钙、钠饱和处理的次生硅酸盐矿物对多环芳烃(菲)吸附与光解行为

Adsorption and photodegradation of phenanthrene on different cation-saturated secondary minerals under UV light

分别对高岭石、蒙脱石和实验室合成水钠锰矿进行金属离子(Na^+和Ca^(2+))饱和处理,比较三种矿物及其金属离子饱和处理矿物对多环芳烃的吸附能力。以发射波长为254nm的氙灯为光源,在上述矿物表面分别进行菲光化学降解实验,探讨不同矿物及其金属离子饱和处理矿物对菲光化学降解能力的区别。比较多环芳烃光化学降解后不同矿物表面的傅里叶变换红外光谱,分析不同矿物表面官能团的变化。利用气相色谱-质谱联用仪分析矿物表面多环芳烃光化学降解中间产物,并推测其降解途径。结果表明金属离子饱和处理的高岭石、蒙脱石、水钠锰矿对多环芳烃(菲)吸附能力均比其未加离子矿物的吸附能力强,但光化学降解速率则相反;降解过程分别会产生酯类、羧酸类、醇类、烷烃类等物质,且随着光解时间的延长最后可能彻底被矿化为水和二氧化碳等小分子物质。

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-Ca^2＋〉 minerals alone; while for kaolinite the order was kaolinite-Ca^2＋〉 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-Ca^2＋〉kaolinite-Ca^2＋ 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.