ZnO, MgO and FeO adsorption efficiencies for direct sky Blue dye: equilibrium, kinetics and thermodynamics studies

Adsorption is one of the promising techniques for the remediation of wastewater and it also offers advantages such as low cost, availability of the adsorbent and ease in operation. The wastewater treatment using smart materials gained much attention and the present investigation evaluated the adsorption efficiencies of ZnO, MgO and FeO for the removal of Direct Sky Blue (DSB) dye. The adsorption affecting parameters, i.e., effect of adsorbent dose, pH, concentration of dye, temperature and contact time were studied in association with dye adsorption. The effect of electrolytes and surfactants was also studied on dye adsorption. The dye adsorption data was analysed using various kinetics parameters, isotherms and thermodynamics models. The maximum adsorption capacities of MgO, FeO and ZnO were recorded to be 46.7, 42.9 and 40.9 mg/g, respectively at the pH 2, adsorbent dose 0.05 g, contact time 75 min, 40 °C and 70 mg/L initial concentration of the dye. The dye adsorption onto MgO followed a Langmuir isotherm, while ZnO followed Temkin isotherm. Langmuir and Temkin isotherms were satisfactory in the case of FeO. Pseudo second order best explained the dye adsorption kinetics. The thermodynamics studies revealed non-spontaneous adsorption of DSB dye onto ZnO, MgO and FeO. In view of promising efficiency, the ZnO, MgO and FeO have potential to apply for dyes adsorption from textile wastewater.