Abstract
TiO2 and TiO2-activated carbon (AC) photocatalysts have been prepared (by sol-gel synthesis), characterized, and tested in the removal of diuron from water under simulated solar light. The preparation variables of the two series of catalysts are: (i) heat-treatment temperature of bare TiO2 (350, 400, 450 and 500 °C) and (ii) activated carbon content (0.5, 1, 5, and 10 wt.%) in TiO2-AC samples heat-treated at 350 °C. The activated carbon was previously prepared by hydrothermal carbonization of saccharose and has spherical shape. The heat-treatment temperature does not determine the efficiency of TiO2 for diuron photocatalytic degradation, but clearly influences the diuron adsorption capacity. The capacity of TiO2-AC samples for diuron removal increases with the carbon content and it is the result of combined diuron adsorption and photodegradation. Thus, the sample with highest carbon content (10 wt.% nominal) leads to the highest diuron removal. The TiO2-AC photocatalysts have proved to be capable of degrading diuron previously adsorbed in dark conditions, which allows their regeneration.
Highlights
As intensive agriculture involves the use of large quantities of herbicides, they are becoming emerging pollutants whose concentration in waters and soils is alarmingly increasing all over the world
TiO2 and TiO2 -carbon photocatalysts have been synthetized by sol-gel, being the first submitted to a post-synthesis heat treatment at different temperatures, and the second prepared with different amounts of activated carbon (AC) and heat-treated at 350 ◦ C
The surface area of the TiO2 -carbon samples increases with the carbon content, and the incorporation of AC does not affect TiO2 crystallinity
Summary
As intensive agriculture involves the use of large quantities of herbicides, they are becoming emerging pollutants whose concentration in waters and soils is alarmingly increasing all over the world. Herbicides are toxic and usually persistent compounds, being very harmful for natural ecosystems [1]. The problem of available water resources scarcity is growing in many areas of the Earth. Biodegradation of organic/inorganic pollutants is often viable, a variety of pollutants, such as some pesticides, are recalcitrant to conventional biological treatments [2]. For this reason, more powerful degradation technologies are required
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