Background: Organophosphates are one of the most common pesticides in the world. One of the most commonly used toxins in this group is malathion, which is classified by the EPA as Group III carcinogenic substances. Therefore, due to the high consumption of this pesticide and its pathogenicity, it should be eliminated in an appropriate manner. One of the elimination ways is the use of advanced oxidation processes. The aim of this study was to determine the photocatalytic removal of malathion pesticide by g-C₃N₄/Fe₃O₄/Ag nanocomposite.
Method: In this study, g-C₃N₄/Fe₃O₄/Ag nanocomposites synthesized by hydrothermal method were used for photocatalytic removal of malathion. The variables studied were pH, nanocomposite dose, and contaminant concentration. Furthermore, the radical effects of ammonium oxalate, tert-butanol, and benzoquinone were analyzed on the experiment procedure.
Results: The best removal efficiency of malathion at pH = 7, the dose of 0.5 g/l, and contaminant concentration 10 mg/l at 60 min was 100%. By increasing the catalyst dose up to 0.5 g/L, the efficiency increased. However, with increasing contaminant concentration, the removal efficiency decreased. Additionally, the removal efficiency of malathion in the presence of ammonium oxalate, tert-butanol, and benzoquinone radicals was 93.36%, 44.78%, and 90.71%, respectively, and the reaction kinetics followed the first equation with R² = 0.9852. 
Conclusion: Therefore, g-C₃N₄/Fe₃O₄/Ag has a high potential for malathion removal moreover can be used to remove various pollutants from aqueous solutions.