A mini-review on rare earth metal-doped TiO2 for photocatalytic remediation of wastewater

Abstract

Titanium dioxide (TiO2) has been considered a useful material for the treatment of wastewater due to its non-toxic character, chemical stability and excellent electrical and optical properties which contribute in its wide range of applications, particularly in environmental remediation technology. However, the wide band gap of TiO2 photocatalyst (anatase phase, 3.20 eV) limits its photocatalytic activity to the ultraviolet region of light. Besides that, the electron-hole pair recombination has been found to reduce the efficiency of the photocatalyst. To overcome these problems, tailoring of TiO2 surface with rare earth metals to improve its surface, optical and photocatalytic properties has been investigated by many researchers. The surface modifications with rare earth metals proved to enhance the efficiency of TiO2 photocatalyts by way of reducing the band gap by shifting the working wavelength to the visible region and inhibiting the anatase-to-rutile phase transformations. This review paper summarises the attempts on modification of TiO2 using rare earth metals describing their effect on the photocatalytic activities of the modified TiO2 photocatalyst.

Photocatalytic Treatment of Pesticides Using TiO2 Doped with Rare Earth

“…Another effect, which inhibits the recombination process and therefore increases the photocatalytic yield of titania, is the formation of the Ti 3+ species and the oxygen vacancies, both act as photo-generated hole capturers (valence band), and together they are charged and at the same time, the oxygen of the medium traps the photo-generated electrons (conduction band); and this increases the separation of the photo-generated species. Ti 3+ is oxidized in the presence of the oxygen present to generate the anion superoxide (O 2 À ), which reacts with the photo-generated holes in order to produce hydroxyl radicals (OH *) in an aqueous medium, and thus be able to oxidize any organic compound present in this system [6].…”

“…In recent years, the elimination of these compounds in water has been reported by methods, physical [3], biological [4], and chemical [5]. Of the latter, advanced oxidation processes, such as heterogeneous photocatalysis, have been shown to be very efficient in the chemical transformation of pollutants up to their mineralization to CO 2 and other harmless compounds [6].…”

Organosulfur adsorbents by self-assembly of titania based ternary metal oxide nanofibers

“…It is noted that the interactions of different atoms/ domains within the ternary metal oxides would cause disorder of the crystalline phases, where defects on the surface of the materials can be benecial for catalytic applications. 23 suggest that (i) the minor materials are amorphous, (ii) the dopants are incorporated into the TiO 2 nanober crystal phase, or (iii) they are below the detection limit of XRD. Table 2 shows the anatase crystallite sizes calculated using the anatase (101) peaks and the Scherrer equation.…”

“…Lanthanum oxide has been used to stabilize the anatase phase at higher temperatures and has been noted to promote catalytic performance. [21][22][23] While not necessarily considered a stabilizing dopant, TiO 2 modied with the copper group metal/oxides and lanthanum have found applications in CO oxidation, dehydrogenation, 24 CO and O 2 gas sensors, 9 and photocatalysts. 25 Following up on previous research with thiol adsorbents, the current study synthesized nanobrous ternary metal oxides of Cu-group/La 2 O 3 /TiO 2 via the sol-gel route and tested their selective adsorption properties.…”

Glass beads immobilized doped TiO2 NPs with enhanced adsorption efficiency for arsenic(III) from aqueous solution

“…Titanium dioxide NPs have been recognized to be the best photocatalyst among other semiconductors due to its less toxicity, eco-friendly nature, low cost, high efficiency, oxidizing photo-generated holes and high stability in wide pH range [21]. However, the fundamental limits with TiO 2 NPs are the wide band gap energy of 3.20 eV, which can only be activated in UV light, and the transitions from anatase to rutile phase.…”