In this study, we investigated using the main composition of pipe deposits from water distribution networks as catalyst to activate dual-oxidant H2O2/Na2S2O8 system to produce radicals for perchloroethylene and chloramphenicol removal. According to the results, the degradation efficiency of perchloroethylene by H2O2/Na2S2O8 system was 92.05% within 8 h. Due to the slow conversion between ≡Fe3+ and ≡Fe2+, the hydroxylamine was introduced to reduce reaction time. As for the results, the degradation efficiency of chloramphenicol in the H2O2/Na2S2O8 system with hydroxylamine assistance was 73.31% within 100 min. Meanwhile, several key affecting factors and the kinetic models were investigated. The primary radicals were identified by electron paramagnetic resonance and radical scavenging tests. Eleven degradation products were confirmed by high-resolution liquid chromatography-mass spectrometry. The result of this study provided the theoretical basis for resource utilization of pipe deposits in water treatment in case of emerging contamination events.

Perchloroethylene (PCE) is an important organic solvent, which is widely used in the cleaning industry of machinery, electronic parts and clothing, as well as in the production of medicine, textiles, and chemicals (Zhong et al. 2019). Chloramphenicol (CAP) is a bacteriostatic broad-spectrum antibiotic, which is widely used in disease treatment, animal husbandry and aquaculture (Cao et al. 2020). PCE and CAP have been detected in surface water, ground water and even drinking water because of the unreasonable usage and disposition. PCE and CAP can cause various diseases including leukemia, kidney and liver tumors (Zhong et al. 2019), bone marrow depression and aplastic anemia (He et al. 2020) which are serious and widespread problems (Shapiro et al. 2004; Walters et al. 2010).

Various remediation technologies were used to remove PCE and CAP from water. It is well-known that the advanced oxidation processes (AOPs) based on hydroxyl radicals (•OH) and sulfate radicals () are considered as effective methods to mineralize organic pollutants (Wu et al. 2018). Hydrogen peroxide (H2O2, HP), peroxymonosulfate(KHSO5·0.5KHSO4·0.5 K2SO4, PMS) and persulfate(Na2S2O8, PS) are the common oxidants to produce radicals for degrading pollutants (Luo et al. 2021a). The •OH-AOPs and -AOPs have their respective advantages. The •OH-AOPs have a high reaction rate and are nonselective for organics, -AOPs are stable and selective and has a longer half-life time than •OH. However, in order to achieve the same efficiency, the PS or PMS dosage must be very high which leads to higher salinity in the system (Gu et al. 2019). The dual-oxidant system could reduce oxidant usage and utilize their respective advantages in removal pollutants and have faster degradation rate (Chen et al. 2020; He et al. 2020; Song et al. 2020). The combined application of HP and PS to generate •OH and has been studied to treat various pollutants including levofloxacin (Epold et al. 2015), erythromycin (Li et al. 2017), trichloroethylene (Yan et al. 2013), 2,4-dinitrotoluene (Xu et al. 2019), and even industrial wastewater (Chen et al. 2020).

Iron-containing materials are the most commonly used catalysts to activate HP, PS and PMS because of its cost-effectiveness and eco-friendliness (Rastogi et al. 2009; Romero et al. 2010). Some researchers found that the pipe deposits are iron-rich including α-FeOOH, γ-FeOOH, γ-Fe2O3 and Fe3O4, etc. (Oliveira et al. 2012; Cui et al. 2016). The pipe deposits could be used as inexpensive catalysts in heterogeneous Fenton-like oxidation, which attracted increasing attention (Oliveira et al. 2012). In our previous study, we explored the adsorption and degradation capacity of simulated pipe deposits (SGR, the mixture of the major constituents of actual pipe deposits (α- and γ-FeOOH)) for 5-bromosalicylic acid(5-BSA), 32.65% and 87.67% of 5-BSA could be removed by adsorption and SGR/H2O2 oxidation (Huang et al. 2021). The findings of previous study would make an important contribution to pipe deposits recycling. However, the removal time was too long, and the mechanisms and kinetics were not discussed in detail.

In this study, we analyzed and prepared the main composition of pipe deposits, γ-FeOOH, which is used as a catalyst to activate HP/PS in order to produce radicals for PCE and CAP removal. The hydroxylamine (NH2OH, HA) was introduced to increase the degradation rate and shorten the degradation time. Furthermore, the underlying mechanism was investigated by radical scavenging test (RST), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The method may be expected to be used for in situ treatment of polluted water of the network emergency contamination.

Materials

PCE was obtained from Tianjin Bodi Chemicals Co., Ltd FeCl2·4H2O and NaOH were purchased from Sinopharm Chemical Reagent Co., Ltd CAP, H2O2, Na2S2O8, NH2OH, para-chlorobenzoic acid (pCBA) and 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) were obtained from Shanghai Aladdin Biochemical Technology Co., Ltd. Methanol(MeOH), tert-butanol(TBA) and isopropanol were from Tianjin Guangfu Fine Chemical Research Institute. All the chemicals were used without any further purification. All solutions were prepared by deionized water.

Preparation of lepidocrocite

Lepidocrocite (γ-FeOOH) was synthesized at 25 °C. Firstly, 4 g FeCl2·4H2O were added to 100 mL deionized water and continuously stirred, and maintained the solution pH at 6.8 ± 0.1 by adding 1.0 mol L−1 NaOH. Then, air (36 − 72 L h−1) was sent into the solution and maintained pH at 6.8 ± 0.1 until the color of suspension changed from dark green to orange. Finally, the prepared γ-FeOOH was centrifuged and washed with deionized water and dried (Antony et al. 2005).

PCE and CAP removal and detection

All batch removal experiments were conducted in a 100 mL capped bottle at 25 °C. A certain number γ-FeOOH were added to 100 mL aqueous solution containing PCE or CAP. HA, HP and PS were added to the abovementioned solution at appropriate concentration to perform degradation experiments. 0.1 mol L−1 HCl and 0.1 mol L−1 NaOH was used to adjust the pH of pollutant solution. The PCE was extracted by n-hexane and the residual concentration was detected by GC-ECD. The CAP residual concentration was detected by a UV-vis spectrophotometer at 277.6 nm. The detected peak did not shift which indicated that the addition of reagents did not influence CAP detection, as shown in Fig. S1. All experiments were conducted in triplicate.

Confirmed the rate constant of the pollutant with radicals

The rate constant of CAP with radicals (k·OH,CAP) was studied by competition kinetics method (Cao et al. 2020). pCBA (k·OH, pCBA = 5.00 × 109 M−1s−1) was used for the competitor. The adsorption of CAP and pCBA by γ-FeOOH and photodegradation were negligible. The rate constant of CAP with •OH could be estimated by the following equation:
formula
(1)
Rearranging Equation (1) got Equation (2)
formula
(2)
  • k•OH,pCBA was the reaction rate constant of •OH with pCBA.

  • k•OH,CAP was the reaction rate constant of •OH with CAP.

Characterization

Scanning electron microscope (SEM, ZEISS Sigma 500, Instrument Parameter: EHT = 15.00 kV, Signal A = SE2, WD = 8.4 mm, Mag = 20.00 KX) was used to observe the morphology of γ-FeOOH. X-ray diffraction with 2θ range from 10 to 90° was used to analyzed the crystalline structure of γ-FeOOH(XRD, AXS D8 ADVANCE with CoKα radiation (λ = 1.54060 Å)). X-ray photoelectron spectroscopy (XPS, AXIS ULTRA DLD using Al Ka radiation (1,486.6 eV)) were used to explore the surface valence state of γ-FeOOH before and after degradation. The chemical groups on γ-FeOOH surface were detected by Fourier transformation infrared spectroscopy (FTIR, Perkin Elmer Spectrum One). The main radicals were detected by electron paramagnetic resonance (EPR, Bruker, Germany) with DMPO as the spin-trapping agent. The degradation products were determined by high-resolution LC-MS in negative ionization mode using an Agilent 1260 HPLC coupled with ABSciexQTrap 5500 MS with an electrospray ionization (ESI) source. The MS instrumental parameters were set as follows: source temperature, 500 °C; Gas I, 50 arbitrary units; Gas II, 50 arbitrary units; negative ion spray voltage, 4500 V; curtain gas, 50 arbitrary units; entrance potential (EP), 10 V; declustering potential (DP), 100 V; collision energy (CE), 30 V; collision cell exit potential (CXP), 20 V; PIS scan range, 100–1000 amu.

Morphology and structural characterization of γ-FeOOH

γ-FeOOH was a rod-type structure by the SEM observation (Figure 1(a)). The XRD patterns (Figure 1(b)) showed that the diffraction peaks at 2θ = 14.16°, 27.16°, 36.14° and 46.89° were attributed to (200), (210), (301) and (501) lattice planes of Lepidocrocite, syn (JCPDS No. 44-1415) (Shao et al. 2022). The stronger intensity and narrower half peak width suggested that γ-FeOOH was a consistent crystal structure. According to the FTIR spectrum (Figure 1(c)), the peak appeared at 1021 cm−1 was the in-plane of Fe-O-H bending vibrations, while the peak appeared at 753 cm−1 was for the out-plane (He et al. 2018). These results verified the successful preparation of γ-FeOOH. Figure 1(d) showed that the N2 adsorption-desorption isotherms of the prepared γ-FeOOH is type IV with H3 hysteresis loop, demonstrating its microporous/mesoporous structure (Li et al. 2019; Liu et al. 2019). Meanwhile, γ-FeOOH has a rather larger specific surface area (117.567 m2/g), average pore size (23.8672 nm) and pore volume (0.6382 cm3/g). The larger specific surface area could expose more active sites, which was conducive to increasing reaction activity (Lyu et al. 2021).

Figure 1

Characterizations of the prepared γ-FeOOH: (a) SEM image, (b) XRD spectrum, (c) FTIR spectrum and (d) N2 adsorption-desorption curve.

Figure 1

Characterizations of the prepared γ-FeOOH: (a) SEM image, (b) XRD spectrum, (c) FTIR spectrum and (d) N2 adsorption-desorption curve.

Close modal

The degradation PCE and CAP in different systems

The PCE degradation under different systems was explored, the result was showed in Figure 2(a). Due to the volatilization and adsorption, 15.33% PCE was removed. 92.05% PCE was removed in HP/PS system in 8 h. The PCE degradation efficiency in dual-oxidant system was higher than in the single-oxidant system, HP/PS > HP > PS. The removal of CAP in γ-FeOOH, γ-FeOOH/HP/PS, γ-FeOOH/HA/HP, γ-FeOOH/HA/PS and γ-FeOOH/HA/HP/PS was shown in Figure 2(b). When γ-FeOOH was added alone, CAP was not removed indicating that γ-FeOOH had no adsorption. In addition, CAP could not be degraded effectively by γ-FeOOH/HP/PS system, indicating that γ-FeOOH cannot activate HP and PS to produce radicals. When the HA was introduced into the system and the usage of oxidant was the same, the degradation efficiency of CAP in γ-FeOOH/HA/HP, γ-FeOOH/HA/PS and γ-FeOOH/HA/HP/PS system was 63.18%, 14.11% and 73.31% in 100 min, respectively. And the CAP degradation in HP/PS, HP and PS system could be well fitted by the first-order kinetics model as expressed by Equation (3) (Zhou et al. 2014), the detail fitting results of CAP were shown in Figure 2(c) and Table 1.
formula
(3)
  • k is the kinetic rate constant, which can be calculated from the slope of the straight line.

Figure 2

The (a) PCE and (b) CAP degradation under different systems; (c) The kinetic fitting curve of CAP under different systems. Reaction conditions: (a) [PCE]0 = 163 mg L−1, [γ-FeOOH]0 = 22.5 mmol L−1; (b) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = 2 mmol L−1, (Oxidants: [HP]0 = [PS]0 = 4 mmol L−1 in γ-FeOOH/HA/HP and γ-FeOOH/HA/PS system, respectively; [HP]0 = [PS]0 = 2 mmol L−1 in γ-FeOOH/HA/HP/PS system), pH = 6.5, T = 25 °C.

Figure 2

The (a) PCE and (b) CAP degradation under different systems; (c) The kinetic fitting curve of CAP under different systems. Reaction conditions: (a) [PCE]0 = 163 mg L−1, [γ-FeOOH]0 = 22.5 mmol L−1; (b) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = 2 mmol L−1, (Oxidants: [HP]0 = [PS]0 = 4 mmol L−1 in γ-FeOOH/HA/HP and γ-FeOOH/HA/PS system, respectively; [HP]0 = [PS]0 = 2 mmol L−1 in γ-FeOOH/HA/HP/PS system), pH = 6.5, T = 25 °C.

Close modal
Table 1

The kinetic parameters of CAP degradation in different systems and the oxidant decomposition kinetic parameters

Systemk(min−1)R2
γ-FeOOH/HA/HP 0.0103 0.9904 
γ-FeOOH/HA/PS 0.0023 0.9911 
γ-FeOOH/HA/HP/PS 0.0173 0.9740 
HP decomposition (Figure 4(b)0.0139 0.9917 
PS decomposition (Figure 4(c)0.0076 0.9967 
0.0024 0.9980 
Systemk(min−1)R2
γ-FeOOH/HA/HP 0.0103 0.9904 
γ-FeOOH/HA/PS 0.0023 0.9911 
γ-FeOOH/HA/HP/PS 0.0173 0.9740 
HP decomposition (Figure 4(b)0.0139 0.9917 
PS decomposition (Figure 4(c)0.0076 0.9967 
0.0024 0.9980 

The rate constant of γ-FeOOH/HA/HP/PS system was 0.0173 min−1, which was higher than γ-FeOOH/HA/HP(0.0103 min−1) and γ-FeOOH/HA/PS (0.0023 min−1). The results indicated that the HP/PS system has the unique advantages in pollutant removal because of synergistic effect.

Effect of experimental conditions

AOPs are complicated systems, and many factors could influence their performance. In order to better clarify the mechanism of dual-oxidant system, the detailed effect of different experimental conditions on CAP degradation were studied.

Effect of the initial pH

The initial pH is a significant role in the AOPs. In the γ-FeOOH/HA/HP/PS system, the initial pH of the solution was adjusted by using sodium hydroxide or hydrochloric acid and no buffering agents were introduced. As shown in Figure 3(a), the degradation efficiency was over 75% when the pH ranged from 3.0 to 9.0. However, the degradation was obviously inhibited at pH = 11. The variation of solution H+ concentration was monitored (Figure 3(b)). The eventual pH all dropped to acidic, as shown in Table 2. The acidic conditions favored the reaction between γ-FeOOH and oxidant to produce radicals for target pollutant removal. According to the previous studies, if the eventual pH was higher than 4, the iron precipitation formed on the surface of γ-FeOOH that lead to a passivation phenomenon, which was harmful for the CAP degradation. The eventual pH was 6.35 when the initial was pH = 11, the CAP degradation was suppressed. Our results were consistent with previous studies (Rao et al. 2014). The increased H+ was because of the reaction between and H2O to form •OH via one-electron transfer process, as shown in Equation (4). These results demonstrated that the HP/PS dual-oxidant process can remove CAP in acidic and slightly alkaline.
formula
(4)
Table 2

The pH of before and after degradation

The initial pHThe final pH
γ-FeOOH/HA/HP/PS 2.56 
2.82 
3.01 
11 6.35 
Blank (6.5) 2.62 
The initial pHThe final pH
γ-FeOOH/HA/HP/PS 2.56 
2.82 
3.01 
11 6.35 
Blank (6.5) 2.62 
Figure 3

Effect of (a) the initial pH; (b) the H+ concentration variation at different initial pH; Effect of (c) the HP concentration, (d) the PS concentration; (e) the HA concentration and (f) the catalyst dosage on CAP degradation. (Reaction conditions: (a) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = [PS]0 = 2 mmol L−1, [HP]0 = 4 mmol L−1, T = 25 °C; (c) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = [PS]0 = 2 mmol L−1, T = 25 °C; (d) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = 2 mmol L−1, [HP]0 = 4 mmol L−1, T = 25 °C; (e) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HP]0 = 4 mmol L−1, [PS]0 = 2 mmol L−1, T = 25 °C; (f) [CAP]0 = 20 mg L−1, [HA]0 = [PS]0 = 2 mmol L−1, [HP]0 = 4 mmol L−1, T = 25 °C.).

Figure 3

Effect of (a) the initial pH; (b) the H+ concentration variation at different initial pH; Effect of (c) the HP concentration, (d) the PS concentration; (e) the HA concentration and (f) the catalyst dosage on CAP degradation. (Reaction conditions: (a) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = [PS]0 = 2 mmol L−1, [HP]0 = 4 mmol L−1, T = 25 °C; (c) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = [PS]0 = 2 mmol L−1, T = 25 °C; (d) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HA]0 = 2 mmol L−1, [HP]0 = 4 mmol L−1, T = 25 °C; (e) [CAP]0 = 20 mg L−1, [γ-FeOOH]0 = 5.6 mmol L−1, [HP]0 = 4 mmol L−1, [PS]0 = 2 mmol L−1, T = 25 °C; (f) [CAP]0 = 20 mg L−1, [HA]0 = [PS]0 = 2 mmol L−1, [HP]0 = 4 mmol L−1, T = 25 °C.).

Close modal

Effect of the initial HP or PS concentration

HP and PS are the main source of radicals. It is important to optimize the dose of oxidants for the effective degradation of organic pollutants. Figure 3(c) and 3(d) described the effect of HP and PS concentration on CAP degradation. The increase of initial HP and PS concentration resulted in a noticeable enhancement in CAP degradation, which was because of there being the enough radicals. According to the experimental results, 2 mmol L−1 PS and 4 mmol L−1 HP was the optimum dosage, the CAP degradation efficiency could reach to 78.43% in 100 min. However, when the HP or PS concentration were further increased, the degradation efficiency decreased. The excessive HP and PS might result in the scavenge of •OH and into the lower oxidizing ability species, which led to the low degradation efficiency. The detail process was shown in Equations (5)–(8) (Cai et al. 2016; Gao et al. 2022).
formula
(5)
formula
(6)
formula
(7)
formula
(8)

Effect of the iron ore dosage

The influence of the iron ore dosage on CAP degradation was investigated using the catalyst from 1.4 mmol L−1 to 11.2 mmol L−1, as shown in Figure 3(f). The increase of catalyst dosage provided more active sites for the reaction of HP/PS with antibiotics, resulting in high degradation rate. In contrast to our previous studies about the goethite activating HP/PS system (He et al. 2020), the lepidocrocite system did not have an induction period because the lepidocrocite has a larger specific surface area than goethite, which causes more ≡Fe3+ to be reduced and to accumulate more radicals with the catalyst dosage at the same time.

The residual HP and PS concentration and the kinetics fitting curves

The Figure 4(a) exhibited the residual HP and PS concentration in γ-FeOOH/HA/HP/PS system. After 100 min, the consumption of HP and PS was 75.37% and 42.81%, and the decomposition of PS was two-stage reaction. The Figure 4(b) and 4(c) were the kinetics fitting curves of HP and PS decomposition in γ-FeOOH/HA/HP/PS system, respectively. The detail kinetic parameters were shown in Table 1. HP decomposition was fitted well by the first-order kinetics model and the rate constant was 0.0139 min−1. PS decomposition was a two-phase reaction. In the initial phase (0–60 min), the rate constant was 0.0076 min−1. In the second phase (60–100 min), the rate constant was 0.0024 min−1. At the beginning of the reaction, PS was rapidly decomposed due to the accumulation of a large amount of ≡Fe2+ by HA reduction. The HA was consumed which led to the slow conversion of ≡Fe3+ to ≡Fe2+. Therefore, the PS decomposition entered a slow process.

Figure 4

(a) The HP and PS residual concentration; the HP (b) and PS (c) decomposition kinetics fitting curves.

Figure 4

(a) The HP and PS residual concentration; the HP (b) and PS (c) decomposition kinetics fitting curves.

Close modal

The confirmation of active species and reaction rate constants

In order to confirm the primary radicals in CAP degradation by γ-FeOOH/HA/HP/PS system, DMPO was used as a trapping agent to conduct the EPR test. DMPO can react with radicals to generate adducts, such as DMPO-OH and DMPO-SO4. The strong EPR signal (shown in the Figure 5(a)) was DMPO-OH, simultaneously, the low peaks were most likely to be DMPO-SO4. PS may be first activated by γ-FeOOH to produce and then react with the adsorbed water to lead to the production of abundant •OH via one-electron transfer process, which was consistent with the H+ increase. The similar phenomenon has reported in previous studies (Huang et al. 2014; Duan et al. 2016).

Figure 5

(a) The EPR spectra; (b) The radical scavenging tests; (c) The kinetics curves of pCBA and CAP. represented the DMPO-OH adduct, represented the DMPO-SO4 adduct.

Figure 5

(a) The EPR spectra; (b) The radical scavenging tests; (c) The kinetics curves of pCBA and CAP. represented the DMPO-OH adduct, represented the DMPO-SO4 adduct.

Close modal

Methanol (MeOH), tert-butanol (TBA) and isopropanol were used as quenchers to perform the quenching tests (Figure 5(b)). The reaction rate constants were = 1.6 − 7.7 × 107 M−1s−1, k•OH/MeOH = 1.2 − 2.8 × 109 M−1s−1, = 4.0 − 9.1 × 105 M−1s−1 and k•OH/TBA = 3.8 − 7.6 × 108 M−1s−1, respectively (Wang et al. 2017). The CAP degradation was completely suppressed by MeOH, TBA and Isopropanol, suggesting that •OH was the primary radical in the CAP degradation by γ-FeOOH/HA/HP/PS system (Hou et al. 2017).

The competition kinetic method was used to test the reaction rate constants of CAP with radicals at original pH by using pCBA as the competitor (Cao et al. 2020), as shown in Figure 5(c). According to our previous research, the k·OH,CAP was 6.10 × 109 M−1s−1 in γ-FeOOH/HA/HP system. The k·OH,CAP was 4.24 × 1010 M−1s−1 in the initial phase (0–60 min) and 8.15 × 109 M−1s−1 in the second phase (60–100 min) in γ-FeOOH/HA/HP/PS system, respectively. The rate was higher in the double oxidant system than in the single oxidant system. The result further confirmed the advantages of dual-oxidant system.

The role of hydroxylamine

The introduction of HA into HP/PS system could lead to a significant increase of the CAP removal efficiency. The degradation efficiency of CAP increased from 3.69% to 81.60% with HA concentration increasing from 0 mmol L−1 to 3 mmol L−1, but the degradation efficiency decreased slightly when the HA concentration increased to 4 mmol L−1, as shown in Figure 3(e). The HA accelerated the reduction of ≡Fe3+ to produce ≡Fe2+ for activating HP and PS. However, the competitive consumption of radicals with excess HA was the reason for the slight decrease of CAP degradation efficiency (Luo et al. 2021b). The dynamic fitting curves of CAP degradation under different HA dosage was shown in Figure 6(a). The whole reaction process was two-stage reaction kinetics. In the fast reaction stage, plenty of ≡Fe3+ was rapidly restored by HA, which caused the fast degradation of CAP. After HA was consumed, the generation of ≡Fe2+ was slow, the formation of reactive species was hindered, leading to a follow-up slow oxidation stage (Li et al. 2020).

Figure 6

(a) The kinetic fitting curves under different HA concentration; The XPS spectrum of (b) Fe2p and (c) O1s of γ-FeOOH before and after degradation.

Figure 6

(a) The kinetic fitting curves under different HA concentration; The XPS spectrum of (b) Fe2p and (c) O1s of γ-FeOOH before and after degradation.

Close modal

The XPS spectra of γ-FeOOH before and after the catalytic reaction were favorable to evaluate the changes of Fe (Figure 6(b)) and O (Figure 6(c)) valence state in the HP/PS activation. The peaks at 711.61 eV and 725.21 eV belonged to the binding energy of 2p3/2 and 2p1/2 of ≡Fe3+ of γ-FeOOH. After degradation, the new peaks at 710.65 eV and 724.25 eV appeared which were ≡Fe2+ (Guo et al. 2019a; Wang et al. 2020). And ≡Fe3+ and ≡Fe2+ were 58.22% and 41.78% of the total iron surface atoms after reaction. This result suggested that the reduction of ≡Fe3+ to ≡Fe2+ occurred on the surface of γ-FeOOH. In addition, the O 1s peaks could be split into the lattice oxygen (Olat, Fe-O-Fe and Fe-OH) at 530.03 eV and 531.20 eV, the surface adsorbed oxygen (Osurf) at 532.04 eV and the adsorbed molecular water (Oads) at 533.50 eV with atomic ratio of 69.84%: 23.78%: 6.38% before the degradation (Baltrusaitis et al. 2007; Kim et al. 2021). After the degradation, the atomic ratio of Olat, Osurf and Oads was 45.71%: 37.35%: 16.95%, respectively. The ratio of Olat reduced, the ratio of Osurf and Oads increased. The increase in the proportion of Oads might be attributed to more adsorbed molecular water on the surface of γ-FeOOH. The slight decrease in Olat was attributed to the surface reduction from ≡Fe3+ to ≡Fe2+. If the leaching iron concentration was less than 3.92 mg L−1, the process was heterogeneous catalysis (Chou et al. 2001). The leaching concentration of iron ion was 0.843 mg L−1 after 100 min in HP/PS system. All the results confirmed that the degradation process occurs on the γ-FeOOH surface.

The degradation intermediates were detected through LC-MS, and eleven degradation intermediates were observed, and the details are exhibited in Figure 7 and Fig. S2. The oxidation and dehydration of CAP leaded to produce P1 (Chen et al. 2019). The center C connecting aromatic ring was attacked to produce P2 and P3. Simultaneously, the ring was opened to form the intermediate P4 (Yang et al. 2021). The radical attacked CAP by dechlorinate, dehydration and oxidation that result in the formation of P5-P7. The •OH attacked P5 to generate the hydroxylated product P8 (Guo et al. 2019b). A further attacking by radicals led to the the formation of P9-P11.

Figure 7

The possible degradation products by γ-FeOOH/HA/HP/PS system.

Figure 7

The possible degradation products by γ-FeOOH/HA/HP/PS system.

Close modal

In brief, the CAP degradation process by γ-FeOOH could be depicted as follows. The HA restored the ≡Fe3+ into ≡Fe2+. The HP and PS interacted with ≡Fe2+ to produce highly oxidative radical species(•OH or ). Then, these radical species attacked CAP and effectively transformed it into intermediates P1-P11.

In order to resource utilization of pipe deposits from water distribution networks, the primary composition of pipe deposits was employed as catalyst to active HP and PS to produce radicals for degradation pollutant. 92.05% PCE was oxidative degradation after 8 h. 73.31% CAP was removed in 100 min after the HA introduction. Furthermore, the reaction rate was HP/PS(0.0173 min−1) > HP(0.0103 min−1) > PS(0.0023 min−1) and the reaction rate constant of radicals with CAP in HP/PS system was obvious higher. All the results implied that the dual-oxidant system has the unique advantages in pollutant removal. According to the result of XPS and ICP, the CAP degradation by HP/PS system was surface reaction. Eleven degradation intermediates were detected by LC-MS. The pipe deposits from water distribution networks has the capability to remove PCE and CAP in water. Although the effects of water quality and hydraulic conditions were not investigated, this study highlighted the advantage of HP/PS dual-oxidant system and the potential application of pipe deposits in water treatment in case of emerging contamination events.

This work was supported by the National Natural Science Foundation of China (No. 51778177) and Open Project of State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (No. 2021TS10).

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Dan Zhong: Resources, Funding acquisition; Fu He: Methodology, Investigation, Writing – original draft, Writing – review & editing; Wencheng Ma: Supervision; Yichuan Wu: The PCE degradation test; Jiaju Dong: Project administration.

All relevant data are included in the paper or its Supplementary Information.

Antony
H.
,
Legrand
L.
,
Maréchal
L.
,
Perrin
S.
,
Dillmann
P.
&
Chaussé
A.
2005
Study of lepidocrocite γ-FeOOH electrochemical reduction in neutral and slightly alkaline solutions at 25 °C
.
Electrochimica Acta
51
(
4
),
745
753
.
Baltrusaitis
J.
,
Cwiertny
D. M.
&
Grassian
V. H.
2007
Adsorption of sulfur dioxide on hematite and goethite particle surfaces
.
Physical Chemistry Chemical Physics
9
(
41
),
5542
5554
.
Cai
C.
,
Zhang
Z.
,
Liu
J.
,
Shan
N.
,
Zhang
H.
&
Dionysiou
D. D.
2016
Visible light-assisted heterogeneous Fenton with ZnFe2O4 for the degradation of Orange II in water
.
Applied Catalysis B: Environmental
182
,
456
468
.
Cao
Y.
,
Qiu
W.
,
Zhao
Y.
,
Li
J.
,
Jiang
J.
,
Yang
Y.
,
Pang
S.-Y.
&
Liu
G.
2020
The degradation of chloramphenicol by O3/PMS and the impact of O3-based AOPs pre-oxidation on dichloroacetamide generation in post-chlorination
.
Chemical Engineering Journal
401
,
126146
.
Cui
Y.
,
Liu
S.
,
Smith
K.
,
Yu
K.
,
Hu
H.
,
Jiang
W.
&
Li
Y.
2016
Characterization of corrosion scale formed on stainless steel delivery pipe for reclaimed water treatment
.
Water Research
88
,
816
825
.
Duan
X.
,
Su
C.
,
Zhou
L.
,
Sun
H.
,
Suvorova
A.
,
Odedairo
T.
,
Zhu
Z.
,
Shao
Z.
&
Wang
S.
2016
Surface controlled generation of reactive radicals from persulfate by carbocatalysis on nanodiamonds
.
Applied Catalysis B: Environmental
194
,
7
15
.
Gao
Y.
,
Wang
Q.
,
Ji
G.
&
Li
A.
2022
Degradation of antibiotic pollutants by persulfate activated with various carbon materials
.
Chemical Engineering Journal
429
,
132387
.
Hou
X.
,
Huang
X.
,
Jia
F.
,
Ai
Z.
,
Zhao
J.
&
Zhang
L.
2017
Hydroxylamine promoted goethite surface Fenton degradation of organic pollutants
.
Environmental Science & Technology
51
(
9
),
5118
5126
.
Huang
Z.
,
Bao
H.
,
Yao
Y.
,
Lu
W.
&
Chen
W.
2014
Novel Green activation processes and mechanism of peroxymonosulfate based on supported cobalt phthalocyanine catalyst
.
Applied Catalysis B: Environmental
154–155
,
36
43
.
Kim
B. G.
,
Park
J.
,
Choi
W.
,
Han
D. S.
,
Kim
J.
&
Park
H.
2021
Electrocatalytic arsenite oxidation using iron oxyhydroxide polymorphs (α-, β-, and γ-FeOOH) in aqueous bicarbonate solution
.
Applied Catalysis B: Environmental
283
,
119608
.
Lyu
C.
,
Zhang
L.
,
He
D.
,
Su
B.
&
Lyu
Y.
2021
Micrometer-sized NiOOH hierarchical spheres for enhanced degradation of sulfadiazine via synergistic adsorption and catalytic oxidation in peroxymonosulfate system
.
Chinese Chemical Letters
33 (2), 930–934.
Oliveira
C.
,
Santos
M. S. F.
,
Maldonado-Hódar
F. J.
,
Schaule
G.
,
Alves
A.
&
Madeira
L. M.
2012
Use of pipe deposits from water networks as novel catalysts in paraquat peroxidation
.
Chemical Engineering Journal
210
,
339
349
.
Rao
Y. F.
,
Qu
L.
,
Yang
H.
&
Chu
W.
2014
Degradation of carbamazepine by Fe(II)-activated persulfate process
.
Journal of Hazardous Materials
268
,
23
32
.
Rastogi
A.
,
Al-Abed
S. R.
&
Dionysiou
D. D.
2009
Sulfate radical-based ferrous–peroxymonosulfate oxidative system for PCBs degradation in aqueous and sediment systems
.
Applied Catalysis B: Environmental
85
(
3
),
171
179
.
Romero
A.
,
Santos
A.
,
Vicente
F.
&
González
C.
2010
Diuron abatement using activated persulphate: effect of pH, Fe(II) and oxidant dosage
.
Chemical Engineering Journal
162
(
1
),
257
265
.
Shao
Y.
,
Sun
Q.
,
Wang
L.
,
Zhan
W.
,
Zhang
H.
&
Zhong
H.
2022
Migration and transformation of Sb are affected by Mn(III/IV) associated with lepidocrocite originating from Fe(II) oxidation
.
Journal of Environmental Sciences
115
,
308
318
.
Shapiro
S. D.
,
Busenberg
E.
,
Focazio
M. J.
&
Plummer
L. N.
2004
Historical trends in occurrence and atmospheric inputs of halogenated volatile organic compounds in untreated ground water used as a source of drinking water
.
Science of The Total Environment
321
(
1
),
201
217
.
Wang
Z.
,
Lai
C.
,
Qin
L.
,
Fu
Y.
,
He
J.
,
Huang
D.
,
Li
B.
,
Zhang
M.
,
Liu
S.
,
Li
L.
,
Zhang
W.
,
Yi
H.
,
Liu
X.
&
Zhou
X.
2020
ZIF-8-modified MnFe2O4 with high crystallinity and superior photo-Fenton catalytic activity by Zn-O-Fe structure for TC degradation
.
Chemical Engineering Journal
392
,
124851
.
Xu
X.
,
Yang
Y.
,
Jia
Y.
,
Lian
X.
,
Zhang
Y.
,
Feng
F.
,
Liu
Q.
,
Xi
B.
&
Jiang
Y.
2019
Heterogeneous catalytic degradation of 2,4-dinitrotoluene by the combined persulfate and hydrogen peroxide activated by the as-synthesized Fe-Mn binary oxides
.
Chemical Engineering Journal
374
,
776
786
.
Zhou
L.
,
Shao
Y.
,
Liu
J.
,
Ye
Z.
,
Zhang
H.
,
Ma
J.
,
Jia
Y.
,
Gao
W.
&
Li
Y.
2014
Preparation and characterization of magnetic porous carbon microspheres for removal of methylene blue by a heterogeneous Fenton reaction
.
ACS Appl Mater Interfaces
6
(
10
),
7275
7285
.

Author notes

These authors contributed equally to this paper.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).

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