Distribution and Conversion of Polycyclic Aromatic Hydrocarbons

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The distribution and conversion of polycyclic aromatic hydrocarbons during the hydrothermal treatment of sewage sludge Ying Li, Yunbo Zhai, Yun Zhu, Chuan Peng, Tengfei Wang, Guangming Zeng, Debin Wu, and Xin Zhao Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b01523 • Publication Date (Web): 27 Jul 2017 Downloaded from http://pubs.acs.org on July 31, 2017

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The distribution and conversion of polycyclic aromatic hydrocarbons during the hydrothermal treatment of sewage sludge Ying Lia,b, Yunbo Zhaia,b，*, Yun Zhuc,d,*，Chuan Penga,b, Tengfei Wanga,b, Guangming Zenga,b, Debin Wue， Xin Zhaoe a

College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China

b

Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, P. R. China

c

Office of Scientific R& D, Hunan University, Changsha 410082, P. R. China

d

Shenzhen Institutes of Hunan University, Shenzhen 518000, P. R. China

e

CNPC ECONOMICS &TECHNOLOGY RESEARCH INSTITUTE 100000, P. R. China

ABSTRACT In this paper, the solid residue and liquid residue were obtained by hydrothermal process of sewage sludge. The effect of reaction temperature (180°C-260°C), retention time (30min-90min), and co-solvent (ethanol volume proportion) (0%-100%) on the PAHs distribution and formation were investigated. The results showed that the concentration of total polycyclic aromatic hydrocarbons (TPAHs) in solid phase slightly decreased with the increasing of temperature while in liquid phase the TPAHs concentration increased, which decreased from 3.862µg/g to 2.808µg/g in solid residue, and in liquid residue increased from 2.755µg/ml to 2.974µg/ml and then decreased to 1.961µg/ml. There was no tremendous influence by retention time, since the TPAHs concentration in solid residue decreased from3.020µg/g to 2.808µg/g, and in liquid residue slightly increased from1.80µg/ml to 1.961µg/ml. The concentrations of TPAHs showed the minimum level at 260°C -30%, the PAHs with *

Corresponding Author. Tel.+86 731 8882 2829,Fax. +86 731 8882 2829. E-mail Address: [email protected](Y.B. ZHAI), [email protected](Y. ZHU)

ACS Paragon Plus Environment

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different ring number also showed decreased at 30%, then increased at 80%, finally decreased at 100%. The conversion pathway of PAHs formation was discussed in this paper: the three parameters exerted the influence on the distribution and formation of PAHs by affected the decomposition and synthesis of organic matters and the mutual transformations of PAHs. Keywords: Polycyclic aromatic hydrocarbons; sewage sludge; hydrothermal process; co-solvent 1. Introduction Sewage sludge (SS) is an inevitable byproduct of urban sewage treatment plants. With the increasing urbanization process and the increasing amounts of domestic wastewater, the final disposal of sludge has become a very complex issue. Landfill and composts are two of the most conventional methods for sewage sludge disposal. However, these methods do not conform to the trend of sustainable development, since Sludge is a dependent carrier of many homogeneous contaminants (such as PAHs, heavy metals and pathogenic microorganisms), and has a strong affinity for them, which dramatically limits its extensive application 1.2. PAHs in the process of wastewater purification successfully adsorbed on the surface of the sludge, and can be retained for a long time in the sludge.3.4 When the sludge compost as agricultural fertilizer, the PAHs enter into soil by adsorption of soil organic matter and then exist for a long time which can be absorbed by the vegetation of the root and food chain gradually to the soil ecosystem and human health hazard due to its lipid solubility. Additionally, land-use limitations and odor pollutants can’t be avoided. Recently, people pay more attention to the advantages of SS disposal by thermodynamic treatment, which can not only achieve the sludge minimization and harmless, but also make the sludge-derived biochar regard as agricultural fertilizer. The hydrothermal treatment (HT) technology is under the conditions of high temperature, pressurized, and anoxic environment (the tempera-


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ture ranges in 180-260 °C, the pressure depends on the steam pressure of subcritical-water and gas development during feedstock decomposition), which is one of the most popular processing method. HT acts as an innovative technology transforming biomass into a highly carbonaceous product--biochar, which opens up a new idea for the transformation of plentiful waste biomass into innovative materials as soil amendments and nutrient conservation that can be used as agricultural applications. The biomass materials including rice stem 5, paper sludge 6, lignocellulosic biomass 7, wheat straw 8, green waste 9, water hyacinth 10, and loblolly pine 11. During the process of hydrothermal treatment, the decomposition process of waste biomass includes hydrolysis of the organic matrix, followed by the loss of function, such as dehydration, decarboxylation, recondensation and aromatization 12.13. At the subcritical condition, water is still maintained in liquid phase and acts as a non-polar solvent 14, which greatly reduce its dielectric constant, surface tension, and viscosity, thereby weakening the hydrogen bonding network of water molecules. Hence the penetrabtion of the extactant into the steam matrix was accelerated and the solubility of organic compounds of biomass was enhanced 5.15. The subcritical water generally promotes ion chemistry and suppresses free radical reactions, which strength bond cleavage of hydrogen bonds, particularly hydrolysis. Furthermore, the radical polymerization is suppressed by saturation of organic compounds by donation of hydrogen ions; organic solvents are more powerful in this effect 13.16. Singh et al., (2015), and Celikbag et al., (2016) have reported that organic contaminants solubility in solution increased when adding organic solvent (such as ethanol) as additives in comparison with the single solution 17.18. Ethanol is a kind of green, environmental, non-toxic organic solvent. Maharajh, D.M., (1986) have discussed that naphthalene were dissolved more easily in the heated water environment, and the increasing of eth-


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anol concentration had a positive effect on the solubility of PAHs 19. Teoh et al., (2014b) have reported that the solubility of anthracene increased exponentially with the increase of temperature in the co-solvent of ethanol and water under subcritical conditions 20. Jia et al., (2015) have reported that base on the ethylene flame combustion model, the addition of ethanol can accelerated the formation of PAHs, especially naphthalene 21

. Numerous studies have studied on the quantitative research and formation mechanism of PAHs in the process of pyrolysis 21-26. Few studies

discussed the formation and transformation of PAHs in the HT process or studied on the effects of organic solvents on the production and formation of PAHs in the HT process, most of them only are limited to establish the model 27-28, and there is no response to the dynamic and quantitative analysis of the results. Hence, the purpose of this paper is to investigate how the hydrothermal treatment affect the TPAHs conversion and the distribution of PAHs content at different temperature (180,220,260 °C), at different retention time (30,60,90 min) and at different co-solvent condition (ethanol/water, v/v, 0%,30%,50%,80%,100%) in solid and liquid residues. Moreover, the liquid products will increase the fluidity of the hydrocarbons and pollute the environment to a large extent during hydrothermal process. Therefore, the experimental results can also optimize the hydrothermal conditions and the concentration of PAHs in solid and liquid products are the lowest. 2.Experimental 2.1 Materials preparation Dewatered SS was taken from a wastewater treatment plant in Changsha, China. The sewage sludge was collected during summer 2016,


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which were discharged the activated sludge from the secondary sedimentation tank. A few representative subsamples were taken for the present experiments, and were carefully transported to the laboratory. After drying (about 25°C for few weeks) in the dark, samples were ground and passed through a 100-mesh, finally stored in a dry glass bottle. The initial moisture content of sludge was 87.29%. 2.2 Biochar preparation HT experiments were conducted in a 500 mL 316 stainless steel reactor equipped with an automatic temperature controller and auto-stirred. The pressure depends on the steam pressure and gas development during feedstock decomposition. SS powder was homogenously mixed with solvent at a ratio of 1:10 after loaded into the reactor. (Around 10 g of sludge was loaded with 100 ml co-solvent into the reactor and the autoclave was heated to desired temperature, keeps constant speed at 120 r/min). HTC experiments were performed at 180, 220, 260°C, and maintained for the reaction time of 30, 60, 90min, while the another were performed maintained at 260°C for 90min at different co-solvent ratio (ethanol /deionized water, v/v) 0%,30%,50%,80%,100%, respectively. At the end of preset time, the reactor was allowed to cool down in room temperature. Solid and liquid products were separated by vacuum filtration apparatus with microfiltration filters, gaseous phase and their volatilisation products (collectively referred to as gaseous products), since the gas phase product was not conveniently collected, no analysis was performed. After that, the solid residues were taken in a beaker and oven-dried over night until its weight was stable, which were weighted solid residues. The solid residues produced were referred as temperature- solvent ratio, e.g. the solid residues which called as 260°C–30% stands for the sample obtained at 260°C and ethanol / deionized water (v/v, 30/70).


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2.3PAHs analysis 2.3.1PAHs pretreatment The PAHs in the solid residues and raw sludge were extracted using ultrasonic sequential extractions for 12h with 1:1 (v: v) acetone/nhexane as the extractant. Zhai et al.,( 2016) reported that co-extractant is superior to single-extractant in extraction efficiency and acetone/nhexane as extraction agent has the best effect 29. Subsequently, previous extraction solvents were accumulated into another conical flask through filtration with anhydrous sodium sulfate to remove residual water at the same time and repeat 5 times. Janosz-Raiczyk et al., (2001) have demonstrated that the recovery of PAH in the sludge is significantly dependent on the separation method and the highest PAH concentration was using anhydrous sodium sulfate for separation30. Then, the dried and combined solution were concentrated by rotary evaporator and diluted to 1 mL with the addition of the mixed internal standard solution and collected at -4°C until analysis. 2.3.2 GC-MS analysis of PAHs The PAH analyses were performed with a gas chromatograph mass spectrometer (GCMS-QP2010 Plus, Shimadzu corporation, Japan) equipped with an DB-5MS:(30 m × 0.25 mm i.d. × 0.25 µm film thickness) capillary column, using helium as the carrier gas, total residence time persists 43.33min. The samples were injected in splitless mode (sampling time: 1.00 min, total flow: 5.5 ml/min), and the ion source temperature was control at 250°C, the injection port temperature was set at 200°C. The ionization was performed in the electron impact (EI) mode (70 eV) and used reference ions for the qualitative analysis of PAHs under SIM (Select ion scanning model). The column oven temperature pro-


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gram was: 50°C held for 2min, 18 °C/min to 200 °C held for 2 min, 4 °C/min to 240 °C held for 2 min, 2.5°C/min to 255 °C held for 3 min, and 4.5°C/min to 300 °C 29. The effective recovery of 16 PAHs were basically maintained at 80% -120%, with the exception of naphthalene, which recovery was 34% due to its easy evaporation. The lower limit of quantification of PAHs was determined by three times the standard deviation of the standard curve of the lowest concentration. The LOQ of naphthalene(Nap), fluorine(Fl), anthracene(An), indeo(1,2,3-cd) pyrene(InP), dibenzo(a,h)anthracene(DbA), Benzo(g,h,i)perylene(BghiP) were maintained at 0.1-0.5ng/m3, the LOQ of acenaphthele(Acep), pyrene(Pyr), benz(a)anthracene(BaA), chrysene(Chr), benz(k)fluoranthene(BkF), benzo(a)pyrene(BaP) were maintained at 0.0017ng/m3, and the LOQ of acenaphthylene(Ace), phenanthrene(Phe), fluoranthene(Flu), benzo(a)fluranthene(BaF)were maintained at 0.02-0.07 ng/m3. Each sample test is repeated three times, the following analysis of all data are the average three times. 3. Results and discussion 3.1 The characterization of PAHs distribution in the solid residue and liquid residue during the HT 3.1.1Effects of temperature on the characterization of PAHs distribution in the solid and liquid residues Fig.1 The 16 priority PAHs regulated by U.S. Environmental Protection Agency (USEPA) were classified based on their ring numbers, including 2-ring to 6-ring PAHs. 2-ring PAHs includes Nap, Ace, Acep, Fl; 3-ring PAHs includes Phe, An, Flu; 4-ring PAHs including Pyr, BaA, Chr, BaF, BkF; 5-ring PAHs includes BaP, InP, DbA; 6-ring includes BghiP.


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The transition of PAHs in the initial sludge to the liquid products (referred to as liquid residue), solid products (called solid residue). As shown in Fig.1 (a), the Phe and An were the major PAHs, the concentration of Nap, Ace, Acpy and Flu increased with the increasing of temperature, while the Phe, An, BaA, Chr, BaF, BkF dramatically decreased with the increasing of temperature. As shown in Fig.1 (b), the Nap, Phe and An were the dominated PAHs, all species of PAHs were decreased with the increase of temperature, except the Nap, Flu, An, BaA, Chr, InP, BghiP, DbA, which increased with the increasing of temperature. As shown in Table1, the composition of PAHs in raw sludge was dominated by2-ring, 3-ring and 4-ring PAHs, while 5-ring and 6-ring PAHs were lower than the method of detection limit. The TPAHs concentration in the solid residue significantly decreased with the increasing of reaction temperature, and in the liquid residue increased with the increasing of reaction temperature. With the reaction temperature increased from 0°C to 260°C, the TPAHs concentration in solid residue decreased from 3.862µg/g to 2.808µg/g, and in liquid residue increased from 2.755µg/ml to 2.974µg/ml and then decreased to 1.961µg/ml. PAHs in the liquid phase will increase the mobility of hydrocarbons, which is dangerous for the environment. It can be seen that the temperature at 260 °C is the best condition, because the concentration of PAHs in solid and liquid products are the lowest. Compared with the original sludge, the contents of TPAHs decreased by 3.26%, 15.67% and 27.29% respectively after heating up 180, 220 and 260 °C. The concentration of PAHs with different ring number showed different trend with the increasing of reaction temperature, 3-ring and 4-ring PAHs concentration decreased, especially 3ring PAHs decreased dramatically, from 2.042µg/g to 0.837µg/g at 260 °C, whereas the 2-ring PAHs concentration increased from 0.623µg/g to 1.373µg/g from 0 °C to 260 °C, and the 5-ring and 6-ring PAHs increased to 0.179µg/g and 0.039µg/g during the heating period. In this work,


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the result obtained was in conformance with some authors 1.31-33 , which have also noted that the decrease of the concentration of PAHs with increase of temperature in solid residue. Table1 3.1.2 Effects of retention time on the characterization of PAHs distribution in the solid and liquid residues Fig.2 The effect of retention time on PAHs concentration in the residues was shown in Fig.2 and Table2. Similar with the reaction temperature, the TPAHs concentration in solid residue decreased with the increasing of retention time, but the TPAHs concentration in liquid residue increased. When the retention time increased from 30min to 90min, the TPAHs concentration in solid residue decreased from3.020µg/g to 2.808µg/g, and in liquid residue slightly increased from1.80µg/ml to 1.961µg/ml. As shown in Fig.2 (a), the An was the major PAHs, the concentration of Nap, Ace, Acpy and Flu increased with the increasing of retention time, while the Phe, An, BaA, Chr, BaF, BkF dramatically decreased. As shown in Fig.2 (b), the Nap, Ace, Acpy, Flu, An and Phe were the dominated PAHs. As shown in Table2, the concentration of PAHs with different ring number has no great change, with slightly decreased trend. Table2 3.1.3Effects of co-solvent proportion on the characterization of PAHs distribution in the solid and liquid residues Fig.3


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The effects of ethanol volume proportion on PAHs distribution in the residues was shown in Fig.3. According to the Fig.3 (a), all the PAHs concentration reduced with increasing of ethanol proportion, besides Nap, Ace, Acpy, Flu, which first reduced at 260°C -30% and dramatically increased with increasing the ethanol ratio, and finally reduced at 260°C -100%. The Nap, Fl and Phe were the dominated products in solid residue. According to the Fig.3 (b), all the PAHs concentration increased with the increasing of ethanol proportion, besides Acpy, Fl, Phe, An, Pyr, BaA, Chr, BaF, BkF, BaP, which first reduced at 260°C -30%, and significantly increased at 260°C -100%. As Table3 shown, with the ethanol volume proportion increasing from 0%-100%, the TPAHs concentration in solid residue reduced from 2.808 µg/g to 1.650 µg/g at 260°C -30% and then increased to 2.571 µg/g at 260°C -80%, and finally decreased to 2.087µg/g at 260°C -100%. The TPAHs concentration in liquid residue first reduced from 1.961 µg/ml to 1.332 µg/ml at 260°C -30% and then increased to 2.256µg/ml at 260°C -100%. The results showed that the concentrations of TPAHs showed the minimum level at 260°C -30%, which minimizes the risk to the environment. Furthermore, it not only reduces the PAHs in the solid product, but also the lowest concentration of PAHs in the liquid phase. The concentration of PAH with different ring number also exhibited trends similar to the TPAHs concentration in solid residue, especially 2-ring PAHs changed dramatically, reduced from 1.373 µg/g to 0.715 µg/g and then increased to 1.773 µg/g and finally decreased to 1.362µg/g. The concentration of PAH with different ring number in liquid residue showed the different trend, the 2-ring, 3-ring, 4-ring and 5-ring PAHs concentration showed the similar trend with the TPAHs concentration in liquid residue, but the 6-ring PAHs decreased when the ethanol volume proportion added the 50%, then increased at 260°C -80%.


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Table3 3.2 The conversion of PAHs in the solid residue and liquid residue during the HT The SS not only contains a variety of organic matters, such as lignin, crude fat, protein and others, but also contains a small amount of PAHs and other pollutants 34, which all generate the PAHs during the hydrothermal treatment. The conversion pathways of PAHs can be concluded from two aspects: (1) The decomposition and synthesis of organic matter (mainly are the lignin, protein and aromatic hydrocarbons) in SS; (2) PAHs between the mutual transformations in SS. The details of conversion pathway are shown as Fig.4. The lignin can generate benzene and phenol by occurring series of depolymerization, dehydroxylation, demethoxylation reactions, then generating a series of addition reaction and dehydrogenation to form the 2-ring PAHs (naphthalene). Zhou et al., ( 2014a) have also reported that the benzene and phenol were the precursors of PAHs formation 35. The protein by occurring cleavage form alkanes and alkenes substance, following to a series of addition reaction and cyclization form small molecular PAHs (naphthalene). The aromatic hydrocarbons form small molecular PAHs (naphthalene) by occurring addition reaction with acetylene. The conversion pathway of protein and aromatic hydrocarbons are dominated by the HACA reaction, which is the well-known reaction pathways for the main organic matters decomposition and synthesis of PAHs 36.37. Hence, we can speculate that the increase of 2-ring PAHs concentration in solid residues with the temperature are the result of the decomposition and synthesis of organic matter in SS, and the higher temperature can promote the decomposition of organic matter into PAHs. In comparison, the influence of residence time of PAHs concentration is smaller.


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The PAHs between the mutual transformations including the decomposition of higher molecular PAHs into small molecular PAHs under the heat condition; the addition reaction of the small molecular PAHs and form the higher molecular PAHs, which are dominated by the “naphthalene zigzag” reaction 38. The former one may be explained the decrease of 3-ring and 4-ring PAHs with the increasing of temperature and retention time, and the higher temperature and prolong retention time have a positive effect on the decomposition of higher molecular PAHs. The latter one can be explained the increase of the 5-ring and 6-ring PAHs with the increasing of temperature and retention time, and the higher temperature and prolong retention time can promote the recombination of small molecular PAHs. The influences of temperature and retention time also have an influence on the distribution of PAHs in solid-liquid phase. It was found that the concentration of PAHs in solid phase decreased with the increasing of temperature and retention time, while the PAHs concentration in liquid phase increased, and although more PAHs formation from the organic matters, the PAHs concentration in solid residue decreased. Which is may related with the transition of PAHs are continuously transferred to the gas phase and liquid phase, because PAHs have a higher solubility and more close to reach boiling point as the temperature increases 1. The decomposition of organic matter is affected by the solvent environment, and the organic solvent plays an important role in the distribution of PAHs in solid-liquid phase. While the ethanol volume fraction at 30%, low concentration of alcohol and water mixed solvent have positive effects on protein to form a more compact conformation. The concentration of the hydrophobic groups of protein in aqueous system is lower than a certain critical concentration, owing to the hydrophobic effect is mutual exclusion, thus adding alcohol solvent in the system can destroy


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the natural conformation of proteins, and weakening the interaction of hydrophobic groups, which will conducive to the formation of protein structure more closely. Hence the macromolecular material decomposition is abating, and generate small molecule PAHs also reduce 38. When continue to improve the ethanol proportion, protein unfold and form a loose conformation, this phenomenon may be caused by hydrophobic interactions between protein hydrophobic groups and alcohol molecule, the hydrophobic hydration increase non-polar solute solubility in water and is not conducive to molecular aggregation, hence improving macromolecular material hydrolysis and accelerating the decomposition of protein 35. These above mentioned reasons also showed that PAHs concentration in solid residue decreased at the ethanol volume proportion of 30%, and PAHs concentration increased when the volume proportion of ethanol increased to 80%, finally the PAHs concentration decreased at 100%. The co-solvent has impact on the solubility of PAHs in the subcritical solvent, which also show that the increasing of PAHs concentration in liquid residue. When the temperature is raised to 260 °C, the sludge is in the supercritical fluid (The critical temperature and pressure of ethanol are 240.7 °C and 6.137MPa respectively), and the solute capacity of the sludge increase greatly, hence the PAHs concentration the liquid product shows the increasing trend. Moreover, ethanol dehydration reaction also occurring to produce ethylene in the pressurized atmosphere and high temperature, after a series of ethylene cyclization and then dehydrogenation form to benzene, benzene react with hydrocarbon through a series of addition reaction to form PAHs. Park et al., ( 2002), Sivaramakrishnan et al., (2010) and H. Xu et al., (2013) have discussed that ethanol dissociation to produced ethylene and water channels in the 500K-2000K were dominant 40-44. Fig.4


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3.3 FTIR analysis (1) The peak at 1455 cm-1was attributed to the –C=C stretching is corresponding to aromatic ring carbon 42.44.45. As shown in Fig.5(a)(b)(c), the vibration intensity dramatically reduced with the increasing temperature, suggesting that the less the content of aromatic hydrocarbons with the increasing of temperature. And compared with the original sludge, the content of PAHs after hydrothermal treatment is greatly reduced; The vibration intensity of aromatic hydrocarbon skeleton decreases slightly, suggesting that the more content of aromatic hydrocarbons from solid to other phase when residence time to extend to a certain range; The vibration intensity first reduced from 260°C -0% to 260°C -30% and then increased when the ethanol proportion was 80%, finally the vibration intensity was decreased at 260°C -100%, which were consistent with the concentration of TPAHs in solid resides. (2) The band at 1645 cm-1was associated with the stretching vibration of –C=O in amide I and carboxylate groups while the band at 1540 cm-1was assigned to –N–H in-plane bending of amide II and secondary amines 46. As shown in Fig.5 (a), the peak at 1540 cm-1disappeared, implying a complete hydrolysis of amide II or secondary amines from labile proteins with increasing temperature. As shown in Fig.5 (c), When the ethanol proportion increased at 30%, the vibration intensity slightly increased, which implying that the proteins decomposition is abated. While the ethanol proportion was ever-increasing at 80%, the vibration intensity slightly reduced, which suggesting that the proteins decomposition is promoted. At the ethanol proportion at 100%, the vibration intensity slightly increased, which indicating that the proteins decomposition is under restrictions. These changes are consistent with the changes in the concentration of TPAHs, which also shows that the concentration of PAHs and protein hydrolysis have a great relationship. 4. Conclusions


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The effect of reaction temperature, retention time and co-solvent ratio (v/v) on distribution of the PAH concentrations and conversion pathway were investigated, which based on the GC/MS quantitative analysis the solid and liquid residues, the proposed pathway of PAHs were also investigated. The major conclusion of the present study can be summarized as follows: 1) During the hydrothermal process, the TPAHs concentration in solid residue decreased with increasing reaction temperature. The influences of temperature on the PAHs concentration were mainly by accelerating the degradation and synthesis of organic matter and the mutual transformation of PAHs, which resulted in the increase of 2-ring, 5-ring and 6-ring PAHs, but 3-ring and 4-ring PAHs concentration decreased. The temperature of 260 °C is the best condition, the PAHs concentration in solid and liquid products are the lowest, which is minimize the risk to the environment. The retention time exert not great influence on the PAHs concentration and distribution in solid-liquid phase, for the solid product, the concentration of TPAHs is minimum at 90min; for liquid products, the concentration of TPAHs at 60min which is less harmful to the environment. 2) During the heating process, the influence of ethanol –water as co-solvent on the distribution of PAHs and formation was mainly by affecting the decomposition of organic matters of SS (especially the reaction characteristics of protein) and solubility of PAHs at the cosolvent environment. This leads to the concentrations of TPAHs in solid and liquid products showed the minimum level at 260°C -30%. Acknowledgements This research was financially supported by the project of National Natural Science Foundation of China (Nos. 51679083), the Interdisciplinary Research Funds for Hunan University (2015JCA03), the scientific and technological project of Changsha City (KQ1602029), Supported by PetroChina Innovation Foundation (2016D-5007-0703) and the project of Shenzhen Science and technology Funds （JCYJ20160530193913646）.


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Table1. The distribution of PAHs concentration with different ring number in solid residue and liquid residue at different temperature Table2. The distribution of PAHs concentration with different ring number in solid residue and liquid residue at different residue time Table3. The distribution of PAHs concentration with different ring number in solid residue and liquid residue at different ethanol volume proportion Table1 Samples

SS

180-90s

220-90s

260-90s

2-ring

0.623±0.02

3-ring

0.766±0.06

1.066±0.011

1.373±0.021

1.347±0.033

1.437±0.012

0.881±0.013

2.042±0.08

1.896±0.06

1.333±0.012

0.837±0.028

1.057±0.013

1.039±0.022

0.694±0.012

4-ring

1.197±0.03

1.074±0.03

0.766±0.031

0.380±0.036

0.289±0.033

0.321±0.008

0.236±0.008

5-ring

0.000

0.000

0.078±0.005

0.179±0.002

0.000

0.103±0.003

0.113±0.003

6-ring

0.000

0.000

0.014±0.002

0.039±0.004

0.000

0.019±0.001

0.036±0.001

TPAHs

3.862±0.13

3.736±0.15

3.257±0.061

2.755±0.079

2.974±0.046

1.961±0.037

2.808±0.091

180-90l

220-90l

s l

Solid residue (µg/g); Liquid residue(µg/ml).


260-90l

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1 2 3 Table2 4 5 Samples SS 6 2-ring 7 0.623±0.04 8 3-ring 2.042±0.011 9 10 4-ring 1.197±0.015 11 5-ring 12 0.000 13 6-ring 0.000 14 15 TPAHs 3.862±0.066 16 s 17 Solid residue (µg/g); 18 l Liquid residue(µg/ml). 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Energy & Fuels

260-30s

260-60s

260-90s

260-30l

260-60l

260-90l

1.154±0.021

1.272±0.013

1.373±0.021

0.826±0.013

0.879±0.014

0.881±0.012

1.053±0.012

0.884±0.011

0.837±0.013

0.569±0.011

0.585±0.008

0.694±0.011

0.665±0.006

0.435±0.010

0.380±0.008

0.292±0.011

0.256±0.013

0.236±0.011

0.123±0.001

0.150±0.002

0.179±0.004

0.088±0.001

0.095±0.002

0.113±0.004

0.026±0.001

0.029±0.001

0.039±0.002

0.025±0.001

0.031±0.001

0.036±0.001

2.808±0.048

1.800±0.037

1.845±0.038

3.020±0.041

2.770±0.037


1.961±0.039

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Table3 Samples

260-0%s

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260-30%s

260-50%s

260-80%s

260-100%s

260-0%l

260-30%l

260-50%l

260-80%l

260-100%l

2-ring

1.373±0.018

0.715±0.011

1.415±0.013

1.773±0.014

1.362±0.012

0.881±0.008

0.869±0.010

1.102±0.010

1.242±0.013

3-ring

0.837±0.012

0.601±0.010

0.512±0.010

0.473±0.006

0.438±0.007

0.694±0.006

0.188±0.005

0.206±0.008

0.243±0.010

0.318±0.007

4-ring

0.380±0.011

0.245±0.008

0.210±0.008

0.185±0.002

0.152±0.003

0.236±0.003

0.168±0.007

0.207±0.007

0.199±0.004

0.174±0.003

1.525±0.018

5-ring

0.179±0.008

0.073±0.003

0.105±0.007

0.102±0.002

0.099±0.001

0.113±0.003

0.070±0.004

0.071±0.003

0.086±0.003

0.169±0.003

6-ring

0.039±0.002

0.015±0.001

0.037±0.002

0.038±0.001

0.037±0.001

0.036±0.002

0.038±0.001

0.036±0.001

0.043±0.002

0.071±0.001

TPAHs 2.808±0.051 s Solid residue (µg/g); l Liquid residue(µg/ml).

1.650±0.033

2.278±0.04

2.087±0.024

1.961±0.022

1.332±0.027

1.622±0.029

1.813±0.032

2.256±0.032

2.571±0.025


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Energy & Fuels

Fig.1 The distribution of PAHs concentration in solid residue (a) and liquid residue (b) at different temperature Fig.2 The distribution of PAHs concentration in solid residue (a) and liquid residue (b) at different residue time Fig.3 The distribution of PAHs concentration with different ring number in solid residue (a) and liquid residue (b) at different ethanol volume proportion Fig.4 Schematic diagrams of conversion pathway of PAHs formation from different organic matters of SS Fig.5 FTIR spectral for SS and corresponding biochar at different temperature (a), at different residue time (b), and at different ethanol proportion(c)

Fig.1


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Fig.2

Fig.3


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Energy & Fuels

Fig.4


Energy & Fuels

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Fig.5 ACS Paragon Plus Environment

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Distribution and Conversion of Polycyclic Aromatic Hydrocarbons

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