Ozone(O3) is an important atmospheric oxidant. Black carbon(BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere,leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS). Combined with ion chromatography(IC),DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2.Relative humidity or 254 nm UV(ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol(DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites.
Anodization is a popular method of preparing TiO_2 nanotube array films(TiNTs) by using direct current(DC)power as the driving voltage.In this study,three driving voltage modes,namely,the sine alternating current(sine) mode,the full-wave rectification of sine waves via four diodes(sine-4D,where D means diode) mode,and the DC mode,were used to prepare TiNTs by anodization.At 20 V,TiNTs were formed under sine-4D mode but only irregular porous TiO_2 films were formed under DC mode.At 50 V,TiNTs formed under both the sine-4D and DC modes.No TiNTs formed in the sine mode anodization at either 20 or 50 V.Compared with the DC mode,the sine-4D mode required a lower oxidation voltage for TiNT formation,which suggests that sine-4D is an economical,convenient,and efficient driving voltage for TiNT preparation by anodization.The morphologies and structures of TiNT samples anodized at 50 V in the sine-4D and DC modes at different oxidation time(1,5,10,30,60,and 120 min) were analyzed.TiNT growth processes were similar between the studied modes.However,the growth rate of the films was faster under the sine-4D mode than the DC mode during the first 30 min of anodization.
We designed photoelectrochemical cells to achieve efficient oxidation ofrhodamine B (RhB)without the need for photocatalyst or supporting electrolyte.RhB,the metal anode/cathode,and O2 formed an energy-relay structure,enabling the efficient formation of O2^- species under ultraviolet illumination.In a single-compartment cell (S cell)containing a titanium (Ti)anode,Ti cathode,and 10mg·mL^-1 RhB in water,the zero-order rate constant of the photoelectrochemical oxidation (kPEC)of RhB was 0.049mg·L^-1·min^-1,while those of the photochemical and electrochemical oxidations of RhB were nearly zero.kPEC remained almost the same when 0.5mol·L^-1 Na2SO4 was included in the reactive solution,regardless of the increase in the photocurrent of the S cell.The kpEc of the illuminated anode comoartment in the two-compartment cell,including a Ti anode,Ti cathode,and 10mg·mL^-1 RhB in water,was higher than that of the S cell.These results support a simple,eco-friendly,and energy saving method to realize the efficient degradation of RhB.
