Enhanced photocatalytic reduction of Hg(II) in aqueous medium by 2-aminothiazole-modified TiO2 particles

Abstract

Este trabalho descreve a síntese e caracterização da titânia modificada pelo ligante 2-aminotiazol e sua aplicação na foto-redução de íons Hg (II) em meio aquoso. Espectros obtidos na região do infravermelho confirmaram a modificação química da matriz de titânia. A quantidade de grupos 2-aminotiazol ligados à superfície da titânia foi determinada por meio da análise de nitrogênio, utilizando-se o método de Kjeldahl. Todos os experimentos de fotoredução foram feitos em um foto-reator cilíndrico termostatizado a 298 K. O catalisador modificado, 2-aminotiazol titânia (TiAT), apresentou maior capacidade de foto-redução dos íons Hg(II) nos valores de pH estudados (3, 7 e 9). Além disso, os estudos de sorção mostraram que o TiAT apresentou um menor tempo de equilíbrio e uma maior capacidade de sorção dos íons Hg(II), demonstrando que o processo de sorção desempenha um papel fundamental no mecanismo de foto-redução.This work describes the synthesis and characterization of 2-aminothiazole-modified titania and its application on Hg (II) photoreduction in aqueous medium. Infrared spectroscopy confirmed the chemical modification of the titania matrix. The number of 2-aminothiazole groups attached to the titania was determined by Kjeldahl's method. The photocatalytic experiments were carried out in a cylindrical photoreactor thermostatted at 298 K. The resulting modified photocatalyst 2-aminothiazole titania (TiAT) revealed an enhance in the Hg (II) photoreduction capacity at studied pH values (3, 7 and 9). In addition, sorption studies showed that the photocatalyst TiAT presented a lower equilibrium time and a higher sorption capacity of Hg(II) ion, demonstrating that sorption plays a fundamental role in the photoreduction mechanism.Keywords: TiO 2 , 2-aminothiazole, photocatalysis, 3-chloropropyltrimethoxysilane IntroductionFor the past few decades, growing interest has been demonstrated in mercury treatment in aqueous medium due to its toxic, bioaccumulative properties and because of its resistance to biological or chemical degradation in the environment, as is the case of many organic pollutants (e.g. phenol and its derivatives). 1,2 Mercury and its compounds are often converted by bacteria to more toxic species, such as methylmercury, representing a potential risk to human health and to fish-consuming animals. 3 The major source of mercury pollution in aquatic environments is industrial and consists of products such as chloralkali, paint, catalysts used in the metallurgical, pharmaceutical, chemical and petrochemical industries, in electronics, cosmetics, thermometers, gauges, and batteries, as well as agricultural products such as pesticides, fungicides, herbicides, insecticides and bactericides. 4 Various physical and chemical methods have been used in the removal of mercury from water and wastewater streams. However, these processes are inefficient, generating secondary wastes in the form of by-products that must often be disposed of as hazardous. The most promising methods of treatment include sorption, ion exchang...

Synthesis of Poly(2-aminothiazole) for Selective Removal of Hg(II) in Aqueous Solutions

“…It was reported that AT and its derivatives demonstrated excellent adsorption performance to heavy metal ions. AT-modified silica gel and TiO 2 particles were reported to be able to remove heavy metal ions including Ni­(II), Cu­(II), Cd­(II), Zn­(II), and Pb­(II) from fuel kerosene, fuel ethanol, and aqueous solutions, − respectively. Recently, it was reported that AT-functionalized polyacrylonitrile resin enabled separation and preconcentration of Hg­(II) from multicomponent solutions containing Ni­(II), Cu­(II), Cd­(II), Zn­(II), and Pb­(II) .…”

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