Intermediate formation during photodegradation of phenol using lanthanum doped tin dioxide nanoparticles

Lanthanum (La)-doped tin dioxide (SnO₂) nanoparticles were synthesized by a modified sol-gel method at room temperature. The samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photocatalytic activity of La:SnO₂ samples were investigated by studying the degradation profile of phenol and its by-products in water. The treated samples were analyzed by HPLC-UV and a UV-Vis spectrophotometer. Benzoquinone, catechol, resorcinol, hydroquinone, acetic acid, and 2-propanol were identified as phenol degradation intermediates. Maximum concentration acquired was in the order of catechol, resorcinol, hydroquinone, and benzoquinone, which was observed in the beginning stages while iso-propanol and acetic acid were observed in the final stages of phenol degradation. We achieved a complete photodegradation of a 10 ppm aqueous phenol solution and intermediates with 0.6 % of SnO₂:La nanoparticles in 120 min under artificial solar irradiation. A maximum degradation rate constant of 0.02228 min^-1 of propanol and a minimum of acetic acid 0.013412 min^-1 were recorded at 37 °C.