Modeling and optimization process parameters of acid activation of bentonite by response surface methodology

Abstract

The effect of acid activation on the textural properties of a bentonite from Serbia was investigated using response surface methodology. The influence of activation parameters (temperature, time, acid normality, solid-to-liquid ratio and stirring rate) on the specific surface area, pore volume, pore diameter and bulk density of the activated bentonite samples has been studied using response surface methodology based on central composite rotatable design (CCRD). The specific surface areas of the activated samples were chosen for the selected process response. The quantitative relationship between the specific surface areas and different levels of the quoted factors was used to determine the optimized levels of these factors by CCRD. The analysis of the variance of the quadratic model demonstrates that the response surface methodology was one of the suitable methods to optimize the best operating conditions to maximize the specific surface area of the bentonite. Three dimensional plots are used to demonstrate the relations between the specific surface areas and the paired factors (when the other factors was kept constant) describing the behavior of bentonite in the process of acid activation. The specific surface area and the textural properties of the acid-activated bentonite are strongly affected by the process parameters. The optimum conditions to obtain the maximum specific surface area of acid-activated bentonite were as follows: temperature 90 degrees C, acid normality 4.5, stirring rate 450 rpm, solid-to-liquid ratio of 1:4.5 and duration 3 h. Under these conditions, the experimental values agreed with the values predicted by the analysis of variance, indicating a high fitting accuracy (R(2)=0.927) of the model used and the success of the response surface methodology in optimizing the process parameters of the acid activation of bentonite.