OIL SPILL CLEANUP BY HYDROPHOBIC SILICA AEROGELS AND SPILLED OIL INTERACTION WITH SUSPENDED SEDIMENTS

Date

2016-08-15

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Abstract

Silica aerogel is a promising adsorbent for oil spill cleanup. To make it an economic and environmentally-friendly adsorbent, the effectiveness of thermal regeneration of silica aerogels is investigated in this study. After hydrocarbon desorption at 80 °C, the adsorption capacities of regenerated silica aerogels decrease from 12.4 ± 0.6, 11.2 ± 0.6, and 13.6 ± 0.5 g/g to 12.3 ± 0.5, 6.5 ± 0.2, and 2.3 ± 0.3 g/g for toluene, petrol, and diesel, respectively. Pore sizes decrease after all hydrocarbon desorption, which causes the adsorption capacities of regenerated silica aerogels to decrease. In addition, incomplete desorption of diesel and its oxidation further decrease the adsorption capacity of regenerated silica aerogels. To improve the diesel desorption, desorption experiments were conducted at 200 °C. Under aerobic condition, severe diesel oxidation takes place during its desorption, which destroys the mesopores of silica aerogels. Therefore, the adsorption capacity of regenerated silica aerogels for diesel decreases to 1.4 ± 0.2 g/g, while under anaerobic condition, no diesel oxidation occurs during its desorption. The pore size (13.2 ± 1.5 nm) and adsorption efficiency (10.0 ± 0.3 g/g) of regenerated silica aerogels only decrease slightly. This study provides new insights on the physico-chemical changes of silica aerogels during its regeneration. Also, a novel regeneration approach under anaerobic condition is developed for practical applications. The spilled oil potentially can be mixed in water bodies with either fresh or saline water condition. Researches were extended to carry out laboratory measurements of settling velocities of sediments, flocs, and Oil-Sediment Aggregations (OSAs). Kaolin was used as the sedimentation source and two different hydrocarbons, diesel and motor oil, were selected as spilled oil. The experimental results indicate that the salinity is an important factor for the aggregation of flocs and OSAs. Meanwhile, the higher sediment concentration would result in higher settling velocities for sediments, flocs, and OSAs. Much higher shear strain rate tends to strength aggregation of OSAs, and as a result increases the settling velocity. It is also noted that the viscosity of the hydrocarbon liquid does not seem to have a significant effect on the settling velocity of the formed OSAs.

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Keywords

Silica aerogels, Oil spill, Settling velocity, Oil-Sediment Aggregations

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