Flaky and nanospherical birnessite and birnessite-supported Pt catalysts were successfully prepared and characterized by means of Xray diffraction （XRD）,transmission electron microscopy （TEM）,energy dispersive spectroscopy （EDS） and N2 adsorption-desorption.Effects of the birnessite morphology and Pt reduction method on the catalytic activity for the complete oxidation of formaldehyde （HCHO） were investigated.It was found that flaky birnessite exhibited higher catalytic activity than nanospherical birnessite.The promoting effect of Pt on the birnessite catalyst indicated that the reduction method of the Pt precursor greatly influenced the catalytic performance.Flaky birnessite-supported Pt nanoparticles reduced by KBH 4 showed the highest catalytic activity and could completely oxidize HCHO into CO2 and H2O at 50℃,whereas the sample reduced using H2-plasma showed lower activity for HCHO oxidation.The differences in catalytic activity of these materials were jointly attributed to the effects of pore structure,surface active sites exposed to HCHO and the dispersion of Pt nanoparticles.
Linlin LiuHua TianJunhui HeDonghui WangQiaowen Yang
Mesoporous SBA-15 with different Fe2O3 loading were synthesized by an in-situ coating progress for removals of dichlorodiphenyl- trichloroethane （DDT） and its derivatives, i.e., 1,1-dichloro-2,2-bis-（p-chlorophenyl）ethane （DDD） and 1,1-dichloro-2,2-bis-（4-chloro -phenyl） ethane （DDE）. The results from XRD （X-ray diffractometer）, TEM （transmission electron microscopy） indicated that the iron could be well dispersed on SBA-15 within 6 wt.% Fe2O3 loading. Nitrogen adsorption-desorption tests indicated that the synthesized materials were characterized by ordered meso-structure, high surface area and large pore volume. DDTs were removed from aqueous media in 12-hr treatment and high removal efficiency of DDTs was achieved at over 94%. DDTs could be completely degraded at 350°C under the existence of SBA-15 with 4 wt.% Fe2O3 loading. The final degradation products of DDT were dichlorobenzophenone （DCB） and bis-（4-chloro-phenyl） methane （DDM）, suggesting a complete dechlorination from trichloromethyl.
