Degradation of glyphosate in soil photocatalyzed by Fe3O4/SiO2/TiO2 under solar light.

Xuan Xu,Fangying Ji,Zihong Fan,Li He

doi:10.3390/ijerph8041258

Abstract

In this study, Fe3O4/SiO2/TiO2 photocatalyst was prepared via a sol-gel method, and Fe3O4 particles were used as the core of the colloid. Diffraction peaks of Fe3O4 crystals are not found by XRD characterization, indicating that Fe3O4 particles are well encapsulated by SiO2. FTIR characterization shows that diffraction peaks of Ti-O-Si chemical bonds become obvious when the Fe3O4 loading is more than 0.5%. SEM characterization indicates that agglomeration occurs in the Fe3O4/SiO2/TiO2 photocatalyst, whereas photocatalysts modified by Fe3O4/SiO2 present excellent visible light absorption performance and photocatalytic activity, especially when the Fe3O4 loading is 0.5%. Photocatalytic degradation of glyphosate in soil by these photocatalysts under solar irradiation was investigated. Results show that 0.5% Fe3O4/SiO2/TiO2 has the best photocatalytic activity. The best moisture content of soil is 30%∼50%. Degradation efficiency of glyphosate reaches 89% in 2 h when the dosage of photocatalyst is 0.4 g/100 g (soil), and it increased slowly when more photocatalyst was used. Soil thickness is a very important factor for the photocatalytic rate. The thinner the soil is, the better the glyphosate degradation is. Degradation of glyphosate is not obviously affected by sunlight intensity when the intensity is below 6 mW/cm2 or above 10 mW/cm2, but it is accelerated significantly when the sunlight intensity increases from 6 mW/cm2 to 10 mW/cm2.

Highlights

Glyphosate is a kind of organophosphorus herbicide which is widely used in agriculture for weed control since it can inhibit the synthesis of aromatic amino acids in plants by inhibiting the synthase activity of 5-enol acetone shikimate-3-phosphate salt (EPSP) [1,2]
Research on glyphosate degradation has mainly focused on wastewater treatment processes [5,6,7], but glyphosate in the environment is mainly found in the soil, so it is essential to develop effective methods that can remove glyphosate from soil
Glyphosate cannot diffuse to the catalyst surface fast when the moisture content is lower than 30%

Summary

Introduction

Glyphosate is a kind of organophosphorus herbicide which is widely used in agriculture for weed control since it can inhibit the synthesis of aromatic amino acids in plants by inhibiting the synthase activity of 5-enol acetone shikimate-3-phosphate salt (EPSP) [1,2]. Research on glyphosate degradation has mainly focused on wastewater treatment processes [5,6,7], but glyphosate in the environment is mainly found in the soil, so it is essential to develop effective methods that can remove glyphosate from soil. Photocatalytic technology, especially TiO2 photocatalysis, has been extensively developed in the field of organic pollutant treatment [8,9,10,11]. It is normally only applied in wastewater treatment, and is rarely utilized for in situ soil treatment [12,13]. Recombination of electrons and holes reduces the efficiency of radiation, and lead to the loss of photocatalytic activity

Objectives

Methods

Results

Conclusion