The Use of a Nanoscale Copper Catalyst in the Catalytic Decomposition of Water Polluted with Organic Dyes

A supported copper catalyst was used as a catalyst for the decomposition of organic dyes using a commercial chlorinating agent. The catalytic process achieved complete decomposition in only 2 min. Different catalyst to dye concentration ratios is studied to determine the optimal conditions. The catalyst is fully characterized using XRD, SEM, and EDX analysis

The Photocatalytic Activity of TiO 2

In this research different composites of impregnated TiO2 with LTA or FAU zeolites were used as different weight% ratio for photodegradation of organic dye. Normal laboratory UV-lamps were used as a source of UV irradiation. In addition a setup of system of mirrors was used to collect real Jeddah sunlight. A comparison of UV and real sunlight photodegradation activity showed that the real sunlight enhances new centers of active sites exhibiting higher catalytic activity than that of UV irradiated samples

Impact of Block Length and Temperature over Self-Assembling Behavior of Block Copolymers

Self-assembling behavior of block copolymers having water-soluble portion as one of the blocks plays key role in the properties and applications of the copolymers. Therefore, we have synthesized block copolymers of different block length and investigated their self-assembling behavior with reference to concentration and temperature using surface tension and conductance measurement techniques. The results obtained through both techniques concluded that critical micelles concentration (CMC) was decreased from 0.100 to 0.078 g/dL with the increase in length of water insoluble block and 0.100 to 0.068 g/dL for the increased temperature. ΔGmic was also decreased with the increase in temperature of the system, concluding that the micellization process was encouraged with the increase in temperature and block length. However, ΔHmic values were highest for short block length copolymer. The surface excess concentration obtained from surface tension data concluded that it was highest for short block length and vice versa and was increased with the increase in temperature of the system. However, the minimum area per molecule was largest for highest molecular weight copolymers or having longest water insoluble block and decreases with the increase in temperature

Catalytic stereoselective addition to alkynes. Borylation or silylation promoted by magnesia-supported iron oxide and cis-diboronation or silaboration by supported platinum nanoparticles

Iron oxide nanoparticles supported on magnesia (FeO/MgO) have been prepared by NaBH4 reduction of Fe(SO4) on MgO and spontaneous reoxidation upon storage. XPS of FeO/MgO indicates the presence of Fe(0) (16%) and Fe(II) (84%) on this solid. TEM images show that catalytically active FeO/MgO is constituted by iron oxide nanoparticles of about 25 nm dispersed on fibrous MgO. FeO/MgO in the presence of catalytic amounts of triphenylphosphine promotes highly regio- and stereoselective monoborylation of aromatic, aliphatic, terminal and internal alkynes. Chemical analysis of the liquid after the reaction and control experiments using Fe(II) salts in the absence or presence of PPh3 supports that catalysis is heterogeneous. The possibility that trace amounts of copper impurities present in the iron precursor influence the catalytic activity of FeO/MgO was studied using a commercially available high-purity Fe(SO4) as precursor (99.999% Fe purity) showing again good (but lower) activity. In addition, a control experiment using as catalyst MgO containing 30 times higher amounts of Cu than that present in low purity Fe did not lead to complete alkyne conversion, although product formation was observed in a large extent. Alkynes react with complete chemoselectivity versus alkenes. In contrast to FeO/MgO, Pt supported on MgO or active carbon efficiently promotes the stereoselective diboronation and silaboration of alkynes in the absence of triphenylphosphine at lower temperature to render the cis configured diboronated and silaborated alkene.Financial support by the Spanish Ministry of the Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) and the Generalidad Valenciana (Prometeo 2012-014) is gratefully acknowledged. This work was also funded by the Deanship of Scientific Research (DSR), King Abdulaziz University under grant No. 75-130-35-HiCi. The authors, therefore, acknowledge technical and financial support of KAU.Khan, A.; Asiri, AM.; Kosa, SA.; García Gómez, H.; Grirrane, A. (2015). Catalytic stereoselective addition to alkynes. Borylation or silylation promoted by magnesia-supported iron oxide and cis-diboronation or silaboration by supported platinum nanoparticles. Journal of Catalysis. 329:401-412. https://doi.org/10.1016/j.jcat.2015.05.006S40141232

Plasmonic osmium hydrosols: Preparation, characterization, and properties

A simple route for the synthesis of mesoporous and plasmonic chitosan supported osmium hydrosols (Os0) has been reported using osmium (III)-sodium borohydride redox reaction at room temperature. The composition and morphology of nanoparticles were determined with XRD, XPS, TEM, EDX, SEM, FTIR and N2-adsorption desorption techniques. No SPR band of Os0 at 485 nm was observed for the same redox reaction with cetyltrimethylammonium bromide (CTAB) for ca. 120 min at room temperature. The surface oxidation of Os0 into OsO2 was detected by XRD and XPS. XRD shows the presence of chitosan onto the surface of nanoparticles. The average pore size, and pore volume were found to be 7.23 nm, and 0.239 cc/g, respectively, for Os0. The persulfate activation catalytic activity was tested in situ chemical oxidation of basic red 2 (safranin) under activated and un-activated persulfate. Safranin was adsorbed onto the Os0 and complex was formed. The oxidation of dye follows pseudo-first order kinetics (kapp = 14.8 × 10-3 min−1 at [S2O82-] = 3.3 mM). The activated system showed a much higher dye oxidation rate compared to either S2O82- or Os0 alone. The activation energy (Ea = 105 kJ/mol) was calculated for the system by using Arrhenius equation. The reaction mechanism of Os0 activation of persulfate was elucidated and discussed

Silver-platinum bimetallic nanoparticles as heterogeneous persulfate activator for the oxidation of malachite green

Fabrication of noble metal nanoparticles by using green chemical method with plant extract as reducing agent to the in situ oxidation toxic water contaminants have been the subject of various investigators due to their enhanced catalytic efficiencies. This paper describes the extraction of caffeic acid from Artemisia herba-alba aqueous extract, and preparation of silver (Ag), platinum (Pt), and silver-platinum (Ag-Pt) nanoparticles with caffeic acid as a reducing and capping agent. The as-prepared Ag-Pt NPs was used as a heterogeneous activator of persulphate (K2S2O8) for the in situ chemical oxidation of malachite green (MG). The Ag-Pt NPs shows no surface Plasmon resonance absorption band. The malachite green dye was completely decolorized in presence of Ag-Pt/K2S2O8 system. SO4-• and HO• radicals generated by the cleavage of S2O82- peroxide activation with Ag-Pt were responsible for the MG decolorization as well as mineralization. The Ag-Pt NPs acted as a sacrificial electron donor. The Ag-Pt NPs were characterized by using conventional techniques such as, UV–visible, FTIR, SEM, TEM, EDX, XPS, and XRD spectroscopic methods

Effect of Pr, Sm, and Tb Doping on the Morphology, Crystallite Size, and N 2 O Decomposition Activity of Co 3 O 4 Nanorods

Cobalt(II,III) oxide, Co 3 O 4 , is a promising catalyst for nitrous oxide direct decomposition. In this paper we report effect of doping with some rare earth (RE) elements (Pr, Sm, and Tb) on the morphology and crystallite size of Co 3 O 4 nanorods. The various precursors (RE/Co oxalates) were prepared via the microwave assisted method and subsequent calcination. The decomposition pathway of these precursors was followed using thermogravimetric analysis (TGA). Based on thermal analysis results, Pr-, Sm-, and Tb-doped Co 3 O 4 samples were obtained via the calcination in static air at 500 ∘ C for their oxalate precursors. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and hydrogen temperature programmed reduction (H 2 -TPR) were used to characterize the RE-doped cobalt oxide catalysts. The activity of the prepared catalysts was investigated for N 2 O direct decomposition and compared with that of the undoped Co 3 O 4 catalyst. It was shown that the promoted Co 3 O 4 catalysts revealed higher activity compared to the unpromoted one. The dependence of the activity on both the catalysts particle size and the reduction behaviour was discussed

New Method for Removal of Organic Dyes Using Supported Iron Oxide as a Catalyst

In this study, we perform a catalytic decomposition of organic dye over Fe2O3-CeO2-TiO2-γ-Al2O3 catalyst in the presence of molecular oxygen and chlorate ions. The results showed that organic dye acts as a sensitizer during this process. The mechanism of the allover process is hypothesized. Several techniques were employed for the characterization of the catalyst, including XRD, SEM, EDAX, and thermal analysis and catalytic activity. The analysis showed that iron is the main active centers, and we have two types of active centers in this process: surface iron and dissolved iron in titanium dioxide. The dissolved iron was found to be the most active center; however, after Fe/Ti = 2.76, a synergism was observed to be occurring between the two active centers

Understanding the Origin of the Photocatalytic CO2 Reduction by Au- and Cu-Loaded TiO2: A Microsecond Transient Absorption Spectroscopy Study

Recent photocatalytic data for CO2 reduction by H2O using simulated sunlight have shown that, while TiO2 Evonik P25 containing Au nanoparticles (NPs; Au/P25) generates considerably higher amounts of hydrogen than methane, when P25 contains Au-Cu alloy NPs the selectivity toward methane increases dramatically. To gain insight into this photocatalytic behavior, in the present work we have performed a transient absorption spectroscopy study in the microsecond time scale of three samples, namely, Au/P25, Cu/P25, and (Au, Cu)/P25 using 355 (UV) and SR nm (visible) lasers. The transient spectra exhibit as common features a narrower peak at about 320 nm and a broad band from 400 to 800 run. Using oxygen as electron quencher and methanol as hole quencher, the transient signals have been assigned to charge separation. Several cases were observed, including: (i) absence of quenching attributed to the lack of accessibility of the quencher to the site, (ii) quenching of the signal, or (iii) increase of the transient signal intensity attributed to less charge recombination by removal of one of the charge carriers. Of relevance to understand the origin of the photo catalytic CO2 reduction by H2O is the quenching of the charge separated state by these two reagents. In this way, it was observed that H2O exerts a remarkable influence to the transient signal, quenching its intensity in the three samples at the two irradiation wavelengths, except for (Au, Cu)/P25 upon 532 run excitation. Importantly, the distinctive behavior due to the presence of Cu has been attributed to the observed quenching by CO2 of the broad 400-800 nm band when excitation is performed with UV 355 nm light.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa Grant CTQ2012-32315), the Deanship of Scientific Research (DSR), King Abdulaziz University, under Grant No. 75-130-35-HiCi, and Marie Curie Project PIEF-GA-2011-298740 is gratefully acknowledged. The authors acknowledge technical and financial support of KAU. We also thank the Generalidad Valenciana for postgraduate research contract to H.G.B. (Prometeo 2012/2013).Baldovi, HG.; Neatu, S.; Khan, A.; Asiri, AM.; Kosa, SA.; García Gómez, H. (2015). Understanding the Origin of the Photocatalytic CO2 Reduction by Au- and Cu-Loaded TiO2: A Microsecond Transient Absorption Spectroscopy Study. Journal of Physical Chemistry C. 119(12):6819-6827. doi:10.1021/jp5106136S681968271191