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| Adsorption and photodegradation of phenanthrene on different cation-saturated secondary minerals under UV light |
| Received:September 29, 2015 |
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| KeyWord:kaolinite;smectite;birnessite(δ-MnO2);cation-saturated minerals;PAHs;adsorption;photodegradation |
| Author Name | Affiliation | E-mail | | SHEN Lian-yu | College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China | | | QIAN Li-hui | College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China | | | DAI Jing-yu | College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China | daijy@njau.edu.cn | | LI Jia-yu | College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China | | | ZHOU Qiang | College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China | |
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| Abstract: |
| Polycyclic aromatic hydrocarbons(PAHs) are important organic pollutants in the environment. Soil minerals are critical to their transportation and degradation. In the present study, adsorption and photodegradation of phenanthrene on different clay minerals including kaolinite, smectite, and birnessite were investigated. Both bare minerals and those saturated with Ca and Na cations were used. The surface properties of clay minerals before and after 48 h photodegradation were further characterized by Fourier Transform Infrared Spectrometer(FTIR). Photodegradation intermediates were analyzed by using a gas chromatography coupled with mass spectrometer(GC-MS). The transformation pathways and photolysis mechanisms were then proposed. Results indicated that cation-saturated clay minerals had higher adsorption capacity for phenanthrene than the corresponding original minerals. However, phenanthrene was less prone to be photodegraded on cation-saturated minerals. For smectite and birnessite(δ-MnO2), the adsorption capacity followed an order of mineral-Na+> mineral-Ca2+> minerals alone; while for kaolinite the order was kaolinite-Ca2+> kaolinite-Na+> kaolinite. Original 2:1 aluminosilicate smectite had higher adsorption ability than original 1:1 aluminosilicate kaolinite. However, adsorption ability was kaolinite-Na+>smectite-Na+, and smectite-Ca2+>kaolinite-Ca2+ after saturation with cations. Moreover, kaolinite showed the highest photodegradati on potential for phenanthrene among cation-saturated minerals, followed by birnessite and smectite. However, increased aromaticity on mineral surface was found after UV irradiation. The main intermediate products of phenanthrene photodegradation were esters,carboxylic acids,alcohols,alkanols,alkane et al. All the intermediate organic compounds could be mineralized ultimately. |
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