May 2020

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Kinetics of zinc recovery from enyigba sphalerite in a binary solution of acetic acid and sodium nitrate

Ikechukwu A. Nnanwube, Judith N. Udeaja, Okechukwu D. Onukwuli

Abstract Low-temperarure hydrometallurgical leaching process has been identified as a viable route for recovering metals from their ores. In this study, the physicochemical characterization and dissolution kinetics of zinc recovery from sphalerite obtained from Enyigba in a binary solution of acetic acid and sodium nitrate was carried out. The physicochemical characterization of the ore was carried out using X-ray fluorescence; X-ray diffraction; Scanning electron micrograph, and Fourier transform infrared. The results show that the ore exists largely as zinc sulphide. The results showed that about 92.4% of sphalerite dissolved at the optimum conditions. The values of activation energy, reaction order, Arrhenius constant, and reaction constant were estimated as 34.603 kJ/mol, 0.706, 430.953 s-1, and 2.22 × s-1, respectively. The kinetic data analysis showed that the experimental data followed the diffusion-controlled equation of the shrinking core model with chemical reaction as the rate-controlling mechanism. Hence, a binary solution of acetic acid and sodium nitrate has proved to be a viable means of recovering zinc from sphalerite.

[ FULL TEXT PDF 1-11 ] DOI: 10.22587/ajbas.2020.14.5.1

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Chromatographic Conditions for Baseline Resolution of Dipterocarpus semivestitus Extracts

Nur Afiqatul Fatin Rosli, Nurhuda Manshoor

Abstract A HPLC-based chromatographic method was developed for a separation of Dipterocarpus semivestitus extracts. Two samples obtained from the stem and leaves of the plant were used and being analysed on a reversed-phase column chromatography. The optimized parameter in development of UHPLC method was the gradient composition of the mobile phase. Only the gradient of mobile phase was altered, while the flow rate, column temperature and injection volume were keep constant. The results showed that the optimum chromatographic condition was achieved when a gradient elution was adopted, with the solvent composition of ACN:H2O from 30:70 to 60:40 in 14 minutes for the stem extract, whereas for the leaves extract, the solvent composition was at ACN:H2O from 25:75 to 75:25 during the same chromatographic-run time. The injection volume of 5 μL is best for a 1 mg/ml sample concentration. The temperature was maintained at 35°C and the flow rate was at 0.5 ml/min. Apart from good quality of separation and resolution, the elution time was also taken into consideration. The result shows that UHPLC is able to provide baseline resolution within a short chromatographic run.

[ FULL TEXT PDF 12-18 ] DOI: 10.22587/ajbas.2020.14.5.2

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Comparison of Different Polynomial Degrees for Correcting the Instrumental Drift of Scintrex CG-5 Autograv Gravimeter

Basem Elsaka

Abstract Reducing the gravity field raw data influenced by drift effect is remarkable as a pre-processing correction step. Most of the research groups deal with the drift effect as a linear function when reducing the drift effect from the gravimeters raw data. This would be suitable for short time period of gravity data. However, for a long time period this will lead to a poor approximation to the time-varying components of the gravity field. The main objective of this contribution is to correct the drift effect comparing linear in addition to five non-linear polynomial functions using about one month (from 12 December 2019 till 13 January 2020) of gravity data measured by the Scintrex CG-5 Autograv gravimeter. The results of this investigation show that the non-linear drift functions surpass in the accuracy of the linear drift. In particularity, the non-lineal 6th-degree polynomial provides the most promising drift of sub nanoGal/day accuracy. Reduced gravity signal from the drift effect using the 6th-degree polynomial shows the standard deviation of about 3.310 Gal with respect to the linear drift (29.59 Gal) and the other applied non-linear polynomials (2nd – 5th degree) ranging from 17.35 – 8.44 Gal, respectively. Since the drift effect may differ from gravimeter to another depending on the sensor age, temperature, and other external influences such as vibration due to transport and shocks, the outcome of this study should be considered for any gravity field survey accomplished by CG-5 gravimeter. Therefore, it is recommended to apply non-linear polynomial functions to correct and interpret the gravity variations in an optimal way.

[ FULL TEXT PDF 19-25 ] DOI: 10.22587/ajbas.2020.14.5.3

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