Photocatalytic Degradation of Malathion Using Hydroxyapatite Derived from <i>Chanos chanos</i> and <i>Pangasius dory</i> Bones

Abstract

Farmers widely use malathion, even in households, and significant amounts seep through groundwater and effluent wastewater. It is toxic to animal and human life. Hence, its removal from wastewater is necessary. Here, we report the applicability of hydroxyapatite as a catalyst in the UV-light-assisted degradation of malathion. The hydroxyapatite was synthesized via calcination from milkfish (MF1000) and cream dory (CD1000) bones. FTIR and PXRD results proved the successful synthesis of hydroxyapatite from the fish bones. SEM images revealed that the synthesized hydroxyapatite varies in size from 19 to 52 nm with a pseudo-spherical morphology. Degradation efficiency increases when catalyst dosage or irradiation time are increased. Degradation efficiencies range from 8.18% to 67.80% using MF1000 and from 20.50% to 67.90% using CD1000. Malathion obeys first-order kinetics with a kinetic constant up to 7.0289 × 10−3 min−1 for 0.6 g catalyst loading. Meanwhile, malathion obeys second-order kinetics with a kinetic constant up to 1.1946 × 10−3 L min−1 mg−1 for 0.6 g loading. Across all catalyst loadings, CD1000 has faster degradation kinetics compared to MF1000. The results of this study validate that the calcined fish bones are effective in removing malathion in an aqueous solution, which significantly lessens the detrimental effects of pesticides in groundwater and wastewater.

Keywords

• malathion
• photocatalysis
• hydroxyapatite
• wastewater