Exploring the critical dependence of adsorption of various dyes on the degradation rate using Ln3+-TiO2 surface under UV/solar light

Abstract

a b s t r a c tThe degradation of structurally different anionic dyes like Alizarin Red S (ARS) Amaranth (AR), Brilliant Yellow (BY), Congo Red (CR), Fast Red (FR), Methyl Orange (MO), and Methyl Red (MR) were carried out using Ln 3+ (Ln 3+ = La 3+ , Ce 3+ and Gd 3+ ) doped TiO 2 at different pH conditions under UV/solar light. All the anionic dyes underwent rapid degradation at acidic pH, while resisted at alkaline conditions due to the adsorptive tendency of these dyes on the catalyst surface at different pH conditions. Gd 3+ (0.15 mol%)-TiO 2 exhibited better activity compared to other photocatalyst ascribed to half filled electronic configuration of Gd 3+ ions. It is proposed that Ln 3+ serves only as charge carrier traps under UV light, while it also act as visible light sensitizers under solar light. Irrespective of the catalyst and excitation source, the dye degradation followed the order: AR > FR > MO > MR > ARS > BY > CR. The results suggest that pre-adsorption of the pollutant is vital for efficient photocatalysis which is dependent on the nature of the substituent's group attached to the dye molecule.

Synthesis, characterization and photocatalytic activity of nano sized undoped and Ga doped SrTi0.7Fe0.3O3 for 2,4,6-trichlorophenol photodegradation

“…The positive role of doping can be attributed to (i) introduction of mid-band gap states by the dopants serving as effective charge carrier traps; (ii) altering the surface acid-base properties of the catalyst thus enhancing the extent of adsorption of the pollutant molecules on the catalyst surface [53]. Fig.…”

Catalytic activity of Fe3−Cu O4 (0 ≤x≤ 0.25) nanoparticles for the degradation of Amaranth food dye by heterogeneous electro-Fenton process

“…Many synthetic dyes and their derivatives, especially aromatic amines and phenol compounds are harmful to environment, i.e., may cause problems such as changes in water color, odor, eutrophication and bioaccumulation [4,5]. Some of the available treatments for wastewater contaminated with dyes consist in the use of microorganisms and biosorption direct systems [6][7][8], or adsorption using various inorganic compounds [9][10][11][12]. However, these processes are not effective with respect to total removal of dyes and their intermediates.…”

Adsorption and visible light-driven photocatalytic degradation of Rhodamine B in aqueous solutions by Ag@AgBr/SBA-15

“…However, photocatalytic degradation efficiency did not further increase when 50Ag@AgBr/SBA-15 dosages exceeded 0.3 g/L, which may be due to the M a n u s c r i p t 15 agglomeration and sedimentation of photocatalyst itself, hindered light penetration resulting from turbidity at higher catalyst dosages [48,49]. The inset of Fig.S4 (b) shows that the RhB photocatalytic degradation follows well the second-order kinetic model 1/C=k 2 t+1/C 0 , where C and C 0 are the RhB concentration at time (t) and t=0, respectively, and k 2 is the rate constant.…”

“…As seen in Fig. S5 (b), the rate constant of the second-order kinetics decreases from 77.4E -4 min -1 to 4.28E -4 min -1 , which could be ascribed to the fact that the increased concentration of RhB would result in fewer photons reaching the surface of the photocatalyst, fewer oxidative radicals and active sites blocked by RhB adsorbed on the catalyst surface, thus leading to lower photocatalytic degradation rate [48,51,52]. On the other hand, during the RhB degradation process, some intermediates produced may compete with organic molecules, which limited the adsorption and active sites on the surface of the 50Ag@AgBr/SBA-15 [53].…”

“…At 0.1 g/L 50Ag@AgBr/SBA-15 dosage, photocatalysis contributed only 32% RhB degradation in 300 min, but 82% RhB degradation at 0.4 g/L 50Ag@AgBr/SBA-15 dosage. The increased 50Ag@AgBr/SBA-15 dosage could provide more photocatalytic active sites, increasing the adsorption of RhB and generation of active radicals [48].…”