Juhani Kronholm

Pressurized hot water extraction coupled with supercritical water oxidation in remediation of sand and soil containing PAHs

Water is an alternative solvent and reaction medium compatible with green ideology. Extraction with pressurized hot water (PHW) and oxidation with supercritical water (SCW) are techniques that exploit the altered physico-chemical properties of heated and pressurized water for the treatment of solid and liquid wastes. On-line coupled pressurized hot water extraction (PHWE) and supercritical water oxidation (SCWO) equipment was constructed to extract polyaromatic hydrocarbons (PAHs) from sea sand and a real soil sample and to break down the compounds through oxidation with hydrogen peroxide. Overall, the best extraction recoveries were obtained at 300 °C with 20 min extraction time. The compounds with the highest molecular mass were the most difficult to extract. Compared with Soxhlet extraction, PHWE gave better recoveries, especially for the compounds with low molecular mass. The oxidation efficiencies (conversions of the PAHs) increased with oxidant concentration and reaction time. Conversions of compounds other than PAHs were good and total organic carbon was clearly decreased under the optimized conditions. Technically the equipment performed safely and effectively, and the PHWE-SCWO procedure gave good extraction recoveries and oxidation efficiencies.

Environmentally friendly laboratory-scale remediation of PAH-contaminated soil by using pressurized hot water extraction coupled with pressurized hot water oxidation

Water is an alternative solvent and reaction medium to many conventional organic solvents. In pressurized hot water extraction (PHWE) and pressurized hot water oxidation (PHWO) the altered physico-chemical properties of heated and pressurized water are exploited for the treatment of wastes in solid and liquid states. On-line coupled PHWE and PHWO equipment was used to extract polyaromatic hydrocarbons (PAHs) from a soil sample and then to destruct them with potassium persulfate as oxidant. In PHWE experiments, study was made of the effects of flow direction and flow rate in the extraction vessel on the recovery of PAHs. Compared with Soxhlet extraction, PHWE gave better recoveries overall. In PHWE–PHWO, temperature, flow rate (reaction time) and oxidant concentration affected the conversion of the PAHs. It was important that temperature was high enough and reaction time long enough for effective oxidation. These parameters had thus to be chosen carefully for optimal results. Under optimized conditions almost 100% PAH conversions were obtained, and also a clear reduction in total organic carbon content of the effluent was evident. However, some organics remained in the effluent after the procedure, and a considerable amount of sulfate was released in water. Further treatment of the effluent is thus required as a final step.

Pressurised hot water extraction ofn-alkanes and polyaromatic hydrocarbons in soil and sediment from the oil shale industry district in estonia

BackgroundOrganic pollutants formed during thermal treatment of oil shale and then released from the solid waste (semicoke) to aquatic life are a major concern in Estonia. Efficient environmentally friendly techniques are being sought for the analysis of soil and sediments for pollutants and for the clean up of contaminated areas. The altered physico-chemical properties of pressurised hot water can be exploited in the extraction of organics from solid samples. For example, the relative permittivity, hydrogen bonding ability and viscosity of water are decreased and diffusivity is increased with temperature. In addition, water is environmentally friendly, cheap, non-flammable and readily available. In small-scale or pilot-scale operations, pressurised hot water extraction (PHWE) can also be used in the purification of contaminated soil and sediments.ObjectivePHWE and conventional Soxhlet extraction were applied to extract organic compounds from soil and sediment samples collected from various locations around a semi-coke mound in a mining district in northeastern Estonia. One important aim was to compare the extraction efficiencies of the two techniques. Another aim was to determine the pollutants in soil in the vicinity of the semi-coke mound and the sediments of two rivers (the Purtse River flowing to the Gulf of Finland and the Kohtla River feeding into the Purtse) and in canals between the Kohtla River and the semi-coke mound.MethodsThe PHWE equipment was self-constructed and applied with temperatures of 300 and 350°C (P = ca. 200 bar). Soxhlet extraction was carried out for 20 h with dichloromethane as a solvent. All extracts were cleaned up with a silica gel column, concentrated and analysed by gas chromatography-mass spectrometry (GC-MS). Organic matter contents of the samples were determined.Results and DiscussionAlkanes and polyaromatic hydrocarbons (PAHs) were the main compounds found in the GC-MS analysis after.PHWE and Soxhlet extractions. In general, recoveries for short-chainn-alkanes (C10-C16) and PAHs with two benzene rings (i.e. naphthalene, acenaphthylene, acenaphthene and fluorene) were better with PHWE at 350°C than with Soxhlet extraction. These compounds are relatively volatile and may be lost during Soxhlet extraction. For longer chainn-alkanes, recoveries were better with Soxhlet extraction than with PHWE. The longer chain compounds are less polar than the shorter chain compounds and not so easily recovered by PHWE. For PAHs with more than two benzene rings, PHWE at 350°C produced roughly similar recoveries as Soxhlet extraction. PHWE extraction efficiency forn-alkanes was better at 350°C than at 300°C due to the lower polarity and increased diffusivity of water and better thermal desorption of the compounds at higher temperatures. For the same reasons, PHWE was generally more efficient at 350°C than at 300°C for PAHs, especially for the compounds with highest molar masses. Organic matter content was the greatest in the samples with high PAH and alkane concentrations, showing that organic matter is a good sink for hydrophobic micropollutants. The highest concentrations ofn-alkanes (maximum individual alkane concentrations ca. 8 µg/g) and PAHs (maximum individual PAH concentrations ca. 20 µg/g) were found in the soil under the semi-coke mound, showing that the compounds were flushed down with water. Almost concentrations ofn-alkanes and PAHs as high as under the mound were found within the mound and in sediment from the canal ca. 10 m from the mound. Sediment from the Kohtla River where it meets the Purtse River, ca. 14 km from the semi-coke mound, was also contaminated with the compounds. Only somen-alkanes were found at the mouth of the Purtse River indicating that the major part of the pollutants were accumulated in the sediments of the Kohtla River.ConclusionsThe PHWE equipment was reliable and safe to use. PHWE produced better recoveries for short-chain alkanes (C10-C16) and PAHs with two benzene rings than did Soxhlet extraction, but it was less efficient than Soxhlet for larger compounds. The two extraction methods together thus provide a good tool for extractingn-alkanes and PAHs. PAH and alkane concentrations were the most abundant in the samples with high organic matter content. The samples collected near the semi-coke mound and in the Kohtla River were contaminated withn-alkanes and PAHs, but only somen-alkanes were found in the Purtse River, showing that the heaviest contamination of soil and sediments was localised relatively close to the semi-coke mound.Recommendations and OutlookWith PHWE, the hazardous organic solvents used in extraction processes can be replaced with water. Increasing the volume of the extraction vessel and applying a more efficient heating system and higher flow rate would enable the use of PHWE on a pilot-scale in the remediation of contaminated soil and sediments. With the present equipment, the PHWE-treated samples can also be oxidised directly on-line under supercritical conditions by feeding oxidant to the reactor situated after the extraction vessel. Organics can be completely destroyed with water and carbon monoxide, the main reaction products.

Oxidation of 4-chloro-3-methylphenol in pressurized hot water in liquid and vapor phases

Abstract 4-Chloro-3-methylphenol (c=2.0 mM), representing a model pollutant, was oxidized both in liquid and vapor phases. The oxidant (hydrogen peroxide) was used in an amount equivalent to 10 times that of the model pollutant. Space times were 10–60 s; temperatures, 250–390°C; and pressures 228–311 bar (liquid and supercritical states), or 4–13 bar (vapor phase). The effect of preheating the capillaries delivering the organic matter and oxidant was studied. Excellent oxidation results for 4-chloro-3-methylphenol were obtained in both the vapor and liquid phases, but there was less corrosion (nickel and chromium concentrations in the effluent) in the vapor phase. Better oxidation efficiencies were obtained at lower temperatures and shorter space times, and the formation of reaction products was lower with non-preheated capillaries, i.e. when hydrogen peroxide was not decomposed before entering the reaction zone.

Chromatographic lipid profiling of stress‐exposed cells

Lipidomics is an emerging field of science not only due to its integral part of cell biology and biophysics but also due to the key role of lipids in the modulation of membrane physical properties, signaling, and cell death regulation. The aim of this study was to characterize changes in N-palmitoyl ceramide concentration and in the global lipid profile in macrophages challenged by oxidized low-density lipoprotein and nutrient deprived hepatocytes. For this purpose, a quantitative targeted method based on gas chromatography-mass spectrometry for the determination of total N-palmitoyl ceramide concentrations in the cellular membranes of cells under stress was used. Ultrahigh-performance liquid chromatography-quadrupole-time of flight mass spectrometry was applied for the comprehensive profiling of lipids. In essence, we found that both models of cellular stress caused an increase in N-palmitoyl ceramide levels. In addition, increased levels of other ceramides were observed as well as up- and down-regulation of several other lipid species.