Ab initio and density functional theory calculations have been carried out to investigate the reaction of hydroxyl radical （OH） and 1,1,1-trichloroethane （CH3CCl3）. The potential energy surface has been given acco...Ab initio and density functional theory calculations have been carried out to investigate the reaction of hydroxyl radical （OH） and 1,1,1-trichloroethane （CH3CCl3）. The potential energy surface has been given according to the relative energies calculated at the MP2/cc-pVTZ level after the spin projection （PMP2）. Five reaction channels were identified and the intramolecular hydrogen bonding was observed in some transition state structures. The barrier heights and reaction enthalpies calculated for all possible channels show that the hydrogen abstraction channel is predominant kinetically and thermodynamically. The contribution from other channels was predicted to be minor.展开更多
The conventional “pump-and-treat' technology for subsurface remediation of groundwater contaminated with volatile organic compounds(VOCs) such as 1,1,1-trichloroethane(TCA), a common chlorinated organic solvent, ...The conventional “pump-and-treat' technology for subsurface remediation of groundwater contaminated with volatile organic compounds(VOCs) such as 1,1,1-trichloroethane(TCA), a common chlorinated organic solvent, has limitation of prohibitively long treatment time due to extremely low water solubility of the VOCs. Surfactant-based soil remediation has emerged as the effective technology that substantially reduces the treatment time. In order to make the whole process economical, the surfactant used in soil washing has to be recovered and reused. This study examined the recovery of anionic surfactant, sodium dodecyl sulfate(SDS), from soil remediation fluids containing TCA, using a bench-scale membrane pervaporation unit. The effects of high TCA concentration, surfactant dosage, and flow rate on permeation flux and selectivity(α value) of the process were evaluated. In general, higher surfactant concentration yielded lower TCA flux and constant water flux, resulting in declining α values; higher flow rate of TCA feed stream results in higher VOC flux and selectivity, an indication of the effect of concentration polarization; higher TCA feed concentration produces higher TCA permeation across the membrane, however, the selectivity was virtually unchanged unless the total TCA concentration exceeded 2000 ppm.展开更多
trichloroethane(TCA), a common chlorinated organic solvent and volatile organic compound(VOC), was removed from contaminated groundwater by using a bench-scale membrane pervaporation unit. The effects of TCA concentra...trichloroethane(TCA), a common chlorinated organic solvent and volatile organic compound(VOC), was removed from contaminated groundwater by using a bench-scale membrane pervaporation unit. The effects of TCA concentration, temperature, and flow rate on permeation flux and selectivity(α value) of the process were evaluated. In general, higher temperature leads to higher VOC flux but lower selectivity; higher flow rate of TCA feed stream results in higher VOC flux and selectivity, an indication of the effect of concentration polarization; higher TCA feed concentration produces higher TCA permeation, however, the selectivity was virtually unchanged.展开更多
基金supported by the National Natural Science Foundation of China (No. 20573029)the Natural Science Foundation of Heilongjiang Province (No. B200905)
文摘Ab initio and density functional theory calculations have been carried out to investigate the reaction of hydroxyl radical （OH） and 1,1,1-trichloroethane （CH3CCl3）. The potential energy surface has been given according to the relative energies calculated at the MP2/cc-pVTZ level after the spin projection （PMP2）. Five reaction channels were identified and the intramolecular hydrogen bonding was observed in some transition state structures. The barrier heights and reaction enthalpies calculated for all possible channels show that the hydrogen abstraction channel is predominant kinetically and thermodynamically. The contribution from other channels was predicted to be minor.
文摘The conventional “pump-and-treat' technology for subsurface remediation of groundwater contaminated with volatile organic compounds(VOCs) such as 1,1,1-trichloroethane(TCA), a common chlorinated organic solvent, has limitation of prohibitively long treatment time due to extremely low water solubility of the VOCs. Surfactant-based soil remediation has emerged as the effective technology that substantially reduces the treatment time. In order to make the whole process economical, the surfactant used in soil washing has to be recovered and reused. This study examined the recovery of anionic surfactant, sodium dodecyl sulfate(SDS), from soil remediation fluids containing TCA, using a bench-scale membrane pervaporation unit. The effects of high TCA concentration, surfactant dosage, and flow rate on permeation flux and selectivity(α value) of the process were evaluated. In general, higher surfactant concentration yielded lower TCA flux and constant water flux, resulting in declining α values; higher flow rate of TCA feed stream results in higher VOC flux and selectivity, an indication of the effect of concentration polarization; higher TCA feed concentration produces higher TCA permeation across the membrane, however, the selectivity was virtually unchanged unless the total TCA concentration exceeded 2000 ppm.
文摘trichloroethane(TCA), a common chlorinated organic solvent and volatile organic compound(VOC), was removed from contaminated groundwater by using a bench-scale membrane pervaporation unit. The effects of TCA concentration, temperature, and flow rate on permeation flux and selectivity(α value) of the process were evaluated. In general, higher temperature leads to higher VOC flux but lower selectivity; higher flow rate of TCA feed stream results in higher VOC flux and selectivity, an indication of the effect of concentration polarization; higher TCA feed concentration produces higher TCA permeation, however, the selectivity was virtually unchanged.
