Removal of a Cationic Dye from Aqueous Solution by Microwave Activated Clinoptilolite-Response Surface Methodology Approach

Natural clinoptilolite from Zlatokop deposit, Serbia, was activated by microwave irradiations (10 min, 550 W) and its adsorptive efficiency for removal of crystal violet (CV) dye from aqueous solution was investigated. The process variables were specified by response surface method and the central composite design (CCD). Percentage of dye removal as a function of two numeric factors (the amount of zeolite and the concentration of crystal violet) with five values (rotatibility factor alpha = 0.41) and one numeric factor (contact or agitation time) with three values (rotatibility factor alpha = 1.00) at dynamic ambient conditions and pH = 6 was tested. The optimal conditions for 91.99 % decolorization were predicted to be 2 g of the zeolite in 100 ml of CV aqueous solution with concentration of 250 mg/l, and contact time of 678 s. The model was validated experimentally. Two isotherm models-Langmuir type 2 and Freundlich could describe the adsorption process with high correlation to experimental data. The calculated adsorbent capacity from the CCD (12.625 mg/g) showed a good agreement with the adsorption capacity obtained by Langmuir-2 isotherm (13.477 mg/g) and with pseudo-second-order kinetic model (12.404 mg/g).