Studies of Clinoptilolite-Rich Zeolitic Tuffs from Different Regions and Their Activity in Photodegradation of Methylene Blue

Abstract

The present study focuses on clinoptilolite (CLI)-rich natural zeolitic tuffs and their photocatalytic activity in the degradation of cationic organic dyes. CLI from different regions was tested in the photocatalytic degradation of methylene blue (MB) as a model cationic dye. The photocatalytic tests were performed at room temperature and atmospheric pressure under visible light irradiation. For all the CLI samples, the highest activity was observed at pH = 6. Total MB degradation varied between 70 and 91% (C0 = 10 mg dm–3, 0.2 g dm–3 of photocatalyst, during 300 min). It is suggested that the presence of Fe species in the studied tuffs is responsible for the pho-tocatalytic activity. The activity increases linearly with the Fe content in the tuffs. The MB photo-degradation follows the Langmuir–Hinshelwood kinetic model. The recyclability tests showed good stability and efficiency of the photocatalyst. The degradation rate decreased from 91 to 69% during three reaction cycles, indicating a promising potential of natural zeolites in the treatment of textile industry wastewater.