An Efficient Photocatalyst for Fast Reduction of Cr(VI) by Ultra-Trace Silver Enhanced Titania in Aqueous Solution

Abstract

For the purpose of establishing a simple route to prepare a metal-semiconductor hybrid catalyst efficiently and reduce its cost through precise doping noble metals. In this study, ultra-trace silver doped TiO 2 photocatalysts were fabricated via a "green" ultrasonic impregnation-assisted photoreduction strategy in an ethanol system, and its photocatalytic performance was systematically investigated by utilizing Cr(VI) as the model contaminant. A schottky energy barrier was constructed in Ag@TiO 2 , which served as a recombination center and possessed superior photocatalytic activity for Cr(VI) reduction. The obtained catalysts exhibited a significant e − /h + separation efficiency which directly led to an obvious photocatalytic property enhancement. Then, the resultant Ag@TiO 2 (0.06 wt %, 30 min irradiation) showed about 2.5 times the activity as that of commercial P25 NPs for Cr(VI) degradation. Moreover, after five cycles, it still maintained considerably high catalytic ability (62%). This work provides a deep insight into preparation techniques of metal-semiconductor photocatalyst and broadens their application prospect.

A systematic study of hexavalent chromium adsorption and removal from aqueous environments using chemically functionalized amorphous and mesoporous silica nanoparticles

“…Note that monovalent cations exerted a slightly more influence on the Cr(VI) removal performance of NH 2 -ASNs and NH 2 -MSNs than multivalent ions. The adverse effect of foreign cations on the uptake of Cr(VI) ions has been attributed to the presence of ion exchange during the adsorption process 98,99 . Under the circumstance of increased number of the foreign cations, the electrostatic attraction between the negatively charged Cr(VI) ions and the positively charged NH 3…”

Comparison of ZrO2, TiO2, and α-Fe2O3 nanotube arrays on Cr(VI) photoreduction fabricated by anodization of Zr, Ti, and Fe foils

“…E 0 =+1.35 V versus NHE at pH=0 [23,24] as shown in figure 10. The reduction of Cr(VI) by CB electrons over oxide semiconductor is supported by Electron Spin Resonance (ESR)-5,5-Dimethyl-1-pyrroline N-oxide (DMPO)'s result obtained by Pu et al [25]. Whereas, water will be oxidized by holes in the VB of semiconductors producing O 2 [7] as stated in equation (3).…”

“…This is consistent with Zhong et al [26] findings that observed O 2 production during Cr(VI) photoreduction that also analyzed using the ESR-DMPO method. Despite O 2 is known to be an electron scavenger that could hinder the reduction of Cr(VI), the reaction with electrons also can produce -O , HOO , and H 2 O 2 species that result in the reduction of Cr(VI) to Cr(III) [13,25].…”

Theory‐oriented Synthesis of 2D/2D BiVO4/MXene Heterojunction for Simultaneous Removal of Hexavalent Chromium and Methylene Blue

“…From this point of view, constructing a Schottky junction at the interface between a semiconductor and a metal cocatalyst stands out as this heterojunction structure is extremely efficient for the spatial separation of charge carriers. [17][18][19] Bismuth vanadate (BiVO 4 ) is a widely used photocatalyst due to its attractive properties like narrow band gap (2.4 eV), visible light responsiveness, non-toxicity, high stability and thanks to the strong oxidation ability, BiVO 4 has already been investigated for wastewater treatment by decomposing organic pollutants. [20][21][22][23] Even though two-dimensional (2D) structure endows BiVO 4 with better performance by shortening the transfer distance of charge carriers, the photocatalytic efficiency for simultaneous reduction reaction and oxidation reaction is still at a bottleneck because of the recombination of electrons and holes.…”