ABSTRACT

Water pollution is a concerning issue faced by the world today. Among the pollutants in the water pollution, dyes have become the focus. Dyes have high durability due to their complex molecular structure and can give toxic effects to human and animal even at low concentration. The decolorization of azo dye, methylene blue using locally sourced heterogenous photocatalyst, eggshell ash (ESA) was investigated in this study. The eggshell ash was prepared by calcination at 850for 3 hours and characterized using Fourier transform infrared spectrometer. The decolorization process was carried out by advanced oxidation process (photocatalysis) in the presence of sunlight for 3 hours at various operational conditions such as effect of contact time, catalyst dosage and initial concentration of methylene blue. In order to ascertain the effectiveness of ESA, different catalyst dosage (0.5 – 2.5%) was used for the photocatalytic decolorization of the methylene blue solution. The results obtained showed maximum decolorization efficiency of above 90% at a contact time of 120 minutes. The decolorization efficiency decreased with increase in initial dye concentration while low catalyst dosage (1g/L) favoured the decolorization process. The effect of Kinetic models and adsorption isotherms were also carried out and the results revealed that the kinetics of the process was best described by Pseudo-second order model with a rate constant of 0.0352min^-1 and coefficient of determinant, of 0.943 while intra-particle diffusion model showed that the uptake of methylene blue was more of a film diffusion than the intra-particle diffusion. The adsorption equilibrium was best described by Langmuir isotherm with R² of 0.9999 and adsorption capacity of 0.0213L/mg. The results obtained in this study indicates that ESA is a suitable photocatalyst and economical alternative to conventional photcatalysts.