Degradation of ciprofloxacin and sulfamethoxazole by ferrous-activated persulfate: Implications for remediation of groundwater contaminated by antibiotics
Introduction
Antibiotics are chemotherapeutic agents that inhibit or abolish the growth of microorganisms, such as bacteria, fungi, or protozoa. Recently, the wide occurrence of antibiotics in groundwater raised concerns about potential adverse effects on human health and aquatic ecosystems (Sarmah et al., 2006, Kümmerer, 2009, Barber et al., 2009, Lapworth et al., 2012, Jurado et al., 2012). Municipal sewage treatment plants effluents, animal waste and landfill leachates are regarded as the primary pathways for antibiotics release into groundwater (Barber et al., 2009, Lapworth et al., 2012). The environmental fate of antibiotics in groundwater is mainly controlled by sorption to organic matter and clay minerals, and microbial degradation or transformation (Tolls, 2001, Gao and Pedersen, 2005, Gu and Karthikeyan, 2005, Li and Zhang, 2010). However, owing to the relatively long residence times and persistence due to reducing chemistry and relatively low microbial rates in groundwater, a growing number of antibiotics with considerably high levels have been detected worldwide (Sarmah et al., 2006, Kümmerer, 2009, Barber et al., 2009, Lapworth et al., 2012). The long term exposure to antibiotic contaminated groundwater is believed to cause chronic effects on human beings as well as ecological systems (Isidori et al., 2005, Kümmerer, 2009). In addition, the presence of antibiotics in natural waters may contribute to the spread of antibiotic resistance in microorganisms (Kümmerer, 2009). Thus, developing effective treatment technology for elimination of antibiotics in groundwater is of great scientific, regulatory and public interest.
In situ chemical oxidation (ISCO) is an emerging technology for groundwater remediation due to its applicability to a wide range of contaminants, relatively fast treatment, potentially enhanced post-oxidation microbial activity and cost effectiveness (Tsitonaki et al., 2010). The ISCO technology is mainly based on the generation of reactive species arising from the decomposition of oxidants such as persulfate (S2O82 −) and hydrogen peroxide (H2O2). Among all commonly used ISCO oxidants, persulfate receives wide attention, and generally shows promising results because it can be activated by various approaches to generate free sulfate radical (SO4−, E0 = 2.6 V). It is also easily delivered for long distances in aquifers due to its relatively high stability (Tsitonaki et al., 2010). Even though persulfate can be effectively activated by heat, UV and alkaline pH, transition metal based activation is the most viable method for field application of this oxidation technology (Zhao et al., 2013, Anipsitakis and Dionysiou, 2004, Rastogi et al., 2009b, Nfodzo and Choi, 2011). Fe(II) and Fe(III) are the most commonly used metal activators due to their natural abundance in porous media and benign nature (Tan et al., 2012, Xu and Li, 2010). Similar to the Fenton's reaction, the Fe(II)-persulfate reagent is composed of the transition metal and oxidant. Thus, Fe(II) activated persulfate bears a lot of similarity to Fenton systems and the knowledge from that technology can help us better understanding the mechanism. Once the SO4− is generated, it can propagate a series of reactions involving the formation of other active species, particularly the hydroxyl radical (HO) (Eqs. (1), (2), (3), (4), (5), (6), (7), (8), (9)).
These highly reactive species can oxidize a wide variety of organic and inorganic compounds. However, the low efficiency and competition for SO4− due to excess of Fe(II) or oxidant in Fe(II)-persulfate system have also been highlighted recently (Tsitonaki et al., 2010). In addition, the rapid conversion of Fe(II) to Fe(III) limits the ultimate oxidizing capability of ferrous–persulfate system (Anipsitakis and Dionysiou, 2004, Liang et al., 2004). In order to stabilize the amount of Fe(II) in solution, chelating agents are usually employed (Liang et al., 2004, Tan et al., 2012). For example, ethylene diamine tetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) have been widely used as Fe(II) chelators. However, their unbiodegradability in the environment have also been highlighted recently (Sillanpaa and Pirkanniemi, 2001). Therefore, there is a need to search environmentally safe and highly effective chelating agents for persulfate activation.
The constituents of water matrix may more or less influence the removal efficiency of organic compounds by ISCO as observed in Fenton process and other AOPs (Sirtori et al., 2010, Hu et al., 2007). It is generally accepted that SO4− reacts more selectively with organic compounds than HO through one electron transfer mechanism. Thus, SO4−-based oxidation could be less influenced by water matrix composition. For example, Liang et al. (2006) observed that at a neutral pH, persulfate oxidation of trichloroethylene (TCE) was not affected by the presence of bicarbonate/carbonate concentrations within the range of 0–9.20 mM. A more recent study has reported that SO4−-based technologies showed promising results for the removal of diclofenac and sulfamethoxazole from wastewater treatment plant effluents because of the higher selectivity of SO4− over HO, limiting radical scavenging by natural organic matter and allowing for higher abatement and mineralization rates (Mahdi Ahmed et al., 2012). However, data on the effect of natural water matrix on Fe(II)-persulfate mediated decomposition of organic compounds are still scarce.
In the present study, we assess Fe(II) activated persulfate as a potential ISCO approach for destructing ciprofloxacin (CIP) and sulfamethoxazole (SMX) in water. CIP and SMX have been chosen as model compounds of antibiotic agents because they are among the most frequently detected worldwide (see Table 1) (Kümmerer, 2009, Lapworth et al., 2012). Generally, groundwater may also be contaminated by other pollutants belonging to the same group (e.g., sulfonamide). Thus, comparison of the degradation efficiency and elucidation of the discrepancy among these structurally related compounds are of great interest. Therefore, the main goals of this study are (1) to investigate the kinetics and predominant reactive species responsible for the decomposition of CIP and SMX by Fe(II)-persulfate; (2) to study the effect of water matrix, Fe(II) chelating agents on Fe(II)-persulfate mediated antibiotics degradation and compare the decomposition of SMX with other sulfonamide drugs; (3) to identify the transformation intermediates and elucidate the degradation pathways of CIP and SMX by Fe(II) activated persulfate.
Section snippets
Chemicals
Potassium persulfate (K2S2O8, 99+%) was obtained from Aldrich. Ferrous sulfate heptahydrate (FeSO4 7H2O, ≥ 99.0%) was obtained from Sigma-Aldrich and was used as the catalytic Fe(II) species. Ciprofloxacin (CIP, ≥ 98.0%) and sulfamethoxazole (SMX, 99.0%) were purchased from Fluka. Other sulfonamides, sulfisoxazole (SIX, 99.9%) and sulfachloropyrazine (SCP, 99.9%) and sulfanilic acid (SAA, 97.0%) were purchased from Sigma-Aldrich. These compounds were used in comparison to SMX to assess if
CIP degradation by Fe(II) activated persulfate
Fig. 1 shows the decomposition of 30 μM CIP by Fe(II) activated persulfate at different concentrations of Fe(II) and persulfate. It is evident that CIP decomposition was appreciably enhanced with the increasing concentration of Fe(II) and persulfate. For example, the degradation efficiency of CIP was found to be 36.9%, 73.3% and 95.6% for 30, 150 and 600 μM Fe(II)-persulfate, respectively. This observation can be attributed to a higher amount of reactive radicals (e.g., SO4− and HO) at higher
Conclusions
The degradation of CIP by Fe(II) activated persulfate was found to be much more efficient than SMX. Fe(II) chelating agents showed no enhancement in CIP degradation at near neutral pH. However, CA and EDTA showed some promoting effect on SMX degradation. The degradation of CIP and SMX in river water matrix was comparable to that in Milli-Q water, implying the possibility to use Fe(II)-persulfate to destruct antibiotics under environmental conditions. A comparison of the degradation efficiency
Conflict of interest
The authors declared that they have no conflicts of interest to this work.
Acknowledgements
This work was supported by National Natural Science Foundation of China (No. 20977045 and No. 21177056) and the region Rhône-Alpes in the frame of C-MIRA project. Y. Ji gratefully acknowledges the China Scholarship Council (CSC) for the financial support. The authors also would like to thank the scientific services of Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON).
References (52)
- et al.
Kinetics and mechanism of advanced oxidation processes (AOPs) in degradation of ciprofloxacin in water
Appl Catal B Environ
(2010) - et al.
Electrochemical abatement of the antibiotic sulfamethoxazole from water
Chemosphere
(2010) - et al.
Superoxide mediated production of hydroxyl radicals by magnetite nanoparticles: demonstration in the degradation of 2-chlorobiphenyl
J Hazard Mater
(2013) - et al.
Ultraviolet (UV) light-activated persulfate oxidation of sulfamethazine in water
Chem Eng J
(2012) - et al.
Identification and determination of metabolites and degradation products of sulfonamide antibiotics
Trends Anal Chem
(2008) - et al.
Oxidation of sulfamethoxazole and related antimicrobial agents by TiO2 photocatalysis
Water Res
(2007) - et al.
Toxic and genotoxic evaluation of six antibiotics on non-target organisms
Sci Total Environ
(2005) - et al.
Photocatalytic degradation of atenolol in aqueous titanium dioxide suspensions: kinetics, intermediates and degradation pathways
J Photochem Photobiol A Chem
(2013) - et al.
Emerging organic contaminants in groundwater in Spain: a review of sources, recent occurrence and fate in a European context
Sci Total Environ
(2012) Antibiotics in the aquatic environment—a review—part I
Chemosphere
(2009)
Emerging organic contaminants in groundwater: a review of sources, fate and occurrence
Environ Pollut
Photochemical efficiency of Fe(III)–EDDS complex: OH radical production and 17β-estradiol degradation
J Photochem Photobiol A Chem
Persulfate oxidation for in situ remediation of TCE. II. Activated by chelated ferrous ion
Chemosphere
Influences of carbonate and chloride ions on persulfate oxidation of trichloroethylene at 20 °C
Sci Total Environ
Potential for activated persulfate degradation of BTEX contamination
Water Res
Sulfate radical anion oxidation of diclofenac and sulfamethoxazole for water decontamination
Chem Eng J
Triclosan decomposition by sulfate radicals: effects of oxidant and metal doses
Chem Eng J
Photolytic and photocatalytic decomposition of aqueous ciprofloxacin: transformation products and residual antibacterial activity
Water Res
Effect of inorganic, synthetic and naturally occurring chelating agents on Fe(II) mediated advanced oxidation of chlorophenols
Water Res
Sulfate radical-based ferrous-peroxymonosulfate oxidative system for PCBs degradation in aqueous and sediment systems
Appl Catal B Environ
A global perspective on the use, sales, exposure pathways, occurrence, fate and effects of veterinary antibiotics (VAs)
Chemosphere
Effect of water-matrix composition on trimethoprim solar photodegradation kinetics and pathways
Water Res
Photolytic and photocatalytic degradation of fluoroquinolones in untreated river water under natural sunlight
Appl Catal B Environ
Degradation of diuron by persulfate activated with ferrous ion
Sep Purif Technol
Degradation of sulfamethoxazole in water by solar photo-Fenton. Chemical and toxicological evaluation
Water Res
Photodegradation of sulfamethoxazole in various aqueous media: persistence, toxicity and photoproducts assessment
Chemosphere
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