Kinetics and thermodynamics of bleaching process in aqueous solution using sodium hypochlorite

The kinetics of bleaching process of oxidation of typical dye with a bleaching agent - sodium hypochlorite in aqueous medium was studied. The kinetic runs were executed using spectrophotometer to changes in concentration under pseudo first order whereby concentration of NaOCl was in large excess compared with the concentration of dye. The factors affecting the reaction rate that were studied include the concentration of dye and oxidant, temperature, ionic strength and pH of the bleaching reaction medium and the presence of a variable valence metal ion The result shows that the rate of oxidation increases with increasing in temperature, ionic strength and pH. Increasing in substrate and oxidant concentrations also increase the rate of oxidation. Higher observed rate constant k1 was obtained in the presence of Fe(III)ion. The Arrhenius activation energy for the oxidation in the absence and presence of Fe(III)ion are 56.21 kJmol-1 and 51.21 kJmol-1 respectively. The result of thermodynamic parameters such as the lowering of activation energy (Ea) and the higher value of second rate constants k2 in the presence of Fe (III) ion provide further support for Fe (III) ion enhancement of rate of oxidation

CO hydrogenation catalyzed by alumina-supported osmium: Particle size effects

Alumina-supported catalysts were prepared by conventional aqueous impregnation with [H2OsCl6] and by reaction of organoosmium clusters {[Os3(CO)12], [H4Os4(CO)12], and [Os6(CO)18]} with the support. The catalysts were tested for CO hydrogenation at 250-325 [deg]C and 10 atm, the products being Schulz-Flory distributions of hydrocarbons with small yields of dimethyl ether. The fresh and used catalysts were characterized by infrared spectroscopy and high-resolution transmission electron microscopy. The catalyst prepared from [H2OsCl6] had larger particles of Os (~70 A). The cluster-derived catalysts initially consisted of molecular clusters on the support; the used catalysts contained small Os aggregates (typically 10-20 A in diameter). The catalytic activity for hydrocarbon formation increased with increasing Os aggregate size, but the activity for dimethyl ether formation was almost independent of aggregate size. The hydrocarbon synthesis was evidently catalyzed by the Os aggregates, and the ether synthesis was perhaps catalyzed by mononuclear Os Complexes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25555/1/0000097.pd

A novel zerovalent manganese for removal of copper ions: synthesis, characterization and adsorption studies

Synthesis of nanoscale zerovalent manganese (nZVMn) by chemical reduction was carried out in a single pot system under inert environment. nZVMn was charac�terized using a combination of analytical techniques: Ultraviolet–Visible Spectroscopy, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive X-ray, BET surface area and Point of Zero Charge. The adsorption physicochemical factors: pH, contact time, adsorbent dose, agitation speed, initial copper ion concen�tration and temperature were optimized. The kinetic data fitted better to Pseudo second-order, Elovich, fractional power and intraparticle diffusion models and their validity was tested by three statistical models: sum of square error, Chi-square (v2 ) and normalized standard deviation (Dq). Seven of the two-parameter isotherm models [Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich (DKR), Halsey, Harkin–Jura and Flory–Huggins] were used to analyse the equilibrium adsorption data. The Langmuir monolayer adsorption capacity (Qmax = 181.818 mg/g) obtained is greater than other those of nano-adsorbents utilized in adsorption of copper ions. The equilibrium adsorption data were better described by Langmuir, Fre�undlich, Temkin, DKR and Halsey isotherm models con�sidering their coefficient of regression (R2[0.90). The values of the thermodynamic parameters: standard enthalpy change DH� (?50.27848 kJ mol-1 ), standard entropy change DS� (203.5724 J mol-1 K-1 ) and the Gibbs free energy change DG� revealed that the adsorption process was feasible, spontaneous, and endothermic in nature. The performance of this novel nanoscale zerovalent manganese (nZVMn) suggested that it has a great potential for effective removal of copper ions from aqueous solutio

Enhancing Adsorption Capacity of a Kaolinite Mineral Through Acid Activation and Manual Blending with A 2:1 Clay

The efficiencies of raw and modified kaolinite mineral in removing selected heavy metal ions from their respective aqueous solutions were investigated. The mineral was modified through two different methods; i) activation with HNO3, H2SO4, H3PO4, CH3COOH and C2H2O4 acids to form NK, SK, PK, AK and OK acid activated clays respectively and ii) preparations of 3:1 and 1:1 Kaolinite: Bentonite blends to form UBK and EBK composites respectively through manual blending. The adsorbents were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red Spectroscopy (FTIR) and Brunauer Emmett Teller (BET) analysis for surface area determination. The surface area increased in some of the modified clays from 114.9457 m2/g (RK) to 288.685 m2/g (EBK), 205.92 m2/g (UBK), 162.227 m2/g(NK), 151.335 m2/g (SK), and 115.837 m2/g (OK) but reduced to 113.872 m2/g (PK) and 112.865 m2/g (AK) after modification. Adsorption studies were subsequently conducted out to remove Pb2+, Cd2+ and Ni2+ ions from synthetic solutions. Pb2+ was found to be most removed (383.5 mg g-1 (RK), 591.13 mg g-1 (EBK), 576.61 mg g-1 (UBK), 475 mg g-1 (NK), 450 mg g-1 (SK), and 425 mg g-1 (PK), 375 mg g-1 (OK) and 375 mg g-1 (AK)) with highest removals on the composites

Kinetics and Thermodynamics of Bleaching Process in Aqueous Solution using Sodium Hypochlorite

The kinetics of bleaching process of oxidation of typical dye with a bleaching agent - sodium hypochlorite in aqueous medium was studied. The kinetic runs were executed using spectrophotometer to changes in concentration under pseudo first order whereby concentration of NaOCl was in large excess compared with the   concentration of dye. The factors affecting the reaction rate that were studied include the concentration of dye and oxidant, temperature, ionic strength and pH of the bleaching reaction medium and the presence of a variable valence metal ion The result shows that the rate of oxidation increases with increasing in temperature, ionic strength and pH. Increasing in substrate and oxidant concentrations also increase the rate of oxidation. Higher observed rate constant k1   was obtained in the presence of Fe(III)ion. The Arrhenius activation energy for the oxidation in the absence and presence of Fe(III)ion are 56.21 kJmol-1 and 51.21 kJmol-1 respectively.  The result of thermodynamic parameters such as the lowering of activation energy (Ea) and the higher value of second rate constants k2 in the presence of Fe (III) ion provide further support for Fe (III) ion enhancement of rate of oxidation. &nbsp

KINETICS AND ISOTHERM MODELING OF ADSORPTION OF RHODAMINE B DYE ONTO CHITOSAN SUPPORTED ZEROVALENT IRON NANOCOMPOSITE (C-nZVI)

The kinetics and isotherm modeling ofadsorption ofRhodamine 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 diffusion. The study revealed the great potential of C-nZVI for effective removal of RhB dye. C-nZVI is therefore recommended for civic and industrial effluents treatment

Cleaner energy through liquefaction of Cocoa (Theobroma cacao) pod husk: Pretreatment and process optimization

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 diffusion. The study revealed the great potential of C-nZVI for effective removal of RhB dye. C-nZVI is therefore recommended for civic and industrial effluents treatment