H2S photodegradation by TiO2/M-MCM-41 (M=Cr or Ce): Deactivation and by-product generation under UV-A and visible light

Abstract

M-MCM-41 molecular sieves (M = Ce or Cr) were prepared by a hydrothermal method and impregnated with TiO 2 . The materials were characterized by XRD, N 2 adsorption-desorption, DRS and XPS. Their potential application to photooxidize H 2 S in a wet gas stream was tested in a continuous flow reactor operating at a flow rate of 110 mL·min -1 at 50% relative humidity and using 30 ppm v of the pollutant. The photocatalytic efficiency using UV-A and visible-light was compared to the activity of TiO 2 /MCM-41 without heteroatoms incorporated into the MCM-41 structure. It was found that the incorporation of Ce did not improve the performance of TiO 2 /MCM-41, but Cr-containing samples presented higher initial efficiency and were able to photooxidize H 2 S without formation of SO 2 as a by-product, in contrast to the other prepared samples and to Degussa P-25 TiO 2 . Moreover, no other gaseous by-product was detected. The isomorphic incorporation of Cr into the structure of MCM-41 followed by TiO 2 incorporation produced photocatalysts that presented good adsorption capacity and were much more active under visible-light than under UV-light. This performance represents an important advantage for solar applications. Their photoactivity depended on the concentration of chromium; the highest efficiency was attained with samples with a Si/Cr ratio of 50. Finally, deactivation was observed as a consequence of sulfate accumulation on the surface of the catalyst and reduction of Cr 6+ .

Characterisation of photocatalytic degradation of odorous compounds associated with livestock facilities by means of PTR-MS

“…Therefore, the photocatalytic reactor in this study had less effect on the removal of H 2 S than that of other organic sulphur compounds. However, several studies have found that H 2 S can be removed efficiently in photocatalytic reactors [52][53][54][55][56][57]. When comparing the experimental setups, several possible reasons for this could be proposed.…”

“…In this study, powdered TiO 2 (anatase) was coated on the surface of the TiO 2 filter. However, other researchers have used sol-gel TiO 2 , TiO 2 /M-MCM-41 (M = Cr, Ce), hybrid TiO 2 -SiM g O x or TiO 2 doping with WO 3 [52][53][54][55][56][57]. Lastly, the amount of TiO 2 coated on the ceramic filter may not be sufficient to obtain a sufficiently high density of active sites to adsorb and degrade H 2 S [52].…”

Hierarchical Titanium Dioxide Nanowire/Metal–Organic Framework/Carbon Nanofiber Membranes for Highly Efficient Photocatalytic Degradation of Hydrogen Sulfide

“…The TiO 2 photocatalyst modified with noble metal Cu or Ag displayed increased photocatalytic activity for removing hazardous H 2 S. Moreover, Raquel et al. have synthesized TiO 2 /M‐MCM‐41 (M=Cr) successfully, which can effectively photooxidize H 2 S in contrast to Degussa P‐25 TiO 2 . However, the poor adsorption ability and low surface area of TiO 2 still limit its photocatalytic H 2 S decomposition rate .…”

“…The CNF/TiO 2 nanowire (CTW) membranes possess a high surface area and a versatile step‐by‐step strategy was used to synthesize the MOF shell on the CTWM membranes. Compared with previous reports about H 2 S degradation, the CTWM membranes have some advantages: 1) a simple step‐by‐step self‐assembly strategy was used to synthesize the MOF shell on TiO 2 nanowires, which can enhance H 2 S adsorption capacity and avoids using expensive noble metals to modify. 2) The CTWM membrane had a larger surface area and allowed the simultaneous adsorption and catalysis of H 2 S. 3) Using CNFs as a catalyst carrier can be helpful for the efficient electron transfer and convenient recovery and recycling characteristics.…”

Application of advanced oxidation processes for treatment of air from livestock and industrial facilities

“…3) H 2 S cannot be efficiently removed in the photocatalytic reactor with only TiO 2 (Paper III) [111], and TiO 2 has to be modified by doping other types of photocatalyst or metals on TiO 2 [115][116][117].…”