Simultaneous photocatalytic Cr(VI) reduction and 2,4,6-TCP oxidation over g-C3N4 under visible light irradiation

Abstract

a b s t r a c tIn this study, a rapid reduction of Cr(VI) and degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in a simultaneous manner was reported through the catalysis of g-C 3 N 4 under visible light ( > 420 nm) irradiation. The effects of initial concentration of reactants, dissolved O 2 and pH value were investigated systematically. It indicated that, under the optimized concentration, the Cr(VI) reduction and 2,4,6-TCP oxidation could be accomplished in couple of hours in the presence of g-C 3 N 4 . And also, the O 2 involvement and low pH value were able to significantly improve the removal rate of Cr(VI) and 2,4,6-TCP. In addition, the reaction mechanism was investigated through monitoring the reduced states of Cr(VI) and active oxygen intermediates formed during photoreaction by ESR and XPS, as well as determining the degradation products of 2,4,6-TCP by HPLC-MS. The results supported that the redox reactions of Cr(VI) and 2,4,6-TCP can be performed simultaneously via a synergistic oxidation-reduction mechanism in the presence of g-C 3 N 4 under visible light irradiation.

Acid-treated g-C3N4 with improved photocatalytic performance in the reduction of aqueous Cr(VI) under visible-light

“…In fact, the use of g-C 3 N 4 as photocatalyst in the reduction of aqueous Cr(VI) under UV and visible light irradiation have also been studied in some cases [22][23][24]. However, pure g-C 3 N 4 suffered from low photocatalytic activity resulted from the fast recombination of photogenerated electrons and holes as well as relatively low photoresponse [22][23][24][25][26] the photocatalytic activity or photoresponse of g-C 3 N 4 [22][23][24][25][26]. For example, Dong et al reported that carbon self-doping or incorporation of formate anions could improve the photocatalytic activity of g-C 3 N 4 in Cr(VI) reduction under visible light irradiation [23,24].…”

Chemically controlled growth of porous CeO2 nanotubes for Cr(VI) photoreduction

“…As shown in Fig. 8c, the Cr2p peaks can be curve-fitted with three components at binding energy of 576.8, 581.8 and 586.8 eV, assigned to Cr(III) 2p 3/2 , Cr(VI) 2p 3/2 , and Cr(III) 2p 1/2 , respective [42,43]. The result indicates that Cr(III) species are the dominant existing form on the surface of CeO 2 nanotubes after photocatalysis reactions, and confirms the photoreduction of Cr(VI) occurred under the UV light illumination.…”

“…One of the best strategies to high-efficiency photoreduction of Cr(VI) in aqueous solution is the use of suitable organic sacrificial agents to modify the photocatalysis system and process in synergistically enhanced procedure under light irradiation. Strong synergistic effect between Cr(VI) and methyl orange [21], 2, 4, 6-trichlorophenol [22], phenol [23], 4-chlorophenol [24], etc., dramatically enhances photosensitized removal efficiencies. However, the toxicity and possible incomplete mineralization of the colorful dyes or colorless aromatic compounds will be a risk of secondary contamination in the treatment of Cr(VI).…”

Preparation of fluorine and carbon co-introduced TiO2 at low temperature with enhanced visible-light degradation performance for 2,4,6-trichlorophenol

“…Although many literatures believe that ·OH is another reactive oxygen species, ·OH showed no activity in this study. The formation of O 2 ·− can be expected on the basis of the equations (equations (6)- (10)) [45]. Step I.…”