Browsing by Author "Wu, Guozhong"

Now showing 1 - 8 of 8
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    Combining solvent extraction and bioremediation for removing weathered petroleum from contaminated soil
    (Elsevier Science B.V. Amsterdam, 2013-08-31T00:00:00Z) Wu, Guozhong; Coulon, Frederic; Yang, Yuewei; Li, Hong; Sui, Hong
    This study aimed to remediate a highly contaminated soil with weathered petroleum using an integrated technology combining solvent extraction and biodegradation. Soils were washed using a composite organic solvent consisted of hexane and pentane (4:1 v/v) and then bioremediated in microcosms which were bioaugmentated with Bacillus subtilis FQ06 strains and/or rhamnolipid. The optimal solvent extraction conditions were determined as extraction for 20 min at 25 °C with solvent-soil ratio of 6:1 (v/w). On this basis, total petroleum hydrocarbon was decreased from 140,000 to 14,000 mg kg-1, which was further reduced to < 4000 mg kg-1 by subsequent bioremediation for 132 days. Sustainability assessment of this integrated technology showed its good performance for both short- and long-term effectiveness. Overall results encouraged its application for remediating contaminated sites especially with high concentration weathered hydrocarbons.
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    Correlating asphaltene dimerization with its molecular structure by potential of mean force calculation and data mining
    (American Chemical Society, 2018-04-11) Zhu, Xinzhe; Wu, Guozhong; Coulon, Frederic; Wu, Lvwen; Chen, Daoyi
    Asphaltene aggregation affects the entire production chain of the petrochemical industry, which also poses environmental challenges for oil pollution remediation. The aggregation process has been investigated for decades, but it remains unclear how the free energy of asphaltene association in solvents is correlated to its molecular structure. In this study, dimerization energies of 28 types of asphaltenes in water and toluene were calculated using the umbrella sampling method. Structural parameters related to the atom types and functional groups were screened to identify the factors most influencing the dimerization energy using multiple linear regression, multilayer perceptron, and support vector regression. Results demonstrated that the influence of molecular structure on asphaltene association in water was nonlinear, while attempts to capture the relationship using linear regression had larger error. The linkage per aromatic ring, number of aromatic carbons, and number of aliphatic chains were the top three factors accounting for 52% of the dimerization energy variation in water. Asphaltene dimerization in toluene was dominated by the content of sulfur in aromatic rings and the number of aromatic carbons which contributed to 55% of the energy variation. To the best of our knowledge, this was the first study successfully predicting asphaltene dimerization using molecular structure (R > 0.9) and quantifying simultaneously the relative importance of each structural parameter. The proposed modeling approach supported the decision making on the number of structural parameters to investigate for predicting asphaltene aggregation.
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    Influence and interactions of multi-factors on the bioavailability of PAHs in compost amended contaminated soils
    (Elsevier, 2014-04-12) Wu, Guozhong; Li, Xingang; Kechavarzi, Cédric; Sakrabani, Ruben; Sui, Hong; Coulon, Frederic
    Compost amendment to contaminated soils is a potential approach for waste recycling and soil remediation. The relative importance and interactions of multiple factors on PAH bioavailability in soils were investigated using conjoint analysis and five-way analysis of variance. Results indicated that soil type and contact time were the two most significant factors influencing the PAH bioavailability in amended soils. The other two factors (compost type and ratio of compost addition) were less important but their interactions with other factors were significant. Specifically the 4-factor interactions showed that compost addition stimulated the degradation of high molecular PAHs at the initial stage (3 month) by enhancing the competitive sorption within PAH groups. Such findings suggest that a realistic decision-making towards hydrocarbon bioavailability assessment should consider interactions among various factors. Further to this, this study demonstrated that compost amendment can enhance the removal of recalcitrant hydrocarbons such as PAHs in contaminated soils.
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    Influence of pipeline steel surface on the thermal stability of methane hydrate
    (Elsevier, 2022-10-19) Wu, Guozhong; Tian, Linqing; Ha, Li; Feng, Feng; Yang, Zhifeng; Feng, Jing-Chun; Coulon, Frederic; Jiang, Yuelu; Zhang, Ruifeng
    The thermal stability and surface adhesion of natural gas hydrate are critical for the safety of oil and gas pipelines. The roughness and hydrophobicity of the pipe surface often vary during long-distance transportation, but it remains unclear about how these variances influence the hydrate stability. In this study, twelve molecular models of solid steel pipeline surfaces with random morphology were evaluated and molecular dynamics simulations were performed to gain insights into the kinetics of methane hydrate dissociation, the nucleation and growth of gas bubbles during hydrate decomposition, and the free energy of hydrate adhesion to the solid steel surface. Results demonstrated that the stability of methane hydrate could be decreased by up to 85% by increasing the hydrophobicity of the pipe surface by 52%. The bubble nucleation site of the gas released from hydrate decomposition shifted from bulk water to the solid surface by increasing the surface hydrophobicity (εsw: 3.73–5.74 kJ mol−1), but a highly hydrophobic surface (εsw: 2.73 kJ mol−1) made it hard to form gas bubble on either smooth or rough surface. Moreover, the free energy of hydrate adhesion also depended on the roughness and hydrophobicity of the solid surface, while the largest energy barrier for the adhesion of methane hydrate was found on the hydrophobic surface with high roughness. The findings from this study provided theoretical support for better understanding the methane hydrate evolution principles when the surface properties of the pipe wall changed from naturally occurred events (e.g., metal corrosion) or artificial treatment (e.g. chemical coating).
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    Location optimization of silicon carbide foam packings in the unstirred packing trays reactor for the enhancement of solidified natural gas storage
    (Elsevier, 2022-02-10) Linqing, Tian; Ha, Li; Wang, Li; Chen, Guangjin; Coulon, Frederic; Jiang, Yuelu; Zeng, Xinyang; Zhang, Ruifeng; Wu, Guozhong
    Solidified natural gas technology shows significant potential for storing safely multi-fold volumes of natural gas in clathrate hydrates, but the main concern is the stochastic and slow process of hydrate nucleation making it unstable and unpredictable in practice. To overcome this limitation, methane hydrate was synthesized in a silicon carbide (SiC) ceramic foam packing trays reactor without stirring. Results suggested that the packing trays should be located near the gas-water interface instead of immersed in the aqueous phase, which decreased the induction time by about 98%. Results also highlighted the synergistic effects between the capillary wicking from the porous packings and the water suction from the initially formed hydrate clusters, which pumped water from the aqueous phase into the packings’ pores to provide an unsaturated porous environment for hydrate nucleation. It demonstrated that these two driving forces might also compete for water which became adverse to hydrate formation.
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    Machine learning models for fast selection of amino acids as green thermodynamic inhibitors for natural gas hydrate
    (Elsevier, 2022-12-13) Wu, Guozhong; Coulon, Frederic; Feng, Jing-Chun; Yang, Zhifeng; Jiang, Yuelu; Zhang, Ruifeng
    Natural amino acids are non-toxic thermodynamic hydrate inhibitors without negative environmental impact, but it is difficult to accurately select the appropriate amino acid as a quick response to the operational conditions changes in the natural gas pipeline. The objective of this study was to develop mathematical models to predict the hydrate formation temperature (HFT) in presence of amino acids, capture the relationship between amino acid structure properties and their hydrate inhibition strength, and determine the optimal type and concentration to use. The HFT prediction was evaluated using multiple linear regression (MLR) and three machine learning methods including random forest (RF), M5 Rule (M5R) and support vector machine (SVM). After parameter optimization using the trial-and-error method, the coefficient of determination (R2) of the four models were 0.9328, 0.9793, 0.9795 and 0.9980, respectively. The SVM prediction of HFT outperformed other models as the root mean square error (RMSE) was 83%, 76% and 69% lower than that of the MLR, RF and M5R, respectively. Results also demonstrated that the relative importance of the amino acid concentration to the hydrate phase equilibrium was 5-fold higher than that of the intrinsic properties of the amino acid molecular. The SVM model proposed in this study served an easy-to-use tool for reliable prediction of HFT by just providing a new set of input data. This made it possible to accurately determine the minimum concentration of amino acids to be used during the gas pipeline transportation.
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    Pilot Application of SVE-Enhanced Bioremediation Technology for in situ Clean-up of a Light Oil-Contaminated Site
    (HARD Publishing; 1999, 2012-12-31T00:00:00Z) Yang, Yuewei; Wu, Guozhong; Li, Xingang; Coulon, Frederic; Li, Hong; Sui, Hong
    Light oil (isooctane) removal using soil vapor extraction (SVE) enhanced bioremediation (BR) was investigated by four steps, including: (i) amendment of substrates in batches (ii) continuous induction of contaminants for 15 days (iii) in situ acclimation for 100 days (iv) biodegradation assisted with SVE venting for 120 h at 20 m³·h-1 Results showed that the total removal efficiency was up to 90% after BR-SVE treatments. BR contributed predominantly to isooctane removal during the last 36 h of BR-SVE treatment. This implied that it would be an important strategy to limit water content at the early stage while increasing water supply at the end stage during implementation of BR-SVE, because water content was a significant factor hindering SVE but favoring BR. The overall results demonstrated a good complementarity between SVE and BR, and a potential for their combination in real-world applications.
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    Recycling of solvent used in a solvent extraction of petroleum hydrocarbons contaminated soil.
    (Elsevier Science B.V., Amsterdam., 2011-02-15T00:00:00Z) Wu, Guozhong; Li, Xingang; Coulon, Frederic; Li, Hong; Lian, Jingyan; Sui, Hong
    The application of water washing technology for recycling an organic composite solvent consisting of hexane and pentane (4:1; TU-A solvent) was investigated for extracting total petroleum hydrocarbons (TPH) from contaminated soil. The effects of water volume, water temperature, washing time and initial concentration of solvent were evaluated using orthogonal experiments followed by single factor experiments. Our results showed that the water volume was a statistically significant factor influencing greatly the water washing efficiency. Although less important, the other three factors have all increased the efficacy of water washing treatment. Based on a treatment of 20g of contaminated soil with a TPH concentration of 140mgg(-1), optimal conditions were found to be at 40°C, 100mL water, 5min washing time and 660mgg(-1) solvent. Semi-continuous water extraction method showed that the concentration of the composite solvent TU-A was reduced below 15mgg(-1) d.w. soil with a recovery extraction efficiency >97%. This finding suggests that water washing is a promising technology for recycling solvent used in TPH extraction from contaminated soils