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Microwave (MW) is applied to enhance pentachlorophenol (PCP) removal using zerovalent iron (ZVI, Fe 0 ) or granular activated carbon (GAC) as the dielectric media. Applying MW energy at 700 W for 20 s, the results show that Fe 0 is capable of enhancing the CB removing 2.7 times (91% vs. 34 %) than GAC. Because Fe 0 has higher dielectric loss (39.5 F/m vs. 8.3 F/m), it absorbs more MW energy to speed up the oxidation rate resulting in a faster temperature rise than GAC. Thus, in the presence of MW, Fe 0 is superior to GAC for PCP removal. Additionally, excessive MW exposure will damage the surface structure of either Fe 0 or GAC causing excessive electric charges to accumulate in the media that brings about the phenomenon of sparks.

Organic compounds such as chlorobenzene cannot be effectively decomposed with currently available biological and chemical treatment methods. Preliminary studies show that nano-scale zero-valent iron particles irradiated by microwave is effective in decomposing chemically refractive organic compounds such as chlorobenzene. In this study, microwave is applied to enhance chlorobenzene removal using micron-scale iron particles and nano-scale zero-valent iron particles suspended in the chlorobenzene solution as the dielectric media. The results show that better chlorobenzene removal can be achieved when the chlorobenzene solution is irradiated with 250 W microwave for 150 s than without microwave irradiation. The microwave radiation increases iron reaction rate and surface activity, thus enhancing the chlorobenzene removal. The microwave-induced iron particles cause the chlorobenzene activation energy to drop 34.0% for micronscale iron and 16.1% for nano-scale zero-valent iron. They can remove 13.6 times more chlorobenzene for micro iron, and 3.6 times more chlorobenzene for nano iron. We have demonstrated that the microwave-induced nano-scale iron particles are effective in treating toxic organic substances as demonstrated in this laboratory study.

Reducing the input excess air or airflow rate to a furnace or boiler will result in decreasing transmission rate of the thermal flow from the radiation zone to the convection heating surface zone in the furnace. Results of the plant‐scale test presented in this article show that if the furnace is operated at 3.6 × 107 kcal/h of combustion capacity, decreasing the residual O2 concentration in the furnace flue gas from 4% to 2.5% will save 9.3 × 103 m3 of natural gas consumption, and 2.1 × 104 tons of CO2 emission annually. For the boiler tested in the study, 1.8 × 105 m3 of natural gas consumption and 3.9 × 105 tons of CO2 emission will be reduced annually if it is operated with 90 ton/h steam yield. Hence, controlling the input excess air (or oxygen) as an important operating alternative to enhance thermal efficiency, and alleviate environmental impact of a heater furnace and boiler has been confirmed in this research. © 2011 American Institute of Chemical Engineers Environ Prog, 2012