en Environmental Health Environmental Health پژوهشي Original Article &nbsp; <table align="left" cellpadding="0" cellspacing="0" hspace="0" vspace="0"> <tbody> <tr> <td align="left"><strong>Background & Aims of the Study:</strong> Dyes are one of the most hazardous materials in various industries which can problems in health human, environment and ecosystem. The purpose of this study is the removal of Acid Orange 25 (AO25) diazo dye in aqueous solutions by adsorption onto clinoptilolite (CP) zeolite: study kinetic and isotherm model: experimental design and optimization.<br> <strong>Materials & Methods:</strong> CP zeolite have been characterized by scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR). The effective factors for the removal of dye were determined and optimized using Taguchi (L₉ (3⁴)) orthogonal array experimental design method with four factors having three levels for each factor. The most influenced of each factor on the process determined using Analysis of Variance (ANOVA) method. The isotherms of dye adsorption such as: Langmuir and Freundlich were studied.<br> <strong>Results:</strong> The Taguchi results showed that pH=4 (level 1), dye concentration=30 ppm (level 2), agitation speed=160 rpm (level 3) and adsorbent dosage=55 mg/l (level 2) was optimum conditions for this process. The interaction between pH&times;adsorbent dosage was the most influencing interaction. The percent of each process parameter on the removal of dye was found to be in the following the order: pH (7.217%), dye concentration (2.604%), agitation speed (86.539%) and adsorbent dosage (3.618%). The results showed that the dye adsorption onto CP followed Langmuir isotherm. Adsorption kinetics of dye onto CP followed the pseudo-second-order kinetic model.</td> </tr> </tbody> </table> <div style="clear:both;"></div><strong>Conclusions:</strong> The results showed that the adsorption process can be suitable method to removal dyes in aqueous solutions.<br> <br> &nbsp; Zeolite, Adsorption kinetic, Taguchi experimental design, Isotherm, Azo dye. 139 149 http://jhygiene.muq.ac.ir/browse.php?a_code=A-10-103-3&slc_lang=en&sid=1 Reza Moradi reza.moradi_bi@yahoo.com 0000-0001-5020-2944 Yes Department of Chemistry, Tuyserkan Branch, Islamic Azad University, Tuyserkan, Iran Javad Hosseini No Department of Chemistry, Tuyserkan Branch, Islamic Azad University, Tuyserkan, Iran