Kinetic Studies of Catalytic Oxidation of Cyclohexene Using Chromium VI Oxide in Acetic Acid Medium

Cyclohexene was oxidized using chromium (VI) oxide (CrO3) in pure acetic acid medium. The products of oxidation were analysed using simple qualitative analysis, IR spectroscopy and Gas chromatography-Mass spectrometry (GC/MS). Kinetics studies were carried out to determine the order of reaction, rate constant and the activation energy with respect to the oxidant using pseudo-order approximation method. The influence of Cu2+, Co2+ and Fe2+ as catalysts were also investigated. Qualitative analyses of the products revealed the presence alcohols and ketones while the GC/MS shows the presence of cyclohexanol (2.46%), cyclohexanone (5.05%), 2-cyclohexen-1-one (59.37%), 1,2-cyclohexanediol monoacetate (9.88%), 2-hydroxy-cyclohexanone (1.75%) and bi-2-cyclohexen-1-yl (5.16%). The reaction order was shown to be 2nd order with respect to the CrO3 with activation energy of 45.32 kJ mol-1 while Co2+ and Fe2+ indicated some catalytic activity on the reaction

Mechanism for partial oxidation of Cyclohexene by Chromium (VI) oxide in acetic acid

The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media has been studied. The reaction products were analysed using classical method, IR and GC/MS analyses. The major products of the oxidation reaction in acetic acid medium are cyclohexanol, cyclohexanone, cyclohex-2-en-1-one, cyclohexan-1,2-diol monoacetate and  Bi-2-cyclohexen-1-yl. However, no reaction was observed between cyclohexene and chromium (VI) oxide in aqueous medium. Based on the result a mechanism for the oxidation reactions has been proposed involving dissociation of acetic acid to form an acetate anion which attacks the chromium (VI) oxide to form an acetochromate ion. The latter then attacks cyclohexene to form an acetochromate cyclohexenyl ion intermediate which undergoes electron shift and rearrangement to produce cyclohexanone and chromium (IV) oxide, thereby regenerating the acid. The proposed mechanism suggests that the acetic acid serves both as homogeneous catalyst as well as medium for the reaction

Trace metal levels of drinking water sources in parts of Osun State, Nigeria

This study was carried out to investigate the portability of drinking water sources available to people in parts of Osun State, Nigeria, especially with respect to trace metal levels. The trace metal contents were determined over a period of six months covering both the rainy and dry seasons. Tap, well, stream and borehole water from five towns (Osogbo, Iwo, Ejigbo, Ile-Ife and Ilesha) in Osun State were analysed using Atomic Absorption Spectrophotometer. The concentrations of the metals analyzed range (µg/mL) as follows: Fe (0.18-0.30), Mn (0.33-0.37), Zn (0.11-0.14), Cu (0.05-1.0), Pb (0.01-0.03), Hg (Nd-0.03), As (Nd-0.03), Cd (Nd-0.04), Cr (0.02-0.05), and Ni (0.02-0.05) while the mean levels (ug/mL) were of the order: Hg (0.01) < Pb (0.02) = As (0.02) = Cd (0.02) < Ni (0.03) < Cr (0.04) < Cu (0.08) < Zn (0.13) < Fe (0.25) < Mn (0.36). The results indicated a significant correlation in the metal contents of the water samples from the various locations as well as the various water sources. The trace metals contents (Fe, Mn, Zn, Cu, Cr and Ni) were below or equal to the limits set by WHO for drinking and domestic water while the toxic metals (Pb, Hg, As and Cd), recorded values higher than the safe limits set by WHO hence, the water sources are capable of constituting serious health hazards. Key Words:     Trace Metals, Water, Borehole, Well, Stream, Tap, Toxicit

Kinetics and mechanism of oxidation of D-xylose and L-arabinose by chromium(VI) ions in perchloric acid medium

The kinetics of oxidation of D-Xylose and L-Arabinose by Cr(VI) ions in perchloric acid medium have been investigated spectrophotometrically under pseudo-first-order conditions. The reactions exhibit first-order rate dependence each on the substrate and oxidant. The order with respect to [H+] is unity while no effect on the reaction rate is found with respect to the ionic strength. The Arrhenius (Ea) and thermodynamic activation parameters (ΔH≠, ΔS≠ and ΔG≠) are evaluated and the reaction mechanism is interpreted in terms of formation of a 1:1 intermediate complex between a protonated chromic acid molecule and a neutral sugar molecule in sharp contrast to the results of our earlier studies on the C6 and C12 sugars

Proximate and nutritional composition of kola nut (Cola nitida), bitter cola (Garcinia cola) and alligator pepper (Afromomum melegueta)

The proximate composition and the mineral content of three (3) traditional ‘snacks’, kolanut (Cola nitida), bitter kola (Garcinia cola) and alligator pepper (Afromomum melegueta) were evaluated. The resultsshow that C. nitida has the highest moisture, crude fat and crude fibre contents of 66.4, 5.71 and 7.13%, respectively. Protein and ash contents were highest in A. melegueta (7.18 and 2.49%, respectively). G. cola has the least content of all nutrients considered except moisture. Generally, C. nitida and G. cola have relatively comparable nutrient compositions while the composition of A. melegueta is relatively different from those obtained for the other two samples. A. melegueta has non-detectable quantity of potassium and phosphorous but has the highest quantity of calcium (388 mg/Kg dry matter), magnesium (960 mg/Kg), iron (37.8 mg/Kg), zinc (32.93 mg/Kg) and manganese (68.53 mg/Kg). C. nitida has the highest content of potassium (3484.67 mg/Kg) and phosphorous (411.43 mg/Kg). G. cola also recorded the least content of all minerals except K and P which were absent in A. melegueta. Manganese was not detected in either of kola nut or bitter kola

Physical, functional, and pasting properties of flours from corms of two Cocoyam (Colocasia esculenta and Xanthosoma sagittifolium) cultivars

Physical, functional and physicochemical properties of flours of five cocoyam (Colocasia spp and Xanthosoma spp) cultivars were evaluated. Colour (L*a*b*) parameters of corms and flours, pasting and functional properties of the flours were determined. Xanthosoma spp showed significantly higher length (95.16–151.46), width (75.29–78.03) and weight (179.20–605.94) than the Colocasia spp., but the parameters did not vary significantly within either Xanthosoma and Colocasia spp. Generally, colour of peeled corms [L* (72.08–78.93); a* (+1.06 − +3.5); b* (+17.65 − +35.80)] was lighter than the flours [L* (69.35–84.97); a* (+0.30 − + 4.76); b* (+4.44 − +23.48)]. The NXs001 showed significantly higher peak (201.71RVU), trough (186.75 RVU), final (289.75 RVU) and setback (103 RVU) viscosities that the other cultivars. Pasting profiles of the cocoyam flours showed similar trend with the NXs001 showing a steeper curve. Pasting temperature and peak time ranged from 87.33 to 92.53 °C and 5.17–6.34 min, respectively. Water absorption capacity, gelling point, pH, foam capacity, bulk density and swelling power varied from 32–69 %, 6.56–7.59, 58.5–72.5 °C, 7.19–14.72 %, 0.94–1.01 g/mL and 3.18–7.36, respectively

Fuel–oxidizer mixtures: their stabilities and burn characteristics

Abstarct A survey of the stability and performance of eleven solid oxidizers and thirteen fuels was performed by differential scanning calorimetry, simultaneous differential thermolysis, and hot-wire ignition. Sugars, alcohols, hydrocarbons, benzoic acid, sulfur, charcoal, and aluminum were used as fuels; all fuels except charcoal and aluminum melted at or below 200 °C. It was found that the reaction between the oxidizer and the fuel was usually triggered by a thermal event, i.e., melt, phase change, or decomposition. Although the fuel usually underwent such a transition at a lower temperature than the oxidizer, the phase change of the fuel was not always the triggering event. When sugars or sulfur were the fuels, their phase change usually triggered their oxidation. However, three oxidizers, KNO3, KClO4, and NH4ClO4, tended to react only after they underwent a phase change or began to decompose, which meant that their oxidization reaction, regardless of the fuel, was usually above 400 °C. KClO4-fuel mixtures decomposed at the highest temperatures, often over 500 °C, with the ammonium salt decomposing almost 100 °C lower. Mixtures with ammonium nitrate (AN) also decomposed at much lower temperatures than those with the corresponding potassium salt. With the exception of the oxidizers triggered to react by the phase changes of the polyols and sulfur, the oxidizer-fuel mixtures generally decomposed between 230 and 300 °C, with AN formulations generally decomposing at the lowest temperature. In terms of heat release, potassium dichromate-fuel mixtures were the least energetic, generally releasing less than 200 J g-1. Most of the mixtures released 1000-1500 J g-1, with potassium chlorate, ammonium perchlorate, and AN releasing significantly more heat, around 2000 J g-1. When the fuel was aluminum, most of the oxidizers decomposed below 500 °C leaving the aluminum to oxidize at over 800 °C. Only two oxidizers reduced the temperature of the aluminum exotherm - chlorate and potassium nitrite. To go to temperatures above 500 °C, unsealed crucibles were necessary, and with these containers, the endothermic volatilization of reactants and products effectively competed against the exothermic decomposition so that heat release values were artificially low

Waste minimization in the remediation of contaminated sites: using the oil belt skimmer technology for the removal of heavy hydrocarbons from groundwater

Modern society increasingly requires achieving the goal of remediation and at the same time minimizing the waste to be disposed. Although the pump and treat is a consolidated technology option for the decontamination of groundwater polluted by heavy hydrocarbons, it generates an excessive amount of waste (typically, dangerous). With the intent of reducing such waste, our study is concerned with the verification of the oil belt skimmer technology for the decontamination of a heavy hydrocarbon-polluted groundwater. For this purpose, several tests at laboratory scale and full-scale experimentations with duration greater than 1 year were carried out. The obtained results showed the feasibility of the investigated technology for groundwater decontamination in the cases where the water mobility (of the aquifer) was low and in the presence of oil thicknesses greater than 2 cm. The heavy hydrocarbon recovery capacities were in the range of 33.3–85.5 l/h with the best performances in the cases of supernatant thickness ≥2 cm and pumping of the water table in such a way that the oil acquires a higher mobility in the aquifer. Moreover, the recovery capacity was found to be dependent on the rainfall pattern as well as on the groundwater fluctuation. Compared to the pump-and-treat system, the investigated technology allowed reducing by 98.7 % the amount of waste to be disposed suggesting the use in presence of high thickness of the oils. Finally, in a view of system optimization, treatment trains based on the combination of the oil belt skimmer technology and the pump-and-treat system should be carefully assessed