ABSTRACT

The extensive use of diesel as fuel has contributed to the current problem of soil contamination, and the aged diesel is a highly toxic pollutant for the soil microbial flora. The objective of the present work was to determine the ability of mono-rhamnolipid surfactants to solubilize weathered diesel absorbed for decades in a loamy sand soil. The mono-rhamnolipids were produced by P. aeruginosa ATCC 9027, using glycerol as the carbon source. The mono-rhamnolipid characterization revealed that 90% of congeners contained saturated fatty acids of short chains. At its CMC (70.3 mg/L), the mixture of mono-rhamnolipids decreased the surface tension of deionized water (30.3 mNm⁻¹) and emulsified complex mixtures of petroleum hydrocarbons (73%). A 0.5% mono-rhamnolipid solution allowed solubilizing the following hydrocarbon fractions identified in the weathered diesel: aliphatics (66 ± 3%), polycyclic aromatic hydrocarbons (PAHs) (23.16 ± 11%), and asphaltenes (41.4 ± 6%). Within the group of PAHs, four PAHs derivatives, well known to be highly carcinogenic and mutagenic to humans, were identified: neutral, methylated, nitrated, and oxydated. The PAHs and the first three derivatives were removed in an average of 20%. However, regarding the oxy-PAHs, the increment of their concentration allowed assuming the biodegradation of the PAHs during the desorption process. Results show that hydrocarbon desorption with mono-rhamnolipid solutions of high content of saturated fatty acids offers an effective and viable alternative for soil bioremediation because of the low concentration of surfactants required (0.2–0.5%), the short treatment times (≈72 h) and above all, because mono-rhamnolipids are biodegradable compounds friendly to the environment.

抽象的

广泛地使用柴油作为燃料已导致当前的土壤污染问题，并且老化的柴油是对土壤微生物群的高毒性污染物。本工作的目的是确定单鼠李糖脂表面活性剂溶解在肥沃的沙土中数十年来吸收的风化柴油的能力。铜绿假单胞菌ATCC 9027使用甘油作为碳源生产单鼠李糖脂。单鼠李糖脂的特征表明，90％的同类物含有短链的饱和脂肪酸。在鼠李糖脂的CMC（70.3 mg / L）下，单鼠李糖脂混合物降低了去离子水的表面张力（30.3 mNmm ^-1）和石油烃的乳化复杂混合物（73％）。0.5％的单鼠李糖脂溶液可溶解风化柴油中确定的以下烃馏分：脂族化合物（66±3％），多环芳烃（PAHs）（23.16±11％）和沥青质（41.4±6％）。在多环芳烃类中，鉴定了四种对人体高度致癌和致突变的多环芳烃衍生物：中性，甲基化，硝化和氧化。PAH和前三个衍生物的平均去除率为20％。然而，对于氧基-PAH，假定其在解吸过程中生物降解，则其浓度的增加是允许的。