Chalcopyrite Leaching in Ammonia-Ammonium Chloride Solutions: Insight into the Dissolution Kinetic Studies

The hydrometallurgical method for processing chalcopyrite ore has gained enormous attention due to the environmental problems emanated by the conventional pyrometallurgical route. Here, hydrometallurgy is considered an alternative that may be more of low-cost and environmentally friendly. Thus, alkaline leaching has been considered an effective, efficient, and acceptable leachant for chalcopyrite ore dissolution. The dissolution kinetics of copper from low-grade chalcopyrite ore was examined in an ammonia-ammonium chloride solution. However, the effect of parameters including leachant concentration, reaction temperature, and particle size was considered. . At optimal conditions (o.4 mol/L NH3-NH4Cl; 75 °C; 43 µm), 81.1% dissolution efficiency was achieved within 120 minutes. The leaching kinetics with activation energy (Ea) of 29.95 kJ/mol is by the proposed diffusion control mechanism. Hence, the dissolution rate was confirmed by characterizing the raw ore and un-leached residue using XRD and SEM-EDS analyses for possible industrial utilities

Isolation, characterization and biological properties of betulin from Entada africana Guill. and Perr. (Mimosaceae).

The present study is aimed at the isolation and characterization of betulin from Entada africana.  A dichloromethane soluble portion of the stem bark methanol/acetone (1:1 v/v) extract was subjected to gradient elution using ethyl acetate in hexane (5 – 30 %) on an open column. A pure compound was obtained with Rf = 0.61 in hexane/ethyl acetate (8:2 v/v) after repeated washing and recrystallization from methanol and coded Enac1. The pure compound was analyzed using IR, 1H & 13C NMR and GC-MS. Clinical isolates of Escherichia coli, Klebsiella pneumoniae, Salmonella typhi and Staphylococcus aureus were used to assess the antibacterial activity of the pure compound while its preliminary Cytotoxicity was evaluated using brine shrimp nauplii. Based on the spectroscopic data obtained and in comparison with literature, the isolated compound was identified as betulin. The minimum inhibitory concentration (MIC) of betulin ranged between 62.50 - 250.00 µg/mL for all the four bacterial isolates in the study while its fifty percent lethal concentration (LC50) was 10.00 µg/mL. Significant Cytotoxicity with moderate antibacterial activity was observed. The study therefore justifies the existence of bioactive compounds in the stem bark of Entada africana and its use in traditional medicine

Nanocomposites transformed from polystyrene waste/antimony, barium and nickel oxides nanoparticles with improved thermal and electrical properties

In this experiment, the oxide nanoparticles were synthesized via chemical precipitation and the nanocomposites were produced using in situ polymerization method with varying nanoparticles contents ranged from 0.1 g to 1.0 g for electrical conductivity and from 0.05 g to 0.25 g for thermal conductivity. The electrical and thermal conductivities of nanocomposites were investigated and compared with the values obtained for untreated polystyrene. It was observed that the electrical and thermal properties were higher for the nanocomposites and increase with increasing nanoparticle concentrations in the samples. It can be observed that nanocomposite containing NiO nanoparticles gave a better electrical and thermal conductivity followed by nanocomposite containing BaO nanoparticles and nanocomposite containing Sb2O3 nanoparticles respectively. It can also be observed that nanocomposite containing NiO nanoparticle showed increase in rate of heat transfer from 1.60 W to 2.60 W, while nanocomposite containing BaO nanoparticles recorded increase in rate of heat transfer from 1.40 W to 2.45 W and nanoomposite containing Sb2O3 nanoparticle showed increase in rate of heat transfer from 1.07 W to 2.21 W, as concentration of nanoparticles increased from 0.05 g to 0.25 g respectively. Conclusively, with these results, the nanocomposite containing NiO nanoparticles gave a better thermal and electrical conductivity by having a better conducting filler network inside the matrix than nanocomposite containing BaO nanoparticles and nanocomposite containing Sb2O3 nanoparticles. It is recommended that during the production of polymer nanocomposite, PS/NiO, PS/BaO and PS/Sb2O3 nanocomposites could be used in electrically conductive devices as well as suitable materials for heat transfer applications

Structural Modification of Cellulosic Fabric via Esterification Using Balanites aegyptiaca Seed Oil

Cellulose fabrics were esterified by using varying volume of Balanites aegyptiaca seed oil. X-ray diffraction analysis was carried on the esterified fabrics and unesterified fabric. The crystallographs of all esterified fabrics gave almost the same profile different from that of control fabric. The control fabric gave a sharp single peak at 24.033º diffractometer angle. Esterified fabrics gave a slightly broad split peaks at lower diffractometer angles which ranged from 20.080 – 22.690º, suggesting that there was structural modification of cellulose. The inter-atomic distance (d-spacing) for control fabric was 3.7027 Å. There was increase in d-spacing which ranged from 3.9192 – 4.4216 Å for esterified fabric. The peak width increased from 1.5º (control) to range of 1.6 – 2.8º (esterified) fabrics. The peaks intensity increased from 5489 (control) to highest value (7798) for 30 cm3 of oil esterified fabric. The crystallite size reduced from 9.9 nm (control) to a maximum value (9.2 nm) for 40 cm3 and to minimum value (5.3 nm) for 10 cm3 oil esterified fabrics. The percentage crystallinity reduced from 65% (control) to a range of 62–63% for esterified fabrics. From the results obtained, it can be concluded that reduction in crystallite size, increase in d-spacing, intensity and peak width were due to the presence of a bulky ester group in the cellulose chain; this may also have led to the observed decrease in percentage crystallinity of the esterified fabrics. This structural modification is expected to have direct consequences on the physical and mechanical properties as well as the dyeing properties of the esterified fabrics

Production of Smokeless Briquetted Fuel by Co-Carbonization of Local Coals and Bitumen

Binary blend of coal-bitumen by weight (10 % bitumen and 90 % preheated coal samples at 150 oC) was developed, followed by partial briquetting and then moulded into cylindrical shape. The moulded briquetted blend was co-carbonized for about 10 hours at a temperature of 550 oC for the production of smokeless fuel. The calorific value and chemical analysis of the smokeless fuel produced were carried out and only the result of volatile matter was found to be above the acceptable range for use in a boiler system. The results of this study revealed that the use of bitumen as a bonding substance has upgraded the weakly coking and the low-grade (non-coking) coals, to a smokeless fuel briquette with high calorific values with an average combustion period of about 2.5 hours

Effect of different aqueous extracts of garlic on some electrolytes and urea levels in rats

Studies on the effect of fresh and dried aqueous extracts of garlic (cold and hot) on Na+, K+, Cl-, HCO3- and urea levels of rats were carried-out. Animals were divided into 5 groups of 5 rats each. Groups I and II were treated with fresh cold and hot extract respectively, while groups III and IV received dried cold and hot extract respectively. Group V served as untreated control. Treatment was by oral administration at 100mg/kg body weight for seven consecutive days. Analysis of the results showed significant (P 0.05). The extracts appeared to have no effect on urea level when compared with the control group. The decrease observed in these electrolytes monitored were more with fresh cold extract than with others. The results therefore suggest that fresh cold garlic extract may be useful in the management of electrolyte related disorders. Key words: Garlic; Electrolytes; Urea Journal of Pharmacy and Bioresources Vol. 2 (1) 2004: 1-

A method of predicting changes in human gene splicing induced by genetic variants in context of cis-acting elements

Background: polymorphic variants and mutations disrupting canonical splicing isoforms are among the leading causes of human hereditary disorders. While there is a substantial evidence of aberrant splicing causing Mendelian diseases, the implication of such events in multi-genic disorders is yet to be well understood. We have developed a new tool (SpliceScan II) for predicting the effects of genetic variants on splicing and cis-regulatory elements. The novel Bayesian non-canonical 5’GC splice site (SS) sensor used in our tool allows inference on non-canonical exons. Result: our tool performed favorably when compared with the existing methods in the context of genes linked to the Autism Spectrum Disorder (ASD). SpliceScan II was able to predict more aberrant splicing isoforms triggered by the mutations, as documented in DBASS5 and DBASS3 aberrant splicing databases, than other existing methods. Detrimental effects behind some of the polymorphic variations previously associated with Alzheimer’s and breast cancer could be explained by changes in predicted splicing patterns. Conclusions: we have developed SpliceScan II, an effective and sensitive tool for predicting the detrimental effects of genomic variants on splicing leading to Mendelian and complex hereditary disorders. The method could potentially be used to screen resequenced patient DNA to identify de novo mutations and polymorphic variants that could contribute to a genetic disorde