Removal characteristics and kinetic analysis of an aerobic vapor-phase bioreactor for hydrophobic alpha-pinene

Biofiltration is considered an effective method to control volatile organic compounds （VOCs） pollution. This study was conducted to evaluate the potential use of a bacterial biofilter packed with wood chips and peat for the removal of hydrophobic α-pinene. When inoculated with two pure degraders and adapted activated sludge, a removal efficiency （RE） of more than 95% was achieved after a start- up period of 11 days. The maximum elimination capacity （EC） of 50 g/（m^3.hr） with RE of 94% was obtained at empty bed retention time （EBRT） of 102 sec. When higher α-pinene concentrations and shorter EBRTs were applied, the REs and ECs decreased significantly due to mass-transfer and biological reaction limitations. As deduced from the experimental results, approximately 74% of ct-pinene were completely mineralized by the consortiums and the biomass yield was 0.60 g biomass/g α-pinene. Sequence analysis of the selected bands excised from denaturing gradient gel electrophoresis revealed that the inoculated pure cultures could be present during the whole operation, and others were closely related to bacteria being able to degrade hydrocarbons. The kinetic results demonstrated that the whole biofiltration for α-pinene was diffusion-limit controlled owing to its hydrophobic characteristics. These findings indicated that this bacterial biofiltration is a promising technology for the remediation of hydrophobic industrial waste gases containing ct-pinene.

Efficient degradation of chlorobenzene in a non-thermal plasma catalytic reactor supported on CeO_2/HZSM-5 catalysts

Chlorobenzene removal was investigated in a non-thermal plasma reactor using CeO2/HZSM-5catalysts.The performance of catalysts was evaluated in terms of removal and energy efficiency.The decomposition products of chlorobenzene were analyzed.The results show that CeO2/HZSM-5 exhibited a good catalytic activity,which resulted in enhancements of chlorobenzene removal,energy efficiency,and the formation of lower amounts of by-products.With regards to CO2 selectivity,the presence of catalysts favors the oxidation of by-products,leading to a higher CO2 selectivity.With respect to ozone,which is considered as an unavoidable by-product in air plasma reactors,a noticeable decrease in its concentration was observed in the presence of catalysts.Furthermore,the stability of the catalyst was investigated by analyzing the evolution of conversion in time.The experiment results indicated that CeO2/HZSM-5 catalysts have excellent stability：chlorobenzene conversion only decreased from 78%to 60%after 75 hr,which means that the CeO2/HZSM-5 suffered a slight deactivation.Some organic compounds and chlorinated intermediates were adsorbed or deposited on the catalysts surface as shown by the results of Fourier Transform Infrared（FT-IR） spectroscopy,scanning electron microscope（SEM） and energy dispersive X-ray spectroscopy（EDS） analyses of the catalyst before and after the reaction,revealing the cause of catalyst deactivation.