Photocatalytic kinetics and cyclic stability of photocatalysts Fe-complex/TiO2 in the synergistic degradation of phenolic pollutants and reduction of Cr(VI)

Abstract

In this paper, the kinetic characteristics and cycle stability of Fe-complex/TiO2 in the process of degradation of phenolic pollutants and reduction of heavy metal Cr(VI) were studied systematically. First, the structural characteristics and photocatalytic activities of Fe(III)-(8-hydroxyquinoline-5-carboxylic acid)-TiO2 (Fe-HQC-TiO2) nanoparticle to degrade phenolic pollutants and reduce Cr(VI) simultaneously had been investigated. Compared with the single degradation, the efficiency of synergistic degradation/reduction had been improved and the degradation/reduction rate had been obviously accelerated. In particular, the cyclic stability of Fe-HQC-TiO2 photocatalyst decreased obviously when it was used to reduce Cr(VI) alone, but it could still keep above 90% after three cycles when it was used for reduction of Cr(VI) and degradation of phenol synergistically. Second, to Fe-HQS/TiO2 nanoparticle or Fe-HQS/TiO2 nanotube (HQS (8-hydroxyquinoline-5-sulfonic acid)), the synergistic degradation/reduction (2,4-dichlorophenol/Cr(VI)) efficiencies were always greater than those of a single degradation/reduction and the time was greatly reduced. All the results indicated that there were interactions between Cr(VI) and phenol or 2,4-dichlorophenol in the photocatalytic process. The possible mechanism of synergistic accelerated degradation of phenolic compounds and reduction of Cr(VI) was proposed by analyzing and testing the surface characteristics of photocatalyst and the properties of photocatalytic system during the synergistic degradation/reduction.

BiVO4–Deposited MIL–101–NH2 for Efficient Photocatalytic Elimination of Cr(VI)

“…This weakened the removal rate with the trapping of AgNO 3 , deducing that e − led a predomination in the photocatalytic process, while the capture of O 2 − or ·OH could also contribute to the drop. The influence caused by the TBA should be ascribed to the equilibrium transmitting to Cr(VI) [ 46 , 47 ]. On the contrary, the removal promotion with the addition of EDTA–2Na may correlated to the enhanced separation of the photogenerated pairs and the increase in the e − [ 48 ].…”

Hierarchical Bi2WO6/TiO2-nanotube composites derived from natural cellulose for visible-light photocatalytic treatment of pollutants

“…As shown in Figure 8c , FE-SEM images of the 70%−Bi 2 WO 6 /TiO 2 -NT nanocomposite after photocatalysis still present the cellulose-derived three-dimensionally porous network structure, and the Bi 2 WO 6 nanoparticles are still uniformly and tightly coated on the TiO 2 nanotube surfaces, revealing the morphological and structural stabilities of the Bi 2 WO 6 /TiO 2 -NT nanocomposite. In the high-resolution XPS spectrum of the Cr 2p region of the 70%−Bi 2 WO 6 /TiO 2 -NT nanocomposite after photocatalysis ( Figure 8d ), there are two strong peaks at 586.8 and 577.2 eV that were attributed to the binding energies of Cr 2p 1/2 and Cr 2p 3/2 , which are assigned to Cr(III) [ 60 ]. Besides, the weak peak at 580.2 eV is indexed to the spin–orbit split line of Cr 2p 3/2 , which corresponds to Cr(VI) [ 54 ], suggesting that the 70%−Bi 2 WO 6 /TiO 2 -NT nanocomposite effectively reduced Cr(VI) into Cr(III) in five cycles.…”

Simultaneous remediation of hexavalent chromium and organic pollutants in wastewater using period 4 transition metal oxide-based photocatalysts: a review

“…On the other hand, the composite Fe(III)-(8-hydroxyquinoline-5-carboxylic acid)-TiO 2 (Fe-HQC-TiO 2 ) demonstrated highly favored simultaneous photocatalytic activities of hexavalent chromium and phenol under visible light irradiation. The study showed that 96.7% and 95% of photocatalytic removal of hexavalent chromium and phenol, respectively, can be achieved within 120 minutes (Guo et al 2020). Fe-HQC-TiO 2 photocatalyst exhibited 66.69 m 2 /g surface area, which is bigger than that of titanium dioxide nanoparticle, 19.96 m 2 /g.…”

“…Fe-HQC-TiO 2 photocatalyst exhibited 66.69 m 2 /g surface area, which is bigger than that of titanium dioxide nanoparticle, 19.96 m 2 /g. Furthermore, the incorporation of iron-complex onto the titanium dioxide nanoparticles significantly tailored the bandgap of titanium dioxide nanoparticles from 3.20 to 2.42 eV, which resulted in the fast charge separation, low recombination of photogenerated electron-hole pairs, and improvement in solar light utilization (Guo et al 2020). For photocatalyst stability, the performance of Fe-HQC-TiO 2 photocatalyst for reduction hexavalent chromium in a single system decreased noticeably after several repeated cycles.…”