Reactive adsorption and catalytic oxidation of gaseous hydrogen sulfide using a prototype air purifier built with...

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 H₂S 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 H₂S 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^-1g^-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 H₂S increases from 10 to 20 ppm. According to density functional theory (DFT), the presence of H₂O vapor enhances the hydroxylation of Bi_x-P25 surface to promote H₂S mineralization through the formation of TiS₃ (i.e., thermodynamic reaction of S atom with the catalytic surface). Complete removal of H₂S 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 H₂S 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 H₂S from the air.