This paper studied the effects of Co, Ni replacement in the Fe1-xCoxFe2O4 and Fe1-yNiyFe2O4 (x, y = 0, , , , ) nanoparticles, pH, weight of nanoparticles/ml of water and time of stirring on the arsenic removal ability. The results showed that small amount of g/l of Fe3O4 nanoparticles after stirring time of 3 minutes can reduce the arsenic concentration from mg/l to mg/l. The removal was also affected by the pH of the water.