Titanium dioxide mediated photocatalytic oxidation is very effective in removing various organic pollutants from water. Nano-sized magnetic photocatalyst, in particular, has the advantage of fast and easy recovery by the application of an external magnetic field, while retaining a high surface area to volume ratio for enhanced mixing. Engineered design of magnetic photocatalyst with the aim of lowering the production cost, and application of the photocatalyst to real water pollutant were demonstrated herein. Magnetite cores with high magnetic susceptibility were obtained from a commercial supplier and coated with an ultrathin silica insulation layer (5 nm) prepared from a low cost sodium silicate precursor, followed by a coating of crystalline titanium dioxide. The morphology and the crystalline structure of composite nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction. The as-prepared particles show high activity in the photooxidation of Natural Organic Matter, a complex water pollutant associated with biofouling and the formation of disinfection by-products in chlorinated water. The photocatalyst exhibits no significant loss of efficiency when recycled, which demonstrates the excellent durability and reusability of the particles.