Titanium dioxide nanoparticles detoxify pirimicarb under UV irradiation at ambient intensities

Abstract

Titanium dioxide nanoparticles (nTiO₂) form reactive oxygen species (ROS) under irradiation by ultraviolet light (UV). This known photocatalytic activity may finally affect the presence and toxicity of organic environmental chemicals, which have not yet been studied at ambient UV intensity. The authors used a three-factorial design to evaluate the interaction of the carbamate insecticide pirimicarb (initial nominal concentration, 20 µg/L), ambient UV irradiation (40 W/m² for 15 min), and nTiO₂(~100 nm; 2.0 mg/L). Pirimicarb, pirimicarb × UV, and pirimicarb × nTiO₂ treatments revealed a median immobilization of Daphnia magna after 72 h ranging between 70 and 80%. This effect seemed to be caused by the initial nominal pirimicarb concentration. However, UV irradiation before an exposure of daphnids in the presence of 2.0 mg nTiO₂/L reduced pirimicarb concentrations to values below the limit of quantification, likely because of the formation of ROS. This reduction was associated with an almost complete removal of toxicity for D. magna. Furthermore, during a second experiment, 0.2 mg nTiO₂/L in combination with 15 min UV irradiation reduced pirimicarb concentrations by approximately 30%. These results indicate a detoxification and therefore remediation potential of the combined application of nTiO₂ and UV irradiation at ambient levels. This potential has not been documented to date in surface waters, where nTiO₂ concentrations in the low to medium µg/L range may occur.

Effect of titanium dioxide nanoparticles on the bioavailability, metabolism, and toxicity of pentachlorophenol in zebrafish larvae

“…However, the photocatalytic degradation of PCP could occur in the presence of high n-TiO 2 concentrations (200 mg/L) under UV illumination condition (450 W), via generation of ROS (e.g., hydroxyl radical) to attack para position of the PCP ring to form a semiquinone radical, which in turn disproportionates to yield detected metabolic products (e.g., p-chloranil and tetrachlorohydroquinone) [37]. Likewise, there is ample evidence to indicate that photocatalytic degrade organic compounds are most likely driven by a UV-induced (especially at 300-388 nm) formation of ROS by n-TiO 2 [14,47,48]. For toxicity assay using aquatic organisms, typical laboratory lighting cycle is usually established by employing fluorescent lamps, which mainly emit visible light.…”

Effects of nanoparticles in fresh waters: risks, mechanisms and interactions

“…Specifically, substantial adverse effects of irradiated nTiO 2 was documented on daphnids (Hund‐Rinke & Simon, ), although similar impacts were not observed in other studies (e.g. Seitz et al ., ; Lee & An, ). Taken together, these results on interactions of ENP with DOM and sunlight highlight again the complexity of toxic effects to be expected in aquatic ecosystems.…”

Photocatalytic oxidation of pirimicarb in aqueous slurries containing binary and ternary oxides of zinc and titanium

“…Thus, the photocatalytic activity of ZnO-TiO 2 systems (Zn 2 TiO 4 with cubic spinel crystal structure, Zn 2 Ti 3 O 8 with cubic defect spinel structure and ZnTiO 3 with cubic or hexagonal structure) is being investigated with the purpose of looking for more efficient materials for photocatalytic applications [16][17][18]. Although the photocatalytic degradation of pirimicarb using ZnO and TiO 2 has been studied from previous researchers [5,19], the effect of ZnO-TiO 2 system for the removal of pirimicarb from water has not been studied. The main goal of this work was to assess the effectiveness of the photocatalytic process for the decontamination of water polluted by pirimicarb, to evaluate the kinetics aspects of the process and the reaction intermediates for understanding the mechanistic details of the photodegradation in the ZnO-TiO 2 systems (ZnO, TiO 2 , Zn 2 TiO 4 and ZnTiO 3 ).…”