Research Article - (2020) Volume 7, Issue 1
Received: 02-Feb-2020
Published:
18-Feb-2020
, DOI: 10.37421/jreac.2020.7.263
Citation: Tevfik Agacayak and Mohamed Taha Osman Abdelraheem Ahmed. "Optimization and Modeling of Leaching Parameters Affecting Nickel Dissolution from Lateritic Ore in Eskisehir (Mihaliccik-Yunusemre) Using Box-Behnken Experimental Design". J Environ Anal Chem 7 (2020).
Copyright: 2020 Agacayak T, et al. This is an open-access article distributed under the terms of the creative commons attribution license which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
In this study, optimization and modeling of leaching parameters affecting nickel dissolution from lateritic ore in Eskişehir (Mihalıççık-Yunusemre) were investigated using Box-Behnken design. Stirring speed (100-400 rpm, temperature (40-80°C), acid concentration (0.1-2 M) and dissolution time (30-180 min) were selected as experimental design parameters. 27 experiments were carried out by Box-Behnken experimental design in Minitab 16.0 program. After leaching experiments, the highest Ni dissolution percentages were obtained as 87.85%. The effective parameters and their interactions in nickel dissolution are described with a mathematical model. The results obtained from the experiments were subjected to ANOVA and multiple regression analysis. The R2 value of the model for nickel dissolution was calculated as 0.980. This showed that the predicted values are in good agreement with the observed values. In addition, three-dimensional response surface and contour graphs of the parameters affecting nickel dissolution efficiency were created and the results were examined.
Nickel • Leaching • Box-behnken design • Optimization
Nickel is an important and strategic metal and mainly used in modern industrial and metallurgical applications because of ıts strength and corrosion resistance [1]. Nickel naturally occurs as sulphides and laterites-type ores. Although the lateritic deposits constitute the largest world reserves of nickel, global nickel production has been supplied from sulfide ores due to the challenges of processing laterite compared to sulfide ores [2,3].
The nickeliferous laterite ore deposits are formed by a weathering process. The top of laterite bedrock layer is mainly hematite without a significant nickel content. This is followed by a limonitic zone with 1.5% nickel. Finally there is a saprolitic layer with up to 4.0% nickel content [4,5].
There are several reagents used in lateritic nickel extraction such as hydrochloric acid, sulphuric acid, citric acid, nitric acid, ammonia, oxalic acid and acetic acid [6-15]. Several studies have been performed using using Box-Behnken design. Polat and Sayan, studied the struvite precipitation with a Box-Behnken design [16]. Koca et al., studied the evaluation of combined lignite cleaning processes, flotation and microbial treatment, and its modelling by Box Behnken methodology [17]. Ozgen et al., examined the effect of smectite content on swelling to hydrocyclone processing of bentonites with various geologic properties by Box Behnken design [18].
The aim of this study is to optimize leaching parameters affecting nickel dissolution from lateritic ore from Eskişehir (Mihalıççık-Yunusemre) using Box-Behnken design. Stirring speed, temperature, acid concentration and dissolution time were selected as experimental design parameters. The results obtained from the experiments were subjected to ANOVA and multiple regression analysis. In addition, three-dimensional response surface and contour graphs of the parameters affecting nickel dissolution efficiency were created and the results were examined.
Materials
In this study, sample of lateritic nickel ore taken from Mihalıççık- Yunusemre/Eskişehir in Turkey was used (Figure 1). Approximately 100 kg of ore samples were brought to the laboratory and crushed to a size of -3.35 mm. The ore was then ground to size less than 106 μm by a rod mill. Chemical analysis of the sample was done by AAS (GBC SensAA model). The chemical composition of the sample is given in Table 1.
Figure 1. Location of Mihalıççık-Yunusemre/ Eskişehir region in Turkey.
| Element | Ni | Fe | Mg | Co |
|---|---|---|---|---|
| Mass fraction (%) | 1.84 | 23.14 | 1.58 | 0.03 |
Mineralogical investigations were carried out on sample by means of Xray diffraction (XRD) analysis, X-ray diffraction (XRD) analysis reaveled that the main minerals are goethite, hematite and wustite. The gangue minerals of the ore are determined as retgersite, gaspeite, quartz and clay type minerals (Figure 2).
Figure 2. XRD analysis of sample.
Leaching tests
Experiments were carried out in 1 L pyrex leach beaker using 10/500 g/mL (solid-liquid ratio) in a temperature-controlled water bath. The leach solution was provided by Heidolph mark RZR 2021 model mechanical stirrer with a teflon-covered impeller.
Box-Behnken design method was applied to determine the effects of nickel dissolution parameters from lateritic ore. The leaching studies were performed according to the full factorial design of experiments. The variables studied were stirring speed, temperature, acid concentration and dissolution time. The variables and levels of full factorial design are presented in Table 2. Each variable was studied at three levels: -1 is for low level, +1 denotes high level, and 0 is used for the midpoint to evaluate the experimental error [16,19].
| Factors | Description | Units | Low value | Center value | High value |
|---|---|---|---|---|---|
| -1 | 0 | 1 | |||
| X1 | Stirring speed | rpm | 100 | 200 | 400 |
| X2 | Temperature | °C | 40 | 60 | 80 |
| X3 | Acid concentration | molar | 0,1 | 0,5 | 2 |
| X4 | Dissolution time | min | 30 | 90 | 180 |
Box-Behnken designs are based on three-level incomplete factorial designs. Graphical representation of Box-Behnken design matrix for three parameters can be seen in Figure 1 [20]. As seen in Figure 3, experiments are usually performed at center levels of parameters. Design Expert Minitab 16.0 program was used for achieving design matrix and obtaining mathematical models of the response variables.
Figure 3. Box-Behnken design with three parameters.
In this study, a Box-Behnken design was applied for modeling and optimization of some operating variables on the leaching of nickel from lateritic ore from Eskişehir (Mihalıççık-Yunusemre). The variables studied were stirring speed, temperature, acid concentration and dissolution time. After leaching experiments, the highest Ni dissolution percentages were obtained as 87.85%. The results obtained from the experiments were subjected to ANOVA and multiple regression analysis by using Minitab 16.0 software. The R2 value of the model for nickel dissolution was calculated as 0.980. This showed that the predicted values are in good agreement with the observed values. In order to gain a better understanding of the effect of the variables on nickel dissolution, three dimensional response surface and contour graphs were created and the results were examined.
The author Mohamed Taha Osman wishes to express sincere thanks to his supervisor in Konya Technical University, Department of Mining Engineering (Faculty of Engineering) Associate Professor Dr. Tevfik Agacayak for his honest help and kind support.
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