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In this study, the degradation of trichloroethylene (TCE) with the existence of tween-80 (TW-80) or sodium dodecyl sulfate (SDS) using peroxymonosulfate (PMS) activated by nano-zero-valent iron (nZVI) was investigated. Over 87.6% TCE (with 1.3 g L−1 TW-80 presence) was degraded by 0.9 mM PMS and 0.12 g L−1 nZVI, while 89.7% TCE (with 2.3 g L−1 SDS presence) was degraded by 1.2 mM PMS and 0.20 g L−1 nZVI, in which more than 71.9% TCE with TW-80 existence and 87.5% TCE with SDS existence were dechlorinated. Besides, the effects of some factors (i.e., PMS and nZVI dosages, initial solution pH, and inorganic anions) on TCE removal were evaluated. The degradation of TCE was restrained continuously with increasing surfactant concentration, and TW-80 was more easily decomposed than SDS in PMS/nZVI system. Furthermore, sulfate radical (SO4–•) and hydroxyl radical (HO•) were demonstrated the main reactive oxygen species (ROS) contributing to TCE degradation and SO4–• played a dominant role through EPR tests and ROS scavenging experiments. Finally, the results of TCE degradation in actual groundwater confirmed that PMS/nZVI process has great advantages and potential in remediation of actual TCE-contaminated groundwater with TW-80 or SDS existence. [ABSTRACT FROM AUTHOR]

In this study, 90.9% fluoranthene (FLT) was degraded in sodium percarbonate (2Na 2 CO 3 ·3H 2 O 2 , SPC) oxidation system by Fe(II) combined with sulfidated nano zero valent iron (S-nZVI) activation within 60 min in aqueous solution. Scavenging experiments and electron paramagnetic resonance detection suggested that HO•, O 2 −•, and 1O 2 contributed to the removal of FLT in SPC/Fe(II)/S-nZVI system. Based on the FLT degradation intermediates that were analyzed by GC-MS in SPC/Fe(II)/S-nZVI process, three potential FLT degradation pathways were speculated. The removal efficiency of FLT was inhibited with the presence of humic acid (HA) unless the concentration of HA was controlled at 1.0 mg L−1, and the presence of 1.0 mg L−1 HA favored the generation of HO•. The excellent removal performance of FLT (88.6%) could be achieved in actual groundwater by increasing the chemical dosages and adjusting the initial solution pH to acid environment. In soil slurry tests, the optimal reaction time and soil/water ratio were obtained as 24 h and 2/10, respectively, and the desired FLT degradation performances were obtained at pH 3 and 5 with the soil/water ratio of 2/10. This work effectively demonstrates the application potential of SPC/Fe(II)/S-nZVI system for the remediation of PAHs contamination in actual industrial sites. [Display omitted] • The mechanisms of FLT removal in aqueous solution were investigated. • HO• was the primary ROS in SPC/Fe(II)/S-nZVI system. • Three degradation pathways of FLT were proposed. • The effect of HA on FLT removal in aqueous solution was explored. • The optimal condition for FLT degradation in soil slurry system reaction time, soil/water, and pH were was clarified. [ABSTRACT FROM AUTHOR]

Trichloroethene (TCE) degradation was investigated in Fe(II)/citric acid (CA) activated persulfate (PS) system containing surfactant sodium dodecyl sulfate (SDS). Only 37.7% removal of TCE was achieved at PS/Fe(II)/CA/TCE molar ratio of 40/20/20/1 in the presence of 2.3 g L−1 SDS with pH unadjusted (pH = 2.96). However, this result was significantly increased to 81% after adjusting the initial solution pH = 9.0. The presence of SDS inhibited TCE degradation and this inhibitory effect was initially increased and then declined with SDS concentration increase from 0 to 9.2 g L−1. Radical scavenger experiments revealed that the major reactive oxygen species (ROS) contributed to TCE degradation were HO• and SO 4 −•, while less contribution was owed to O 2 −•. The intermediates of SDS were identified with GC-MS and possible decomposition pathway of SDS was proposed. The performance of TCE degradation in other solution matrixes were investigated. Actual groundwater tests showed that PS/Fe(II)/CA system possessed huge potential in remediating groundwater contaminated by TCE with SDS presence. This research found that alkaline condition was more favorable for TCE degradation in PS/Fe(II)/CA system in the presence of SDS and the possible reasons for this phenomenon were explored from various aspects. [Display omitted] • The influence of solution pH on the CMC value of SDS was investigated. • The mechanism of higher TCE degradation in alkaline condition was explored. • HO• and SO 4 −• were the primary ROSs in PS/Fe(II)/CA system with the presence of SDS. • Significant TCE degradation in actual groundwater containing SDS was achieved after adjusting solution pH = 9. [ABSTRACT FROM AUTHOR]

Polyvinylpyrrolidone coated nano zero valent iron-copper (PVP-nZVI-Cu) bimetallic nanoparticles were successfully synthesized for dechlorination of trichloroethylene (TCE) into non-toxic byproducts in the presence of persulfate oxidant. The average size of PVP-nZVI-Cu nanoparticles (3–25 nm) was smaller than PVP-nZVI (25–60 nm) and nZVI (50–90 nm) particles due to PVP role in the prevention of iron aggregation and agglomerations. The synthesized PVP-nZVI-Cu nanoparticles were used as an efficient persulfate (PS) activator to generate reactive oxygen species (ROSs) for the degradation of TCE. The complete removal of TCE (99.6%) was achieved in the presence of 0.4 g/L of PVP-nZVI-Cu nanoparticles and 6 mM of persulfate oxidant at acidic pH (3.2) with 82.3% of TCE dechlorination and 84.4% of total organic carbon (TOC) removal within 1 h. Further, the catalytic activity of PVP-nZVI-Cu particles for TCE removal in the presence of four surfactants (TW-80, BRIJ-35, TX-100, and SDS) was also investigated, showing 99%, 83%, 65% and 70% removal of TCE, respectively. The intermediate products of TCE elucidated by GC-MS investigation, i.e., dichloroacetic acid, vinyle chloride, oxalic acid and glyoxylic acid, further transformed into chloride ions, carbon dioxide and water as environmentally friendly end products. The scavenging results revealed that both OH• and SO 4 •— radicals primarily contributed to TCE removal that was further confirmed with EPR analysis. Finally, the test of TCE removal in real groundwater validated that PS/PVP-nZVI-Cu system has significant potential and can be applied for remediation of TCE contaminated groundwater in in-situ practice. [Display omitted] • PVP functionalized Fe/Cu bimetallic nanoparticles were prepared. • Particle size of PVP-nZVI-Cu (3–25 nm) was smaller than nZVI (50–90 nm). • PVP-nZVI-Cu completely removed TCE in the presence of surfactant (TW-80). • OH• and SO 4 •— radicals contributed to the degradation of TCE. [ABSTRACT FROM AUTHOR]

Abstract The surface properties of nanocomposites are influenced by the existence of inorganic species that may affect its performance for specific catalytic applications. The impact of different ionic species on particular catalytic activity had not been investigated to date. In this study, the surface charge (zeta potential) of graphene-oxide-supported nano zero valent iron (G-nZVI) was tested in definitive cationic (Na+, K+, Ca2+ and Mg2+) and anionic (Br−, Cl−, NO 3 −, SO 4 2−, and HCO 3 −) environments. The efficiency of G-nZVI catalyst was inspected by measuring the generation of reactive oxygen species (ROS) for the degradation of 1,1,1-trichloroethane (TCA) in sodium percarbonate (SPC) system. Tests conducted using probe compounds confirmed the generation of OH and O 2 − radicals in the system. In addition, the experiments performed using scavenging agents certified that O 2 − were primary radicals responsible for TCA removal, along with prominent contribution from OH radicals. The study confirmed that G-nZVI catalytic capability for TCA degradation is notably affected by various cationic species. The presence of Ni2+ and Cu2+ significantly enhanced (94%), whereas Na+ and K+ had minor effects on TCA removal. Overall, the results indicated that groundwater ionic composition may have low impact on the effectiveness of G-nZVI-catalyzed peroxide TCA treatment. Graphical abstract Unlabelled Image Highlights • Dominant groundwater cations effect the performance efficiency for degradation • Surface charge and organic ions effect investigated for the degradation of TCA a persistent contaminant in hydrosphere. • Generation of reactive oxygen species for remediation of TCA in percarbonate system • The ionic composition of groundwater has a relatively minor effect on TCA removal for the G-nZVI catalyzed system. [ABSTRACT FROM AUTHOR]

In response to environmental concerns at the global level, there is considerable momentum in the exploration of materials derived from waste that are both sustainable and eco-friendly. In this study, CS-Fe (carbon, silica, and iron) composite was synthesized from coal gasification slag (CGS) and innovatively applied as a catalyst to activate PS (persulfate) for the degradation of trichloroethylene (TCE) in water. Scanning electron microscope (SEM), fourier transmission infrared spectroscopy (FTIR), energy dispersive x-ray spectroscopy (EDS), brunauer, emmet, and teller (BET) technique, and x-ray diffractometer (XRD) spectra were employed to investigate the surface morphology and physicochemical composition of the CS-Fe composite. CS-Fe catalyst showed a dual nature by adsorption and degradation of TCE simultaneously, displaying 86.1% TCE removal in 3 h. The synthesized CS-Fe had better adsorption (62.1%) than base material CGS (36.4%) due to a larger BET surface area (770.8 m2 g−1), while 24.0% TCE degradation was recorded upon the activation of PS by CS-Fe. FTIR spectra confirmed the adsorption and degradation of TCE by investigating the used and fresh samples of CS-Fe catalyst. Scavengers and Electron paramagnetic resonance (EPR) analysis confirmed the availability of surface radicals and free radicals facilitated the degradation process. The acidic nature of the solution favored the degradation while the presence of bicarbonate ion (HCO 3 −) hindered this process. In conclusion, these results for real groundwater, surfactant-added solution, and degradation of other TCE-like pollutants propose that the CS-Fe composite offers an economically viable and favorable catalyst in the remediation of organic contaminants within aqueous solutions. Further investigation into the catalytic potential of coal gasification slag-based carbon materials and their application in Fenton reactions is warranted to effectively address a range of environmental challenges. [Display omitted] • CGS is used to synthesize CS-Fe composite to activate persulfate for TCE degradation. • CS-Fe composite exhibited significant absorbance capacity. • ROS played a dominant role in the degradation of TCE in the PS/CS-Fe system. • PS/CS-Fe system favors acidic solution for efficient degradation of TCE. • The existence of HCO 3 ˉ hindered TCE degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Over 90% NAP could be removed in PDS/Fe(II)/CaSO 3 and PMS/Fe(II)/CaSO 3 systems. • The enhancement mechanism of CaSO 3 on the removal of NAP was illuminated. • SO 4 − was the dominant ROS for NAP degradation in CaSO 3 -enhanced systems. • NAP degradation intermediates and pathways were elucidated. • The applicability of CaSO 3 -enhanced systems in various water matrixes was assessed. Na 2 SO 3 and NaHSO 3 have been widely used as the source of SO 3 2− to participate in the reproduction of Fe(II) in iron-based advanced oxidation processes. In this work, CaSO 3 with low solubility was innovatively introduced and compared with Na 2 SO 3 and NaHSO 3 to investigate their effects on naphthalene (NAP) degradation in Fe(II)-activated peroxydisulfate (PDS) and peroxymonosulfate (PMS) processes. The results showed that CaSO 3 displayed a better performance due to its sustained-release of SO 3 2−, and NAP removal increased from 57.6% and 77.7% to 91.4% and 98.5% in PDS/Fe(II) and PMS/Fe(II) processes, respectively, with the addition of CaSO 3. The enhancement mechanisms of CaSO 3 were illustrated by measuring the variation of iron and SO 3 2− concentrations and by quantitatively determining the production of reactive oxygen species (ROS). The dominant ROS generated in CaSO 3 -enhanced systems was confirmed by scavenging tests. Moreover, NAP degradation intermediates and pathways, as well as the toxicological properties of intermediates, were accordingly elucidated. Finally, CaSO 3 -enhanced systems had a wide application range of pH, and exhibited a great performance on the tolerance of various water matrixes. The significant removal of various contaminants in CaSO 3 -enhanced processes confirmed that these techniques are suitable for the remediation of organic contaminated groundwater. [ABSTRACT FROM AUTHOR]

In this study, ferrous sulfide (FeS) was introduced to nano calcium peroxide (nCP)/Fe(III) system to facilitate the generation of Fe(II), more than 90% of naphthalene (NAP) could be removed at a wide pH range of 3–9. As a heterogeneous reductant, FeS could mitigate competitive reactions with reactive oxygen species (ROS), which favored the NAP degradation. As evidenced by scavenging experiments, HO• was the major ROS contributing to NAP degradation. The role of sulfur species (S2−, SO 3 2−, and S 2 O 3 2−) in nCP/Fe(III) system was investigated with S 2 O 3 2− showing the preferable reactivity in Fe(III) reduction. In addition, the surface-bound HO• and surface Fe(II) were detected and the role of them on NAP degradation was revealed and concluded that both dissolved and surface Fe(II) contributed to NAP degradation, whereas surface-bound HO• was not superior to solution HO• in degrading NAP. Furthermore, nCP/Fe(III)/FeS system showed high feasibility to different solution matrixes and various types of water as well as the broad-spectrum reactivity to other toxic organic pollutants, exhibiting promise for practical application to remediate complex contaminants. [Display omitted] • FeS played a vital role in accelerating Fe(II)/Fe(III) circulation. • The competitive reactions in nCP/Fe(III)/FeS system could be minimized. • Mechanisms of NAP degradation in nCP/Fe(III)/FeS system were revealed. • NAP degradation performances in various water matrixes were investigated. • Excellent reactivity for other organic contaminants was achieved. [ABSTRACT FROM AUTHOR]

Calcium peroxide (CaO 2 ) is a stable hydrogen peroxide (H 2 O 2 ) carrier, and the CaO 2 /Fe(II) system has been applied for treatment of various pollutants. It is commonly reported in the literature that hydroxyl radical (HO ) and superoxide radical anions (O 2 − ) are the two main reactive oxygen species (ROSs) generated in the CaO 2 /Fe(II) system. However, many of the reported results were deduced from degradation performance rather than specific testing of radical generation. Thus, the specific generation of ROSs and the influence of system conditions on ROSs yield are still unclear. To our knowledge, this is the first study specifically focusing on the generation of HO and O 2 − in the CaO 2 /Fe(II) system. Experimental conditions were optimized to investigate the production of HO and O 2 − . The results showed the influences of CaO 2 , Fe(II), and solution pH on HO and O 2 − generation, and the HO generation efficiency was reported for the first time. In addition, the ROSs generation pathways in the CaO 2 /Fe(II) system were elucidated. A strategy for enhancing HO yield is developed, based on the continuously dosing Fe(II). This proposed strategy has implications for the effective application of in situ chemical oxidation employing CaO 2 /Fe(II) for groundwater remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The homogeneous reaction played a dominant role in H 2 O 2 /FeS 2 /NAP system. • FeS 2 performed best compared with S-nZVI and FeS. • Sulfur intermediates from FeS 2 facilitated the iron redox cycle. • FeS 2 performed well in complex environment conditions. Fe-containing natural minerals, such as pyrite, have been conducted an extensive study in Fenton-like processes, however, answers for the role of homogeneous and heterogeneous reactions and their application potentials need to be theoretically demonstrated. In this study, the performance and mechanism of Fenton-like process catalyzed by pyrite were investigated by surface characterizations and degradation experiments using naphthalene as a target contaminant. First, the major role of homogeneous reaction in the naphthalene degradation in H 2 O 2 /pyrite system was confirmed by iron determination and iron quenching tests, where 2,2′-bipyridine was used as the iron quencher. Second, it was clarified that sulfur species including polysulfides, elemental sulfur, and thiosulfate facilitated the Iron redox cycle and the yield of reactive oxygen species, thus enhanced the degradation of naphthalene. Moreover, compared with sulfidated nanoscale zero valent iron and ferrous sulfide, pyrite exhibited superiority in naphthalene degradation due to higher reaction stoichiometry efficiency (0.31) and lower running cost (77 RMB (kg naphthalene)−1). Finally, pyrite showed excellent performance for various pollutants removal and in multiple water environments. This work provides the underlying mechanisms of H 2 O 2 /pyrite process and a solid step forward to pyrite application in the remediation of naphthalene contaminated water. [ABSTRACT FROM AUTHOR]

• CaSO 3 , slow-released SO 3 2− source, was introduced in S(IV)-based AOPs. • Fe(III)/CaSO 3 system was established for the removal of various organic contaminants. • The major ROS, contaminants degradation mechanism, and pathways were revealed. • The degradation performance of contaminants in complex solution matrixes was investigated. • Extensive applications and broad-spectrum of Fe(III)/CaSO 3 system were demonstrated. S(IV)-based advanced oxidation process has been applied for contaminants remediation. However, as a traditional source of sulfite (SO 3 2−), Na 2 SO 3 is extremely soluble in water, resulting in a high concentration of SO 3 2− to quench the generated reactive oxygen species (ROS). In this work, CaSO 3 was introduced instead of Na 2 SO 3 for its slow-released SO 3 2− ability and Fe(III)/CaSO 3 system was established for the removal of trichloroethylene (TCE) and other organic contaminants. The degradation efficiency of TCE reached 94.0% and TCE could be completely dechlorinated and mineralized, while the removal of other contaminants was all over 85.0% at the optimal tested conditions. Through EPR detection, ROS scavenging and probe tests, and quantification of ROS amounts, it was concluded that the dominant ROS in Fe(III)/CaSO 3 system were SO 4 −· and 1O 2 , of which the transformation mechanism of SO 4 −· to 1O 2 was revealed and demonstrated comprehensively. The synergistic contaminants degradation performance in different sulfur-iron-containing systems and in the presence of oxidants was evaluated. The effects of various solution conditions were assessed and Fe(III)/CaSO 3 system was of higher resistance on complex solution matrixes, suggesting the broad-spectrum and application perspective for the remediation of complex contaminants in actual water. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV/PMS could efficiently inactivate ARB and control the risk of photoreactivation. • bla NDM-1 was greater resistance to UV/PMS than bla OXA-58 in the same plasmid. • ARGs base pairs number and length were responsible for ARGs removal. • 1O 2 plays an important role on the plasmid-encoded ARGs removal in UV/PMS. The super-resistant bacteria that produce the New Delhi metallo-β-lactamase 1 (NDM-1) enzyme are becoming a conceivably major worldwide clinical issue with serious consequences. Studying the disinfection and mechanism of super-resistant bacteria and their antibiotic resistance genes (ARGs) is crucial for controlling their spread in the water environment. In this study, the disinfection of the super-resistant bacterium Acinetobacter sp. CS-2 and its transferable ARGs (plasmid-encoded bla NDM-1 and bla OXA-58) by ultraviolet radiation (UV), peroxymonosulfate (PMS), and ultraviolet/peroxymonosulfate (UV/PMS) exposure were investigated. UV/PMS could completely inactivate CS-2 and control the photoreactivation risk, while bacteria that underwent UV and PMS treatment had survival ratios of 0.22% and 0.28%, respectively. The removal efficiencies of bla NDM-1 and bla OXA-58 ranged from 3.64 to 4.05 log, and the advantage of UV/PMS treatment on ARGs damage was further identified by gel electrophoresis analysis. The removal efficiency of bla NDM-1 was lower than that of bla OXA-58 , which was attributed to the low number of adjacent 5′-TT-3′ harbored by bla NDM-1. The removal rate constants of the ARGs by UV treatment were significantly correlated with the number of adjacent base pairs (e.g., 5′-TT-3′, 5′-CT-3′, 5′-TC-3′ and 5′-CC-3′) and length, with R -values ranging from 0.9044 to 0.9512. Singlet oxygen (1O 2) played a vital role in the reduction of bla NDM-1 and bla OXA-58 in the UV/PMS treatment. UV/PMS showed high removal efficiency under natural pH conditions and in the presence of various aqueous ions (e.g., Cl−, SO 4 2− and HCO 3 −). Overall, this study provides new understandings and theoretical support for the risk control of super-resistant bacteria and plasmid-encoded ARGs. [ABSTRACT FROM AUTHOR]

The performance of naphthalene (NAP) degradation in peroxodisulfate (PDS) and peroxymonosulfate (PMS) oxidation systems by nano zero valent iron (nZVI) combined with citric acid (CA) activation was reported in aqueous solution and soil slurry medium. The results in aqueous solution tests indicated that 98.1% and 98.9% of NAP were individually degraded in PDS/nZVI/CA and PMS/nZVI/CA systems within 2 h when the dosages of PDS, PMS, nZVI and CA were 1.0 mM, 0.1 mM, 0.2 mM and 0.1 mM, respectively. The consequences of scavenging tests and electron paramagnetic resonance detection demonstrated that HO• and SO 4 −• were the key factors on NAP removal. The presence of surfactants could consume ROSs and inhibit NAP removal. In addition, GC-MS was applied for the determination of NAP degradation intermediates, and three possible NAP degradation pathways were proposed in PDS oxidation process and two pathways in PMS oxidation process, respectively. The results in soil slurry medium showed that the presence of CA could promote the dissolution of soil minerals and the desorption of NAP from soil medium. 93.5% and 96.8% degradation of NAP were obtained in PDS/nZVI/CA and PMS/nZVI/CA systems within 24 h. Besides, the existence of DOM in soil could promote Fe(II)/Fe(III) cycle and NAP degradation through electron transfer. Based on the NAP degradation performance in the actual groundwater and soil medium, the above findings could provide basis and strong support for the potential application of PDS/nZVI/CA and PMS/nZVI/CA systems in the remediation of NAP contaminated sites. [Display omitted] • NAP degradation in actual groundwater and soil slurry medium was investigated. • HO.• and SO 4 −• were the key factors in PDS and PMS oxidation systems. • The possible degradation pathways of NAP were proposed. • The enhancement of citric acid for NAP removal was illuminated. • The mechanism of NAP degradation influenced by DOM in soil was clarified. [ABSTRACT FROM AUTHOR]

• HSO 3 – significantly enhanced HO• generation and TCE degradation. • HO• was the dominant ROSs in nCaO 2 /Fe(III)/HSO 3 – system. • The double effect of CaO 2 as both oxidant and O 2 source was clarified. • The enhancement mechanism caused by HSO 3 – was revealed. The effect of bisulfite (HSO 3 –) in nCaO 2 /Fe(III)/HSO 3 – system on improving HO• generation and trichloroethene (TCE) removal was innovatively reported. The enhancement mechanism of HSO 3 – for TCE removal in nCaO 2 /Fe(III)/HSO 3 – system was caused not only by the complexing and reducing effects on promoting the conversion of Fe(III) to Fe(II), but also due to the reaction with O 2 in water to produce SO 4 –• for accelerating TCE degradation. A double effect of nCaO 2 as an oxidant source to generate HO• and as a O 2 source to promote SO 4 –• generation was revealed. A pseudo-second-order kinetic model of TCE removal was determined and 94.6% TCE degradation was achieved within 60 min at the nCaO 2 /Fe(III)/HSO 3 –/TCE molar ratio of 6/12/9/1, in which 82.8% TCE was dechlorinated. The scavenger test and EPR detection found that various kinds of reactive oxygen species (ROSs) including HO•, SO 4 –•, O 2 –• and 1O 2 were generated, all contributed to TCE removal and HO• was the dominant one in nCaO 2 /Fe(III)/HSO 3 – system. The effects of surfactant presence and the complex matrix in the actual groundwater were evaluated. The experiments of high efficiency for chlorinated olefins and benzene series removals but low applicability for chlorinated alkanes provided an alternative technique to remedy groundwater based on the various kinds of contaminants performance. [ABSTRACT FROM AUTHOR]

The presence of polycyclic aromatic hydrocarbons (PAHs) in groundwater is making a great threat to human health in the world which has received an increasing environmental concern. Among various Fenton oxidation processes, 97.6%, 92.1% and 89.4% naphthalene (NaP) removals were observed using hydrogen peroxide (H 2 O 2), sodium percarbonate (SPC) and calcium peroxide (CP) as oxidants activated by Fe(II) in ultrapure water tests, respectively. While, the inhibitory effect on NaP degradation caused by the weak alkaline solution pH and the presence of HCO 3 − in actual groundwater could be compensated by doubling dosages of oxidants and Fe(II) to different extent. 98.0%, 49.8% and 11.5% of NaP were degraded by using H 2 O 2 , SPC and CP, respectively, strongly suggesting the best H 2 O 2 performance among them. It was observed that 83.3% and 9.6% inhibition on NaP degradation in H 2 O 2 /Fe(II)/NaP system occurred in the presence of isopropyl alcohol and chloroform, confirming that both hydroxyl radical (HO) and superoxide anion radical (▪) contributed to NaP degradation in Fenton process and HO was the prominent radical. The presence of HO was further demonstrated by electro-spin resonance spectrometer analysis. The identification of transformation products of NaP revealed that hydroxylation and ring rupture were the main NaP degradation pathways. [Display omitted] • H 2 O 2 performed best among H 2 O 2 , SPC and CP for NaP degradation. • HO was the dominant ROSs in H 2 O 2 (SPC or CP)/Fe(II)/NaP system. • HCO 3 — had significant inhibitory influence on NaP degradation. • Hydroxylation and ring rupture were the main NaP degradation pathways. [ABSTRACT FROM AUTHOR]

In this study, amorphous boron was employed as a reductant in traditional Fenton system for the first time to accelerate the regeneration of Fe(II). The degradation of 1,2-dichloroethane (DCA) was only 40.0% in Fenton system, while in the presence of amorphous boron, it could reach to 93.0% in 60 min. HO• was demonstrated to be the major reactive oxygen species (ROSs) and responsible for DCA degradation. Further, the mechanism of amorphous boron-enhanced Fenton system was described as follows. With the addition of amorphous boron, the reduction process occurred on its surface and Fe(III) was regenerated to Fe(II) to further utilize H 2 O 2 and produce more HO• for DCA removal. Meanwhile, amorphous boron was oxidized to B 2 O 3 and a portion of H 3 BO 3 leaching into the solution occurred. Both B 2 O 3 and H 3 BO 3 had no reactivity for Fe(III) reduction. Moreover, DCA could be entirely dechlorinated and mineralized to CO 2 , Cl− and H 2 O. Vinyl chloride (VC) and dichloromethane (DCM) were the mainly intermediates in DCA degradation and two possible pathways were inferred. Eventually, the performance of DCA degradation in complex solution matrixes and for other contaminants removal were tested, demonstrating the broad-spectrum reactivity and superiority of amorphous boron-enhanced Fenton system in the remediation of contaminated groundwater. [Display omitted] • Amorphous boron was employed as a reductant in Fenton system for the first time. • The promotion mechanism of amorphous boron to DCA degradation was illustrated. • DCA degradation mechanism and intermediates were revealed. • The major reactive species for DCA removal was investigated. • The broad-spectrum reactivity of amorphous boron-enhanced system was demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SPC/Fe(II) system in the environment of SDS presence applied to remediate CT under acidic condition. • The role of SDS in the SPC/Fe(II) system in S-ISCO process was investigated. • HO•, O 2 −•, CO 2 −• and 1O 2 were the main ROSs in SPC/Fe(II) system in the environment of SDS. • The mechanisms of the specific redox degradation pathway of CT were revealed. • The SPC/Fe(II) system with SDS presence possessed a great potential for the remediation of CT-contaminated groundwater. This work innovatively found that Fe(II) activated sodium percarbonate (SPC) process could successfully degrade carbon tetrachloride (CT) in the environment of sodium dodecyl sulfate (SDS). CT degradation was remarkably accelerated to 87.2% at the optimum SPC/Fe(II)/CT molar ratio of 5/10/1 with the environment of 0.2 critical micelle concentration (CMC) SDS concentration. Fe(II) could effectively catalyze the decomposition of SPC to generate reactive oxygen species (ROSs). The results demonstrated that SDS enhanced the Fenton system and developed ROSs genertion. Hydroxyl radical (HO•), superoxide radical (O 2 −•), carbon dioxide radical (CO 2 −•), and singlet oxygen (1O 2) were mainly generated in SPC/Fe(II) system under the condition of 0.2 CMC SDS, while CO 2 −• and 1O 2 were the dominant active substances at 2.0 CMC SDS presence. The SPC/Fe(II) process performed much effective for the efficient degradation of CT at the acidic pH condition. The specific redox degradation pathway of CT started from the reduction of CT to •CCl 3 through CO 2 −• and O 2 −• to form intermediates that were further dechlorinated by ROSs. In conclusion, the application of Fe(II) catalyzed SPC in the environment of SDS is a promising technology in converting the oxidation process into the simultaneous existence of oxidation and reduction process. [ABSTRACT FROM AUTHOR]

• PDA decorated Fe/rGO nanocomposite synthesized via a facile approach. • Enhancement in catalytic degradation of TCA. • Enrichment in the generation of reactive oxygen species. • Highly active and stable nanocomposite for TCA degradation in groundwater. The removal of chlorinated hydrocarbons through heterogeneous catalysts from groundwater has become a valuable approach. However, the synthesis of a highly efficient and persistent material especially for trichloroethane (TCA) removal is still immature. In this study, we prepared polydopamine (PDA) embedded Fe/rGO nanocomposite via pH-induced polymerization of dopamine for the degradation of TCA in sodium percarbonate (SPC) system. The experimental outcomes revealed that PDA decorated Fe/rGO not only enhanced the TCA degradation (98%) more economically but also strengthened the stability and recyclability of catalyst compared to bare Fe/rGO. The TEM, XRD, FTIR, XPS and VSM analyses declared the successful preparation of magnetically separable PDA@Fe/rGO nanocomposite. Furthermore, a higher degradation rate of probe compounds in PDA@Fe/rGO/SPC system indicated that PDA decoration improved the formation of active species due to autoxidation of dopamine and reducing capability of PDA. The impact of solution matrix on PDA@Fe/rGO performance elucidated the effect of various species on degradation. The GCMS, TOC analysis and dechlorination experiments validated the formation of non-toxic products and reasonable TOC and chloride ions removal. The PDA@Fe/rGO catalyst can be recycled for six consecutive cycles retaining a 76% along with abundant availability of Fe2+ and Fe3+ species validated using XRD and XPS analysis. The enhanced remediation capacity and improved recyclability of PDA@Fe/rGO nanocomposite can serve as a shining star for the practical application of TCA removal in groundwater. [ABSTRACT FROM AUTHOR]

• FeS significantly enhanced HO generation and TCE degradation. • The synergistic activation mechanism of Fe(II)/FeS was investigated. • HO was the primary ROSs in nCP/Fe(II)/FeS system. • Effective degradation of TCE in actual groundwater was achieved. The performance of trichloroethene (TCE) degradation was significantly improved with the addition of FeS in nanoscale calcium peroxide (nCP) environment and the enhancement of HO generation in nCP/Fe(II)/FeS system was confirmed by comparison with nCP/Fe(II) and nCP/FeS systems. The role of FeS in nCP/Fe(II)/FeS system demonstrated that the majority of reactive oxygen radicals (ROSs) was generated on the catalyst surface due to the heterogeneous reaction through FeS activated nCP in one hand, and the reductive FeS could promote TCE degradation by regenerating Fe(II) from Fe(III) in the other hand. The probe as well as scavenger test results suggested that the major ROSs was HO rather than O 2 −. Over 91.5% TCE could be degraded at the molar ratio of 2/2/4/1 of nCP/Fe(II)/FeS/TCE, in which more than 95.5% TCE was dechlorinated. The effect of surfactants on TCE degradation was evaluated. In contrast, further investigation found that BTEX removal was inhibited with the addition of FeS. In conclusion, this study revealed the well function and fundamental synergistic mechanism of FeS. Moreover, the degradation of TCE in actual groundwater confirmed that nCP/Fe(II)/FeS technique has a great advantage and potential in TCE contaminated groundwater remediation in ISCO practice. [ABSTRACT FROM AUTHOR]