Compatibility of Surfactants and Thermally Activated Persulfate for Enhanced. Subsurface Remediation

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1 Compatibility of Surfactants and Thermally Activated Persulfate for Enhanced Subsurface Remediation Li Wang, Libin Peng, Liling Xie, Peiyan Deng, Dayi Deng* School of Chemistry and Environment, South China Normal University, Guangzhou, Guangdong 516, China *Correspondence Author Tel: S1

2 Table of Contents Sections Section S1 Chemicals 3 Section S2 HPLC analyses of residual surfactant 3 Section S3 C 12 -MADS assisted coal tar solubilization 3 Figures Figure S1 Structures of representative nonionic and anionic surfactants 5 Figure S2 Acid-catalyzed hydrolysis of SLS, AOT and Tween 8 6 Figure S3 Impact of C 12 -MADS and temperature on PAHs solubilization 7 Figure S4 Impact of C 12 -MADS concentration on PAHs solubilization 8 Figure S5 Impact of reaction temperature and C 12 -MADS on individual PAHs oxidation and oxidant utilization efficiencies in the biphasic tar/water system 9 Figure S6 Impact of C 12 -MADS concentration on PAHs oxidation and oxidant utilization efficiencies in the tar/water biphasic system 1 Figure S7 Impact of oxidant concentration on PAHs oxidation and oxidant utilization efficiencies in the tar/water biphasic system 11 Figure S8 Impact of surfactant compatibility on individual PAHs oxidation and oxidant utilization efficiencies in the biphasic tar/water system 12 Figure S9 Two-phase kinetic fitting for naphthalene (NAP) and phenanthrene (PHE) oxidation in the tar/water biphasic system 13 Tables Table S1 Formula and properties of representative nonionic and anionic surfactants 14 Table S2 Clouding/precipitation of surfactants in the presence of persulfate 15 Table S3 Surface tension profiles of surfactants solutions in the presence of persulfate 16 Table S4 Tar composition and viscosity profiles 17 References 19 S2

3 Section S1 Chemicals Standard stock solution containing 18 PAHs, including all 16 PAHs on the list of US EPA Priority Pollutant, was from o2si Smart Solutions, USA. Stock solutions of 1-methylnaphthalene, 2-methylnaphthalene and dibenzofuran were made from pure compounds. All other inorganic reagents were analytical grade or better. Section S2 HPLC analyses of residual surfactants LC-16A HPLC system coupled with an Low Temperature Evaporative Light Scattering Detector (Shimadzu ELSD-LT II) were applied for the analyses of surfactants with a Acclaim TM Surfactant Plus column (Thermo Fisher Scientific, USA) and Athena C8-WP column (CNW Technologies GmbH, CHN). The analytical conditions for each surfactant as follows: Surfactants Column Mobile Phase Drift-Tube temperature (ºC) Gas (Nitrogen) Pressure (Psi) Flow Rate (ml/min) SDBS Acclaim TM Surfactant Plus, mm,5μm Acetonitrile/.1 M NH 4 OAc, ph=5 (7/3 v/v) SDS Acclaim TM Surfactant Plus, mm,5μm Acetonitrile/.1 M NH 4 OAc, ph=5 (7/3 v/v) SLS Acclaim TM Surfactant Plus, mm,5μm Methanol/.1 M NH 4 OAc, ph=3 (85/15 v/v) C 12 -MADS Acclaim TM Surfactant Plus, mm,5μm Methanol/.1 M NH 4 OAc, ph=3 (7/3 v/v) AOT Acclaim TM Surfactant Plus, mm,5μm Acetonitrile/.1 M NH 4 OAc, ph=5 (7/3 v/v) TritionX-1 Brij35 Tween8 Athena C8-WP, mm,5μm Athena C8-WP, mm,5μm Athena C8-WP, mm,5μm Methanol/H 2 O (8/2 v/v) Methanol/H 2 O (9/1 v/v) Methanol/H 2 O (55/45 v/v) Section S3 C 12 -MADS assisted coal tar solubilization Coal tar solubilization experiments. The impact of heating and surfactant to mass transfer and aqueous solubilization of individual PAHs from coal tar to the aqueous bulk phase was studied at 2 C, 4 C, 6 C and 75 C both with and without C 12 -MADS (coal tar, ~1 mg; [C 12 -MADS] = or 1. g/l, 2 ml; 15 rpm) in 4-mL VOA vials sealed S3

4 with silicone/ptfe septa. In addition, the effect of C 12 -MADS concentration on the mass transfer and solubilization of individual PAHs was investigated at 6 C with C 12 -MADS concentration at g/l, 1 g/l, 5 g/l, 1 g/l. At designated intervals (1 min, 2 min, 3 min, 4 min, 1 h, 2 h, 3 h, 4 h, 5 h, 8 h, 12 h, 16 h, etc.), the samples were centrifuged to separate the aqueous solution from coal tar. The aqueous phase containing C 12 -MADS was first diluted to a final C 12 -MADS concentration of.5 g/l. The resulting solution was then extracted with hexane (1 ml aqueous solution with 1 ml hexane), followed by addition of 5 ml of.1 M CaCl 2 solution as the emulsion breaker. PAHs were quantified according to literature procedures. 3 Effects of C 12 -MADS and heating on the solubilization of individual PAHs. The aqueous solubilization of PAHs from coal tar with/without C 12 -MADS at various temperatures is shown in Fig. S3. In the absence of C 12 -MADS, raising the reaction temperature can only accelerate the dissolution rate and raise the solubility of individual PAH to limited extent. On the contrary, C 12 -MADS significantly enhances the solubilization of individual PAHs from coal tar; individual PAHs concentrations in the aqueous bulk phase were one or two orders higher than comparative ones in aqueous solution alone. The enhancement levels are generally much greater for HMW PAHs (high-molecular-weight PAHs) than LMW PAHs (low-molecular-weight PAHs), due to the higher hydrophobicity of HMW PAHs and consequent higher affinity for the hydrophobic cores of surfactant micelles. In addition, greater enhancement levels were observed for PAHs with higher concentrations in the coal tar, among PAHs with similar molecular weight. The enhancement levels are closely related to the surfactant dosage (Fig. S4). A surfactant dosage of 1 g/l, a dosage within the range commonly used in surfactant soil washing, was found to be very effective in facilitating the solubilization of coal tar PAHs in this study, especially HMW PAHs. S4

5 Figure S1 Figure S1 Structures of representative nonionic and anionic surfactants. S5

6 Remaining Surfactant Percentage (%) Figure S Reaction Time (days) SLS AOT Tween 8 Figure S2 Acid-catalyzed hydrolysis of SLS, AOT and Tween 8 ([surfactant] = 1. g/l, 2. ml; ph = ~1, adjusted with sulfuric acid; T = 6 C; 15 rpm). S6

7 Figure S [C 12 -MADS] = 1. g/l Solubilization Ehancing Levels (C/C ) NAP 2MN 1MN ACP DBF FLR PHE ANT [C 12 -MADS] = g/l 2 NAP 2MN 1MN ACP DBF FLR PHE ANT 2 ºC 4 ºC 6 ºC 75 ºC Figure S3 Impact of C 12 -MADS and temperature on PAHs solubilization (coal tar, ~1 mg; [C 12 -MADS] = or 1. g/l, 2. ml; T = 2, 4, 6, 75 C; 15 rpm, 24 h). The solubilizaiton enhancement level (C/C ) was defined as ratios of the concentration of individual PAHs in the bulk aqueous phase under the designated conditions to that in the absence of surfactants at 2 C. S7

8 Solubilization Ehancing Level (C t /C ) Figure S NAP 2MN 1MN ACP DBF FLR PHE ANT 1g/L 5g/L 1g/L Figure S4 Impact of C 12 -MADS concentration on PAHs solubilization. (coal tar, ~1 mg; [C 12 -MADS] =., 1., 5. and 1. g/l, 2. ml; 15 rpm, 24 h). The solubilization enhancement level (C/C ) was defined as ratios of the concentration of individual PAHs in the bulk aqueous phase under designated conditions to that in the absence of surfactants at 2 C S8

9 PAHs Remaining (mmol/g tar) Figure S5 (a).5 [C 12 -MADS] = 1. g/l NAP 2MN 1MN ACP (b) Oxidant utilization efficiencies (mmol/g) [C 12 -MADS] (g L -1 ) 2 C 4 C 6 C 75 C Figure S5 Impact of reaction temperature and C 12 -MADS on (a) individual PAHs oxidation, and (b) oxidant utilization efficiencies in the biphasic tar/water system (coal tar, ~1 mg; [SPS] = 5. g/l + [C 12 -MADS] = 1. g/l, 2. ml; 15 rpm, 3 d). [C 12 -MADS] = g/l DBF FLR PHE ANT FLT PYR BaA CHR B[b,j,k]F BeP BaP DaA ICP Initial 2 C 4 C 6 C 75 C BgP S9

10 Degration (%) Figure S6 (a) ring PAHs 3-ring PAHs 4-ring PAHs 5-ring PAHs 6-ringed PAHs PAHs SPS [C 12 -MADS] : g/l 5 g/l 1 g/l 2 g/l (b) Oxidant utilization efficiencies (mmol/g) [C 12 -MADS] (g L -1 ) utilization efficiencies (mmol/g) Figure S6 Impact of C 12 -MADS concentration on PAHs oxidation and oxidant utilization efficiencies in the tar/water biphasic system (T = 6 C; [SPS] = 5. g/l, 2 ml; coal tar, ~1 mg; 15 rpm, 3 d). S1

11 Degration (%) Figure S7 (a) ring PAHs 3-ring PAHs 4-ring PAHs 5-ring PAHs 6-ring PAHs PAHs [SPS] : 25 g/l 5 g/l 1 g/l S SPS2-2 O 8 (b) Oxidant utilization efficiencies (mmol/g) [SPS] (g L -1 ) utilization efficiencies (mmol/g) Figure S7 Impact of oxidant concentration on PAHs oxidation and oxidant utilization efficiencies in the tar/water biphasic system (T = 6 C; [C 12 -MADS] = 1. g/l, 2 ml; coal tar, ~1 mg; 15 rpm, 3 d). S11

12 PAHs Remaining (mmol/g tar) Figure S8 (a) NAP 2MN 1MN ACP DBF FLR PHE ANT FLT PYR BaA CHR B[b,j,k]F BeP (b) Oxidant utilization efficiencies (mmol/g) BaP DaA ICP BgP Initial SPS only Triton X-1 SDBS C 12 -MADS Blank Triton X-1 SDBS C 12 -MADS utilization efficiencies (mmol/g) Figure S8 Impact of surfactant compatibility on individual PAHs oxidation and oxidant utilization efficiencies in the biphasic tar/water system. (coal tar, ~1 mg; T = 6 C; [SPS] = 5. g/l + [surfactant] = 1. g/l, 2. ml; 15 rpm, 3 d). Blank: only sodium persulfate was added without surfactants present. S12

13 ln(c n /C o n ) Residual PAHs Concentration (mmol/g tar) Figure S9 (a) Reation Time (hours) NAP PHE (b) Reaction Time (hours) NAP NAP linear fit of phase I NAP linear fit of phase II PHE PHE linear fit of phase I PHE linear fit of phase II Figure S9 Two-phase kinetic fitting for naphthalene (NAP) and phenanthrene (PHE) oxidation in the tar/water biphasic system: (a) residual PAHs concentration profiles, (b) two-phase kinetic fitting of NAP and PHE. (T = 6 C; [SPS] = 5. g/l, 2 ml; coal tar, ~1 mg; 15 rpm) S13

14 Table S1 Formula and properties of representative nonionic and anionic surfactants Surfactant Molecular Formula Mw CMC (mmol/l) SDBS C 12 H 25 C 6 H 4 SO 3 Na SDS C 12 H 25 SO 3 Na SLS C 12 H 25 OSO 3 Na C 12 -MADS C 12 H 25 C 12 H 7 O(SO 3 Na) AOT C 2 H 36 O 4 SO 3 Na Brij35 C 12 H 26 O (C 2 H 4 O) n TritonX-1 C 14 H 22 O (C 2 H 4 O) n Tween 8 C 24 H 44 O 6 (C 2 H 4 O) n S14

2 3 = clear = slightly cloudy = moderately cloudy = severely cloudy = slight precipitation = moderate precipitation = severe

15 Reaction Time (days) Table S2 Clouding/precipitation of surfactants in the presence of persulfate* SPS only SDBS SDS SLS C 12 -MADS AOT Brij 35 Triton X-1 Tween 8 Reaction Temperature: 2 C Reaction Temperature: 4 C Reaction Temperature: 6 C = clear = slightly cloudy = moderately cloudy = severely cloudy = slight precipitation = moderate precipitation = severe precipitation * Cloudy seems like milk diluted from different levels; Precipitation means that floccules or crystals can be seen directly. S15

16 Table S3 Surface tension profiles of surfactants solutions in the presence of persulfate* Reaction Time (days) SPS only SDBS SDS SLS C 12 -MADS AOT Brij 35 Triton X-1 Tween 8 Temperature: 2 C Temperature: 4 C Temperature: 6 C *[SPS] = 5. g/l + [surfactant] = g/l or 1. g/l, 2. ml; 15 rpm; ASTM D (Standard Test Methods for Surface and Interfacial Tension of Solutions of Paints, Solvents, Solutions of Surface-Active Agents, and Related Materials) was utilized to measure the surface tension of surfactants/sps solutions. S16

Table S4 Tar composition and viscosity profiles PAHs Abbreviation Structure Concentration (mg/g) Two rings Naphthalene NAP 64.3 ±.5 2-Methylnaphthalene 2MN 23.47 ±.

39 Anthracene ANT 12.77 ±.72 Four rings Fluoranthene FLT 34.2 ±.21 Pyrene PYR 28.54 ±.14 Benzo[a]anthracene BaA 9.27 ±.41 Chrysene CHR 7.95 ±.

17 Table S4 Tar composition and viscosity profiles PAHs Abbreviation Structure Concentration (mg/g) Two rings Naphthalene NAP 64.3 ±.5 2-Methylnaphthalene 2MN ±.17 1-Methylnaphthalene 1MN ±.1 Three rings Acenaphthene ACP 4.25 ±.26 Dibenzofuran DBF ±.28 Fluorene FLR 34.2 ±.21 Phenanthrene PHE 7.32 ±.39 Anthracene ANT ±.72 Four rings Fluoranthene FLT 34.2 ±.21 Pyrene PYR ±.14 Benzo[a]anthracene BaA 9.27 ±.41 Chrysene CHR 7.95 ±.35 Five rings Benzo[b]fluoranthene Benzo[j]fluoranthene Benzo[k]fluoranthene B[b,j,k]F 6.86 ±.27 Benzo[e]pyrene BeP 2.92 ±.12 Benzo[a]pyrene BaP 3.3 ±.12 Dibenz[a,h]anthrancene DaA.36 ±.13 Six rings S17

Indeno[1,2,3-cd]pyrene IcP 1.31 ±.47 Benzo[g,h,i]perlene BgP.95 ±.34 Sum of PAHs 46.32 ± 2.7 Others Asphaltenes 513.8 ± 11.6 Extractable Acids 4.42 ±.4 Extractable Bases 15.6 ±.

18 Indeno[1,2,3-cd]pyrene IcP 1.31 ±.47 Benzo[g,h,i]perlene BgP.95 ±.34 Sum of PAHs ± 2.7 Others Asphaltenes ± 11.6 Extractable Acids 4.42 ±.4 Extractable Bases 15.6 ±.89 Kinematic Viscosity (mm 2 s -1 ) * 2 C C C * ASTM D (Standard Specifications and Operating Instructions for Glass Capillary Kinematic Viscometers) was utilized to measure the kinematic viscosity of coal tars. S18

19 References 1. Shen, J.; Shao, X., Determination of tobacco alkaloids by gas chromatography mass spectrometry using cloud point extraction as a preconcentration step. Analytica Chimica Acta. 26, 561(1-2), Zain, N. N. M.; Abu Bakar, N. K.; Mohamad, S., Study of removal of phenol species by adsorption on non-ionic silicon surfactant after cloud point extraction methodology. Desalination and Water Treatment.214, 57(8), Peng, L.; Wang, L.; Hu, X.; Wu, P.; Wang, X.; Huang, C.; Wang, X.; Deng, D., Ultrasound assisted, thermally activated persulfate oxidation of coal tar DNAPLs. J. Hazard. Mater. 216,318, Mahjoub, B.; Jayr, E.; Bayard, R.; Gourdon, R., Phase partition of organic pollutants between coal tar and water under variable experimental conditions. Water Res. 2,34, (14), Wood, L. J.; Downer, M., Viscosity/temperature equations for coal tar pitches and refined tars. J. Appl. Chem. 1965,15, (9), Myers, D., Surfactant science and technology. 3rd ed.; John Wiley & Sons: 25. S19

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