16 research outputs found
Kinetics, Isotherms and Thermodynamics Studies of Sorption of Cu2+ onto Novel Zerovalent Iron Nanoparticles
A novel nanoscale zerovalent iron (nZVI) is an effective adsorbent forscavenging inorganic and organic toxicants. nZVI was synthesized in a single potsystem using bottom-up approach and were characterized by BET, SEM, EDX andFTIR. In this study, sorption of Cu2+ onto nZVI was carried out vis-Ã -vis theinvestigation of physicochemical parameters (initial metal ion concentration, pH,temperature, adsorbent dose) at 298 K. The sorption data obtained at optimumconditions were subjected to six different isotherm models (Langmuir, Freundlich,Temkin, Dubinin-Raduskevich (D-R), Halsey and Harkin-Jura). However, theequilibrium sorption data were best described by both Langmuir and Temkin isothermmodels with Langmuir maximum monolayer coverage (Qmax) of 40.816 mg/g andregression correlation value (R2 > 0.96) supporting a chemisorption mechanism. Pseudofirst-and second-order, Elovich, fractional power and intra-particle diffusion modelswere applied to the adsorption data in order to investigate the kinetic process; pseudosecond-order fitted the data most. The intra-particle diffusion model suggested that theintra-particle diffusion was one of the rate-limiting steps. The values of the Gibbs freeenergy showed the feasibility and spontaneity of the sorption process. The removalefficiency of Cu2+ (> 98%) onto zerovalent iron nanoparticles revealed that nZVI is apromising and efficient adsorbent that can be utilized by industries on a large scale forwaste treatment.Keywords: Zerovalent Iron nanoparticle; Sorption; Isotherms; Kinetics andThermodynami
Kinetic And Thermodynamic Studies Of Glucose Oxidase Catalysed Oxidation Reaction of Glucose
The kinetics of oxidation of D-glucose catalysed by the enzyme glucose
oxidase has been studied over a wide range of experimental conditions.
The reaction velocities increased with increase in the concentrations
of the glucose oxidase and glucose, as well as increase in temperature
and ionic strength of the solution. The reaction velocity initially
increased with increase in pH, reaching a maximum at pH 6.5 and then
decreased with further increase in pH. The reaction exhibited
saturation kinetics and experimental data were analysed using the
Michaelis- Menten equation. Arrhenius activation energy and
thermodynamic activation parameters were measured and are reported. The
large negative value of entropy of activation \u394S 60 ,
-148.8JK-1mol-1, and positive value of the enthalpy of activation
\u394H 60 , 26.3kJmol-1, give further support to the proposed
mechanism. The results are interpreted in terms of a mechanism
involving both an oxidative half reaction and a reductive half
reaction
Kinetic and Thermodynamic Study of Oxidative Decolourisation of a Typical Food Dye (Tartrazine) in an Aqueous Environment
The study was carried out to describe the kinetics and thermodynamics of hydrogen peroxide oxidation of a typical food dye (Tartrazine). The effect of different operational factors were investigated spectrophotometricallyat wavelength460 nm under pseudo first order reaction.These included concentration of the oxidant and the dye, the pH, ionic strength and temperature of the reacting medium and the presence of transition metal ion as homogenous catalyst. A complete and smooth decolourisation was observed. The results showed that the rate of oxidation of dye increased with increasing in concentration of substrate and oxidant. Increasing in temperature, ionic strength and pH of the basic reaction medium also raised the reaction rate. The rate of oxidation also increased with increasing in the concentration of Fe (III) ion. Pseudo second order rate constant (k2) obtained was 1.95 x 10-3 M-1s-1 and 3.8 x10-3M-1s-1 in the absence and presence of Fe (III) ion respectively. The Arrhenius activation energy for the oxidation in the absence and presence of Fe (III) ion were 47.23 kJmol-1 and 42kJmol-1 respectively. Other thermodynamic parameters showed entropy of activation (ΔS#), free energy of activation (ΔG#) and Enthalpy of activation of the reaction (ΔH#) in the presence of Fe (III) as -34.7 JK-1mol-1, 48.4 kJmol-1 and 40.30 kJmol-1 respectively. The results in the absence of Fe (III) ion were -24.6 JK-1mol-1, 51.2 kJmol-1 and 44.0 kJmol-1respectively. The relative lower activation energy (Ea),fairly higher negative value of (ΔS#) and higher (ΔG#) , with higher rate constant in the presence of Fe(III) ion showed Fe(III) ion enhancement of rate of decolourisation.
Keywords: Tartrazine Food dye, Kinetics, Thermodynamics, Hydrogen Peroxidede colourisation
Synthesis and X-ray studies of ruthenium(II) complexes containing hydrazine and benzyl isocyanide ligands
The reaction of the polymeric species [{RuCl2(COD)}x] (1; x > 2; COD = cyclo-octa-1,5-diene) and hydrazine hydrate in methanol under reflux gave a pale pink solution from which the salt [Ru(COD)(N2H4)4][BPh4]2.CH3OH (2) was isolated on addition of NaBPh4. Treatment of 2 in refluxing acetone in the presence of the ligand benzyl isocyanide give a complex of stoichiometry [Ru(NH2N=CMe2)2(PhCH2NC)4][BPh4]2 (3) on the substitution of the labile COD ligand. The two compounds have been characterized by elemental analyses, IR and NMR measurements and single-crystal X-ray diffraction studies. The ruthenium in both compounds has a distorted octahedral coordination geometry. KEY WORDS: Cycloocta-1,5-diene, Hydrazine hydrate, Isocyanide, Ruthenium Bull. Chem. Soc. Ethiop. 2013, 27(3), 405-411.DOI: http://dx.doi.org/10.4314/bcse.v27i3.
Remediation of aqueous solution of cypermethrin and chlorpyriphos using derived adsorbent from Jatropha curcas
The study focused on assessment of removal of cypermethrin and chloropyriphos in aqueous solution using activated carbon made from Jatropha Curcas. Batch adsorption experiments were carried out under different conditions of parameters such as pH, contact time, adsorbent dosage, and initial concentration of the adsorbate on pesticide adsorption. The adsorption data were described by Langmuir and Freundlich adsorption model. Adsorption capacity of 92.73% and 92.26% of chloropyriphos and cypermetrin respectively were removed by 2g of the adsorbent per 50 cm3 of initial concentration of 0.78 mg/l and 1.50 mg/l chloropyriphos and cypermetrin respectively .This was achieved at 90 min of the contact time and at optimum pH of 6.3.The study demonstrates that the activated carbon made from Jatropha Curcas can be effective in the adsorption of these two pesticides from water bodies. Equilibrium experiment results show that adsorption isotherms of cypermethrin and fit better to Freundlich adsorption isotherm while chloropyriphos fit better on the Langmuir adsorption isotherm.Keywords: remediation, pesticides, Jatropha Curcas, cypermethrin, chloropyriphos, Langmuir and Freundlich equatio
Kinetics and Thermodynamics of Adsorption of Rhodamine B onto Bentonite Supported Nanoscale Zerovalent Iron Nanocomposite
Bentonite clay supported nanoscale zerovalent iron (BC-nZVI) composite was successfully
prepared. BC-nZVI was characterized by physicochemical and spectroscopic techniques. Surface area as
determined by sear’s method is 291.2 cm2 . Adsorption operational parameters were investigated in a
batch technique. At 500 mg/L initial concentration, 120 minutes contact time and pH 3, 454.81 mg/g
quantity was adsorbed. The highest adsorption percentage removal efficiency was obtained at room
temperature. Kinetic data fitted best to pseudo second order and the mechanism was diffusion governed.
The kinetic models were further validated by sum of square error (SSE) and non-linear Chi-square
statistical models (X 2). The values of the thermodynamic parameters: standard enthalpy change ΔH (-
10.597 Jmol -1 )to (-5558 Jmol -1.), standard entropy change, ΔS (-277.804 J mol -1 K -1 )- to (-139.2595 J mol -
1 K -1) and the Gibbs free energy (ΔG) revealed that the adsorption process was feasible, spontaneous and
exothermic in nature. The performance of BC-nZVI enlisted it as a great potential adsorbent for effective
removal of Rhodamine B and therefore recommended for application in industrial effluent treatment
Kinetics and isotherm modeling of adsorption of rhodamine B dye onto chitosan supported zerovalent iron nanocomposite (C-nZVI)
The kinetics and isotherm modeling of adsorption of Rhodamine B (RhB) Dye onto chitosan supported zerovalent iron nanocomposite (C-nZVI)
was successfully studied in a batch technique. The quantity adsorbed increased with increase in initial concentration from 49.33 mg – 242.37 mg
for 200 ppm to 1000 ppm and high percentage removal efficiency (%RE) of 99.72% attained at 90 minutes contact time. Equilibrium data were
analyzed by six isotherm models: Langmuir, Freundlich, Temkin, Dubinin-Kaganer-Raduskevich (DKR), Redlich-peterson and Halsey isotherm
model. Equilibrium data best fitted to Freundlich isotherm supported by Halsey isotherm model. Langmuir monolayer adsorption capacity
(256.41 mg/g) of C-nZVI obtained greater than most adsorbent reported for adsorption of RhB. The mean adsorption free energy, E per
molecule evaluated from DKR model was less than 8 KJmol -1 indicating a physisorption mechanism. The kinetic data best fitted to pseudo
second-order kinetic model as validated by sum of square error (SSE) statistical model and the mechanism controlled by pore dif usion. The
study revealed the great potential of C-nZVI for ef ective removal of RhB dye. C-nZVI is therefore recommended for civic and industrial ef
luents treatment
Kinetics of ethane hydrogenolysis on Os3 (CO)12/Al2O3 catalyst
Bull. Chem. Soc. Ethiop. 1996, 10(2), 143-151
<b>Infrared and ultraviolet spectrophotometric analysis of chromatographic fractions of crude oils and petroleum products</b>
Samples of light, medium and heavy Nigerian crude oils and petroleum products including diesel oil, engine oil (SAE 40) and gasoline (PMS) have been separated into four fractions of saturates, monoaromatics, diaromatics and polyaromatics by elution liquid chromatography. The fractions obtained were analysed using IR and UV-visible spectrophotometry. The infrared data confirmed the presence of methyl and methylene groups in the saturate fractions of the crude oils and petroleum products. The C=C stretching vibrations and C–H out of plane bending vibration of aromatics were also found in the mono-, di- and polyaromatics fractions. The characteristic UV spectra of alkyl benzenes and naphthalenes were observed in the monoaromatic and diaromatic fractions, respectively. The spectra of the polyaromatic fractions indicate the presence of anthracenes and phenanthrenes