A photoelectrochemical methodology to obtain nanorods of crystalline hexagonal trigonal selenium

In situ formed Se-TiO2 as a highly reusable photocatalyst for selenium reduction and removal from industrial wastewater

Selenium (Se) release from anthropogenic activities such as mining, power generation, and agriculture poses considerable environmental and ecological risks. Increasing prevalence and awareness of Se-related issues have driven the development of many innovative Se treatment technologies. Photocatalysis has shown promise towards Se removal from industrial wastewaters with minimal residuals, and is generally considered a low-cost, robust, non-toxic, and potentially solar-powered method. Despite this, its real-world application towards environmental remediation remains extremely limited. This is because research into practical considerations, such as photocatalyst stability and reusability, is often overlooked or understudied in favor of developing academically interesting but impractical materials. In this work, commercial anatase TiO2 is stress tested through fifteen cycles of reuse towards the photocatalytic reduction and removal of selenate in synthetic mining-influenced brine (SMIB) without washing or regeneration. Remarkably, selenate removal exceeds 99.3% throughout all cycles. In situ Se-TiO2 heterojunction formation, and changes to its properties including Se loading, particle size, and crystal phase, are characterized through X-ray absorption spectroscopy, scanning transmission electron microscopy, and diffuse reflectance UV/vis, while their effects on catalyst performance are elucidated. This work underscores the importance of catalyst recyclability for practical photocatalytic environmental remediation and discusses the effects of extensive use on photocatalyst performance.

Electroplating Kinetic of Nanostructured Selenium Films from Citrate Bath

In this work; Cyclic-Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) were used to study the electrodeposition kinetic of selenium films in potentiostatic mode from aqueous solution containing selenium dioxide and sodium citrate at pH = 4.2. Semiconducting proprieties of obtained deposits were investigated by Mott-Schottky measurements whereas the optical ones were performed by UV–Visible spectrophotometry. The morphological characterization was carried out using the scanning electron microscopy (SEM). The obtained results showed that the electrodeposition process of selenium films in citrate bath occurred under diffusional regime as rate-limiting step. Deposition rate of selenium layers on platinum substrate is much superior than in the case of ITO substrate and up to a value of 0.65 μg/cm² s. The HSeO₃⁻/Se system becomes more rapid with the increase of the bath temperature. Obtained deposits are photoactive films that belong to p-type semiconductors with number of charge carriers in order of 10²¹/cm³ and energy band gap about 1.7 eV. The grains of electroplated films have spherical forms, nanometric sizes and strong adhesion on the substrate surface.