Photocatalytic degradation of lignin using Pt/TiO2 as the catalyst

Photocatalytic degradation of lignin was studied with the use of catalysts TiO2 and Pt/TiO2. The influence of several experimental parameters, i.e. pH, catalyst dosage and illumination on lignin degradation was investigated. The results showed that application of UV irradiation alone has almost no effect on the reduction of dissolved organic carbon (DOC) and American Dye Manufacture Institute value (ADMI). However, the addition of TiO2 and Pt/TiO2 reduced the original DOC (251 mg l−1) by more than 40% within 30 min of treatment and the reaction can be simulated with pseudo-first order kinetics. Rapid degradation of lignin was observed in acidic solution using either TiO2 or Pt/TiO2 as the catalyst compared to high pH cases. The content of Pt in the Pt/TiO2 catalyst is 1%. In addition, too much catalyst addition has not increased the DOC and ADMI reduction proportionally. The investigation also indicated that the photocatalytic degradation rates could be enhanced 1–6 times faster after doping TiO2 with Pt in different pH cases. A modified Nernst type model was adopted to simulate the decoloring process using TiO2 and Pt/TiO2 based on the profiles of oxidation reduction potential during the photocatalytic reaction. The developed equation can be used to predict the color removal efficiency of lignin wastewater by the photocatalytic process.