Trace Amounts Of Co Research Articles

Ultrasound-assisted emulsification microextraction of trace amounts of Co and Mn ions prior to flame atomic absorption spectrometry

The present work reports a procedure based on ligandless-ultrasound-assisted emulsification-microextraction of trace amounts of cobalt and manganese ions in water samples prior to flame atomic absorption spectrometry determination (FAAS). Different factors influencing the extraction efficiency of cobalt and manganese ions, such as type and volume of the extraction solvent, pH, extraction time, extraction temperature, and ionic strength were studied and optimized. Cobalt and manganese ions were extracted in an acoustically emulsified media by 20.0 μL carbon tetrachloride. The limits of detection were 0.8 and 0.5 ng mL-1 for Co(II) and Mn(II), respectively (3Sb/m). Eight replicate determinations of a mixture of 100.0 ng mL-1 cobalt and 50.0 ng mL-1 manganese gave a mean absorbance of 0.055 and 0.061 with relative standard deviations of 3.2 and 2.9%, respectively. The proposed procedure was successfully applied to determination of cobalt and manganese in water samples.

Exploring the Limitations of the Use of Competing Reducers to Control the Morphology and Composition of Pt and PtCo Nanocrystals

We have explored size- and shape-controlled synthesis of platinum nanocrystals (Pt NCs) by systematically comparing the differential reducing performance of two competing reducing agents in a one-pot synthesis: hexadecanediol, a weak reducer, and metallic cobalt or superhydride, stronger reducers of Pt. In addition to its role as a metal reducer, Co also functions as a shape-directing agent and is incorporated into the Pt NCs, forming a PtCo alloy structure. By maintaining a constant HDD concentration and systematically increasing the Co content, the shape of the resulting NCs was found to alter from polypods, when no Co was present, to cuboctahedrons and cubes when trace amounts of Co were added, and back to polypods when Co dominated the reduction process. On the other hand, when the concentration of HDD was systematically increased (with Co kept constant), evolution from polypod morphology to prismatic/spherical/cubic NCs, followed by irregular shapes was observed. Both experimental results indicate the importance of the competitive role between the reducing agents, their concentration limits for achieving a controlled morphology, and the presence of Co as a shape-directing agent to alter the NC shape. This allows the exploration of a wide range of NC morphologies without significant modification of the synthesis recipe.

Preferential Oxidation of CO over Pt Catalysts Supported on Mesoporous Aluminosilicates in the Presence of H<sub>2</sub>

. Preferential oxidation (PROX) of CO in the presence of H2 is an important reaction to maintain stable operation of polymer electrolyte fuel cells (PEFCs) since their anode catalyst can be poisoned by trace amount of CO. In this study, we examined PROX reactions mediated by Pt catalysts prepared using several mesoporous silica and aluminosilicate supports such as imogolite (IM), allophane (AP), silica aerogel (SAG), and an amorphous hydroxyl aluminosilicate developed in our research group (HAS). The selectivity of CO oxidation gradually decreased from 80 to 60 % with increasing temperature from 323 to 473 K for Pt/HAS catalyst whereas it increased with temperature from 10 to 40 % for Pt/IM, Pt/AP, Pt/SAG catalysts. These results indicate that Pt supported on HAS may be effective for low-temperature PROX reactions.

KINETIC STUDY OF THE OXIDATWE DECOLORIZATION OF XYLENOL ORANGE BY HYDROGEN PEROXIDE IN MICELLAR MEDIUM

ABSTRACT The kinetics of the oxidation of xylenol orange tetrasodium salt by hydrogen peroxide was investigated in the presence of cationic surfactant (N- dodecylpyridinium chloride) & strongly basic media over the temperature range 20 – 35 °C. The kinetics studies were carried out as a function of different variables like concentration, pH and temperature. The described reaction rate is greatly catalyzed by the presence of trace amount of Co(II) ions & followed pseudo-second- order with respect to dye concentration. Possible mechanism for the catalyzed and uncatalyzed reactions is proposed and found to be coincident with the experimental findings. The derived rate equation is in good agreement with the experimental observations. Thermodynamic parameters were also evaluated. Keywords: Kinetic; Hydrogen peroxide; Xylenol orange; Surfactant; Mechanism e-mail: nasiruk@uok.edu.pk INTRODUCTION Hydrogen peroxide has interesting biological properties and environmentally it is a friendly oxidant. It has been used for the oxidation of various organic compounds. [1 -3] Number of works is found in the literature in which hydrogen peroxide has been used as an oxidant for different dyes.[4 – 7] It is one of the principal oxidizing agents used for the treatment of fabrics, paper, cosmetic products and industrial wastewater due to its low cost, simple handling, effectiveness in destroying the chromospheres and being a friendly alternative to chlorine. The oxidation of dyes has got much attraction since last few years. [8- 10] This has been stimulated by environmental, commercial & social pressures, particularly environmental concerns over residual dyes present in wastewater streams and causing aesthetic pollution. Although, previous studies represent significant steps forward in generating empirical rules governing oxidation, further progress is required in developing the underlying science base.Xylenol orange [3, 3’ bis [N, N’ – Di(carboxymethyl)- aminomethyl- O - cresolsulphone – phthalein tetrasodium salt] (XO), a heterocyclic species which belongs to the acidic class of dyes. This anionic dye, which is stable and water soluble with an absorption peak at 577 nm, was chosen as a representative species for this study.A number of papers have been published on the oxidation of xylenol orange (reductive chromogenic agent) by various oxidizing agent. [11 – 13] In previous work , oxidation of xylenol orange was carried out but detailed kinetics study like reaction mechanism, effect of surfactants and thermodynamic parameters were not studied. In proposed work Co(II) has been used as a catalyst but in previous work other ions were used as catalyst except Co(II) in the oxidation of xylenol orange by bromate.The oxidation of xylenol orange is a very important redox reaction, as it has an environmental concern. It is a textile dye for industrial uses. Current environmental hazards with these dyes and their derivatives revolve around the carcinogenic potential. Different metal ions like copper (II), iron (II) and (III) etc. have been proved to enhance the decolorization of various dyes

Microwave-assisted Pt–Co–Cr/C ternary compound preparation applied as a cathode catalyst for PEMFC

The present study describes the preparation of catalyst nanocomposites comprised of 20 wt.% Pt–Co–Cr (2:1:1) particles attached on the surface of carbon Vulcan XC-72R by microwave radiation; cases of carbon being chemically treated and untreated are considered. Ethylene glycol was used as the solvent and electron source for the microwave-assisted reduction reaction, whereas H2PtCl6⋅xH2O, Co(NO3)3⋅6H2O and Cr(NO3)3⋅9H2O were used as metal precursors. The C powder surface was chemically modified by stirring the C in 8N H2O2 for 48 h. For the nanocomposite in which C was not treated, EDS analysis showed a content of 4.9 wt.% Pt and 1.2 wt.% Cr with only a trace amount of Co. Higher Pt and Cr contents were observed in the catalyst sample prepared from treated carbon (5.6% Pt and 2.2% Cr), but no Co was detected. Chromium appeared as Cr3O4 in both samples confirmed by the XAS spectrum. The obtained phase was therefore Pt–Cr3O4 /C for both samples. The TEM results indicated that the average particle size of Pt–Cr3O4 was 2.22 ±0.41 nm on treated C and 1.93 ±0.34 nm on untreated C. By the CV technique, it was observed that the catalytic activity of the treated carbon Pt–Cr3O4 catalyst was not only higher than that of the untreated carbon Pt– Cr3O4 catalyst, but also higher than that of the standard platinum catalyst.

Preconcentration of Co, Ni, Cd and Zn on naphthalene 2,4,6- trimorpholino-1,3,5-triazin adsorbent and flame atomic absorption determination

A preconcentration method was developed for the determination of trace amounts of Co, Ni, Cd and Zn by atomic absorption spectrometry. The method is based on the retention of the metal cations by naphthalene- 2,4,6-trimorpholino-1,3,5-triazin adsorbent in a column. The adsorbed metals were then eluted from the column with hydrochloric acid and the Co, Ni, Cd and Zn were determined by flame atomic absorption spectrometry. The optimal extraction and elution conditions were studied. The effects of diverse ions on the preconcentration were also investigated. A preconcentration factor of 250 for Co(II), Ni(II) and Zn(II), and 400 for Cd(II) can easily be achieved. Calibration graphs were obtained and the detection limits of the method for Co(II), Ni(II), Cd(II) and Zn(II) were 0.51, 0.49, 0.17 and 0.10 ng mL-1, respectively. The relative standard deviations (RSD) of 0.37-2.31 % for Co, 0.37-3.73 % for Ni, 2.20-2.40% for Cd and 1.50-2.56% for Zn were obtained. The method was also used for the simultaneous preconcentration of these elements and the method was successfully applied to their preconcentration and determination. The method was applied to the determination of Co, Ni, Cd and Zn in several real samples.

Visible Light Photoreduction of CO2 Using CdSe/Pt/TiO2 Heterostructured Catalysts

A series of CdSe quantum dot (QD)-sensitized TiO2 heterostructures have been synthesized, characterized, and tested for the photocatalytic reduction of CO2 in the presence of H2O. Our results show that these heterostructured materials are capable of catalyzing the photoreduction of CO2 using visible light illumination (λ > 420 nm) only. The effect of removing surfactant caps from the CdSe QDs by annealing and using a hydrazine chemical treatment have also been investigated. The photocatalytic reduction process is followed using infrared spectroscopy to probe the gas-phase reactants and gas chromatography to detect the products. Gas chromatographic analysis shows that the primary reaction product is CH4, with CH3OH, H2, and CO observed as secondary products. Typical yields of the gas-phase products after visible light illumination (λ > 420 nm) were 48 ppm g−1 h−1 of CH4, 3.3 ppm g−1 h−1 of CH3OH (vapor), and trace amounts of CO and H2.

Thermal decomposition of 1,3,3-trinitroazetidine in the gas phase, solution, and melt

1,3,3-Trinitroazetidine (TNAZ) was synthesized using the alternative approach based on the transformation of 3-oximino-1-(p-toluenesulfonyl)azetidine in the reaction with nitric acid through intermediate pseudonitrol. The thermal decomposition of TNAZ in the gas phase, melt and m-dinitrobenzene solution in a wide concentration range (5–80%) was studied by manometry, volumetry, thermogravimetry, IR spectroscopy, and mass spectrometry. In the gas phase in the temperature range from 170 to 220°C the thermal decomposition proceeds according to the first-order kinetic law with the activation energy 40.5 kcal mol−1 and pre-exponential factor 1015.0 s−1. The major gaseous reaction products are N2, NO, NO2, CO2, H2O, and nitroacetaldehyde, and trace amounts of CO and HCN are formed. The rate-determining step of the process is the homolytic cleavage of the N-NO2 bond in the TNAZ molecule. In melt at 170–210 °C the thermal decomposition proceeds with the pronounced self-acceleration and the maximum reaction rates are observed at conversions 53.9–67.4%. The solid decomposition products accelerate the reaction. It is most likely that the autocatalysis of TNAZ decomposition in the liquid phase is due to the autocatalytic decomposition of 1-nitroso-3,3-dinitroazetidine, which is formed by the thermal decomposition of TNAZ. In m-dinitrobenzene TNAZ also decomposes with self-acceleration. The higher the concentration in the solution, the more pronounced the self-acceleration. Additives of picric acid moderately accelerate the thermal decomposition of TNAZ, whereas hexamethylenetetraamine additives exert a strong acceleration.

Influence of sulfuric acid baking on leaching of spent Ni–Mo/Al 2O 3 hydro-processing catalyst

A low temperature sulfuric acid baking and mild acid leaching process was explored for maximum dissolution of metal values from a spent Ni–Mo/Al 2O 3 hydro-processing catalyst obtained from a Korean refinery. The spent catalyst was found to be a matrix of γ-Al 2O 3. containing 27.1% Al, 11.6% Mo, 2.5% Ni, 9.7% S, 4.8% C, 1.9% P, 0.4% Si and trace amounts of Co and Fe. Various baking parameters such as baking temperature, sulfuric acid concentration and baking duration were optimized according to 2 3 full factorial method for maximum dissolutions of Mo, Al and Ni during leaching. Under optimum baking conditions (400 °C; 1.28 stoichiometric H 2SO 4; 1 h), > 96% Mo, 99% Al and 95% Ni were readily dissolved from the spent catalyst by 2% v/v H 2SO 4 at 80 °C. Carbon and sulfur analyses of the baked samples and leaching residues indicated only 10–15% of residual hydrocarbons reacted during acid baking, while most of the sulfur (assumed to be metal sulfides) was converted into soluble sulfates/oxy-sulfates. By comparison, direct sulfuric acid leaching of the catalyst resulted in poor dissolution of Mo and Al, even with large excess of acid, thus demonstrating the beneficial effect of sulfuric acid baking.

The genesis of sandstone‐type uranium deposits in the Ordos Basin, NW China: constraints provided by fluid inclusions and stable isotopes

Quartz from sandstone‐type uranium deposits in the east part of the Ordos Basin contains abundant secondary fluid inclusions hosted along sealed fractures or in overgrowths. These inclusions consist mainly of water with NaCl, KCl, CO2 (135–913 ppm) and trace amounts of CO (0.22–16.8 ppm), CH4 (0.10–1.38 ppm) and [SO4]2− (0.35–111 ppm). Homogenization temperatures of the studied fluid inclusions range from 90 to 210°C, with salinities varying from 0.35 to 12.6 wt‐% (converted to NaCl wt%), implying multiple stages of thermal alteration. Although high U is associated with a high homogenization temperature in one case, overall U mineralization is not correlated with homogenization temperature nor with salinity. The H and O isotopic compositions of fluid inclusions show typical characteristics of formation water, with δ18O ranging from 9.8 to 12.3‰ and δD from 26.9 to −48.6‰, indicating that these fluid inclusions are mixtures of magmatic and meteoric waters. The oxygen isotope ratios of carbonates in cement are systematically higher than those of the fluid inclusions. Limited fluid inclusion‐cement pairs show that the oxygen closely approaches equilibrium between water and aragonite at 150°C. Highly varied and overall negative δ13C in calcite from cement implies different degrees of biogenetic carbon involvement. Correlations between U in bulk rocks and trace components in fluid inclusions are lacking; however, high U contents are typically coupled with high [SO4]2−, implying pre‐enrichment of oxidized materials in the U mineralization layer. All these relationships can be plausibly interpreted to indicate that U (IV), [SO4]2− as well as Na, K were washed out from the overlying thick sandstone by oxidizing meteoric water, and then were reduced by reducing agents, such as CH4 and petroleum, likely from underlying coal and petroleum deposits, and possibly also in situ microbes at low temperatures.

Effect of CO and CO 2 impurities on performance of direct hydrogen polymer-electrolyte fuel cells

Mechanisms by which trace amounts of CO and CO 2 impurities in fuel may affect the performance of direct hydrogen polymer-electrolyte fuel cell stacks have been investigated. It is found that the available data on CO-related polarization losses for Pt electrodes could be explained on the basis of CO adsorption on bridge sites, if the CO concentration is less than about 100 ppm, together with electrochemical oxidation of adsorbed CO at high overpotentials. The literature data on voltage degradation due to CO 2 is consistent with CO production by the reverse water–gas shift reaction between the gas phase CO 2 and the H 2 adsorbed on active Pt sites. The effect of oxygen crossover and air bleed in “cleaning” of poisoned sites could be modeled by considering competitive oxidation of adsorbed CO and H by gas phase O 2. A model has been developed to determine the buildup of CO and CO 2 impurities due to anode gas recycle. It indicates that depending on H 2 utilization, oxygen crossover and current density, anode gas recycle can enrich the recirculating gas with CO impurity but recycle always leads to buildup of CO 2 in the anode channels. The buildup of CO and CO 2 impurities can be controlled by purging a fraction of the spent anode gas. There is an optimum purge fraction at which the degradation in the stack efficiency is the smallest. At a purge rate higher than the optimum, the stack efficiency is reduced due to excessive loss of H 2 in purge gas. At a purge rate lower than the optimum, the stack efficiency is reduced due to the decrease in cell voltage caused by the excessive buildup of CO and CO 2. It is shown that the poisoning model can be used to determine the limits of CO and CO 2 impurities in fuel H 2 for a specified maximum acceptable degradation in cell voltage and stack efficiency. The impurity limits are functions of operating conditions, such as pressure and temperature, and stack design parameters, such as catalyst loading and membrane thickness.

CO-Free Hydrogen Production by Membrane Reactor Equipped with CO Methanator

A novel membrane reactor system equipped with a CO methanator was proposed for the efficient production of CO-free hydrogen by a simple and compact reactor unit without any additional purification of hydrogen. It is expected that a trace amount of CO in the permeate can be removed through the methanation at the sacrifice of a minimum amount of hydrogen. The effectiveness of this system was experimentally examined for the steam reforming of methane in the membrane reactor using a thin Pd/Ag membrane with a few defects and a Ru/Al2O3 catalyst for methanation. It was demonstrated that a highly concentrated and practically CO-free hydrogen could be successfully obtained with attaining the high methane conversion beyond the limit imposed by equilibrium, and the amount of hydrogen consumed by the CO and CO2 methanations was much lowered; that is, it was less than ca. 1% of hydrogen permeated through the membrane. Furthermore, the catalytic performance for methanation at relatively high temperature was investiga...

Universal Metastability of Sickle Hemoglobin Polymerization

Sickle hemoglobin (HbS) polymerization occurs when the concentration of deoxyHbS exceeds a well-defined solubility. In experiments using sickle hemoglobin droplets suspended in oil, it has been shown that when polymerization ceases the monomer concentration is above equilibrium solubility. We find that the final concentration in uniform bulk solutions (i.e., with negligible boundaries) agrees with the droplet measurements, and both exceed the expected solubility. To measure hemoglobin in uniform solutions, we used modulated excitation of trace amounts of CO in gels of HbS. In this method, a small amount of CO is introduced to a spatially uniform deoxyHb sample, so that less than 2% of the sample is liganded. The liganded fraction is photolyzed repeatedly and the rate of recombination allows the concentration of deoxyHbS in the solution phase to be determined, even if polymers have formed. Both uniform and droplet samples exhibit the same quantitative behavior, exceeding solubility by an amount that depends on the initial concentration of the sample, as well as conditions under which the gel was formed. We hypothesize that the early termination of polymerization is due to the obstruction in polymer growth, which is consistent with the observation that pressing on slides lowers the final monomer concentration, making it closer to solubility. The thermodynamic solubility in free solution is thus achieved only in conditions with low polymer density or under external forces (such as found in sedimentation) that disrupt polymers. Since we find that only about 67% of the expected polymer mass forms, this result will impact any analysis predicated on predicting the polymer fraction in a given experiment.

Operating characteristics of 40 W-class PEMFC stacks using reformed gas under low humidifying conditions

The small PEMFC stack to be integrated with miniaturized fuel reformer is usually operated under very poor operating conditions such as low relative humidity and reformed gas conditions including trace amounts of CO. Hence, for the stable operation of the stack under such real conditions, the effect of reactants feeding method and stack operating conditions such as stack temperature and gas humidity were experimentally investigated and the optimal operating strategy was suggested. The external-manifolds configuration was not efficient compared to the internal-manifolds due to their poor water management. The fuel introduction to the stack by opposite directions between air and hydrogen enhanced the stack stability, particularly under low humidified conditions, by enhancing water exchange between the two fuel streams. Even 10 ppm of CO in the reformed gas deteriorated the stack performance seriously under low stack temperature or low relative humidity conditions. Hence, for the stable operation of the small PEMFC stack, particularly under practical operating conditions, air-bleeding method seems to be a promising strategy.

Multilayer Nano Ti ∕ TiO2 – Pt Electrode for Coal-Hydrogen Production

Multilayer nanoporous films were obtained by controlling electro-oxidation potentials in a sulfuric acid solution. After etching in a dilute hydrogen fluoride solution, the porous layers were deposited and intercalated with Pt and Pt–Ru to form and electrodes by using the cyclic voltammetric method. An electron diffraction spectroscopy was used to examine the electrode surface structure. The catalytic activity of the electrodes for electro-oxidation of coal shows that the multilayer nanoporous structure improves the electrode performance in comparison to a pure Pt electrode and a Pt coated Ti electrode. The (1:2) electrode shows even better catalytic activity than the . Anode gas analysis shows that the coal electro-oxidation produces mainly with trace amount of CO, and the cathode gas is pure hydrogen. We also observed some lower hydrocarbon by-products, such as methane. The amount of is only of the amount of produced.

A comparative study of solid acids in hydrolysis and steam reforming of dimethyl ether

Abstract The catalytic performances of solid acids (Al2O3 derived from bayerite (PBT), γ-Al2O3 (ALO8), ZSM-5, H-mordenite, and TiO2) in hydrolysis of dimethyl ether (DME) to methanol have been investigated. The stronger and the larger acid sites give rise to higher conversion in hydrolysis; however, fast degradation due to coking and low quality of product are observed. The acid strength of the solid acids is as follows: H-mordenite > ZSM-5 > PBT, ALO8 > TiO2. The apparent activation energies of DME hydrolysis over H-mordenite, ZSM-5, PBT, ALO8, and TiO2 were determined as 73, 76, 101, 146, and 186 kJ mol−1, respectively. Next, steam reforming of dimethyl ether over composites of the solid acid and copper iron spinel was evaluated for hydrogen production. The composites of alumina and Cu spinel are active and durable to produce H2-rich reformate with CO2 as the major products along with trace amounts of CO. The Cu content of 13.3–17.7 wt% in the composites was optimum in terms of reforming performance. Alumina–spinel composites are superior to zeolite–spinel ones with regard to stability. Increasing the steam-to-carbon ratio obviously suppresses the catalyst degradation.

A comparative Raman spectroscopic study of natural gas hydrates collected at different geological sites

Intact natural gas hydrates recovered on the West African margin in the South Atlantic Ocean (ZaiAngo and Neris II projects) and from the Norwegian Sea (Hakon Mosby Mud Volcano) are investigated by micro-Raman spectroscopy at ambient pressure and low temperature. The gas hydrates collected at different geological sites contain a high methane concentration relative to other minor components that are slightly dispersed in the samples. They crystallize in a type I cubic lattice structure as also confirmed by our preliminary synchrotron diffraction results obtained on the ZaiAngo specimen. However, detailed analysis of selected microscopic areas reveals a variation in the gas distribution among the different specimens. Trace amounts of CO 2 and H 2S can be identified by their characteristic vibrational signatures in the 1000–3800 cm − 1 spectral range. They are found to be co-clathrated with methane. Their presence produces a compositional effect on the relative cage occupancy of CH 4, as determined from the integrated band intensity ratio corresponding to the molecular stretching modes of methane in the hydrate. The comparative Raman analysis of synthetic hydrates of H 2S, CH 4 and CH 4-deuterohydrates allows the unambiguous assignment of weak band overtones of trapped methane and co-clathrated H 2S molecular vibrations.

Simultaneous Determination of Cobalt and Nickel Using Morpholinedithiocarbamate (MDTC) as Reagent by First and Second Derivative Spectrophotometry

AbstractA selective and sensitive derivative method has been proposed for the simultaneous determination of trace amounts of Co(II) and Ni(II) with morpholinedithiocarbamate (MDTC) in the presence of sodium lauryl sulphate (SLS). The molar absorption coefficients of the 1:2 complex of Co(II) and Ni(II) at 326 nm and 322 nm are 2.248 × 104 and 2.505 × 104 L mol−1 cm−1 for zero order. The analytical sensitivity for the second derivative of Co(II) and Ni(II) complexes are 0.0044 μg mL−1 and 0.0060 μg mL−1. The developed derivative procedure, using the zero‐crossing technique, has been successfully applied for the analysis of Co(II) and Ni(II) simultaneously in different alloy samples.

An efficient polyoxovanadate-catalyzed oxidative mineralization of phenols with 30% aqueous H 2O 2

Catalytic oxidative mineralization of phenols proceeded at 70 °C in the presence of K 7NiV 13O 38 · 16H 2O using 30% aqueous hydrogen peroxide as oxidant. At an initial concentration of 0.4 M, nitrophenols and p-chlorophenol were decomposed completely in 15 min, and other phenols were decomposed within two hours. It was disclosed that p-nitrophenol was almost completely mineralized into CO 2 and NO 3 - , accompanied with only trace amount of CO, NO 2 - and CH 3NO 2, p-chlorophenol was converted to CO 2 and Cl − with trace amount of CO, and phenol and other phenols bearing electron-rich group were converted to CO 2 and H 2O with trace amount of CO.

Structural and DC resistivity behaviour of Li–Mn–Ni ferrites substituted with trace amount of Co 2+

This paper reports the influence of Co 2+ substitution on the structural parameters and DC resistivity of Li–Mn–Ni ferrites. Samples having the compositional formula Li 0.45− x /2Ni 0.1Mn 0.1Co x Fe 2.35− x /2O 4, with x ranging from 0 to 0.01 in steps of 0.002, were prepared by the conventional ceramic technique. X-ray diffraction has confirmed the single-phase spinel structure of the samples. The lattice parameter and theoretical density of the samples were determined and the latter compared with the experimental density measured by Archimedes Principle. Porosity was found to decrease with substitution. The temperature dependence of DC resistivity shows the semiconducting nature. The resistivity and activation energies increase with the increase of substitution level.