Removal of methylene blue dye from aqueous media by adsorption using nickel oxide modified montmorillonite composite

In this study, the adsorptive removal of methylene blue (MB) from aqueous solutions onto nickel oxide (NiO) modified montmorillonite (NiO-Mt) has been studied and compared with that of commercial bentonite. The influences of various experimental factors such as contact time, adsorbent dosage, pH of solution, initial dye concentration and temperature have been investigated. Batch adsorption studies has manifested that the maximum adsorption capacity of MB is around 99.9 mg/g in 10 min with 25 mg adsorbent mass at an initial concentration of 100 mg/L at ambient temperature of 25°C and natural pH of solution (pH = 5.8 for NiO-Mt and pH = 6.3 for commercial bentonite). The adsorption kinetics and isotherms are well fitted by pseudo-second order and Langmuir models, respectively. The thermodynamic parameters such as the changes in Gibbs free energy, enthalpy, and entropy are determined. The MB adsorption is physical, spontaneous and exothermic for both adsorbents.