Photocatalytic degradation of methylene blue with a nanocomposite system: synthesis, photocatalysis and degradation pathways

Abstract

Three different composites, including a calcined FeOOH supported ZnAl layered double hydroxide (FeOOH-LDO), a calcined ZnAl layered double hydroxide (ZnAl-LDO) and a calcined ZnFeAl layered double hydroxide (ZnFeAl-LDO), were synthesized via a sol-gel method, and their activity for the visible light photocatalytic degradation of methylene blue (MB) was studied. The composites were characterized by PXRD, SEM, and BET techniques, confirming the formation of highly crystalline structures. The activity performance of MB degradation was in the following order: FeOOH-LDO (∼95%) > ZnFeAl-LDO (∼60%) > ZnAl-LDO (∼23%). In addition, a possible photocatalytic degradation reaction mechanism for MB was also proposed. Moreover, the frontier electron densities on the atoms of MB were calculated, which were in satisfactory agreement with the postulated mechanism.

Dissociation of Basic Dyes by Advanced Oxidation: Theoretical Study by DFT Calculations

“…On the other hand, other studies show that the basic dye photodegradation mentioned before begins with the opening of the cycle which is in the middle. The latter is constituted by the heteroatoms [26][27][28] N and S. In the light of this bibliography we conclude that basic dyes degradation leads to the formation of several products which are depending on dyes nature of. In addition, three types of mechanisms have been proposed by researchers for the degradation of basic dyes by advanced oxidation.…”

Yolk–shell microspheres assembled from Preyssler‐type NaP5W30O11014− polyoxometalate and MIL‐101(Cr) metal–organic framework: A new inorganic–organic nanohybrid for fast and selective removal of cationic organic dyes from aqueous media

“…As shown in Figure 10b, the removal efficiency towards MB decreased from 100% at pH = 2 to 40% at pH = 10. From the results, we conclude that the adsorption was effective at acidic pHs (2)(3)(4)(5)(6), because the adsorption of the dye molecules would be facilitated by hydrogen ions (H + ). [66] However, with an increase of pH, chloride anion in MB is exchanged with NaOH to have a displacement reaction, forming NaCl (aq) and MBS + OH − (aq).…”

“…Furthermore, the estimated q e values were in good accordance with the experimental q e values. These results suggested that the [46] MOF/GO 183.4 36 30 min [47] Mesoporous MIL-101 22.5 30 2 h [48] MOF-235 187 300 12 h [49] H 3 PW 12 O 40 @Mn ІІІ porphyrin 10.5 10 24 h [50] MOF-Cu-BTC 15.28 3.19 6 h [51] H 6 P 2 W 18 O 62 @Cu 3 (BTC) 3 18.51 40 - [52] Carbon nanotubes 35.4 35 50 min [53] Activated carbon 135 60 10 min [54] Exfoliated grapheme oxide 17.3 30 80 min [55] Nano-ZIF-8 126 60 30 min [56] Graphene oxide 397 34.8 25 min [23] Zn-DDQ 135 500 70 min [60] MIL-100(Fe) 736 30 90 min [61] ErCu-POM (Er-3) 391 20 -…”

“…Organic dyes are extensively used for cotton, linen, silk, textiles and leather, in the printing paper industry and so on. [1][2][3] However, in recent years, with the rapid development of economy and industry, a large amount of dyecontaining wastewater has been directly discharged without reasonably processing, generating a tremendous threat to aqueous environments and human health on account of toxicity and even carcinogenicity. [4,5] The removal of these pollutants from contaminated aqueous solutions is of great importance in environmental processes.…”

One-Pot Hydrothermal Synthesis of Sulfur-Doped SnO2 Nanoparticles and their Enhanced Photocatalytic Properties

“…1,2 The development of e±cient photocatalysts is critical for practical application of the photocatalysis technology. The reported metal-based photocatalyst systems, to the best of our knowledge, can be generally classi¯ed as oxides or oxyhalides, [3][4][5][6][7][8] sul¯des [9][10][11] and oxysalts.…”