Removal of Diazo Dye Direct Red 28 and Tetra Azo Dye Direct Black 22 Using Synthesized Magnetic Kaolin Supported Zinc Ferrite

Abstract

The presence of dye molecules in water resources has harmful effects on environment. Therefore, it is important to remove dyes from wastewater using eco-friendly materials. In this study, adsorptive removal of diazo dye Direct Red 28 (DR-28) and tetra azo dye Direct Black 22 (DB-22) was investigated by using a new composite, kaolin supported zinc ferrite (KZF) as adsorbent. Characteristics of the composite, KZF were determined using various techniques such as FTIR, SEM, XRD, VSM, and EDS/Mapping. The adsorption of DR-28 and DB-22 on KZF was studied as a function of contact time, initial dye concentration, adsorbent amount, temperature, initial pH of the solution as well as the heat treatment of the composite. The removal of DR-28 was found to be 92.4% for the KZF concentration of 1g/200mL, initial dye concentration of 20 mg/L, contact time of 120 min at original pH and 21 °C. On the other hand the removal of DB22 was found to be 91.7% under the same conditions at 40 °C. The results showed that Langmuir isotherm is suitable for the adsorption of DR-28 and DB-22 on KZF under given conditions. It was found that adsorption of DR-28 on KZF was exothermic while that of DB-22 was endothermic. The enthalpy changes (ΔH0) for the adsorption of DR-28 and DB-22 dyes on KZF were found to be –24.59 kJ/mol and 61.95 kJ/mol respectively. ΔS0 for the adsorption of DR-28 dye was found to be negative while ΔS0 for the adsorption of DB-22 was positive. The kinetic data fitted well to the pseudo second order model for the adsorption of DR-28 and DB-22 on KZF composite. These results showed that the prepared adsorbent KZF could be used as an adsorbent for the efficient removal of anionic dyes.