the present invention relates to a method for recovering an organic - inorganic element - doped metal oxide from a hydrolysable metal compound , accompanied with contaminated water treatment . the present invention comprises steps of : a ) adding a hydrolysable metal compound as a coagulant to a contaminated water to form a separable floc between the hydrolysable metal compound and contaminants present in contaminated water ; b ) separating the separable floc and the pre - treated water after flocculation treatment ; and c ) calcinating the separated floc over 500 ° c . to produce an organic - inorganic element - doped metal oxide . more preferably , the present invention further comprises subjecting the pre - treated water of the step b ) to a microwave treatment to cause a photocatalytic degradation of an organic contaminant that remains in the pre - treated water , with the assistance of the remaining hydrolysable metal compound . a novel titanium compound is found as an alternative coagulant instead of iron and aluminum salts which most widely use in water treatment . ability , capacity and efficiency of flocculation as the proposed titanium coagulant are similar to those of fecl 3 and alum coagulants in terms of removing organic matter . titania produced by calcination of the separated floc after ticl 4 flocculation is mainly doped with c and p atoms .