Photocatalytic reduction of Zn2+, Cu2+ and Pb2+ ions were performed using modified titanium dioxide nanoparticles with histidine (His) and imidazole (IM) as the modifier and characterized by FT-IR, X-RD, FESEM, EDAX, TEM and A.A.S. techniques. The anatase phase titanium dioxide nanoparticles with the size distribution of 25–45 nmwere obtained by the Sol–Gel Method. In the case of Cu2+,the reduction reaction was completed in 10 min. The photo-reduction yields of Pb2+ and Zn2+ ions achieved to 98% removal during 60 and 160 min, respectively. The immobilized modifiers on the TiO2 surface accelerate the electron transfer from TiO2 to the metal ion via imidazole bridge upon ultraviolet light irradiation. This photocatalytic reduction could be proceeded through chemisorption, reduction and desorptionprocesses of metal ions on the surface of modified TiO2, sequentially and repeatably. Herein, methanol was played as an artificial electron donor. These hybrid photocatalysts were reused several times without losing efficiency while the highest reduction yield was achieved for TiO2@His NPs. So, modified TiO2 with amino acids could be an excellent candidate for metal ion reduction by an inexpensive method with advantages of high performance, high activity, reusability, easily prepared, easily separate, environmentally friendly and short reaction time
