Abstract

Arsenic is one of the most toxic contaminants found in the environment and can cause severe toxic effects on human health. Arsenic exists in different forms, commonly as As(III) and As(V), being As(III) the most toxic, which removal is more difficult than the removal of As(V). Various technologies have been utilized for its removal (precipitation, coagulation, membrane separation, oxidation, and adsorption) with far less attention paid to photocatalytic oxidation. Despite that the photoxidation of As(III) employing TiO2-based nanomaterials as photocatalysts, has been reported, there are few studies which show their bifunctionality as photocatalyst and adsorbent simultaneously. This work shows novel results on the capacity of TiO2 nanoparticles to remove arsenic by photooxidation and adsorption. The nanoparticles were synthesized by a hydrothermal method, showing a particle size between 10 and 20 nm, and primarily anatase phase, which is the active phase for photocatalytic reactions. These TiO2 nanoparticles absorb in the visible region of the solar spectrum, making them photoactive under sunlight. Complete photooxidation of As(III) and progressive adsorption of photogenerated As(V) was obtained The time required to photooxidate As(III) by the prepared TiO2 nanoparticles were greatly reduced compared with commercial TiO2. Under simulated solar light irradiation 1000 µg L−1 of As(III) were almost completely oxidized in 10 min by nanoparticles, whereas for commercial TiO2, the time required was 60 min. Moreover, nanoparticles showed high efficiency to absorb all the photogenerated As(V) in the same time, obtaining final As concentrations below 10 µg L−1, which is the WHO (World Health Organization) recommended limit for arsenic in drinking water. In contrast, the commercial TiO2 did not show adsorption capacity. Consequently the conjunction of two properties in a single system, such as photooxidation process of As(III) and progressive adsorption of photogenerated As(V), make this new TiO2 nanomaterial a promising technology for arsenic removal in short times.