Application of Nano-TiO2 /LDPE composite film on photocatalytic oxidation degradation of dichloromethane.

This study focused on the photocatalytic destruction of dichloromethane (DCM) in indoor air using the nano-TiO2 /LDPE composite film as an economical photocatalyst. The nano-TiO2 was dispersed in a polyethylene matrix to form composite film. The photocatalytic activity of the nano-TiO2/LDPE composite films was evaluated through the degradation of dichloromethane (DCM) under UV-C irradiance at specific wavelength of 254 nm. The percentage of nano-TiO2 contents varied from 0, 5, and 10% (wt cat./wt LDPE composite film). The results derived from the kinetic model revealed that the photocatalytic rates of 5 and 10 wt.% nano-TiO2/LDPE composite films follow the first order reaction while the rate of the film without TiO2 followed the zero order reaction. At low concentration of DCM, the rate of photocatalytic degradation of the DCM was slower than that at high DCM concentration. The 10 wt.% of TiO2 content of the nano-TiO2/LDPE composite film yielded the highest degradation efficiency of 78%, followed by the removal efficiency of 55% for the 5 wt.% of TiO2 content of the nano-TiO2/LDPE composite film. In contrast with the composite film containing nano-TiO2, the LDPE film without adding nano-TiO2 expressed the degradation efficiency of 28%.

Kinetic comparison of microbial assemblages for the anaerobic treatment of wastewater with high sulfate and heavy metal contents.

Mixed-microbial assemblages enriched from a septic tank, coastal sediment samples, the digester sludge of a brewery wastewater treatment plant and acidic sulfate soil samples were compared on the basis of growth rate, waste and sulfate reduction rate under sulfate reducing conditions at 30oC. The specific growth rate of various cultures was in the range 0.0013-0.0022 hr-1. Estimates of waste and sulfate reduction rate were obtained by fitting substrate depletion and sulfate reduction data with the Michaelis-Menten equation. The waste reduction rates were in the range 4x10-8-1x10-7 l mg-1hr-1 and generally increased in the presence of copper, likely by copper sulfide precipitation that reduced sulfide and copper toxicity and thus protected the anaerobic microbes. Anaerobic microorganisms from a brewery digester sludge were found to be the most appropriate culture for the treatment of wastewater with high sulfate and heavy metal content due to their growth rate, and waste and sulfate reduction rate.