Photodegradation of organic dyes and industrial wastewater in the presence of layer-type perovskite materials under visible light irradiation

Abstract

Layer-type perovskite materials based on A(I)A(II)Ti(2)O(6) (A(I )= Na or Ag or Cu and A(II) = La) system for the degradation of several organic dyes and industrial wastewater under visible-light irradiation are reported. The known perovskite material NaLaTi2O6 (NLTO) was prepared by a new sol-gel process. Ion-exchange of Na+ ions in NLTO with Ag(+ )or Cu2+ ion led to new perovskite AgLaTi2O6 (ALTO) and Cu-0.5 LaTi2O6 (CLTO) respectively. All the new materials were thoroughly characterized by using PXRD, FESEM, HRTEM, UV-vis DRS, IR, XPS and Solid State Photo-luminescence techniques. The new series of materials were utilized for the degradation of Congo Red dye, 4-chlorophenol and 4,4'-bis(2-sulfostyryl)biphenyl as reference pollutants, as well as industrial wastewater. The mineralization process of Congo Red was evaluated through mass spectrometry, which showed that after 60 min of irradiation, the dye degraded with all fragments disappeared. Degradation and mineralization of industrial wastewater was studied by using a newly designed photoreactor via a two-stage process. Mechanistic studies for the fast degradation of Congo Red and industrial wastewater were carried out in the presence of various scavengers. Finally, the photomineralized wastewater was evaluated by chemical oxygen demand (COD) test and the obtained value is close to the standard value. Highest efficiency of degradation was found for ALTO as the photocatalyst, followed by CLTO and then NLTO.