RESUMEN
Large amount of volatile organic compounds (VOCs) are emitted from industrial, mobile, and domestic sources, causing adverse effects on human health and environment. Among VOCs, toluene and isopropanol (IPA) are commonly used as solvent, soldering flux, and spray paint and their emissions need to be reduced. Several VOCs abatement technologies are available to reduce VOC emission and photocatalytic oxidation of VOC is regarded as a viable technique due to its advantage of utilizing solar energy. TiO2 has been investigated for its oxidation capability toward VOCs because of its good photocatalytic activity. However the utilization is limited to UV due to its wider bandgap; furthermore, its fast recombination rate of electron-hole pair reduces the oxidation rate of VOCs. Black-TiO2 and perovskite-type photocatalyst such as LaFeO3 can be applied to enhance photocatalytic activity due to narrower bandgap and longer electron-hole pair lifetime. In this study, black-TiO2 and LaFeO3 are prepared and investigated for their photocatalytic oxidation rates toward toluene and IPA. Results show that toluene removals achieved with black-TiO2 and LaFeO3 are 89% and 98% while IPA removals are 90% and 94%, respectively. Both photocatalysts show better photocatalytic activity than TiO2 and good absorption capability toward visible light. Graphical abstract.
Asunto(s)
2-Propanol/química , Contaminantes Atmosféricos/química , Compuestos de Calcio/química , Óxidos/química , Titanio/química , Tolueno/química , 2-Propanol/aislamiento & purificación , Contaminantes Atmosféricos/aislamiento & purificación , Catálisis , Restauración y Remediación Ambiental , Luz , Oxidación-Reducción , Procesos Fotoquímicos , Tolueno/aislamiento & purificaciónRESUMEN
A pilot-scale anaerobic membrane bioreactor (AnMBR) was operated for 435â¯days in this study, aiming to treat pharmaceutical solvent wastewater containing m-Cresol (MC), isopropanol (IPA) and N,N-Dimethylformamide (DMF) pollutants at different temperatures of 35⯱â¯3⯰C, 25⯱â¯3⯰C, 15⯱â¯3⯰C and 25⯱â¯3⯰C, respectively. The reactor reached average total removal efficiencies of about 96%, 97.2% and 98% of MC, IPA and DMF at psychrophilic condition (15⯱â¯3⯰C). Higher physical removal rate was obtained at 15⯱â¯3⯰C due to the important contribution of membrane filtration. At this stage, the biogas production, methane content and specific methanogenic activity and extracellular polymeric substances of suspended sludge were observed with the lowest level. Moreover, the kinetic models for solvent degradation were established at different temperatures, results showed the smaller maximum specific substrate degradation rate of MC and IPA, besides, the lowest degradation rate of three solvents were obtained at 15⯱â¯3⯰C.
Asunto(s)
Reactores Biológicos , Aguas Residuales , Anaerobiosis , Metano , Aguas del Alcantarillado , Solventes , Eliminación de Residuos LíquidosRESUMEN
The biodegradation of high concentration isopropanol (2-propanol, IPA) at 16 g/L was investigated by a solvent-tolerant strain of bacteria identified as Paracoccus denitrificans for the first time by 16S rDNA gene sequencing. The strain P. denitrificans GH3 was able to utilize the high concentration of IPA as the sole carbon source within a minimal salts medium with a cell density of 1.5×10(8) cells/mL. The optimal conditions were found as follows: initial pH 7.0, incubation temperature 30°C, with IPA concentration 8 g/L. Under the optimal conditions, strain GH3 utilized 90.3% of IPA in 7 days. Acetone, the major intermediate of aerobic IPA biodegradation, was also monitored as an indicator of microbial IPA utilization. Both IPA and acetone were completely removed from the medium following 216 hr and 240 hr, respectively. The growth of strain GH3 on IPA as a sole carbon and energy source was well described by the Andrews model with a maximum growth rate (µmax)=0.0277/hr, a saturation constant (KS)=0.7333 g/L, and an inhibition concentration (Ki)=8.9887 g/L. Paracoccus denitrificans GH3 is considered to be well used in degrading IPA in wastewater.