Mar Athanasius College

Kothamangalam, India

Mar Athanasius College

Kothamangalam, India
Time filter
Source Type

Kurian M.,Mar Athanasius College | Remya V.R.,Mar Athanasius College | Kunjachan C.,Mar Athanasius College
Catalysis Communications | Year: 2017

Degradation of 4-chlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid was investigated by wet air oxidation over CexFe1 − xO2 (x: 0, 0.25, 0.5, 0.75, 1) nanocatalysts. Complete removal of target pollutants could be effected at atmospheric pressure and near ambient conditions with considerable decrease in TOC and COD. 4-chlorophenol (1000 mg/l) was completely degraded with 59.66% TOC and 84.9% COD removal at 40°C over Ce0.75Fe0.25O2 catalyst whereas 2,4-dichlorophenol (1250 mg/l) conversion with 74.3% TOC and 93.62% COD removal was observed at 50 °C over Ce0.75Fe0.25O2 catalyst. The activity of the catalysts was found to increase on repeated runs. © 2017 Elsevier B.V.

Selven S.,Cochin University of Science and Technology | Selven S.,Mar Athanasius College | Philip R.,Cochin University of Science and Technology
Aquaculture Research | Year: 2013

The effect of ambient salinity on the haemolymph variables of Fenneropenaeus indicus and its susceptibility to Vibrio harveyi infection under salinity stress has been studied. Adult shrimps were acclimated to 5‰ (hypo osmotic), 25‰ (iso osmotic) and 35‰ (hyper osmotic) salinity levels and the animals were injected with a mid logarithmic culture of V. harveyi at sub lethal level and haemolymph parameters were analysed. Haemolymph proteins, intracellular superoxide anion production, phenoloxidase (PO), alkaline phosphatase (ALP) and acid phosphatase (ACP) activity were found to be at elevated level both at 5‰ and 35‰ post challenge. The haematological responses showed a progressive increase (P < 0.05) up to post challenge day 5 (PCD 5) followed by a considerable decline at all salinities with the lowest being at 35‰. The alterations in the variables were higher in shrimps held at 5‰. However, the V. harveyi infection was severe in animals held at 35‰. The reduction in the parameters could be correlated with the decrease in survival rate of shrimps at 35‰ with a concurrent increase in V. harveyi at this salinity. Multiple regression analysis revealed that ACP (P < 0.001), haemocyte protein HCP (P < 0.001) and PO (P < 0.05) could explain 91% variability in the shrimp survival. These parameters may be used as effective shrimp health indicators. It is evident from the study that ambient salinity alters the haemolymph variables, modulates the virulence in V. harveyi and makes the shrimps more vulnerable to infection at higher salinity. The virulence of V. harveyi is increased at 35‰ salinity as being evidenced from the high mortality at this salinity. The study emphasizes the importance of salinity as an important environmental factor both in terms of host susceptibility and virulence of the pathogen. © 2012 Blackwell Publishing Ltd.

Kurian M.,Mar Athanasius College | Nair D.S.,Mar Athanasius College
Journal of Environmental Chemical Engineering | Year: 2014

Cobalt substituted zinc ferrite nanoparticles prepared by sol-gel auto combustion method are efficient catalysts for the wet peroxide oxidation of 4-chlorophenol. Complete degradation of 4-chlorophenol occurs within one hour with all catalysts under study. 90% of the target compound is removed with oxidant concentration as low as 1 ml. Varying the catalyst dosage, it is found that direct correlation between the amount of catalyst present and extent of degradation of 4-chlorophenol is observed, ruling out the heterogeneous- homogeneous mechanism. The catalysts are reusable and the activity of the catalysts remains almost the same after four successive runs. The extent of iron leaching is fairly low after five consecutive cycles indicating the mechanism to be heterogeneous. © 2013 Published by Elsevier Ltd.

Kurian M.,Mar Athanasius College | Nair D.S.,Mar Athanasius College
Journal of Water Process Engineering | Year: 2015

An evaluation of heterogeneous Fenton behavior of nano nickel-zinc ferrite catalysts in the Wet Peroxide Oxidation for the degradation of 4-chlorophenol is presented. A series of spinel type NixZn1-xFe2O4 (x=0.0, 0.25, 0.5, 0.75, 1.0) catalysts were prepared by sol-gel auto combustion method and characterized by X-ray diffraction, Transmission Electron Microscopy, X-ray fluorescence and Fourier Transform Infra-Red spectroscopy. Fenton's reaction was performed over different compositions of nickel zinc ferrite catalysts under neutral conditions and the catalytic activities were studied. The yield of the reaction, based on Gas Chromatographic and Chemical Oxygen Demand (COD) parameters were very high and the experimental results indicated complete degradation of target pollutant with significant reduction of COD with all catalysts within 75min. Zinc substitution enhanced the catalytic activity of nickel ferrite and the un-substituted ZnFe2O4 degraded the target compound completely within 45min. Catalysts were found to be reusable and the extent of iron leaching, quantified by Atomic Absorption Spectroscopic studies was negligible after five consecutive cycles indicating the mechanism to be heterogeneous. Phase analysis of catalyst using XRD after the completion of each catalytic cycle confirmed the stability of the catalyst toward the Wet Peroxide Oxidation of 4-chlorophenol. © 2014 Elsevier Ltd.

Kurian M.,Mar Athanasius College | Nair D.S.,Mar Athanasius College
Journal of Saudi Chemical Society | Year: 2013

The experimental conditions used in the preparation of nano crystalline mixed ferrite materials play an important role in the particle size of the product. In the present work a comparison is made on sol-gel auto combustion methods and co-precipitation methods by preparing Nickel Zinc Ferrite (Ni0.5Zn0.5Fe2O4) nano particles. The prepared ferrite samples were calcined at different temperatures and characterized by using standard methods. X-ray diffraction analysis indicated the formation of single phase ferrite nanoparticles for samples calcined at 500 °C. The lattice parameter range of 8.32-8.49 Å confirmed the cubic spinel structure. Average crystallite size estimated from X-ray diffractogram was found to be between 17 and 40 nm. The IR spectra showed two main absorption bands, the high frequency band ν1 around 600 cm-1 and the low frequency band ν2 around 400 cm-1 arising from tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice. TEM pictures showed particles in the nanometric range confirming the XRD data. The studies revealed that the sol-gel auto combustion method was superior to the co-precipitation method for producing single phase nano particles with smaller crystallite size. © 2013.

Kurian M.,Mar Athanasius College | Nair D.S.,Mar Athanasius College
AIP Conference Proceedings | Year: 2011

Nano crystalline mixed ferrites can be prepared through different methods. In the present work a comparison was made on sol-gel auto combustion method and co-precipitation method by preparing Nickel Zinc Ferrite. The prepared samples were calcined at different temperatures and were characterized by powder XRD, FTIR. X-ray diffraction analysis indicated the formation of ferrite in nanophase. The lattice parameter was found to be in the range 8.31-8.41Ao. This confirms that nano crystalline ferrite samples are in the cubic spinel structure. An average nano crystalline size was estimated from XRD by the Scherrer's equation. FTIR study also confirms the formation of ferrites. Sol-gel auto combustion technique was superior to co-precipitation method for producing single phase nano particles with smaller crystallite size. © 2011 American Institute of Physics.

Moothedan M.,Mar Athanasius College | Sherly K.B.,Mar Athanasius College
Journal of Water Process Engineering | Year: 2016

In this study, utilization of green synthesized nano La2O3 for adsorptive removal of Congo red from aqueous solution was investigated. Crystalline character, particle size, stability, formation and morphology of nano La2O3 were investigated from XRD, FT-IR, TG/DTG, SEM and TEM techniques. The pH impact, sorption kinetics, isotherms and thermodynamics of Congo red adsorption on La2O3 were investigated. The adsorption isotherm data gave better fit to the Freundlich isotherm model, with a maximum Congo red adsorption capacity of 185.64mgg-1. Kinetic data correlated well with the pseudo-first-order kinetic model. Electrostatic force of attraction and H-bonding were conceived as the main adsorption mechanism. 1:1 mixture of NaOH and acetone was an effective desorption agent for desorption of nano La2O3 loaded by Congo red. © 2015 Elsevier Ltd.

Thomas B.,Mar Athanasius College | Skariah B.,Mar Athanasius College
Journal of Alloys and Compounds | Year: 2015

Magnesium doped SnO2 polycrystalline thin films are deposited by Spray pyrolysis by adding small amount of Mg between 0.3 and 1.2 wt%. Mg doping significantly modifies the gas sensing properties of tin oxide thin films by yielding (1 1 0) and (1 0 1) crystallite orientation to accommodate oxygen vacancies which lead to enhanced oxygen adsorption. A correlation is established between the crystallite orientation and the gas sensing magnitude by plotting the texture coefficient. The structure, surface chemical composition, and the optical and electrical properties are studied in relation to the gas sensing magnitude. It is shown that the magnesium doping in SnO2 maintains tetragonal rutile structure in stable cassiterite phase over low doping concentrations. The grain dimensions are influenced by both doping concentration and substrate temperature. Electronic surface states identified by the XPS are deconvoluted to establish the constituent oxygen states, while the EDX compositional analysis indicates added oxygen adsorption. As the temperature is raised for the response measurement, the adsorbed oxygen may transform to O- or O2- which is supported by the increase of film resistance. It is shown that the sensor response to LPG is improved significantly (93%) by the addition of minor amounts of Mg to SnO2 thin film sensors. © 2014 Elsevier B.V. All rights reserved.

Kurian M.,Mar Athanasius College | Babu R.,Mar Athanasius College
Journal of Environmental Chemical Engineering | Year: 2013

Iron aluminium mixed pillared montmorillonite prepared by partial hydrolysis method was exchanged with lanthanum, cerium and thorium metal salts. The pillared montmorillonite shows considerable increase in basal spacing and surface area. 27Al and 29Si nuclear magnetic resonance spectra show the presence of iron substituted Keggin cation as the pillaring species. Energy dispersive X-ray analysis shows the presence of about 2% rare earth metals. The prepared systems are excellent catalysts for hydroxylation of phenol underlining the use of eco-friendly clay catalysts for effective removal of pollutants. A detailed study of reaction variables suggests that oxidation of phenol increases with temperature and maximum conversion is obtained at 90 8C. Hydroquinone selectivity increases with phenol concentration and time but decreases with temperature. © 2013 Elsevier Ltd All rights reserved.

Kurian M.,Mar Athanasius College | Kunjachan C.,Mar Athanasius College
Nano-Structures and Nano-Objects | Year: 2015

Cex Fe1-x O2/Cex Zr1-x O2 (x:0, 0.25, 0.5, 0.75, 1) prepared by coprecipitation method were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), N2 adsorption at -196 °C, Fourier transform Infra Red (FT-IR) spectroscopy, Fourier Transform Raman spectroscopy and thermal analysis (TG-DTA). XRD and TEM analyses reveal the presence of nanoparticles in all oxides beyond solid solution limit. The reduction in lattice parameter values of Ce-Zr/Fe mixed oxides compared to ceria can be attributed to the compositional changes along with particle growth since the ionic radius of Fe/Zr is smaller than that of Ce. Changes in the solid solution structure from cubic fluorite occur as a result of the crystallite growth of Fe2O3/ZrO2 particles on increased Fe/Zr content. Lattice strain measured by Williamson-Hall plot indicates an increase in lattice strain as a result of incorporation of Fe/Zr ions into the ceria lattice. The BET surface area and pore volume of synthesized composites are in the range of 30-10m2/g and 0.004-0.01cm3/g. Raman analysis reveals that iron incorporated ceria lattice have increased oxygen vacancy formation and gradual shrinkage of the unit cell. FT-IR spectra reveal the characteristic Ce-O stretching and crystalline water absorption of synthesized nanoparticles. Thermal analysis data shows these oxides to be thermally stable. © 2015 Elsevier B.V.

Loading Mar Athanasius College collaborators
Loading Mar Athanasius College collaborators