UV photochemical hydride generation using ZnO nanoparticles for arsenic speciation in waters, sediments, and soils samples

Abstract

The environmental disasters that occurred due to the leakage of mining waste in Mariana-MG (2015) and Brumadinho-MG (2019), located in Brazil, attracted the attention of the scientific community. This designated efforts to investigate the environmental consequences of toxic waste in the affected ecosystem. Therefore, a simple, easily executed and accessible method was presented for arsenic speciation [As(III), As(V), and DMA]. Using an atomic absorption spectrometer coupled to the hydride generation system, the heterogeneous photocatalysis was applied in the reduction of As(V) and DMA to As(III). After the optimization, a calibration curve was constructed, with LODs equivalent to 3.20 μg L⁻¹ As(III), 3.86 μg L⁻¹ As(V), and 6.68 μg L⁻¹ DMA. When applying the method for quantification in environmental samples, a concentration of up to 103.1 ± 9.4 μg L⁻¹ As(V) was determined for surface water samples. The soil samples, 84.1 ± 3.6 μg L⁻¹ As(III) and 112.4 ± 9.9 μg L⁻¹ As(V) were quantified, proving the contamination of the ecosystems impacted by the environmental disasters. We proceeded the study through an addition/recovery method with samples of water, soil, and sediments (collected from impacted environments). Recovery values were equivalent to 99.0% for As(III), 93.8% for As(V), and 99.2% for DMA. Photocatalytic reduction mechanism of As(V) and DMA to As(III) by heterogeneous photocatalysis.