Reaction behaviors and kinetics of catalytic oxidation of benzene, toluene, and ethyl acetate with feed concentrations in the range of 700-5,000 ppm over Pd/ZSM-5 catalyst were investigated. Results for single components show that ethyl acetate (T ₅₀ = 190-200°C) is more easily oxidized than benzene (T ₅₀ = 215-225°C) and toluene (T ₅₀ = 225-235°C). The conversion of ethyl acetate was increased with the increase of its feeding concentration, while the opposite behaviors were observed for benzene and toluene as their conversion rates were decreased with the increase of the inlet concentration. Different behaviors were observed in catalytic oxidation of volatile organic compound (VOC) multi-components, the presence of benzene or toluene inhibits the conversion of ethyl acetate, and the aromatic hydrocarbons inhibit each other in all cases. Ethyl acetate possesses obvious inhibitory effect on benzene oxidation, while it is interesting to note that ethyl acetate has a promotion effect on toluene conversion. The kinetic data were fitted by the Power-law and Mars-van Krevelen kinetic models. The fitting result shows that the Power-law model is more suitable for predicting the conversion of benzene than the other VOCs, and the Mars-van Krevelen model can accurately express the reaction rate of all investigated VOCs.

The impact of autochthonous anaerobic bacteria on the release of metals in river sediment was studied. The sediments were characterized and bacterial activity was monitored in a batch reactor, where the sediments were incubated with a synthetic substrate solution containing glucose as carbon source. The results showed that metal release was correlated to the bacterial growth (carbon mineralization). In particular, a relationship between iron reduction and metal release was observed indicating that iron-reducing bacteria had a strong influence. By reductive dissolution of iron oxides, bacteria also released their associated toxic elements into the liquid phase. While organic analysis showed acetate and butyrate production leading to a decrease in pH and indicating a Clostridium fermentative bacteria activity, the results did not indicate any direct role of organic acids in the dissolution of iron and their associated metals.

Introduction The pyrolytic method was employed to recycle metals and brominated compounds blended into printed circuit boards (PCBs). Methods PCBs were crushed into pieces 4.0-4.8 mm in size, and the crushed pieces were pyrolyzed at temperatures ranging from 200 to 500°C. The compositions of pyrolytic residues, liquid products, and exhaust were analyzed by inductively coupled plasma atomic emission spectrometer, inductively coupled plasma mass spectrometry, and gas chromatography-mass spectrometry. Pyrolytic exhaust was collected by an impinger system in an ice bath cooler to analyze the composition fraction of the liquid product, and uncondensable exhaust was collected for gas constituent analysis. Results Phenol, methyl-phenol, and bromo-phenol were attributed mainly to the liquid product. Metal content was low in the liquid product. In addition, CO, CO₂, CH₄, and H₂ were the major components of pyrolytic exhaust. Conclusions Brominated and chlorinated compounds—i.e., dichloromethane, trans-1,2 dichloroethylene, cis-1,2 dichloroethylene, 1,1,1-trichloroethane, tetrachloromethane, bromophenol, and bromoform—could be high, up to the several parts per million (ppm) level. Low molecular weight volatile organic compounds (VOCs)—i.e., methanol, acetone, ethyl acetate, acrylonitrile, 1-butene, propene, propane, and n-butane—contributed a large fraction of VOCs. The concentrations of toluene, benzene, xylene, ethylbenzene, and styrene were in the ppm range.