N. Aslan

Bio-dissolution of Cu, Mo and Re from molybdenite concentrate using mix mesophilic microorganism in shake flask

Abstract The application of the response surface methodology and the central composite design (CCD) technique for modeling and optimization of the influence of some operating variables on copper, molybdenum and rhenium recoveries in a bioleaching process was investigated. Three main bioleaching parameters, namely pH, solid concentration and inoculum percent, were changed during the bioleaching tests based on CCD. The ranges of the bioleaching process variables used in the design were as follows: pH 1.46–2.14, solid concentration 0.95%–11.05%, and inoculum percent 1.59%–18.41%. A total of 20 bioleaching tests were carried out by the CCD method according to software-based designed matrix. Empirical model equations were developed according to the copper, molybdenum and rhenium recoveries obtained with these three parameters. Model equations of responses at the base of parameters were achieved by using statistical software. The model equations were then individually optimized by using quadratic programming to maximize copper, molybdenum and rhenium recoveries individually within the experimental range. The optimum conditions for copper recovery were pH 1.68, solid concentration 0.95% and the inoculum 18.41% (v/v), while molybdenum and rhenium recoveries were 2.18% and 24.41%, respectively. The predicted values for copper, molybdenum and rhenium recoveries were found to be in good agreement with the experimental values. Also jarosite formation during bioleaching tests was also investigated.

Application of Response Surface Method and Central Composite Design for Modeling and Optimization of Gold and Silver Recovery in Cyanidation Process

In this study, application of the Response Surface Methodology and the Central Composite Design (CCD) technique for modeling and optimization the influence of some operating variables on gold and silver recovery in a cyanidation process were investigated. Three main cyanidation parameters, namely grinding time, sodium cyanide concentration, and alkalinity of solution, were changed during the concentration tests based on CCD. The range of values of the cyanidation process variables used in the design was as follows: grinding time, 32.61–44.39 min, sodium cyanide concentration, 1989–4511 ppm, and pH, 9.32–12.68. A total of 20 cyanidation tests were designed and carried out in the CCD method according to software-based designed matrix. According to the results, i.e., gold and silver recoveries with these three parameters, empirical model equations, were developed. Second-order equations of responses at the base of parameters were achieved by using statistical software. The model equations were then individually optimized by using quadratic programming to maximize both gold and silver recoveries within the experimental range. The optimum conditions were found to be 41.89 min for grinding time, 3665.28 ppm for cyanide concentration, and pH 9.32, for achieving the maximum gold recovery (96.23%). Similarly, the conditions for maximum silver recovery were 65.62% at 44.39 min for grinding time, 4511.34 ppm for cyanide concentration, and pH 12.68. The predicted values for gold and silver recoveries were found to be in a good agreement with the experimental values, with R 2 as correlation factor being 0.91 and 0.94, respectively.

Using float–sink data in simple equations to predict sulfur contents

Abstract In this study, the interpretation of float–sink test data by simple equations on coals of different origins with respect to sulfur content has been investigated. Primarily, the cumulative weight and sulfur content of the floating fraction have been determined for each coal in all relative densities tested. For deriving of the equations, the recoveries of both non-sulfur and sulfur compounds in cumulative floating part have been calculated. Then, the relationship between the recoveries and relative densities has been stated as simple equations and the calculated values from equations have been compared with the experimental results. Furthermore, it has been found that these types of equations are suitable for the interpolation of sink–float data. The results reveal that the float–sink test results can be stated by simple equations relating to the sulfur content.

Investigating the effect of testing parameters on adhesive wear using Taguchi method

Abstract The aim of this study is to investigate the effect of working parameters on wear resistance of steels in terms of applied load, hardness and revolution per minute (rpm) using the Taguchi method. Pin-on-roller type of apparatus was used for adhesive wear tests. The operating parameters were investigated by employing the orthogonal array, signal-to-noise ratio and analysis of variance. The experimental wear test results show that the hardness of the materials is the major parameter among the controllable factors. After the hardness, the applied load and the rpm sequentially have influence on the wear resistance of three types of steels; AISI 1050, AISI 4140 and AISI 8620. The best wear testing parameters were determined for current conditions of the steels. A good agreement between the predicted and experimental wear amounts is observed.