Functionalized Graphene Oxide with Bismuth and Titanium Oxide Nanoparticles for Efficiently Removing Formaldehyde from the Air by Photocatalytic Degradation-Adsorption Process

Formaldehyde(HCHO)is formed through the oxidation of volatile organic compounds(VOCs)and can cause human cancer.Bismuth oxide and titanium oxide nanoparticles-functionalized nanographene oxide(Bi_(2)O_(3)/TiO_(2)@NGO)were used to rapidly remove the HCHO from the air by a photocatalytic degradation-adsorption process(PC-DAP).The formaldehyde vapor in pure air was generated in a dynamic system within a chamber,and flowed over Bi_(2)O_(3)/TiO_(2)@NGO adsorbent inside a fixed-bed quartz reactor(FBQR)under UV irradiation at optimized conditions(250C).At atmospheric pressure,the flow rate and gas hourly space velocity(GHSV)were adjusted to 300 mL/min and 100-450 L/h,respectively.The radicals of HCHO and nanographene oxide(NGO)were generated through the UV-photochemical process,enhancing the chemical adsorption through the radicals’interactions.On the other hand,the semi-degradation process by catalytic oxidation process converted some HCHO into raw materials of CO_(2)and H_(2)O,while the unconverted HCHO was physically absorbed by NGO.Finally,the HCHO concentration in the outlet system was measured by gas chromatography with a flame ionization detector(GC-FID)after derivatizing formaldehyde with 2,4-dinitrophenylhydrazine(DNPH)and acetonitrile.Therefore,efficient removal of HCHO from the air,the removal efficiency of more than 95%,was achieved through physical/chemical adsorption and the semi-degradation.The mean removal efficiencies for HCHO with Bi_(2)O_(3)-TiO_(2)@NGO,TiO_(2)@NGO,Bi_(2)O_(3)@NGO,and NGO were 98.7%,73.6%,61.8%,and 11.4%,respectively(n=10,RSD<5%).The methodology was validated by spiking different concentrations of standard HCHO into pure air.