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

Jelena Pavlović,Nataša Novak Tušar,Nataša Zabukovec Logar,Nevenka Rajić,Andraž Šuligoj,Mojca Opresnik

doi:10.3390/catal12020224

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 photocatalytic activity. The activity increases linearly with the Fe content in the tuffs. The MB photodegradation 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.

Highlights

With the increasing demand for some industrial products and the need for a higher standard of living, synthetic organic dyes have become indispensable in industries such as textiles, paper, printing, rubber, leather, cosmetics, and food
The removal of organic dyes from wastewater has become an important task for environmental protection
In previous studies of the photocatalytic activity of a SnO2 -containing clinoptilolite [24], we found that the natural clinoptilolite from the Serbian deposit Slanci exhibits photocatalytic activity in the degradation of methylene blue (MB)

Summary

Introduction

With the increasing demand for some industrial products and the need for a higher standard of living, synthetic organic dyes have become indispensable in industries such as textiles, paper, printing, rubber, leather, cosmetics, and food. Most dyes are toxic and carcinogenic, and their presence in water even at low concentrations causes severe environmental damage, including human health consequences [1,2,3]. The removal of organic dyes from wastewater has become an important task for environmental protection. Advanced oxidation processes (AOPs) are considered effective for the removal of organic dyes from water media under mild reaction conditions. The high efficiency is attributed to the generation of highly reactive species, such as hydroxyl radicals, under radiation. These species interact with the dye molecules and cause their degradation and even mineralization [4,5]

Methods

Results

Conclusion