Reactive adsorption and catalytic oxidation of gaseous hydrogen sulfide using a prototype air purifier built with bismuth-doped titanium dioxide.

A prototype air purifier (AP) module has been constructed using bismuth-doped titanium dioxide (Bi _x -P25: x(%) as Bi/Ti molar ratios of 1.1, 2.1, 3.3, 5.3, and 8.7). The reactive adsorption property of Bi _x -P25 materials is evaluated against H ₂ S gas at a recirculation rate of 160 L min ^-1 in a 17 L closed chamber. The AP (Bi _5.3 -P25) exhibits superior performance against 10 ppm H ₂ S in dry air under dark conditions (i.e., without light irradiation), with a removal efficiency (X _H2S )= 99% in 5 mins, reaction kinetic rate (r (at X = 10%))= 7.3 mmol h ^-1 g ^-1 , and partition coefficient= 0.18 mol kg ^-1 Pa ^-1 . As such, its superiority is evident over the reference AP (P25) filter with X _H2S < 10%. The clean air delivery rate (CADR) of AP (Bi _5.3 -P25) increases noticeably from 9.9 to 17.8 L min ^-1 with increasing relative humidity (RH) from 0 to 80%, respectively. In contrast, the CADR decreases from 9.9 to 5.8 L min ^-1 as the H ₂ S increases from 10 to 20 ppm. According to density functional theory (DFT), the presence of H ₂ O vapor enhances the hydroxylation of Bi _x -P25 surface to promote H ₂ S mineralization through the formation of TiS ₃ (i.e., thermodynamic reaction of S atom with the catalytic surface). Complete removal of H ₂ S on the Bi _5.3 -P25 surface is also confirmed consistently through gas chromatography-mass spectrometry (GC-MS), in-situ diffuse reflection infrared spectroscopy (in-situ DRIFTS), and elemental analysis (EA). This work represents the first utilization of Bi _x -P25 materials fabricated on an AP platform toward the desulfurization of H ₂ S at room temperature (RT). The practical utility of Bi _x -P25 is overall validated by its eminent role in reactive adsorption and catalytic oxidation (RACO) of H ₂ S from the air.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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