Photocatalytic degradation of methyl orange in water using oyster shell-derived calcium oxide nanoparticles

Abstract

In response to the Philippine-textile-industry goal of adapting sustainable waste management practices, oyster shells as abundant waste, can be valorized for photocatalytic wastewater treatment. Moreover, aeration and water quality as lesser-known parameters were assessed. Here, a nano-sized calcium oxide (CaO NP) photocatalyst from oyster shells was prepared with a 57 % CaO yield. Instrumental characterization confirmed its nanoparticle size, elemental composition, and narrow bandgap, which favor adsorption-photodegradation. The optimum photocatalyst dose achieved 93.7 % removal efficiency and was significantly maximized to 98.5 % under aerated conditions. CaO NP is reusable with stable performance and has first-order dye degradation kinetics. Aerated photocatalytic treatment of simulated wastewater showed a significant reduction in color and chemical oxygen demand with acceptable final pH. Furthermore, the treated wastewater is dischargeable to Class C waters by Philippine environmental standards, proving its successful remediation and application as a dispersible and recyclable photocatalyst for removing methyl orange in water.