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Pyrolysis of waste materials to produce biochar is an excellent and suitable alternative supporting a circular bio-based economy. One of the properties attributed to biochar is the capacity for sorbing organic contaminants, which is determined by its composition and physicochemical characteristics. In this study, the capacity of waste-derived biochar to retain volatile fuel organic compounds (benzene, toluene, ethylbenzene and xylene (BTEX) and fuel oxygenates (FO)) from artificially contaminated water was assessed using batch-based sorption experiments. Additionally, the sorption isotherms were established. The results showed significant differences between BTEX and FO sorption on biochar, being the most hydrophobic and non-polar contaminants those showing the highest retention. Furthermore, the sorption process reflected a multilayer behaviour and a relatively high sorption capacity of the biochar materials. Langmuir and Freundlich models were adequate to describe the experimental results and to detect general differences in the sorption behaviour of volatile fuel organic compounds. It was also observed that the feedstock material and biochar pyrolysis conditions had a significant influence in the sorption process. The highest sorption capacity was found in biochars produced at high temperature (> 400 °C) and thus rich in aromatic C, such as eucalyptus and corn cob biochars. Overall, waste-derived biochar offers a viable alternative to be used in the remediation of volatile fuel organic compounds from water due to its high sorption capacity. [ABSTRACT FROM AUTHOR]

An accurate and sensitive analytical method for the determination of diesel-range organics (DRO) is the basis to monitoring and soil remediation studies. In the present work, the determination of DRO in different water and soil samples was optimized. Solvent extraction procedures, i.e. ultrasonic assisted extraction (USAE) (for water samples) and accelerated solvent extraction (ASE) (for soil samples), and a solvent-free procedure, headspace solid phase microextraction (HS-SPME), were optimized to achieve the highest recoveries for the simultaneous determination of all DRO. One hour of USAE for water samples and ASE of soil samples at 100°C, 2000 psi and two extraction cycles lead to analytical recoveries of 70‒100%. Using HS-SPME, 30 min of incubation at 90°C were sufficient to achieve analytical recoveries up to 90% for water and soil samples. HS-SPME enables higher preconcentration factors, which makes this method more appropriate for samples with trace DRO concentrations. [ABSTRACT FROM AUTHOR]

Soil and groundwater contamination around a fuel distribution station in Tomiño (NW Spain) was evaluated. For this purpose, top and subsoil (up to 6.4 m) and groundwater were sampled around the station, approximately in a 60-m radius. Samples were analysed by HS-SPME-GC-MS to identify and quantify volatile fuel organic compounds (VFOC) (MTBE, ETBE and BTEX) and diesel range organics (DRO). Analysis and fingerprinting data suggested that the contamination of soil and groundwater was provoked by a fuel leak from underground storage tanks. This was reflected by hydrocarbon indices and principal component analysis, which discriminated a direct source of contamination of the subsoil samples around the station. The contaminants probably migrated from tank nearby soils to surrounding soils and leached to groundwater, following a SW direction. Irrigation with contaminated groundwater provoked a severe contamination of topsoils, which were enriched with the lightest components of gasoline and diesel. Fingerprinting also revealed the continuity of the leak, reflected by the presence of volatiles in some samples, which principally appeared in fresh leaks. MTBE was detected in a very high concentration in groundwater samples (up to 690 μg L−1), but it was not detected in fresh gasoline. This also evidenced an old source of contamination, probably starting in the mid-1990s, when the use of MTBE in gasoline was regulated. [ABSTRACT FROM AUTHOR]