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Photocatalytic Degradation of Malathion using Hydroxyapatite derived from Chanos chanos and Pangasius dory bones
* 1, 2 , * 3
1  Nanotechnology Research Laboratory, Department of Chemical Engineering, University of the Philippines Diliman, Quezon City, Philippines
2  Department of Chemical Engineering, University of Santo Tomas, España Blvd., Sampaloc, Manila, Philip-pines
3  Chemical Engineering Department, Adamson University, Manila, Philippines
Academic Editor: Antoni Sánchez


Farmers widely use malathion, even in households, and significant amounts of 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 from 19 to 52 nm in size with a pseudo-spherical morphology. Degradation efficiency increases when catalyst dosage or irradiation time is increased. Degradation efficiencies range from 8.18% to 67.80% using MF1000 and from 20.50% to 67.90% using CD1000. Malathion obeys the first-order kinetics with a kinetic constant up to 7.0289 x 10-3 min-1 for 0.6 g catalyst loading. Meanwhile, malathion obeys second-order kinetics with a kinetic constant up to 1.1946 x 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 impacts lessening the detrimental effects of pesticides in groundwater and wastewater.

Keywords: malathion; photocatalysis; hydroxyapatite; wastewater