Adsorption of 4-Toluene Sulfonic Acid on Modified Bentonite : Optimization by Response Surface Methodology


Abstract: Adsorption of 4-toluene sulfonic acid (4-TSA) onto modified bentonite (ODTMA-bentonite) was carried out. ODTMA-bentonite was synthesized by placing quaternary ammonium surfactant (octadecyltrimethyl ammonium bromide) on Çankırı sodium bentonite (ÇNa-B) having a cation exchange capacity of 85 meq/100 g clay. Response surface methodology based on a 5-level, 4-variable central composite rotatable was used to evaluate the effects of important parameters on the adsorption of 4-TSA on ODTMA-bentonite. Temperature (25-45 °C), agitation rate (30-170 rpm), the amount of organobentonite (0.1-1.5 g) and initial 4-TSA concentration (100-500 mg/l) were chosen as process variables for the optimization. Of these parameters, initial 4-TSA concentration and the amount of organobentonite had significant effects compared with temperature and agitation rate. The optimum values for the tested variables in selected ranges for the maximum adsorption of 4-TSA onto ODTMA-bentonite were found to be an adsorption temperature of 45 °C, an agitation rate of 170 rpm, an organobentonite level of 1.5 g and an initial concentration of 500 mg/l. The coefficient of determination (R^{2}) for the model is 0.987. Probability value is 1.635 x 10^{-10} (P - value < 0.01). This p-value demonstrates a very high significance for the regression model. The predicted maximum adsorption in the selected ranges of 4-TSA on ODTMA --bentonite was 428 mg/l. An actual experimental value of 421 mg/l was obtained.

Keywords: Adsorption, Smectite, Organobentonite, Response surface methodology.

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