White and Red Brazilian São Simão's Kaolinite-TiO2 Nanocomposites as Catalysts for Toluene Photodegradation from Aqueous Solutions.

Lucas D Mora,Sophia Korili,Tiago H Da Silva,Eduardo J Nassar,Miguel A Vicente,Beatriz González,Lorrana V Barbosa,Emerson H De Faria,Antonio Gil,Vicente Rives,Larissa F Bonfim,Raquel Trujillano,Maria Elena Pérez-Bernal,Katia J Ciuffi

doi:10.3390/ma12233943

Abstract

The presence of volatile organic compounds in groundwater is a major concern when it is used as a drinking water source because many of these compounds can adversely affect human health. This work reports on the preparation and characterization of white and red Brazilian São Simão’s kaolinite-TiO2 nanocomposites and their use as catalysts in the photochemical degradation of toluene, a significant volatile organic compound. The nanocomposites were prepared by a sol-gel procedure, using titanium bis(triethanolaminate)diisopropoxide as a precursor. Thermal treatments of the nanocomposites led to different polymorphic titania phases, while the clay changed from kaolinite to metakaolinite. This structural evolution strongly affected the photocatalytic degradation behavior—all the solids efficiently degraded toluene and the solid calcined at 400 °C, formed by kaolinite and anatase, showed the best behavior (90% degradation). On extending the photochemical treatment up to 48 h, high mineralization levels were reached. The advantage of photodegradation using the nanocomposites was confirmed by comparing the results from isolated components (titanium dioxide and kaolinite) to observe that the nanocomposites displayed fundamental importance to the photodegradation pathways of toluene.

Highlights

With the population growth in recent years, there has been an increase in the generation and accumulation of industrial pollutants [1]
Our results showed that photodegradation of toluene could occur under sunlight in the presence resultsbased showed photodegradation toluene could occur under sunlight indifferent the presence of theOur catalysts on that white and red kaoliniteofsuggesting a degradation mechanism from of the catalysts based on white and red kaolinite suggesting a degradation mechanism different from that the typically suggested partial hydrolysis in water (Figure 10)
Heterogeneous catalysts using white and red kaolinites as supports were prepared for application to toluene photodegradation in an aqueous solution

Summary

Introduction

With the population growth in recent years, there has been an increase in the generation and accumulation of industrial pollutants [1]. According to United Nations (UN), one in three people do not have access to safe drinking water [2,3] and there is an urgent need for the development of effective removal techniques against the pollutants found in rivers, seas, lakes, etc. Volatile organic compounds (VOCs) are hazardous pollutants, being present in air and groundwater. Their release from numerous industrial sources, even in very low concentrations (

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