Degradation of octylphenol and nonylphenol by ozone - part I: direct reaction

This aqueous reaction between ozone and two alkylphenols (APs), namely octylphenol (OP) and nonylphenol (NP), has been investigated. Both compounds are important endocrine disrupting chemicals, which arise from the biodegradation of alkylphenol ethoxylates and are often found at relatively high concentrations in wastewater effluents. In this paper the results of an experimental study are presented which provide values for the reaction rate constants between molecular ozone and undissociated OP and NP, and overall reaction rate constants for the degradation of the two APs at pH values in the range of 7-9. The kinetic rate constants for OP and NP degradation by molecular ozone were 4.33(+/-0.18) x 10(4) and 3.90(+/-0.10) x 10(4) M(-1) s(-1), and the reaction stoichiometry was similar in both cases and equal to approximately 1.3:1 ([O3]:[AP]). The overall second order reaction rate constants for the two APs increased significantly with increasing pH, which is believed to be mainly due to the increasing influence of indirect radical reaction with increasing pH; this aspect is considered in more detail in a companion paper. A preliminary investigation of the reaction mechanism suggests that an initial product of ozonation is hydroxyl-alkyl phenol.     

Removal of selected endocrine disrupting chemicals and personal care products in surface waters and secondary wastewater by ozonation

This study investigated the removal of parabens, N,N-diethyl-m-toluamide (DEET), and phthalates by ozonation. The second-order rate constants for the reaction between selected compounds with ozone at pH 7 were of (2.2 +/-0.2) X 10(6) to (2.9 +/-0.3) X 10(6) M 1/s for parabens, (2.1+/- 0.3) to (3.9 +/-0.5) M-1/s for phthalates, and (5.2 +/-0.3) M-1/s for DEET. The rate constants for the reaction between selected compounds with hydroxyl radical ranged from (2.49 +/-0.06) x 10(9) to (8.5 +/-0.2) x 10(9) M-1/s. Ozonation of selected compounds in secondary wastewater and surface waters revealed that ozone dose of 1 and 3 mg/L yielded greater than 99% depletion of parabens and greater than 92% DEET and phthalates, respectively. In addition, parabens were found to transform almost exclusively through the reaction with ozone, while DEET and phthalates were transformed almost entirely by hydroxyl radicals (.OH).     

Photo-Fenton-assisted ozonation of p-Coumaric acid in aqueous solution

The degradation of p-Coumaric acid present in olive oil mill wastewater was investigated as a pretreatment stage to obtain more easily biodegradable molecules, with lower toxicity that facilitates subsequent anaerobic digestion. Thus, photo-Fenton-assisted ozonation has been studied and compared with ozonation at alkaline pH and conventional single ultraviolet (UV) and acid ozonation treatments. In the combined process, the overall kinetic rate constant was split into various components: direct oxidation by UV light, direct oxidation by ozone and oxidation by hydroxyl radicals. Molecular and/or radical ozone reaction was studied by conducting the reaction in the presence and absence of tert-butylalcohol at pHs 2, 7 and 9. Ozone oxidation rate increases with pH or by the addition of Fenton reagent and/or UV radiation due to generation of hydroxyl radicals, *OH. Hydrogen peroxide and ferrous ion play a double role during oxidation since at low concentrations they act as initiators of hydroxyl radicals but at high concentrations they act as radical scavengers. Finally, the additional levels of degradation by formation of hydroxyl radicals have been quantified in comparison to the conventional single processes and an equation is proposed for the reaction rate as a function of studied operating variables.     

Ozonation of Procaine Penicillin G formulation effluent Part I: Process optimization and kinetics

Ozonation characteristics of synthetic Procaine Penicillin G (PPG) formulation effluent were investigated in a semi-batch ozone reactor at different pH (3, 7 and 12), ozone feed rates (600-2600 mg h-1) and COD values (200-600 mg l-1). Ozonation of aqueous PPG effluent resulted in 37 (82)% COD removal after 60 (120) min ozonation when the reaction pH was kept constant at pH=7.900 mg l-1 (corresponding to 50% of the total introduced) ozone was absorbed during a reaction period of 1 h. The effects of increasing the applied ozone dose and the initial COD on the COD abatement rates of PPG effluent were also studied. Results have indicated that increasing the ozone dose and decreasing the COD content both have positive effects on COD removal rates. The significant contribution of the free radical (.OH) reaction pathway to PPG ozonation could be traced using tert-butyl alcohol as the .OH probe compound at varying concentrations. The bimolecular reaction rate constants for the direct reaction of PPG with ozone were found as 152 and 2404 M-1 h-1 at pH=3 and 7, respectively, using the gas phase ozone partial pressures determined from of the outlet gas stream analysis. It could be demonstrated that ozone decomposition to free radicals being triggered by increasing the pH from 3 to 7 is essential for the rate enhancement of PPG effluent ozonation.     

Kinetics of photodegradation and ozonation of pentachlorophenol

The oxidation of 2,3,4,5,6-pentachlorophenol (PCP) has been carried out by a photodecomposition process using a polychromatic UV irradiation, and by an ozonation process. In the photodegradation process, the pH accelerated the decomposition rate and the approximate first-order rate constants were evaluated, with values between 0.16+/-0.005 min(-1) at pH=3 and 0.26+/-0.007 min(-1) at pH=9. A more rigorous kinetic study led to the determination of the quantum yields of the reaction, with values of 200+/-7x10(-3) mol/Eins for pH=3 and 22+/-1.1x10(-3) mol/Eins for pH=9. In the ozonation process, the rate constants for the reaction between ozone and PCP were determined by means of a competition kinetics, with values in the range from 0.67x10(5) to 314x10(5) l/mols. The specific rate constants for the un-dissociated and dissociated forms of PCP were also calculated. Finally, in both processes, the intermediate reaction products were identified, the most important being tetrachlorocatechol, tetrachlorohydroquinone and tetra-p-chlorobenzoquinone. Free chloride ion released, which was favored at high pHs, was also followed in both processes.     

Enhancement of ozone oxidation and its associated processes in the presence of surfactant: degradation of atrazine

In this study, the degradation of atrazine (ATZ) by ozone (O3) oxidation and its associated processes (i.e. UV, UV/O3) in the presence and absence of surfactant was investigated and compared. A non-ionic surfactant, Brij 35, was selected. It was found that the presence of a low concentration of surfactant could improve the removal of ATZ by increasing the dissolution of ozone and the indirect generation of hydroxyl radicals. The saturated ozone level and the reaction rate constants were increased with increasing the concentration of surfactant and then decreased at higher surfactant doses at pH level of 2.5. A similar trend was observed at pH level of 7.0 in the presence of bicarbonate ion, because it is capable of deactivating the hydroxyl radicals generating at higher pH level. However, when the radical reactions become dominant in the ozonation (at pH 7.0 without bicarbonate), the saturated ozone level was higher than that with bicarbonate and the kinetic rate constants were increased first and levelled off with increasing of the dose of surfactant. Through the examining of a proposed unit performance index, the low concentration of surfactant is surely beneficial to the ozonation process. Besides, the direct photolysis and photo-assisted ozonation were compared to the ozonation. A significant enhancement on the decay rate of ATZ was resulted exclusively by adding the surfactant. An enhancement index for quantifying the improvement of the various processes was developed.     

Rapid reductive dechlorination of atrazine by zero-valent iron under acidic conditions

The dechlorination of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) via reaction with metallic iron under low-oxygen conditions was studied using reaction mixture pH values of 2.0, 3.0, and 3.8. The pH control was achieved through addition of sulfuric acid throughout the duration of the reaction. The lower the pH of the reaction mixture, the faster the degradation of atrazine. The surface area of the sulfuric acid-treated iron particles was 0.31 (+/- 0.01) m2 g-1 and the surface area normalized initial pseudo-first order rate constants (kSA, where rate = kSA x (surface area/l) x [Atrazine]) at pH values of 2.0, 3.0, and 3.8 were equal to, respectively, 3.0 (+/- 0.4) x 10(-3) min-1 m-2 l, 5 (+/- 3) x 10(-4) min-1 m-2 l, and 1 (+/- 1) x 10(-4) min-1 m-2 l. The observed products of the degradation reaction were dechlorinated atrazine (2-ethylamino-4-isopropylamino-1,3,5-triazine) and possibly hydroxyatrazine (2-ethylamino-4-isopropylamino-6-hydroxy-s-triazine). Triazine ring protonation may account, at least in part, for the observed effect of pH on atrazine dechlorination via metallic iron.     

Homogeneous degradation of 1,2,9,10-tetrachlorodecane in aqueous solutions using hydrogen peroxide, iron and UV light

The homogeneous degradation of the polychlorinated n-alkane, 1,2,9,10-tetrachlorodecane (T4C10), was studied in aqueous solutions of hydrogen peroxide, including Fenton and photo-Fenton reaction conditions. All solutions were adjusted to a pH of 2.8 and an ionic strength of 0.1 M NaClO4 prior to photolysis. T4C10 (2 x 10(-6) M) was substantially degraded by the H2O2/UV system (1.0 x 10(-2) M H2O2), with 60% disappearance in 20 min of irradiation in a photoreactor equipped with 300 nm lamps of light intensity 3.6 x 10(-5) Ein L(-1) min(-1) (established by ferrioxalate actinometry). The reaction produced stoichiometric amounts of chloride ion indicating complete dechlorination of the chlorinated n-alkane. T4C10 degraded very slowly under Fenton (Fe2+/H2O2/dark) and Fenton-like (Fe3+/H2O2/dark) conditions. However, when the same solutions were irradiated, T4C10 degraded more rapidly than in the H2O2/UV system, with 61% disappearance in 10 min of exposure. The rapid degradation is related to the enhanced degradation of hydrogen peroxide to oxidizing *OH radicals under photo-Fenton conditions. Degradation was inhibited in both the H2O2/UV and photo-Fenton systems by the addition of KI and tert-butyl alcohol due to *OH scavenging.     

臭氧氧化法处理焦化废水生化出水的反应动力学

对臭氧氧化去除焦化废水生化出水COD的反应动力学及其影响因素进行了实验研究,结果表明,在臭氧投加量为8．50mg／min,反应温度为20＇E和初始pH为10．61条件下,对COD的降解符合表观一级反应动力学模型,其相关系数R。=0．9991,表观反应速率常数k。。=1．01×10^-3s-1。该条件下,臭氧氧化对COD的降解主要来源于高活性羟基自由基的强氧化作用。在不同的臭氧投加量（4．25～12．75mg／min）、不同的反应温度（10～40℃）和不同的初始pH（3．76～12．53）下,COD的降解也同样遵循一级反应动力学规律。随着臭氧投加量的增大,COD降解的表观反应速率常数从（0．554×10^-3）s-1增加到（1．06×10＆-3）s-1;随着反应温度的升高,表观反应速率常数从（0．427×10^-3）s-1增加到（1．40×10-3）s-1,温度越高反应速率提高的幅度却越小;在初始pH3．76～10．61范围内,表观反应速率常数从（0．218×10^-3）s-1增加到（1．01×10^-3）s-1,在初始pH为12．53时表观反应速率常数下降到（0．857×10^-3）s-1。     

Kinetics of quinoline degradation by O3/UV in aqueous phase

The kinetics of quinoline degradation by O3/UV in aqueous phase was studied in this paper. It was found that the stoichiometric factor for the number of ozone molecule consumed by per quinoline molecule was 1. The second-order rate constants at 15 degrees C for the direct reaction of quinoline with ozone and that for the reaction of quinoline with *OH were determined to be 51.0 and 7.24 x 10(9) M(-1)s(-1), respectively. In O3/UV reaction system, *OH was the more important oxidant to degrade quinoline than ozone. For a comparison, in O3 reaction system, the relative importance of the two oxidants depended on the pH value greatly. To make the degradation of quinoline more practical, improvement of the concentration of *OH is more feasible.     

Photooxidation of naphthalenesulfonic acids: comparison between processes based on O(3), O(3)/activated carbon and UV/H(2)O(2)

The aim of the present study was to analyze and compare the efficacy of UV photodegradation with that of different advanced oxidation processes (O(3), UV/H(2)O(2), O(3)/activated carbon) in the degradation of naphthalenesulfonic acids from aqueous solution and to investigate the kinetics and the mechanism involved in these processes. Results obtained showed that photodegradation with UV radiation (254 nm) of 1-naphthalenesulfonic, 1,5-naphthalendisulfonic and 1,3,6-naphthalentrisulfonic acids is not effective. Presence of duroquinone and 4-carboxybenzophenone during UV irradiation (308-410 nm) of the naphthalenesulfonic acids increased the photodegradation rate. Addition of H(2)O(2) during irradiation of naphthalenesulfonic acids accelerated their elimination, due to the generation of ()OH radicals in the medium. Comparison between UV photodegradation 254 m and the advanced oxidation processes (O(3), O(3)/activated carbon and UV/H(2)O(2)) showed the low-efficacy of the former in the degradation of these compounds from aqueous medium. Thus, among the systems studied, those based on the use of UV/H(2)O(2) and O(3)/activated carbon were the most effective in the oxidation of these contaminants from the medium. This is because of the high-reactivity of naphthalenesulfonic acids with the *OH radicals generated by these two systems. This was confirmed by the values of the reaction rate constant of *OH radicals with these compounds k(OH), obtained by competitive kinetics (5.7 x 10(9) M(-1) s(-1), 5.2 x 10(9) M(-1) s(-1) and 3.7 x 10(9) M(-1) s(-1) for NS, NDS and NTS, respectively).     

Application of the EPR spin-trapping technique for the investigation of the reactions of carbonate, bicarbonate, and phosphate anions with hydroxyl radicals generated by the photolysis of H2O2

The spin trapping technique with electron paramagnetic resonance (EPR) detection of spin adducts was applied for the investigation of the reaction of hydroxyl radicals, generated by the photolysis of hydrogen peroxide, with bicarbonate and carbonate anions. The results have been compared with those obtained for aqueous solutions of hydrogen peroxide as well as solutions containing phosphate buffers at pH values identical with those of the carbonate, and bicarbonate solutions. Both the carbonate, and bicarbonate anions quenched the hydroxyl radicals more efficiently than phosphate buffers. The effect depended on the anion concentrations, and it was most pronounced in the presence of carbonate. Rate constants for the reaction of OH with the investigated anions have been calculated. They are very close to values reported in the literature, obtained using optical detection of the carbonate and phosphate radicals.     

Benzotriazoles, Alkylphenols and Bisphenol A in Municipal Wastewaters and in the Glatt River, Switzerland

- DOI: http://dx.doi.org/10.1065/espr2006.01.295 Background Many organic micropollutants occur at trace concentrations in municipal wastewater effluents and in the aquatic environment. Some of these xenobiotic chemicals can be considered as 'emerging' contaminants and some are suspect to have endocrine disrupting effects. Among the latter are nonylphenol (NP), octylphenol (OP) and bisphenol A (BPA), which deserve special attention due to their ubiquitous occurrence in the aquatic environment. The complexing agents benzotriazole (BT) and tolyltriazole (TT) are applied as anticorrosive agents (e.g. in cooling and hydraulic fluids, in antifreezing fluids, in aircraft deicing fluids, in dish washing liquids for silver protection), as antifogging agents and as intermediates for the synthesis of various chemicals. The environmental occurrence of NP and OP is caused by the fact that they are intermediate products (metabolites) in the biodegradation of alkylphenol polyethoxylate surfactants. BPA is globally used for the production of polycarbonate and epoxy resins. Methods BT, TT, NP, OP and BPA were quantitatively determined in municipal wastewater effluents in Switzerland and in the Glatt River. The analytes were enriched by solid-phase enrichment. BT and TT were determined underivatized by electrospray LC/tandem MS. Reversed-phase LC was performed on octylsilica columns with isocratic water/methanol elution. Multiple reaction monitoring of the positive ions provided selective and sensitive detection for reliable quantifications. NP, OP and BPA were determined by GC/MS after derivatization with N-methyl-N-(trimethylsilyl)-trifluoroacetamide. Results and Discussion BT and TT concentrations in primary and secondary effluents of municipal wastewater treatment plants varied from below 10 to 100 μg/L. The ranges of the concentrations in the Glatt River in ng/L were 636–3,690 for BT, 122–628 for TT, 68–326 for NP, 6–22 for OP and 9–76 for BPA. The corresponding mass flows in g/d were 93–1,870 for BT, 18–360 for TT, 24–183 for NP, 1–16 for OP and 2–72 for BPA. The concentrations and mass flows of NP in the River Glatt were drastically lower than the analogous values found 15 years ago. Thus, a substantially decreased environmental exposure can be observed due to the reduction of the use of alkyphenol polyethoxylate surfactants in Switzerland. The current concentrations of NP, OP and BPA are within the ranges reported for weakly impacted surface waters. Conclusion The investigated contaminants occur at quantitatively measurable but varying concentrations in municipal wastewaters and in the Glatt River reflecting their ubiquitous input into wastewaters and their different behaviour during biological wastewater treatment.     

Oxidation of MCPA and 2,4-D by UV radiation, ozone, and the combinations UV/H2O2 and O3/H2O2

The phenoxyalkyl acid derivative herbicides MCPA (4-chloro 2-methylphenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) were oxidized in ultrapure water by means of a monochromatic UV irradiation and by ozone, as well as by the combinations UV/H2O2 and O3/H2O2. In the direct photolysis of MCPA, the quantum yield at 20 degrees C was directly evaluated and a value of 0.150 mol Eins(-1) was obtained in the pH range 5-9, while a lower value of 0.41 x 10(-2) mol Eins(-1) was determined at pH=3. Similarly, for 2,4-D a value of 0.81 x 10(-2) mol Eins(-1) was deduced, independent of the pH of work. The influence of the additional presence of hydrogen peroxide was established in the combined process UV/H2O2, and the specific contribution of the radical pathway to the global photo-degradation was evaluated. The oxidation by ozone and by the combination O3/H2O2 was also studied, with the determination of the rate constants for the reactions of both herbicides with ozone and hydroxyl radicals at 20 degrees C. These rate constants for the direct reactions with ozone were 47.7 and 21.9 M(-1) s(-1) for MCPA and 2,4-D respectively, while the found values for the rate constants corresponding to the radical reactions were 6.6 x 10(9) and 5.1 x 10(9) M(-1) s(-1).     

Hydrogen peroxide-assisted UV photodegradation of Lindane

Aqueous solutions of gamma-hexachlorocyclohexane (Lindane) were photolyzed (lambda=254 nm) under a variety of solution conditions. The initial concentrations of hydrogen peroxide (H(2)O(2)) and Lindane varied from 0 to 20 mM and 0.21 to 0.22 microM, respectively, the pH ranged from 3 to 11, and several concentration ratios of Suwannee River humic acid and fulvic acid were dissolved in the irradiated solutions. Lindane rapidly reacted, and the maximum reaction rate constant (9.7 x 10(-3) s(-1)) was observed at pH 7 and initial [H(2)O(2)]=1 mM. Thus, 90% of the Lindane is destroyed in approximately 4 min under these conditions. In addition, within 15 min, all chlorine atoms were converted to chloride ion, indicating that chlorinated organic by-products do not accumulate. The reactor was characterized by measuring the photon flux (7.04 x 10(-6) E s(-1)) and the cumulative production of *OH during irradiation. The cumulative *OH production during irradiation was fastest at an initial [H(2)O(2)]=5 mM (k=0.77 micro M s(-1)).     

Kinetics of oxidation of chlorobenzenes and phenyl-ureas by Fe(II)/H2O2 and Fe(III)/H2O2. Evidence of reduction and oxidation reactions of intermediates by Fe(II) or Fe(III)

The rates of degradation of 1,2,4-trichlorobenzene (TCB), 2,5-dichloronitrobenzene (DCNB), diuron and isoproturon by Fe(II)/H2O2 and Fe(III)/H2O2 have been investigated in dilute aqueous solution ([Organic compound]0 approximately 1 microM, at 25.0 +/- 0.2 degrees C and pH < or = 3). Using the relative rate method with atrazine as the reference compound, and the Fe(II)/H2O2 (with an excess of Fe(II)) and Fe(III)/H2O2 systems as sources of OH radicals, the rate constants for the reaction of OH* with TCB and DCNB were determined as (6.0 +/- 0.3)10(9) and (1.1 +/- 0.2)10(9) M(-1) s(-1). Relative rates of degradation of diuron and isoproturon by Fe(II)/H2O2 were about two times smaller in the absence of dissolved oxygen than in the presence of oxygen. These data indicate that radical intermediates are reduced back to the parent compound by Fe(II) in the absence of oxygen. Oxidation experiments with Fe(III)/H2O2 showed that the rate of decomposition of atrazine markedly increased in the presence of TCB and this increase has been attributed to a regeneration of Fe(II) by oxidation reactions of intermediates (radical species and dihydroxybenzenes) by Fe(III).     

Hydroxyl radical scavenging role of chloride and bicarbonate ions in the H2O2/UV process

Simultaneous effect of inorganic anions, such as chloride and bicarbonate ions, on the scavenging of hydroxyl radicals (HO*) in the H2O2/UV process is the focus of this paper. The model compound of n-chlorobutane (BuCl) was used as the probe of HO*. By changing the pH conditions (2-9) and the concentrations of NaCl (0.25-2500 mM) and NaHCO3 (25 mM), the variation of HO* concentrations and the rate of H2O2 decomposition were compared. In general, the BuCl and H2O2 follow closely the first-order reaction within the first 10 and 40 min, respectively. In the presence of chloride alone at the pH range of 2-6, the HO* concentration in the reaction mixture increases with the increase of pH, and the HO* concentration at pH = 6 is 100 times of that at pH = 2. Including bicarbonate species in the solution, the peak HO* concentration was found at a certain pH, which shifts from 4, 5, to 5-7, as the molar ratios of chloride/bicarbonate species increase from 1 to 100. In addition, without bicarbonate species HO* concentration decreases significantly with increasing chloride concentration but remained rather unchanged beyond 1250 mM. In contrast, the HO* scavenging in the presence of bicarbonate species became relatively significant only when the chloride concentration reached beyond 250 mM. Throughout all experiments of different water quality conditions, the H2O2 decomposition rate remains rather unchanged.     

Oxidative degradation of dimethylsulfoxide by locally concentrated hydroxyl radicals in streamer corona discharge process

This study systematically investigates the characteristic degradation behaviors of dimethylsulfoxide (DMSO) by the streamer corona discharge process (SCDP) in water. The analysis of the oxidized intermediates of DMSO shows that hydroxyl radical (*OH) is the main oxidant responsible for the degradation of DMSO in the SCDP. The various experiments on the degradation and mineralization of DMSO, and the effect of the *OH scavenger suggest that the SCDP produces locally concentrated *OHs in and around the plasma channel. This explanation was also supported by the formation of H(2)O(2) and the effect of the *OH scavenger on the H(2)O(2) production rate in the SCDP. Based on the kinetic data for the degradation of DMSO and the production of H(2)O(2) in the SCDP, the volume of the active region in which the *OHs are concentrated, and the effective concentration of *OH in that region were estimated to be 0.21 microl and 5.0 x 10(-3)M, respectively. This level of *OH concentration in the SCDP is approximately 10(7)-10(9) times higher than that generated in ordinary advanced oxidation processes using *OH. The ramifications of the results obtained in this study on successful water treatment using the SCDP are also discussed.     

Occurrence of alkylphenol polyethoxylates in the St. Lawrence River and their bioconcentration by mussels (Elliptio complanata)

A study was conducted in 1999 to determine the occurrence of alkylphenol polyethoxylates in the St. Lawrence River and their bioconcentration by mussels (Elliptio complanata). Concentrations of selected contaminants were measured in surface water, municipal effluent, sediments and mussels. Analyses were performed on 4-tert-octylphenol (4-t-OP), 4-n-nonylphenol (4-n-NP), nonylphenol polyethoxylates (NP(1-16)EO), nonylphenol-mono and di-ethoxycarboxylic acids (NP(1)EC and NP(2)EC), and octylphenol-mono and di-ethoxycarboxylic acids (OP(1)EC and OP(2)EC). Mussels (Elliptio complanata) taken from a reference lake were placed in cages and submerged for 62 days at two sites in the St. Lawrence River, 1.5 km upstream and 5 km downstream of the outfall of a municipal wastewater treatment plant. The results showed that many of the target chemicals were present in all matrices studied: in water, at ppt and ppb levels, and reaching ppm levels in sediments and mussels. Concentrations of these contaminants were higher in matrices sampled at the downstream site than in those drawn at the site upstream of the Montreal effluent outfall, especially in sediments. Likewise, the slight, but not significant, bioconcentration of certain alkylphenol polyethoxylates (AP(n)EO) in the mussels was more noticeable at the downstream site than at the upstream site.