Oxidation of Benzene by Persulfate in the Presence of Fe(III)- and Mn(IV)- Containing Oxides: Stoichiometric Efficiency and Transformation Products

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1 SUPPORTING INFORMATION SECTION Oxidation of Benzene by Persulfate in the Presence of Fe(III)- and Mn(IV)- Containing Oxides: Stoichiometric Efficiency and Transformation Products aizhou Liu, Thomas A. Bruton, Wei Li, Jean Van Buren, Carsten Prasse, Fiona M. Doyle, and David L. Sedlak* Department of Chemical and Environmental Engineering, University of California at Riverside, Riverside, CA USA Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 9472 USA Department of Material Science and Engineering, University of California at Berkeley, Berkeley, CA 9472 USA Submitted to Environmental Science & Technology * Corresponding author, sedlak@berkeley.edu, phone (51) S1

2 Table of Content Text S1: Experimental setup and material preparation... 4 Text S2: Control of dissolved O 2 concentration in samples... 5 Text S3: igh-resolution mass spectrometry and its operating conditions... 5 Text S4: Nuclear magnetic resonance (NMR) and solid-phase extraction (SPE)... 6 Text S5: Proposed mechanism on the transformation of S 2 O Text S6: Kinetics of SO 4 - and persulfate radical calculation... 9 Text S7: Kinetics of organic radicals in the benzene/so 4 - system Text S8: Estimate of phenol loss due to direct reaction of SO 4 - or O with phenol in the presence of benzene Table S1 Characterization of aquifer materials, clay materials and pure minerals Table S2 Chemical composition of synthetic groundwater used in this study Table S3 Comparison of the production of aldehyde-like compound relative to phenol by S 2 O 8 2- and 2 O Table S4 Comparison of oxidant yield in synthetic groundwater and MQ water from persulfate activation by different minerals* Figure S1 Measurement of total benzene (i.e., aqueous benzene plus adsorbed benzene) in a 5 g/l pyrolusite suspension Figure S2 Changes in (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of ferrihydrite (Fe(O) 3(s) ). Initial benzene=1 mm, initial persulfate=1 mm, ferrihydrite concentration=5 g/l, p= Figure S3 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of pyrolusite (β-mno 2(s) ). Initial benzene=1 mm, initial persulfate=1 mm, pyrolusite concentration=5 g/l, p= Figure S4 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of montmorillonite. Initial benzene=1 mm, initial persulfate= 1 mm, montmorillonite concentration=5 g/l, p= Figure S5 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of nontronite. Initial benzene=1 mm, initial persulfate 1 mm, nontronite concentration 5 g/l, p Figure S6 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material AFTCS. Initial benzene=1 mm, initial persulfate=1 mm, AFTCS concentration=5 g/l, p= S2

3 Figure S7 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material CADOU. Initial benzene=1 mm, initial persulfate=1 mm, CADOU concentration=5 g/l, p= Figure S8 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material AWBP. Initial benzene=1 mm, initial persulfate=1 mm, AWBP concentration=5 g/l, p= Figure S9 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material CAROL. Initial benzene=1 mm, initial persulfate=1 mm, CAROL concentration=5 g/l, p= Figure S1 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material AMTAL. Initial benzene=1 mm, initial persulfate=1 mm, AMTAL concentration=5 g/l, p= Figure S11 Identification of aldehyde-like compound as the oxidation product of benzene by SO 4 - radicals Figure S12 NMR spectra of the unknown compound confirm a ring cleavage product with a fragment identified as an enal Figure S13 Formation of a bisulfite adduct of the unknown ring-cleavage product over time. The increase of the peak area for the bisulfite-adduct product indicated the presence of an aldehyde moiety. 1 mm bisulfite was mixed with SPE-enriched ring-cleavage product Figure S14 Formation of aldehyde-like product during persulfate activation by minerals. (A) Ferrihydrite; (B) Pyrolusite. Mineral mass loading=5 g/l, initial total benzene=1 µm, initial S 2 O 8 2- =1 µm, borate buffer=5 mm, p= S3

4 Text S1: Experimental setup and material preparation All chemicals used in this study were reagent grade or higher. Solutions were prepared using deionized water (resistivity >18.2 MΩ, Millipore system). Four types of pure minerals were employed in this study, i.e., amorphous ferrihydrite (Fe(O) 3(s) ), goethite (α-feoo (s) ), pyrolusite (β-mno 2(s) ) and silica (SiO 2 ). Pyrolusite and ferrihydrite were directly obtained from Sigma-Aldrich. Pyrolusite was used without further processing. Ferrihydrite was aged in deionized water buffered at p 8. with 5 mm borate for 2 weeks prior to experiments, with daily p adjustment to 8. by adding 1 mm NaO. After that, ferrihydrite suspension was centrifuged and the particles were washed three times with deionized water before finally dried with a freeze dry system. Silica obtained as pure sand (ACROS Organics) was rinsed in.1 M ClO 4 at a concentration of 3 g/l. After 24 hours, the solution was decanted and replaced. This step was repeated for 3 consecutive days. After that, silica particles were freeze-dried. Goethite was synthesized by aging freshly made ferrihydrite in a concentrated NaO solution at 7 ºC for 6 hours. Two clay materials, nontronite and montmorillonite were used. Five aquifer solids were used, denoted as AWBP, AFTCS, CAROL, CADOU and AMTAL. The characterization of materials is listed in Table S1 and can be found in a recently published paper. 1. S4

5 Text S2: Control of dissolved O 2 concentration in samples The dissolved O 2 concentration in the solution was adjusted by purging with air, N 2, or pure O 2. In most cases, the solution was saturated with air (i.e., with a dissolved O 2 concentration of 25 µm). In cases where O 2 -free conditions were needed, the suspension was purged with N 2 and kept in a glove box during the experiments. For those samples, the residual O 2 concentration was always less than 3 µm. For experiments conducted at elevated O 2 concentrations, the solution was purged with pure O 2 in a 1-L volumetric flask without headspace at 4 o C and was sealed before raising the temperature back to 23 o C. This process yielded a dissolved O 2 concentration of 41 µm. Text S3: igh-resolution mass spectrometry and its operating conditions Chromatographic separation was achieved using a ydro-rp column (15 x 4.6 mm) equipped with a guard column (both Phenomenex)..1% Acetic acid (A) and methanol (B) were used as eluents. The percentage of (A) was changed linearly as follows: -2 min, 1%; 8 min, 4%; 11 min, 5%; 12 min, 5%, 12.1 min 1%, 18 min, 1%. Injection volume was set to 5 µl. QTOF analysis was performed in negative ESI-MS mode in both fullscan (8 4 m/z) and targeted MS/MS mode to obtain exact mass and structural information of the unknown compound. The source parameters were set to: gas temperature 3 C, gas flow: 12 L min -1, nebulizer: 3 psi, capillary voltage: 3 V. S5

6 Text S4: Nuclear magnetic resonance (NMR) and solid-phase extraction (SPE) To prepare the sample for nuclear magnetic resonance (NMR), solid-phase extraction (SPE) was used to both separate the unknown compound from benzene and phenol and to concentrate the product. SPE cartridges (BondElut C18; 1g sorbent) were conditioned using 5 ml of heptane, 5 ml acetone and 5 ml methanol followed by 25 ml of DI water adjusted to p 2 using 1 M 2 SO 4. To produce the unknown, 2 L of a 1mM benzene solution containing 1 mm persulfate were exposed to UV light from a low-pressure g lamp. Formation of the unknown compound was monitored by PLC/UV and the experiments were terminated when its peak area reached a plateau (usually within 5 hours). Unbuffered ultrapure water was used to minimize potential interferences of salts in the NMR analysis. No significant differences between buffered and unbuffered water were observed with respect to the unknown compound. After loading the samples to SPE cartridges (5 ml per cartridge, sample p was adjusted to p 2), cartridges were first washed with 5 ml of DI water at p 2. The unknown compound was then eluted using 1 ml of DI water at p 7, leaving benzene and phenol on the cartridges for later elution with 1 ml of methanol. This procedure was repeated several times to achieve an overall enrichment factor of 2. The final sample was subjected once more to the SPE procedure described above but using D 2 O (p 2) for washing of the cartridge and C 3 CN-d 3 for elution of the unknown. NMR analysis ( 1 -NMR, 1, 1 -COSY, 1, 1 -NOESY, 1, 13 C- SQC) was performed within 24 h to minimize degradation of the unknown compound. NMR spectra were acquired on a Bruker Avance 6 Mz instrument. S6

7 Text S5: Proposed mechanism on the transformation of S 2 O 8 - SO 4 - is generated from Fenton-like reactions: M n+ + S 2 O 8 2 M (n 1)+ + S 2 O 8 (S1) M (n 1)+ + S 2 O 8 2 M n+ + SO 4 + SO 4 2 (S2) Previous kinetics studies did not specifically examine the decomposition pathways of persulfate radical (S 2 O 8 - ). If S 2 O 8 - were to react with metals to generate peroxymonosulfate SO 5 - : M n+ + S 2 O 8 + 2O M (n 1)+ + 2SO 5 (S3) SO 5 - could reduce another metal, producing SO 4 - and O 2 : 14,2-4 M n+ + SO 5 M (n 1)+ + SO (S4) 2SO 5 2SO 4 +O 2 (S5) A combination of Reactions S3-S5 becomes: 3 M n+ + S 2 O 8 + 2O 3 M (n 1)+ + 2SO 4 +O (S6) Considering Reactions S1, S2 and S12, every 2 moles of S 2 O 2-8 generate 3 moles of SO - 4, resulting in a maximum sulfate radical yield of 15%. Alternatively, S 2 O - 8 could undergo reactions that do not produce additional SO - 4, in which case the maximum sulfate radical yield for the overall process would be 5%. S7

8 In the absence of benzene, there are three reactions that act as sinks for SO 4 - : 5,6,7 SO 4 + S 2 O 8 2 S 2 O 8 + SO 4 2 k 7 = M -1 s -1 (S7) SO O SO O + + k 8 =66 s -1 (S8) SO 4 +O SO O k 9 =7 1 7 M -1 s -1 (S9) In the absence of benzene, the major reaction that acts as a sink for O is: 8,9 O + S 2 O 8 2 S 2 O 8 +O k 1 = M -1 s -1 (S1) Therefore, the decomposition of S 2 O 8 - could proceed through the pathway indicated below: 2 O SO O 2 S 2 O 8 - S5 S3 SO 5 - S4 M n+ M (n-1)+ M n+ M (n-1)+ SO - 5 (S7) S 2 O 8 2- O 2 + SO 4 - S8 2 O S9 O - (S1) S 2 O 8 2- O S8

9 Text S6: Kinetics of SO 4 - and persulfate radical calculation Fate of SO 4 - in the absence of benzene: In the absence of benzene, Reactions S7-S9 are the three reactions that act as sinks for SO ,11,12 When S 2 O 2-8 is activated (Reaction S1-S2), one mole of S 2 O - 8 is generated for every mole of SO - 4 generated. In addition, S 2 O is also lost through reactions with SO 4 - (Reaction S7). The branching ratio for -SO 4 in the absence of benzene is k 7 [S 2 O 2-8 ]/(k 8 + k 9 [O - ]). At p 8 and 1 mm S 2 O , approximately half of the SO 4 reacts with S 2 O 2-8. Relative concentration of SO 4 - : In the absence of benzene, Reaction S1 becomes the major reaction that acts as a sink for O. 13,14 Therefore, d [O ] dt = k * SO, - + k / O - SO, - k 12 [S 3 O * 3- ] O Under steady-state conditions: [O ] 44 = k * SO, - + k / O - k 12 [S 3 O * 3- ] SO, - 44 With 1 mm S 2 O 8 2- and at p 8., [O ] ss =.5[SO 4 - ] ss. Therefore, the state-steady concentration of SO 4 - is approximately 2 times higher than O under experimental conditions employed in this study. Fate of SO 4 - in the presence of benzene: In the presence of 1 mm benzene, the following reaction becomes the major sink for SO 4 - : S9

10 + SO!- 4 + SO (C 6 6 ) (C 6 +! 6 ) k 11 = M -1 s -1 (S11) The branching ratio for SO 4 - in the presence of benzene is k 11 [benzene]/(k 7 [S 2 O 8 2- ]+k 8 + k 9 [O - ]). At p 8, 1 mm S 2 O 8 2- and 1 mm benzene, essentially all SO 4 - reacts with benzene. In the presence of benzene, there is an additional sink for O : 15 + O! (C 6 6 ) (CD) (C 6 7 O! ) k 12 = M -1 s -1 (S12) At steady-state conditions: [O ] 44 = k * SO, - + k / O - k 12 S 3 O * 3- + k 13 [Benzene] SO, - 44 With 1 mm benzene, 1 mm S 2 O 8 2- and at p 8., [O ] ss =.1[SO 4 - ] ss. Therefore, the state-steady concentration of SO 4 - is still 2 orders of magnitude higher than O under experimental conditions in the presence of benzene in this study. S1

11 Text S7: Kinetics of organic radicals in the benzene/so 4 - system The hydroxylcyclohexadienyl (CD, i.e., C 6 7 O ) radical can react with O 2 at the ortho position: 15 (C 6 7 O ) S13,f + O 2 + S13,r (o-c 6 7 O 3 ) OO S14 O 2 k 13,f = M -1 s -1 k 13,r = s -1 k 14 = s -1 In addition, CD radical can react with O 2 at the para-position as follows: S16 + O 2 (C 6 7 O ) + O 2 S15,f R15,r OO (p-c 6 7 O 3 ) S17 O O k 15,f = M -1 s -1 k 15,r = s -1 k 16 = s -1 k 17 = s -1 Based on the kinetics rate constants in the reactions above, 15 the steady-state concentration of organic peroxy radicals are: d [o C 6 7 O 3 ] dt d [ p C 6 7 O 3 ] dt = k 13, f [O 2 ][CD] k 13,r [o C 6 7 O 3 ] k 14 [[o C 6 7 O 3 ] = = k 15, f [O 2 ][CD] k 15,r [ p C 6 7 O 3 ] k 15 [ p C 6 7 O 3 ] k 16 [ p C 6 7 O 3 ] = Under air-saturated conditions (i.e., [O 2 ]=25 µm), the steady-state radical concentrations are: S11

12 [o C 6 7 O 3 ] ss = k 13, f [O 2 ] k 14 + k 13,r [CD] ss =.45[CD] ss k [ p C 6 7 O 3 ] ss = 15, f [O 2 ] [CD] ss = 3.51[CD] ss k 16 + k 17 + k 15,r Therefore: [ p -C 6 7 O 3 ] ss = 8[o -C 6 7 O 3 ] ss, and p-c 6 7 O 3 accounts for 99% of C 6 7 O 3. The formation of phenol originates from both o-c 6 7 O 3 and p-c 6 7 O 3. Because the branching ratio of k 13, f [o C 6 7 O 3 ] ss k 15, f [o C 6 7 O 3 ] ss = [CD] ss [CD] ss = Phenol is predominantly formed from o-c 6 7 O 3. S12

13 Text S8: Estimate of phenol loss due to direct reaction of SO 4 - or O with phenol in the presence of benzene. Phenol is produced from benzene reacting with SO 4 - : + SO!- 4 + SO (C 6 6 ) (C 6 +! 6 ) k 18 = M -1 s -1 (S18) Phenol produced in this reaction can also react with SO 4 - : + SO!- 4 Products k 19 = M -1 s -1 (S19) At a given reaction time t, there is competitive kinetics between benzene and phenol: d [benzene] t dt = k 18 [benzene] t [SO 4 ] ss d [ phenol] t dt = k 19 [ phenol] t [SO 4 ] ss Transform the above differential equation to numerical integration between reaction time t 1 and t 2 : ([benzene] Δ[benzene] t2 t 1 = k t1 +[benzene] t2 ) 18 [SO 4 ] ss,t1 t 2 2 (t 2 t 1 ) ([ phenol] Δ[ phenol] t2 t 1 = k t1 +[ phenol] t2 ) 19 [SO 4 ] ss,t1 t 2 2 (t 2 t 1 ) S13

14 Therefore, Δ[ phenol] t 2 t 1 = k [ phenol] 19 t1 +[ phenol] t2 [SO 4 ] ss,t1 t k 18 [benzene] t1 +[benzene] 2 (t 2 t 1 ) t2 Δ[ phenol] t2 t 1 is the loss of phenol that should be accounted for as the oxidation product of benzene. Therefore, the total amount of phenol produced between the reaction time t 1 and t 2 is: Δ[ phenol] produced,t2 t 1 = Δ[ phenol] measured,t2 t 1 + Δ[ phenol] t2 t 1 Based on the calculation, [phenol] t2-t1 is a very small fraction, i.e., [phenol] t2-t1 is <.1% of [phenol] measured, t2-t1. Therefore, the loss of phenol due to reaction with SO 4 - is negligible. In addition, since [O ] ss is 2 orders of magnitude smaller than [SO - 4 ] ss, and the rate constant of phenol reacting with O (k= M -1 s -1 ) is similar to that of phenol reacting with SO - 4 (k= M -1 s -1 ), the loss of phenol due to reaction with O is negligible as well. S14

15 Table S1 Characterization of aquifer materials, clay materials and pure minerals. 1 Table 2 e Properties of aquifer materials. Surface area was measured in our laboratory while the other properties were Material Type Material Name BET Surface area (m 2 /g) Total Fe (wt %) Total Mn (wt %) Sand (wt %) Silt (wt %) Clay (wt%) CADOU %.1% 84% 16% 4% Aquifer Material CAROL %.2% 63% 18% 19% AWBP %.3% 82% 1% 8% AFTCS %.3% 6% 22% 18% AMTAL %.12% 64% 22% 14% Clay Material Nontronite %.1% % Montmorillonite %.5% % Pure Mineral Geothite α-feoo (s) Ferrihydrite Fe(O) 3(s) Pyrolusite β-mno 2(s) % % % Silica SiO 2(s) S15

16 Table S2 Chemical composition of synthetic groundwater used in this study. Chemical parameter Concentration Na + 23 mg/l Ca 2+ Mg SO 4 Cl - Br - NO CO 3 TDS Suwannee River NOM p 8 2 mg/l 5 mg/l 2 mg/l 35.5 mg/l.1 mg/l 1 mg/l 1 mm 166 mg/l 1 mg C/L The solution was buffered at p 8. with 5 mm borate. The use of high buffer concentration was necessary to maintain a constant p throughout the experiment. Experimental condition is with 5 g/l of minerals, initial persulfate concentration 1 mm and p 8. In experiments with benzene, the initial concentration of benzene was 1 mm. S16

17 Table S3 Comparison of the production of aldehyde-like compound relative to phenol by S 2 O 8 2- and 2 O 2. Relative ratio of aldehyde-like compound to phenol (1 4 AU/µM) * S 2 O 8 2- activation 2 O 2 activation Goethite.33 ± ±.1 Ferrihydrite 6.2 ± 2.4 Aldehyde not detected Pyrolousite.26 ±.9 Aldehyde not detected * The concentration of aldehyde-like compound is expressed as 1 4 adsorption units (AU) at the wavelength of 36 nm. The concentration of phenol is express as µm. S17

18 Table S4 Comparison of oxidant yield in synthetic groundwater and MQ water from persulfate activation by different minerals*. Yield of SO 4 - from S 2 O 8 2- Synthetic Groundwater Yield of SO 4 - from S 2 O 8 2- MQ water Goethite 155% ± 6% 167% ± 1% Ferrihydrite 2% ± 1% 26% ± 8% Pyrolousite 37% ± 5% 62% ± 12% * Experimental condition: initial benzene=1 mm; initial persulfate=1 mm; mineral solids=5 g/l; p=8.; ionic strength=5 mm. S18

19 5% 1 Total benzene (µm) Benzene concentration Adsorbed fraction 4% 3% 2% 1% Fraction of adsorbed benzene % Reaction time (Day) Figure S1 Measurement of total benzene (i.e., aqueous benzene plus adsorbed benzene) in a 5 g/l pyrolusite suspension. Adsorbed benzene was recovered by acetonitrile extraction. Initial added benzene was 1 µm, pyrolusite concentration was 5 g/l, p was buffered at 8. with 5 mm borate. S19

20 1 A 8 [S 2 O 8 2- ] (µm) 6 4 No ferrihydrite or benzene 2 Ferrihydrite only Ferrihydrite + benzene B [Benzene] (µm) No ferrihydrite or persulfate Ferrihydrite only Ferrihydrite + persulfate Figure S2 Changes in (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of ferrihydrite (Fe(O) 3(s) ). Initial benzene=1 mm, initial persulfate=1 mm, ferrihydrite concentration=5 g/l, p=8.. S2

21 1 A 8 [S 2 O 8 2- ] (µm) No pyrolusite or benzene Pyrolusite only Pyrolusite + benzene B 8 [Benzene] (µm) 6 4 No pyrolusite or persulfate 2 Pyrolusite only Pyrolusite + persulfate Figure S3 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of pyrolusite (β-mno 2(s) ). Initial benzene=1 mm, initial persulfate=1 mm, pyrolusite concentration=5 g/l, p=8.. S21

22 1 A 8 [S 2 O 8 2- ] (µm) No montmorillonite or benzene Montmorillonite only Montmorillonite + benzene B 8 [Benzene] (µm) No montmorillonite or persulfate Montmorillonite only Montmorillonite + persulfate Figure S4 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of montmorillonite. Initial benzene=1 mm, initial persulfate= 1 mm, montmorillonite concentration=5 g/l, p=8.. S22

23 1 A 8 [S 2 O 8 2- ] (µm) No nontronite or benzene Nontronite only Nontronite + benzene B 8 [Benzene] (µm) No nontronite or persulfate Nontronite only Nontronite + persulfate Figure S5 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of nontronite. Initial benzene=1 mm, initial persulfate 1 mm, nontronite concentration 5 g/l, p 8.. S23

24 1 8 A [S 2 O 8 2- ] (µm) 6 4 No AFTCS or benzene 2 AFTCS only AFTCS + benzene B [Benzene] (µm) No AFTCS or pertsulfate AFTCS only AFTCS + persulfate Figure S6 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material AFTCS. Initial benzene=1 mm, initial persulfate=1 mm, AFTCS concentration=5 g/l, p=8.. S24

25 1 8 A [S 2 O 8 2- ] (µm) 6 4 No CADOU or benzene 2 CADOU only CADOU + benzene B 8 [Benzene] (µm) No CADOU or persulfate CADOU only CADOU + persulfate Figure S7 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material CADOU. Initial benzene=1 mm, initial persulfate=1 mm, CADOU concentration=5 g/l, p=8.. S25

26 12 [S 2 O 8 2- ] (µm) A No AWBP or benzene AWBP only AWBP + benzene B [Benzene] (µm) No AWBP or persulfate AWBP only AWBP + persulfate Figure S8 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material AWBP. Initial benzene=1 mm, initial persulfate=1 mm, AWBP concentration=5 g/l, p=8.. S26

27 1 8 A [S 2 O 8 2- ] (µm) 6 4 No CAROL or benzene 2 CAROL only CAROL + benzene B [Benzene] (µm) No CAROL or persulfate CAROL only CAROL + persulfate Figure S9 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material CAROL. Initial benzene=1 mm, initial persulfate=1 mm, CAROL concentration=5 g/l, p=8.. S27

28 1 8 A [S 2 O 8 2- ] (µm) 6 4 No AMTAL or benzene 2 AMTAL only AMTAL + benzene B [Benzene] (µm) No AMTAL or persulfate AMTAL only AMTAL + persulfate Figure S1 Changes of (A) persulfate concentration and (B) total benzene concentration via persulfate activation in the presence of aquifer material AMTAL. Initial benzene=1 mm, initial persulfate=1 mm, AMTAL concentration=5 g/l, p=8.. S28

29 A Eluent Peaks Phenol Unknown product Benzene Adsorp4on*intensity* B Wavelength*(nm)* S29

30 C Figure S11 Identification of aldehyde-like compound as the oxidation product of benzene by SO - 4 radicals. (A) PLC-UV chromatogram of one sample obtained after persulfate was activated in the presence of benzene and minerals; (B) UV Spectra of the aldehyde-like product; (C) QTOF-LC-MS scan in negative mode of the aldehyde-like product. An exact mass of m/z was obtained, which corresponds to the sum formula C 6 5 O 3 (Δppm: 5.6).Fragmentation of the m/z 125 revealed cleavage of CO (-28 Da; fragments and 69.35). At higher collision energies fragment increased indicating the cleavage of 2 O (-18 Da) from fragment S3

31 [ppm] ppm [ppm] Figure S12 NMR spectra of the unknown compound confirm a ring cleavage product with a fragment identified as an enal. 1 NMR (top left), 1,1-NOESY (top right), 1,1-COSY (bottom left), 1,13C-SQC (bottom right). 1 NMR (6 Mz, CD3CN) δ 9.32 (d, 1, J = 1), 8.63 (s, 2 ), 7.44 (d, 1, J = 15), 6.93 (dd, 1, J = 1, 15). 1-13C SQC (6 Mz, 151 Mz, CD3CN) δ (9.32, 198.5), (8.63, 185), (7.44, 143), (6.93, 115). MestReNova and inmr (Mestrelab Research SL) were used to process the NMR spectra. Chemical shifts are reported in ppm and calibrated to residual solvent peaks. Coupling constants are reported in hertz. Unidentified peaks in the SQC are due to contamination with phenol. S31

32 Peak area unknown compound [-] Unknown Compound Bisulfite adduct time [min] Peak area bisulfite adduct [-] Figure S13 Formation of a bisulfite adduct of the unknown ring-cleavage product over time. The increase of the peak area for the bisulfite-adduct product indicated the presence of an aldehyde moiety. 1 mm bisulfite was mixed with SPE-enriched ring-cleavage product. S32

33 Aldehyde-like compound (AU, X1 4 at 36 nm) Aldehyde-like compound (AU, X1 4 at 36 nm) A [O ] = 3 µm [O ] = 25 µm Time (Day) B 2 2 [O ] = 3 µm Time (Day) 2 [O ] = 25 µm 2 Figure S14 Formation of aldehyde-like product during persulfate activation by minerals. (A) Ferrihydrite; (B) Pyrolusite. Mineral mass loading=5 g/l, initial total benzene=1 µm, initial S 2 O 8 2- =1 µm, borate buffer=5 mm, p=8.. S33

34 References 1 Liu,.; Bruton, T. A.; Doyle, F. M.; Sedlak, D. L. In situ chemical oxidation of contaminated groundwater by persulfate: activation by Fe(III)- and Mn(IV)-containing oxides and aquifer materials. Environ. Sci. Technol. 214, 48, Anipsitakis, G. P.; Dionysiou, D. D. Degradation of organic contaminants in water with sulfate radicals generated by the conjunction of peroxymonosulfate with cobalt. Environ. Sci. Technol. 23, 37 (2), Zhang, T.; Zhu,.; Croué, J. P. Production of sulfate radical from peroxymonosulfate induced by a magnetically separable CuFe 2 O 4 spinel in water: efficiency, stability and mechanism. Environ. Sci. Technol. 213, 47 (6), Zhang, Z.; Edwards, J. O. Chain lengths in the decomposition of peroxomonosulfate catalyzed by cobalt and vanadium. Rate law for catalysis by vanadium. Inorg. Chem. 1992, 31 (17), Kolthoff, I. M.; Miller, I. K. The chemistry of persulfate. I. The kinetics and mechanism of the decomposition of the persulfate ion in aqueous medium. J. Am. Chem. Soc. 1951, 73 (7), errmann,.; Reese, A.; Zellner, R. Time-resolved UV/VIS diode-array absorption spectroscopy of SO - x (x=3, 4, 5) radical anions in aqueous solution. J. Mol. Struct. 1995, 348, Peyton, G. R. The free-radical chemistry of persulfate-based total organic carbon analyzer. Mar. Chem. 1993, 41, Buxton, G. V.; Greenstock, C. L.; elman, W. P.; Ross, A. B. Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals ( O/ O - ) in aqueous solution. J. Phys. Chem. Ref. Data. 1988, 17, Das, T. N. Reactivity and role of SO - 5 radical in aqueous medium chain oxidation of sulfite to sulfate and atmospheric sulfuric acid generation. J. Phys. Chem. A. 21, 15, Kolthoff, I. M.; Miller, I. K. The chemistry of persulfate. I. The kinetics and mechanism of the decomposition of the persulfate ion in aqueous medium. J. Am. Chem. Soc. 1951, 73 (7), S34

35 11 errmann,.; Reese, A.; Zellner, R. Time-resolved UV/VIS diode-array absorption spectroscopy of SO - x (x=3, 4, 5) radical anions in aqueous solution. J. Mol. Struct. 1995, 348, Peyton, G. R. The free-radical chemistry of persulfate-based total organic carbon analyzer. Mar. Chem. 1993, 41, Buxton, G. V.; Greenstock, C. L.; elman, W. P.; Ross, A. B. Critical review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals ( O/ O - ) in aqueous solution. J. Phys. Chem. Ref. Data. 1988, 17, Das, T. N. Reactivity and role of SO - 5 radical in aqueous medium chain oxidation of sulfite to sulfate and atmospheric sulfuric acid generation. J. Phys. Chem. A. 21, 15, Pan, X. M.; Schuchmann, M. N.; von Sonntag, C. Oxidation of benzene by the O radical: a product and pulse radiolysis study in oxygenated aqueous solution. J. Chem. Soc. Perkin Trans. 1993, 2, S35