Potential Application of Periwinkle Shell Ash as Photocatalyst for the Heterogeneous Photocatalytic Decolourisation of Congo Red Dye in Aqueous Solution

Abstract

The potential of locally sourced periwinkle shell ash (PSA) has been explored as an alternative photocatalyst for the photocatalytic decolourisation of Congo red dye. The effect of process parameters such as irradiation time, initial dye concentration, catalyst dosage, pH of the solution and the addition of hydrogen peroxide (H₂O₂) on the extent of photodegradation was investigated. The optimum values of the process parameters were: irradiation time, 50 minutes; initial dye concentration, 10 mg/L; PSA dosage, 7 g/L and pH, 4. The addition of H₂O₂ enhanced the photodegradation process with almost 100 percent decolourisation achieved. The adsorption equilibrium was well described by the Langmuir isotherm equation (R²=0.999) indicating mono layer type adsorption while the diffusion mechanism and kinetics of the process were well described by the intra-particle diffusion and Langmuir-Hinshelwood kinetic models with high R² values of 0.998 and 0.999 respectively.