Ram Prasad

A Review on CO Oxidation Over Copper Chromite Catalyst

CO is a toxic and detrimental air pollutant. It not only affects human beings but also vegetation and indirectly increases global warming. An estimate has shown that vehicular exhaust contributes about 64% of the CO pollution in developed countries. Due to the exponentially increasing number of automobiles on roads, CO concentrations have reached an alarming level in urban areas and regulatory measures had been adopted to curb the menace of vehicular pollution. To control vehicular exhaust pollution, end-of-pipe-technology using noble metals catalytic converters are recommended. The increasing prices of noble metals with the increasing number of vehicles motivates the investigation of material concepts to reduce the precious metal content in automotive catalysts or to find a substitute for noble metals. Among non-noble metals, copper chromite is found to be most promising and exhibits comparable activity for CO oxidation to that of precious metals. Further, low cost, easy availability and advance synthesis methods with stabilizer, promoter, etc. advocates for the use of copper chromite as an auto exhaust purification catalyst. There is a lot of literature available on copper chromite catalyst for CO oxidation, but still there is a gap in the literature for a review article solely devoted to copper chromite catalyst for CO oxidation. Therefore, in an attempt to fill this gap, the present review updates and evaluates the progress and future scope for copper chromite catalyst for purification of exhaust gases of low sulfur contents. The requirement to develop successful methods to reclaim the components of the spent copper chromite catalyst for its safe disposal is also discussed. The paper is useful for people who want to quickly know the state of art and all the aspects concerning the investigated materials. A total of 265 references have been cited.

Structural and vibrational studies of molecular conductors using quantum mechanical methods: 1,3-Dithiole-2-thione, 1,3-dithiole-2-one, 1,3-dioxole-2-one and 1,3-dioxole-2-thione

Computations were carried out by employing the RHF and density functional theory (DFT) methods to investigate the geometries, atomic charges, harmonic vibrational frequencies for the 1,3-dithiole-2-thione (DTT), 1,3-dithiole-2-one (DTO), 1,3-dioxole-2-thione (DOT) and 1,3-dioxole-2-one (DOO) molecules and their radical cations. The geometrical parameters and atomic charges on various atomic sites of the DTT and DOT molecules and their radical cations suggest extended conjugation in these systems. Contrary to this, for the DOO(+) and DTO(+) ions there is no evidence in favour of such conjugation, however, the neutral molecules exhibit some conjugation. Harmonic forced field and vibrational mode calculations provided convincing theoretical evidence for the reassignment of some fundamental vibrational modes for all the four molecules. In going from the neutral species to the charged ions for all the four cases the CC stretching frequency is found to decrease drastically. The CS stretching frequency reduces drastically for the DTT and DOT molecules as compared to their radical cations whereas the CO stretching frequency is found to increase in going from the neutral molecule to its radical cation for the DOO and DTO molecules. The ring stretching mode with a(1) symmetry and CC and CO/S stretching modes in these molecules appear to help in conversion of neutral molecule into respective radical cation and neighbouring radical cation into respective neutral molecule. Thus, there appears the feasibility of stretching vibrational mode coupling with electron transfer.

Solid-state thermal degradation behaviour of 1-D coordination polymers of Ni(II) and Cu(II) bridged by conjugated ligand

Monometallic complexes [Cudadb·yH2O]n (2) and [Nidadb·yH2O]n (3) and heterobimetallic complex [Cu0.5Ni0.5dadb·yH2O]n (4) {where dadbH2xa0=xa02,5-Diamino-3,6-dichloro-1,4-benzoquinone (1); yxa0=xa02–4; nxa0=xa0degree of polymerization} were characterized by elemental analysis, atomic absorption spectroscopy, infrared spectroscopy (FTIR) and powder X-ray diffraction. The thermal behaviour of the complexes was studied by thermal analysis (TG/DTA) under air as well as under helium atmospheres. The released gaseous products were investigated by evolved gas analysis performed by an online coupled mass spectrometer (TG/DTA-MS). Thermal degradation of 2 under helium atmosphere is distributed over five steps, whereas 3 and 4 exhibited only four degradation steps due to overlap of second and third degradation steps of into one major step. All the complexes exhibit three steps degradation under air. The complex 2 loses NH group in the second and HCl/Cl2, CO groups simultaneously in third steps of decomposition under helium, whereas it loses NH and CO groups simultaneously in low temperature region of second step of degradation under air atmosphere as the loss of CO group is facilitated by air. EGA-MS under air and helium atmospheres shows that HCl, CO/CO2 and (CN)2 fragments are lost simultaneously at multiple steps, and not successively as predicted earlier. Rate of evolution of most evolved gases exhibits several maxima as a consequence of degradation followed by recombination reactions. Final residues under air and helium atmospheres correspond to the metal oxides and metals along with some carbonaceous matter.

Mixed ligand complexes of β-diketonates: synthesis, characterization, and FAB mass spectral analysis

Complexes of the type MLL′ · nB (where M = Ni(II) and Cu(II); LH and L′H = 2,4-pentanedione (acacH), 1-phenyl-1,3-butanedione (bacH), and 1,3-diphenyl-1,3-propanedione (dbmH); n = 0 to 2 and B = water or pyridine) have been synthesized and characterized. IR spectra are consistent with uninegative bidentate ligands. Magnetic moments and electronic spectral studies reveal high-spin octahedral geometry for nickel(II) complexes and distorted octahedral stereochemistry for copper(II) complexes. Frozen chloroform solution ESR spectra of the copper(II) complexes display significant Jahn–Teller distortion and dimeric behavior of the complexes in solution. FAB mass spectra of the copper(II) complexes also exhibit peaks corresponding to dimers. Molecular, pseudo-molecular, dimeric pseudo-molecular, and fragment ion peaks in unit resolution mass spectra have been identified with the help of their isotope distribution pattern expected due to natural abundances of the 63Cu and 65Cu isotopes. All the FAB mass spectral peaks from the fragment ions containing copper have been interpreted on the basis of isotope distribution pattern.

Removal of Cd(II) Ions from Simulated Wastewater by HCl Modified Cucumis sativus Peel: Equilibrium and Kinetic Study

This paper describes the adsorption of Cd(II) ions from aqueous solutions by modified Cucumis sativus peel (CSP) by HCl treatment. The optimum pH, adsorbent mass, contact time, and initial ion concentration were determined. The maximum removal efficiency was 84.85% for 20 mg/L Cd(II) ion at pH 5. The adsorption isotherms were obtained using concentrations of the metal ions ranging from 5 to 150 mg/L. The adsorption process follows Langmuir isotherm and pseudo-second-order reaction kinetics. CSPs exhibit monolayer adsorption capacity of 58.14 mg/g at 298 K. The paper also discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results establish that the adsorption process was spontaneous and endothermic under normal conditions.

Mycorrhiza - Eco-Physiology, Secondary Metabolites, Nanomaterials

Although declared as a research priority more than 40 years ago, the knowledge about the magnitude and mechanisms of carbon (C) fluxes between plants and their mycorrhizal fungal symbionts remains fragmentary. In spite of a number of experiments with isotopically labeled C documented rapid and directed C transfer from the host plant to its mycobionts, the molecular mechanisms and their regulation involved in such a transport remain largely unknown. It seems that in many arbuscular mycorrhizal (AM) symbioses, the C costs remains well below 10% of the C fixed photosynthetically by the host plants. Higher values were detected in the past only under specific situations such as in young plants, under low light intensities, and/or for particular partner combinations, involving very costly (in terms of C demand) and little nutritionally beneficial AM fungi such as Gigaspora sp. Ecological context of the common mycorrhizal networks in terms of redistribution of symbiotic C costs and nutritional benefits on one hand and C movement through soil food webs beyond mycorrhizal hyphae on the other are briefly discussed in this chapter, and further research challenges and open knowledge gaps with respect to C fluxes in mycorrhizal plants are outlined.

Synthesis, characterization, and solid state electrical conductivity of coordination polymers with copper and zinc

Heterobimetallic complexes [Cu x Zn1− x (dadb)u2009·u2009yH2O] n {where dadbu2009=u20092,5-diamino-3,6-dichloro-1,4-benzoquinone (1); xu2009=u20091 (2), 0.5 (4), 0.25 (5), 0.125 (6), 0.0625 (7), and 0 (3); yu2009=u20092; nu2009=u2009degree of polymerization} were synthesized and characterized. All metal complexes are stable at room temperature but weakly absorb moisture on exposure to air. Monometallic 2 exhibits subnormal magnetic moment whereas 3 exhibits diamagnetism. Heterobimetallic complexes exhibit normal magnetic moments. Heterobimetallic complexes are characterized from powder X-ray diffraction, thermal analysis, and electron spin resonance (ESR) spectral studies. Delocalization of unpaired electron from metal to ligand has been inferred from ESR and natural bond orbital (NBO) analysis. Greater delocalization of unpaired electron of Cu(II) on ligand of 4 as compared to that of 2 is reflected from NBO analysis. Heterobimetallic complexes show higher conductivity than monometallic complexes; all the complexes exhibit semiconductor behavior.

Mycorrhiza - Nutrient Uptake, Biocontrol, Ecorestoration

Mycorrhizal fungi are one of the commonly occurring living organism in soil facilitating plants in growth, development, stress tolerance, soil pollutants remediation, C-sequestration, food security and agricultural sustainability. Mycorrhizal fungi assist the plants in nutrient absorption by extending mycorrhizal hyphae network beyond the rhizosphere. Mycorrhizal inoculation alters the root architecture and studies showed that nutrient absorption capacity of inoculated root is much better than non-inoculated. For a long time, it is assumed that roots absorb nutrients only through direct pathway (DP) only while contribution of AM fungi in nutrients uptake by mycorrhizal pathway (MP) has been ignored. But now the development in scientific methods and tools, enabled the researcher to explore MP mechanism for macro and micro nutrients, moreover suppression of heavy metal stress to the plants. Besides that, mycorrhizal fungi obtain around 20% of photosynthesized C from the plant in exchange of nutrients. Moreover, this C triggers nutrient uptake and their translocation. Plant hormones and root exudates also influence the infection formation and development, they also point out new sites for the interaction of mycorrhizal fungi and plant roots. Nutrient mobility by MP is more secure and economical than DP. Understanding about the nutrient exploration, mobilization, and uptake in root-mycorrhizal interaction has been discussed here at molecular level. Contribution of plant and mycorrhizal transporters have been discussed which need further understanding. Also contribution of mycorrhizal inoculation on nutrient uptake compared with non-inoculated roots were discussed. I. Ortaş (*) Department of Soil Science and Plant Nutrition, University of Çukurova, Faculty of Agriculture, Adana, Turkey e-mail: iortas@cu.edu.tr M. Rafique Department of Soil Science and Plant Nutrition, University of Çukurova, Faculty of Agriculture, Adana, Turkey Department of Plant Science, Faculty of Biological Sciences, Quaid-I-Azam University, Islamabad, Pakistan