Modelling and Optimization of Sepiolite Activation with Citric Acid Using Factorial Experimental Design and Response Sur
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ORIGINAL PAPER
Modelling and Optimization of Sepiolite Activation with Citric Acid Using Factorial Experimental Design and Response Surface Methodology Selma Yonar 1 & Emmanuel lkechukwu Ugwu 2 & Eyup Sabah 1 Received: 8 August 2020 / Accepted: 16 September 2020 # Springer Nature B.V. 2020
Abstract In this study, the effects of several parameters such as the acid concentration, mixing time, temperature, solid rate, and mixing rate on the specific surface area (BET) and cation exchange capacity (CEC) of sepiolite activated by citric acid were investigated using factorial experimental design and response surface methodology. While the specific surface area and cation exchange capacity of nitric acid activated sepiolite were chosen as the responses, the acid concentration, time, temperature, solid rate, and mixing rate were the process parameters. The relationship between the process parameters and the responses was obtained and used in the determination of the optimal conditions. The result showed that the specific surface area and cation exchange capacity of the acid-activated sepiolite were strongly affected by the process parameters. The optimal conditions for achieving the maximum specific surface area and minimum cation exchange capacity were 95.73 °C, 8.64%, 4.99 N, 1 h, and 450 rpm for temperature, solid rate, acid concentration, activation time, and the mixing rate, respectively. The experimental and predicted values for the SBET and the CEC were obtained as 450.97 m2/g and 449.97 m2/g, and 6.79 meq/100 g and 6.86 meq/100 g, respectively. The results obtained from this study clearly indicated that the actual values were in good conformity with the predicted values as evidenced by small errors of 1.00% and 0.07% for the SBET and CEC, respectively. As a result, the SBET and CEC of the Sep activated by citric acid were strongly affected by the process parameters, especially the solid rate for the SBET and the temperature for CEC. It was found that citric-acid activated Sep had a SBET approximately 2.5 times higher than that of the untreated Sep while the CEC of Sep may be strongly eliminated by citric acid treatment. Thus, the mineral structure was progressively transformed into amorphous silica coming from the tetrahedral sheet of the generated fibrous silicates, whose SBET was larger than that of the raw Sep. Keywords Sepiolite . Citric acid . Activation . Statistical design . Response surface methodology . Factorial experimental design
1 Introduction Modification of clays is of much importance as it helps in increasing its range of applicability for the adsorption of colour pigments and extraction of metals as well as for other scientific and industrial purposes. The acid activation process with a hot solution of mineral acids such as hydrochloric acid, sulphuric acid, phosphoric acid, nitric acid, and organic acids * Eyup Sabah [email protected] 1
Department of Mining Engineering, Faculty of Engineering, Afyon Kocatepe University, 03200 Afyonkarahisar, Turkey
2
Department of Civil Engineering, Michael
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