Extractive recovery of vanadium (V) from hydrochloric acid solutions using alkanols (1-butanol and 1-octanol) dissolved in n-heptane has been investigated by liquid-liquid extraction, propelled by the need to proffering alternatives to the scarce and relatively costly organophosphorous extractants. At the studied pH range (1.0-4.0), with 1-butanol as extractant, the percentage V(V) extraction (extraction efficiency, E%) reached optimum (E% = 63.3) at pH of 0.5, and for 1-octanol, optimum E% was 73.3 at pH 1.0.Increasing concentration of HCl at the studied range (1.0-6.0 mol L -1 ) was found to have an appreciable effect on percentage V(V) extraction. With both extractants, E% peaked at 6.0 mol L -1 HCl with values 86.7 and 70.0% for 1-butanol and 1-octanol, respectively. With increase in the concentration of extractants, both extractants produced a trend of increase/decrease in E% for V(V), suggesting the extraction of two different species. The optimal percentage extraction values were 76.7 and 96.7% observed at log[1-butanol] = 0.81 mol L -1 and log[1-octanol] = 0.49 mol L -1 , in that order. The determined enthalpy change, ΔH, for 1-butanol and 1-octanol systems were -19.9kJ mol -1 and -37.1 kJ mol -1 , respectively, indicating exothermic extraction processes. On the number of required extraction stages, 1-octanol gave a higher extraction efficiency after three consecutive extractions (E% = 99.3) than 1-butanol (E% = 88.6). Recycling experiment showed 1-octanol as more recyclable than 1-butanol (Recycling coefficient R.C. = 1.0 for 1-octanol while R.C. < 1.0 for 1-butanol). All extractants mixed with 1-butanol were found antagonistic. All added foreign ions decreased E% for V(V). From slope analysis, analytical and spectra data, the extracted complexes have been formulated as VO 2 Cl·nROH and (VO 2 Cl) m ·nROH (where m >> n) at low and high concentrations of extractant, respectively. On the whole, 1-octanol could be adjudged a better extractant for vanadium (V) under the prevailing experimental conditions.

Tyrosinase catalyzes formation of browning in plants, foods and vegetables. Sweet potato (Ipomea batatas) undergoes browning after harvesting or during post-harvest operations leading to spoilage and loss of economic value. The physico-chemical properties of purified tyrosinase from I. batatas are here described with a view to providing information on the suitability or otherwise of the enzyme for several industrial and biotechnological processes. The enzyme was purified using new approach resulting into final yield and purification fold of 76% and 7.1, respectively. The molecular weight (native) was 48.3 ± 2.5 kDa as estimated on Sephadex G-100. Highest tyrosinase activity was obtained at pH 6.5 while that of temperature was 50C. Kinetic parameters studies resulted to 2.5 ± 1.2 mM and 451 ± 23.7 units/mg for Michaelis constant (K m ) and maximum velocity (V max ), respectively. This led to catalytic efficiency, k cat /K m of 1.45 × 10 5 s -1 M -1 . It was concluded that, tyrosinase from I. batatas possesses remarkable properties that could be exploited for biotechnological processes.

The literature is flooded with scientific information on most durability properties except water absorption coefficient of masonry units like sandcrete blocks. Also, while waste papers disposal is a systemic problem due to ineffectiveness of waste management system in developing countries, the price of cement is on the increase. This situation, ultimately, causes a bane in achievement of low-cost housing development considering the fact that sandcrete blocks are predominantly used as walling elements for such undertakings. In this study, solid core sandcrete blocks were produced with waste paper ash (WPA) utilized as partial replacement of cement at 5 % and 10 % volumetric levels. Chemically, the WPA was found to show similarity with cement in terms of SiO2, Al2O3, and CaO contents. Density and water absorption coefficient of the block samples were determined. While density ranged from 1682 to 1872 kg/m3, water absorption coefficient varied from 27.04 to 23.49 kg/m2h0.5. Statistically, no significant difference was revealed at p < 0.05 between experimentally-measured water absorption coefficients and those obtained using the model developed for prediction based on density of the samples. Thus, utilization of WPA as described herein could help to reduce the cost of procuring cement and in turn, enhance low-cost building construction. Also, with the developed model (showing dependence of water absorption coefficient on density), durability of sandcrete blocks exposed to moisture –prone environment could be easily predicted.

Further to the previous study on the extractive recovery of V(V) from HCl solution by some alkanols, the extraction of V(V) from HCl solutions by 1-pentanol and 3-methyl -1-butanol (isomers) dissolved in n-heptane were investigated in the present study, still propelled by the need to proffering viable alternatives to the scarce and relatively costly organophosphorous extractants, and also compare the extraction efficiency of straight-and branched-chain extractants. At the studied pH range (0.5-4.0) with 1-penttanol as extractant, the percentage V(V) extraction (extraction efficiency, E%) reached optimum E%= 40.0 at pH of 3.0 and for 3-methyl-1-butanol, optimum E% was 36. respectively, indicating exothermic/endothermic extraction processes. The isomer 3-methyl -1-butanol gave a higher extraction efficiency after a three-stage extraction (E% = 92.5) than 1-pentanol (E% = 83.4). Recycling experiment revealed both to be recyclable. From slope analysis, analytical and spectra data, the extracted complexes have been formulated as VO 2 Cl.nROH and (VO 2 Cl) m .nROH (where m>> n) at low and high concentrations of extractant, respectively. On the whole, 3-methyl-1-butanol was assessed as fairly better as an extractant for vanadium (V) at lower temperature experimental conditions. The effect of methyl branched-chain played an insignificant role on the extraction.

ABSTRACT. This paper aims at determining the total energy and bond lengths of some polyatomic organic molecules, using quantum Monte Carlo (QMC) CASINO-code. The QMC code employed the VMC and DMC methods in the computations with emphasis on DMC, and using Slater-Jastrow trial wave-function formed from Hartree-Fock orbitals. The calculated results show that our reported values are in good agreement with the experimental values of both Hehre et al., and Linus Pauling. The total energies obtained in this study are 6 significant figures more accurate than those of previous studies.