 ± 0.75 nm. Single phase Pd2.8Sn was also prepared without the ZnO support, via the polyol method. Powder X-Ray diffraction data from the unsupported nanoalloy shows that the unit cell of Pd2.8Sn is face centred cubic with the Pd and Sn atoms occupying randomly the same crystallographic position. The chemical formula was calculated from a combination of ICP and PXRD analyses

Analysis of emerging contaminants: A case study of the underground and drinking water samples in Chandigarh, India

The present report deals with the analysis of emerging contaminants and the quality of drinking and underground water supply in Chandigarh, India. A water sampling monitoring and analysis was conducted by collecting a total of 54 samples of underground & drinking water of Chandigarh to analyse the health risk associated with the spread of emerging contaminants in the water sources. The quality of water samples was also assessed by measuring the colour, odour, temperature, pH, electrical conductivity (EC), biological oxygen demand (BOD), dissolved oxygen (DO), total dissolved solids/ salts (TDS) and hardness. For the estimation of the emerging contaminants (Endosulphan (ES) and Hexachlorohexane (HCH)) in the water samples, an extraction procedure was carried out by dispersive liquid-liquid extraction method followed by analysis using gas chromatography-mass spectrometry (GC-MS). The levels of ES and HCH obtained were compared with the drinking water standards of the Bureau of Indian Standards (IS: 10500). The levels of HCH and ES in all the water samples tested were found to be below the detection limit. It cannot be denied that the industrial discharge and other agencies seems to be complying with the regulations. The Initiatives by the Central and State Govt of India seems to have created sensitivity and awareness among the public specifically among the farmers. The limit of detection (LOD) were 1.0 × 10−3 and 2.4 × 10−3 ppm for ES and, HCH respectively. However, some water pollution indicators such as TDS, EC, DO and total hardness were found to exceed the limits specified by the Bureau of Indian Standards (BIS)

Enhanced Wastewater Remediation Using Mesoporous Activated Wheat Straw Biochars: A Dye Removal Perspective

The escalating contamination of water bodies by synthetic dyes necessitates innovative and ecoconscious strategies for wastewater treatment. In this study, activated biochars BC-800 (1:0.25), BC-800 (1:0.5), and BC-800 (1:1) from wheat straw were synthesized. Here, ratios denote the mass relationship between wheat straw and potassium hydroxide; “800” represents the pyrolysis temperature. These activated biochars were rigorously characterized revealing the most efficient material, BC-800 (1:1), presenting a surface area of 2578.82 m2/g and average pore diameter of 5.51 nm. Across parallel batch experiments, it effectively extracted synthetic dyes (rhodamine B (RhB), methylene blue (MB), and methyl orange (MO)) from wastewater within 15–20 min, primarily through chemisorption pathways. Increased surface area and porosity resulted in a greater dispersion of adsorption sites including C═C linkages (π–π interactions) and H-bonding via surface carbonyl groups (C═O). To understand the adsorption mechanism, Langmuir, Freundlich, and Temkin isotherm models were employed to investigate the equilibrium adsorption behavior. Results show that BC-800 (1:1) followed the Freundlich isotherm (R2: 0.9659 for RhB, 0.9927 for MB, and 0.9979 for MO, respectively), showing dye molecules form multilayers on the surface of the biochar (π-stacking). Biochar recycling through chemical regeneration demonstrated sustained dye removal efficiency >90% for BC-800 (1:1) over multiple cycles