Preparation of Y-H_3PW_(12)O_(40)/TiO_2 and La-H_3PW_(12)O_(40)/TiO_2 by hydrothermal method and its photocatalytic activity for dinitrotoluene decomposition

A series of mesoporous materials （H3PW12O40/TiO2, Y-H3PW12O40/TiO2 and La-H3PW12O40/TiO2） were prepared by a modified sol-gel-hydrothermal route, which realized the load and modification of H3PW12O40 at the same time. The prepared samples were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, nitrogen adsorption-desorption analysis, ultraviolet-visible absorption spectrum （UV-Vis） and scanning electron microscopy （SEM）. The XRD and FT-IR results displayed that the catalysts had uniform anatase phase and the primary Keggin structure of H3PW12O40 remain intact. Nitrogen ad-sorption-desorption analysis suggested that suitable doping of rare earth elements could increase the specific surface area from 177.9 m2/g （H3PW12O40/TiO2） to 229.5 （1 wt.%Y-H3PW12O40/TiO2） or 236.1 m2/g （1 wt.%La-H3PW12O40/TiO2）. Results of UV-Vis spectra showed that the band of the 1 wt.%Y-H3PW12O40/TiO2 and 1 wt.%La-H3PW12O40/TiO2 have an obvious redshift compared with the H3PW12O40/TiO2. Additionally, the composites were used as heterogeneous photocatalysts to the degradation of dinitrotoluene （DNT）. It is the first time that polyoxometalate （POM） is applied in the degradation of explosive wastewater.

Fenton oxidation of 2,4- and 2,6-dinitrotoluene and acetone inhibition

The performances and kinetic parameters of Fenton oxidation of 2,4-and 2,6-dinitrotoluene(DNT)in water-acetone mixtures and explosive contaminated soil washing-out solutions were investigated at a laboratory scale.The experimental results show that acetone can be a significant hydroxyl radical scavenger and result in serious inhibition of Fenton oxidation of 2,4-and 2,6-DNT.Although no serious inhibition was found in contaminated soil washing-out solutions,longer reaction time was needed to remove 2,4-and 2,6-DNT completely,mainly due to the competition of hydroxyl radicals.Fenton oxidation of 2,4-and 2,6-DNT fit well with the first-order kinetics and the presence of acetone also reduced DNT’s degradation kinetics.Based on the comparison and matching of retention time and ultraviolet(UV)spectra between high performance liquid chromatography(HPLC)and standards,the following reaction pathway for 2,4-DNT primary degradation was proposed:2,4-DNT→2,4-dinitro-benzaldehyde→2,4-dinitrobenzoic acid→1,3-dinitrobenzene→3-nitrophenol.

High-gravity intensified iron-carbon micro-electrolysis for degradation of dinitrotoluene

The application of iron–carbon(Fe–C)micro-electrolysis to wastewater treatment is limited by the passivation potential of the Fe–C packing.In order to address this problem,high-gravity intensified Fe–C micro-electrolysis was proposed in this study for degradation of dinitrotoluene wastewater in a rotating packed bed(RPB)using commercial Fe–C particles as the packing.The effects of reaction time,high-gravity factor,liquid flow rate and initial solution pH were investigated.The degradation intermediates were determined by gas chromatography-mass spectrometry,and the possible degradation pathways of nitro compounds by Fe–C micro-electrolysis in RPB were also proposed.It is found that under optimal conditions,the removal rate of nitro compounds reaches 68.4%at 100 min.The removal rate is maintained at approximately 68%after 4 cycles in RPB,but it is decreased substantially from 57.9%to 36.8%in a stirred tank reactor.This is because RPB can increase the specific surface area and the renewal of the liquid–solid interface,and as a result the degradation efficiency of Fe–C micro-electrolysis is improved and the active sites on the Fe–C surface can be regenerated for continuous use.In conclusion,high-gravity intensified Fe–C micro-electrolysis can weaken the passivation of Fe–C particles and extend their service life.