Kinetics Study on Adsorption of Three Azo Dyes (Reactive Red 198, Cationic Red GTL 18 and Cationic Red GRL 46) by Zeolite Clinoptilolite

Background and Adsorption processes are widely used in removing pollutants from waste waters، particularly those that are not easily biodegradable such as dyes. In this study natural zeolite، which is easily found in many places، was used as a low-cost adsorbent for removal of dye from effluents. Adsorption of Azo dyes including two basic and one reactive (Reactive Red 198(RR-198)، Cationic Red GTL (BR-18) and Cationic Red GRL (BR-46)) were studied by natural zeolite clinoptilolite. In batch experiments we evaluated sorbent dose، contact time، concentration of dyes and ph. The adsorption isotherm was also determined using the adsorption data. Kinetics of dye adsorption by zeolite was also studied. The remaining concentration of dyes was measured by spectrophotometer. Increase in sorbent dose and contact time increased adsorption rate. Optimal contact times for BR-18، RR-198 and BR-46 were 90، 90 and 120 minutes، respectively. By increasing the sorbent does for basice dyes، adsorption efficiency increased up to 99 percent. The best pH for basic dyes was found to be 9. The adsorption rate increased by decrease in dye concentration. It was found that adsorption isotherms for the examined three dyes fitted to the Langmuir isotherm. The kinetic studies indicated that the adsorption for dyes followed the pseudo-second-order. Results indicate that clinoptilolite has good adsorption capacity for basic dyes. Natural zeolite is found easily in many places and could be used as acceptable and affordable for decontamination applications.