Abstract
The purpose of this study is to prepare a new activated carbon from olive stones for use in gold recovery by carbon-in-leach (CIL) and carbon-in-pulp (CIP). The preparation method chosen was physical activation using steam. The effect of four process parameters: the residence time for carbonization, the activation temperature, the residence time for activation, and steam flow, were studied by the mean of response surface method (RSM) in order to optimize the yield, iodine index, and attrition characteristics. These two last responses were used as primary indicators of gold recovery capacity and mechanical strength. The results obtained show that optimal activated carbon can be prepared under the following conditions: a carbonization time of 157 minutes, activation at 921°C for 53 minutes, and a water vapour flow of 0.18 mL/min. This optimum carbon has an iodine value greater than 1100 mg/g and an attrition index in the order of 0.74%. These values reflect the quality of the precursor (olive stones) as a raw material for the development of an effective new activated carbon for the gold mining industry.
Highlights
The purpose of this study is to prepare a new activated carbon from olive stones for use in gold recovery by carbon-in-leach (CIL) and carbon-inpulp (CIP)
In recent years considerable research has been reported on activated carbon from agricultural wastes, such as olive stones (Yavu et al, 2010), acorn shells (Sahin and Saka, 2013), peanut shells (Wu, Guo, and Fu, 2013), grape seeds (Jimenez-Cordero, 2014), coconut shells (Yalcin and Arol, 2002; Gratuito, 2008), palm shells (Sumathi, 2009), cherry stones (Jaramilloa, Gomez-Serrano, and Alvareza, 2009), macadamia nut shells (Eddy, 2011), apricot stones (Soleimani and Kaghazchi, 2008), and bagass (Syna and Valix, 2003)
Activated carbon has had a tremendous impact on the technology and economics of gold recovery
Summary
The centre points are repeated five times in order to calculate the variance of experimental error and to test the reproducibility of the data. The coefficients of correlation (R2 = 0.976, R2A = 0.950) between the maximum capacities of adsorption calculated by the model and those determined experimentally are satisfactory Analysis of this response (Y2) shows that the activation temperature (X2) and the time of activation (X3) have a strong impact on the development of the porous texture during activation. A long activation time leads to the weakening of the carbon structure and increases the surface area by opening up the micropores, as indicated by a higher iodine number. The decrease of the band at 1700 cm-1 corresponding to C=O may be due to the decomposition of these groups during
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