Presence Of Inorganic Ions Research Articles

Voltammetric Determination of Quercetin and Rutin on Their Simultaneous Presence on an Electrode Modified with Polythymolphthalein

A voltammetric method is developed for the determination of quercetin and rutin in the simultaneous presence on a glassy carbon electrode modified with carbon nanofibers and polythymolphthalein. The conditions of the potentiodynamic electrolysis of thymolphthalein providing the maximum difference in the oxidation potentials of quercetin and rutin equal to 136 mV are found. Thymolphthalein electropolymerization should be carried out in a 100 μM solution by the 10-fold cycling of the potential from 0 to 1.7 V at a sweep rate of 75 mV/s in phosphate buffer solution with pH 7.0. The electrode modified with polythymolphthalein is characterized by scanning electron microscopy, cyclic voltammetry, and electrochemical impedance. It is found that the oxidation of quercetin proceeds irreversibly, and that of rutin, quasi-reversibly with the participation of two electrons and two protons and is controlled by the adsorption of analytes on the electrode surface. The analytical range is 0.025–1.00 μM for both analytes, and the limits of detection are 7.3 nM for quercetin and 4.7 nM for rutin. The selectivity of the electrode response to quercetin and rutin in the presence of inorganic ions, saccharides, and ascorbic and p-coumaric acids is shown. The developed method is tested on real samples (linden Tilia L. flowers and onions).

Amperometric sensor based on MWNT and electropolymerized carminic acid for the simultaneous quantification of TBHQ and BHA

Amperometric sensor based on the layer-by-layer combination of multi-walled carbon nanotubes and electropolymerized carminic acid deposited on the glassy carbon electrode surface (poly(carminic acid)/MWNT/GCE) has been developed for the simultaneous quantification of tert-butylhydroquinone (TBHQ) and butylated hydroxyanisole (BHA). Conditions of poly(carminic acid) coverage obtaining have been found on the basis of TBHQ and BHA peak potential separation and oxidation currents. The best parameters have been observed for poly(carminic acid) electrodeposited from 50 μmol L−1 monomer solution by seven-fold cycling of potential in the range of 0.3–0.8 V with the scan rate of 50 mV s−1 in Britton-Robinson buffer (BRB) pH 2.0. Electrodes have been characterized by scanning electron microscopy (SEM) and electrochemical methods. Good resolution of TBHQ and BHA oxidation potentials equalled to 190 mV has been obtained on the poly(carminic acid)/MWNT/GCE vs. 146 mV on MWNT/GCE. The oxidation currents are 2.1- and 1.8-fold increased on polymer-modified electrode for TBHQ and BHA, respectively. Parameters of TBHQ and BHA electrooxidation on poly(carminic acid)/MWNT/GCE have been calculated. Sensor response is linear in the range of 0.50–75 μmol L−1 for TBHQ and 0.25–75 μmol L−1 for BHA with the limits of detection of 0.36 and 0.23 μmol L−1, respectively. Sensor selectivity in the presence of inorganic ions, ascorbic acid and α-tocopherol is confirmed. The sensor developed has been tested on the linseed oil. The recovery of 100–103% confirm high accuracy of the approach.

The Selective Electrochemical Sensing of Naringin Using Electropolymerized Ellagic Acid Film

Electrochemical sensor on the basis of glassy carbon electrode (GCE) covered with multi-walled carbon nanotubes and electropolymerized ellagic acid (polyEA/MWNT/GCE) has been developed for the naringin determination. Polymeric film has been obtained by potentiodynamic electrolysis. The working conditions of polymeric coverage formation (scans number, supporting electrolyte pH, monomer concentration and electrolysis parameters) providing the best naringin response have been found. Ellagic acid (EA) electropolymerization has to be performed from 10 μM monomer by sevenfold cycling of potential in the range of 0.0–1.0 V at the scan rate of 100 mV s−1 in phosphate buffer (PB) pH 7.0. Scanning electron microscopy (SEM) confirms successful modification of the sensor surface with evenly distributed 30–50 nm spherical particles providing 9.6-fold increase of the electrode effective surface area vs GCE. Naringin electrooxidation parameters on polyEA/MWNT/GCE have been found. Sensor acting under conditions of differential pulse voltammetry in PB pH 6.5 provides linear dynamic ranges of 0.050–1.0 and 1.0–100 μM with the detection and quantification limits of 14 and 47 nM, respectively. The selectivity of sensor towards naringin in the presence of inorganic ions, saccharides, hesperidin, ascorbic and phenolic acids is proved. The sensor developed has been successfully tested on grapefruit juices.

The utilization of Fe-doped g-C3N4 in a heterogeneous photo-Fenton-like catalytic system: the effect of different parameters and a system mechanism investigation.

In this study, a series of Fe-doped g-C3N4 (Fe–C3N4) samples was synthesized and characterized via X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflection spectroscopy (UV-vis DRS), and photoluminescence (PL) spectroscopy. The photocatalytic activity of the synthesized Fe–C3N4 was investigated toward methylene blue (MB) degradation with hydrogen peroxide (H2O2) assistance. The results showed that the Fe–C3N4 heterogeneous photo-Fenton-like system showed excellent catalytic performance when the pH value was varied from 3.0 to 9.0. Evaluating the effects of various inorganic anions in the Fe–C3N4 heterogeneous photo-Fenton-like system, HCO3− showed a dual effect on MB degradation, and Cl− and NO3− showed an inhibitory effect on MB degradation. Evaluating the effects of inorganic cations, Al3+, Mg2+, and Ca2+ strongly inhibited MB degradation. Recycling experiments demonstrated that Fe–C3N4 possesses good reusability and stability. Quenching experiments were carried out, and it was found that hydroxyl radicals (·OH) were the primary active species in the system. Besides, nine intermediates were identified via LC/MS, and a possible MB degradation pathway in the system was proposed. This study could promote the application of this Fe–C3N4 heterogeneous photo-Fenton-like system in realistic dye wastewater.

Oxidation of sulfonamides by ferrate(VI): Reaction kinetics, transformation byproducts and toxicity assesment

This study was aimed at the degradation of sulfonamides (SNs) via oxidation with Fe(VI). The reaction kinetics, identification of degradation byproducts and their toxicity were investigated. The pH solution and Fe(VI) loading had significant effects on the degradation of the sulfonamides. The maximum degradation rate occurred at pH 3.0 with a 6:1 ratio Fe(VI): sulfonamide, obtaining 100% degradation of 15 mg L−1 SN within 5 min. Although Fe(VI) also showed an appreciable reactivity towards SNs (kapp = 9.85–19.63 × 102 M−1 s−1) at pH 7. The influence of solution pH on the values of kapp can be explained considering the specific reaction between Fe(VI) and SNs. Degradation rates are also influenced by the presence of inorganic ions in different water matrixes. For this reason, ions present in groundwater enhanced the SNs degradation through a synergistic effect among carbonates, sulfates and Fe(VI).Degradation byproducts identified, through UPLC analysis, allowed us to proposed three degradation pathways depending on pH. At acid pH there is a cleavage of C–S and S–N bonds. At neutral pH nitroso and nitro-derivates are formed. At basic pH hydroxylation is the main reaction.The cytotoxicity assay of HEK-293 and J774 cell lines exposed to Fe(VI) indicated that transformation byproducts had a lower toxicity than SNs as baseline products. Accordingly, this research suggests that Fe(VI) can act as a chemical oxidant to remove SNs antibiotics and it can be used to treat antibiotic pollution in wastewater.

Impact of salinity on colloidal ozone aphrons in removing phenanthrene from sediments

Polycyclic aromatic hydrocarbons (PAHs) tend to adsorb and accumulate on sediments owing to their hydrophobicity and persistence. Salinity is the predominant factor determining the PAH partition between aqueous and solid phases in freshwater, estuaries and seawater. This study focuses on the impact of salinity on the phenanthrene (PHE) removal from sediments using an in situ and targeted remediation technology – colloidal ozone aphrons (COAs). The ozone-encapsulated colloidal aphrons exhibited increasing air holdup but decreasing stability with the salinity increasing from 0.5‰ to 35‰. The hydrophobic attraction between Tween-20-coated bubbles and the hydrophobic solid surface weakened at high salinities. The presence of inorganic ions in the aqueous phase could lead to the salting-out of nonionic compounds (PHE, Tween-20 and even ozone), hindering detaching and degrading PHE from the solid phase. Anyhow, COAs achieved high efficiencies of washing (88.0–90.2%) and oxidative degradation (74.0–76.5%) particularly for the hydrophobic sediments with highly concentrated PHE (200.4 μg/kg) over the investigated salinities. The flushing effect imposed by the bubble flow played an important role, which was not greatly influenced by salinity. Although the dissolved natural organic matter competed with PHE for COAs and led to low PHE removal, the efficiency was improved by successive COA addition.

Effects of Molecular-Level Compositional Variability in Organic Aerosol on Phase State and Thermodynamic Mixing Behavior.

The molecular-level composition and structure of organic aerosol (OA) affect its chemical/physical properties, transformations, and impacts. Here, we use the molecular-level chemical composition of functionalized OA from three diverse field sites to evaluate the effect of molecular-level compositional variability on OA phase state and thermodynamic mixing favorability. For these ambient sites, modeled aerosol phase state ranges from liquid to semisolid. The observed variability in OA composition has some effect on resulting phase state, but other factors like the presence of inorganic ions, aerosol liquid water, and internal versus external mixing with water are determining factors in whether these particles exist as liquids, semisolids, or solids. Organic molecular composition plays a more important role in determining phase state for phase-separated (verus well-mixed) systems. Similarly, despite the observed OA compositional differences, the thermodynamic mixing favorability for OA samples with aerosol liquid water, isoprene oxidation products, or monoterpene oxidation products remains fairly consistent within each campaign. Mixing of filter-sampled OA and isoprene or monoterpene oxidation products is often favorable in both seasons, while mixing with water is generally unfavorable.

Faceted TiO2 photocatalytic degradation of anthraquinone in aquatic solution under solar irradiation

Anthraquinone (AQ), a common oxygenated polycyclic aromatic hydrocarbon (PAH) in the water environment, often occurs with higher concentrations than its parent anthracene as it is the dominant intermediate from anthracene during both wastewater treatment and transformation in natural waters. During the elimination of PAHs and their intermediates, the water matrix often induces positive or negative effects. In this paper, photocatalytic degradation of AQ in the presence of inorganic ions (NO3−, HCO3−, Fe3+) and organic matter (humic acid) was studied with {101} and {010}-TiO2 as sunlight-driven photocatalysts. Meanwhile, the effect of dissolved oxygen (DO) on photocatalytic degradation of AQ was evaluated. The results showed that NO3− had a slight suppressing effect, while HCO3– and Fe3+ promoted the photocatalytic activity due to formation of new oxidizers (CO3− and H2O2). Interestingly, HA could envelope {101}-TiO2 to inhibit photodegradation; however, it had almost no effect on {010}-TiO2 due to the different surface structures and properties. High dissolved oxygen content in water could markedly promote the photodegradation of AQ. This was consistent with the results of scavenging experiments, which demonstrated that O2– and h+ played more important roles than OH did. A small amount of benzene was detected as an intermediate product of AQ by LC-QTOF-MS analysis. Hopefully, this work can contribute to the understanding of the potential of water remediation by faceted photocatalysts.

Degradation of norfloxacin in aqueous solution with UV/peroxydisulfate.

The frequent detection of antibiotics in water bodies gives rise to concerns about their removal technology. In this study, the degradation kinetics and mechanisms of norfloxacin (NOR), a typical fluoroquinolone pharmaceutical, by the UV/peroxydisulfate (PDS) was investigated. NOR could be degraded effectively using this process, and the degradation rate increased with the increasing dosage of PDS but decreased with the increasing concentration of NOR. In real water, the degradation of NOR was slower than that in ultrapure water, which indicated that laboratory results cannot be directly used to predict the natural fate of antibiotics. Further experiments suggested that the degradation of NOR was the most fast under neutral condition, the existence of HA or FA inhibited the degradation of NOR, and the presence of inorganic ions (NO3 -, Cl-, CO3 2- and HCO3 -) had no significant effect on degradation of NOR. Total organic carbon (TOC) removal rate (40%) indicated NOR was not completely mineralized, and six transformation products were identified, and possible degradation pathways of NOR had been proposed. It can be prospected that UV/PDS technology could be used for advanced treatment of wastewater containing fluoroquinolones.

Degradation of root exudates in closed hydroponic systems using UV/H2O2: Kinetic investigation, reaction pathways and cost analysis

Qualitative screening of reused nutrient solution (RNS) displays the presence of several organic acids. In this study, the degradation by UV/H2O2 of three of those organic acids (benzoic (BA), phthalic acid (PhA) and succinic acid (SA)) present in RNS was investigated. The results indicated that (i) the degradation rate of BA was faster than that of PhA and SA and (ii) by increasing the contact time the degradation of all acids was improved. For example, the removal of BA increased from 83% and 91% when increasing the contact time from 90 min to 270 min in the presence of 50 mg L−1 and UV. A maximum COD (30%) and UV254 (68%) removal were obtained when 200 mg L−1 H2O2 was applied for 90 min. No significant change was observed in terms of parameters such as PO43− and NO3− while electrical conductivity (EC) and pH were slightly changed during the oxidation process. Pseudo- first -order represented well the experimental data for the degradation of the selected organic acids in RNS (particularly for BA and PhA), exhibiting high linear correlation coefficients (R2 ≥ 0.96). Moreover, the results showed that the decomposition of organic acids was significantly influenced in the presence of inorganic ions in RNS. GC–MS analysis revealed the presence of several intermediate products during the oxidation process and the primary reaction pathway of benzoic acid was accordingly proposed. Finally, a bench scale cost investigation showed that low concentration H2O2 (50 mg L−1) in longer time (270 min) is more cost effective than high concentration H2O2 (200 mg L−1) in a shorter time (90 min).

EDTA enhanced removal of sulfamethazine by pre-magnetized Fe0 without oxidant addition

This study presents a novel pre-magnetized Fe0/ethylenediaminetetraacetic acid/air (pre-Fe0/EDTA/air) Fenton-like system to remove sulfamethazine (SMT). SMT removal only reached 10.6% in pre-Fe0/air system (0.2 g L−1, SMT 3 mg L−1, pH 5) while reached 88.5% in pre-Fe0/EDTA/air system within 1 h (0.2 g L−1, SMT 3 mg L−1, EDTA 2 mM, pH 5). EDTA could combine with FeII or FeIII to keep iron soluble in the solution and the fast activation of molecular oxygen by Fe-EDTA complex could induce the fast and more production of H2O2. It was found that much more H2O2 (5.1 mg L−1) and OH radical (26.4 μM) were produced in the pre-Fe0/EDTA/air system than in the pre-Fe0/air system (0.06 mg L−1, 0.6 μM) within 1 h. The degradation rate of SMT (1 0 3) in pre-Fe0/EDTA/air system (38.4 min−1) was also 2.3 times as large as that in the Fe0/EDTA/air system (17.0 min−1), owing to the fast corrosion rate of pre-Fe0. 81.5 mgL−1 total Fe ions could be generated in pre-Fe0/EDTA/air while 53.6 mg L−1 in Fe0/EDTA/air. Fe0 dosage (0.05–0.8 g L−1) and EDTA dosage (0–8 mM) were optimized and the optimal dosage for Fe0 and EDTA was 0.2 g L−1 and 2 mM, respectively. The degradation rate of SMT in pre-Fe0/EDTA/air system were 1.6–2.9 times at different initial pH (3–6) and 2.3–3.1 times in the presence of inorganic ions (SO42−, Cl− and HCO3−) and natural organic matter (NOM) compared with Fe0/EDTA/air system. Decrease of Fe0 contact angle in the presence of magnetization and EDTA enhanced the corrosion rate of Fe0. Accordingly, pre-Fe0/EDTA/air system would be a cost-effective and promising eco-friendly alternative for removal of SMT.

Heterogeneous catalytic degradation of methylparaben using persulfate activated by natural magnetite; optimization and modeling by response surface methodology

AbstractBACKGROUNDIn this study, a naturally magnetic semiconductor mineral (NM‐SCM) was used as a highly active, easily separable and green catalyst to activate persulfate (SPS) for the degradation of methylparaben (MeP) in aqueous solution by a heterogeneous catalyst system (SPS/NM‐SCM). NM‐SCM properties were characterized using field emission scanning electron microscope (FESEM), Brunauer–Emmett–Teller (BET), X‐ray diffraction (XRD), energy‐dispersive X‐ray (EDX) and vibrating sample magnetometer (VSM) analyses. The effects of contributing factors such as solution pH, NM‐SCM loading, SPS dosage and initial MeP concentration on MeP degradation were analyzed using response surface methodology (RSM) and Box–Behnken design (BBD).RESULTSThe RSM model obtained from the present study (R2 > 0.99) showed a suitable correlation between the predicted values and experimental results of MeP degradation. Under optimized conditions (pH 6.5, SPS 5 mmol L−1, NM‐SCM 0.3 g L−1 and MeP 10 µmol L−1), a removal efficiency of 99.5% and a mineralization degree of 37% were achieved. The removal efficiency of MeP was reduced in the presence of inorganic ions as follows: chloride > nitrate > carbonate > phosphate. After five successive catalyst reuses, the degradation efficiency was >90%, indicating the excellent potential reusability of NM‐SCM catalyst.CONCLUSIONOwing to the generation of highly reactive oxidizing species (SO4•−) and easy separation of the catalyst, the integration of NM‐SCM and SPS has great potential for the degradation of MeP from water and wastewater matrices. © 2019 Society of Chemical Industry

Sulfate radical induced degradation of β2-adrenoceptor agonists salbutamol and Terbutaline: Implication of halides, bicarbonate, and natural organic matter

The presence of inorganic ions and organic matter in natural water would cause unpredictable consequence on the oxidation efficiency and pathways of sulfate radical (SO4−) based advanced oxidation process (SR-AOPs). In this study, the impacts of water constituents, namely, halides (including chloride (Cl−) and bromide (Br−)), bicarbonate (HCO3−) and natural organic matter (NOM) on SO4− induced degradation of salbutamol (SAL) and terbutaline (TBL) were evaluated systematically. Our results indicated that chloride exhibited no effect on oxidation efficiencies of SAL and TBL, while Br−, HCO3− and NOM all showed inhibitory effects. Specifically, the detrimental effect of bromide was mainly attributed to the scavenging of SO4− to form the less reactive species, Br2−. By using laser flash photolysis (LFP), the second-order rate constants of Br2− with SAL and TBL were estimated to be 2.1 and 3.9 × 108 M−1 s−1, respectively, much smaller than those with SO4− (3.7 × 109 M−1 s−1 for SAL and 4.2 × 109 M−1 s−1 for TBL). Moreover, bromine addition products of SAL and TBL were detected in the presence of Br−, which were believed to be more toxic than the parent compounds. Similar to bromide, HCO3− could also quench SO4− to generate carbonate radical (CO3−), also less reactive than sulfate radical with SAL (4.8 × 107 M−1 s−1) and TBL (3.2 × 108 M−1 s−1). In the case of NOM, a light screening effect was regarded as the major factor responsible to the decrease of reaction rates, while sulfate radical scavenging played a very limited role. The present work would increase the awareness of secondary reactions during SR-AOPs, as more toxic products were generated in the case of bromide.

Highly efficient activation of peroxymonosulfate by natural negatively-charged kaolinite with abundant hydroxyl groups for the degradation of atrazine

In this study, natural kaolinite, an abundant, low cost, thermally and chemically stable, and easily recyclable material was evaluated for the performance to activate peroxymonosulfate (PMS) by the degradation of atrazine. Based on radical quenching experiments and electron spinning resonance (ESR) spectra, hydroxyl radical (OH) and sulfate radical (SO4−) were identified to be the primary reactive species. The effects of catalyst loading, initial reaction pH, PMS dosage, initial atrazine concentration, and the presence of inorganic ions (Cl−, NO3−, HCO3− and H2PO4−) were also investigated in this work. Interestingly, the presence of H2PO4− enhanced the degradation efficiency of atrazine via promoting the decomposition of PMS. The transformation products were detected on a quadrupole time-of-flight liquid chromatography/mass spectrometer (Q-TOF-LC-MS) and the possible degradation pathway of atrazine was proposed. Based on comprehensive characterizations of crystal phase and crystallinity, porosity and pore structure, surface morphology, functional groups, and valence state of specific elements, the catalytic ability of natural kaolinite towards PMS is attributed to the abundant surface-bonded and structural hydroxyl groups. This study provides new insights of PMS activation by natural minerals for the degradation of refractory and deleterious contaminants in wastewater treatment.

A stable 1D mixed-valence CuI/CuII coordination polymer with photocatalytic reduction activity toward Cr(Ⅵ)

A new one-dimensional coordination polymer, [CuII(L)2][CuI(bpy)]2·4H2O (BUC-20) (H2L = cis-1,3-dibenzyl-2-imidazolidone-4,5-dicarboxylic acid, bpy = 4,4-bipyridine), was synthesized solvothermal condition. The crystal structure of BUC-20 was analyzed, and its properties like band energy, water stability, and photocurrent were clarified. BUC-20 exhibited outstanding photocatalytic Cr(VI) performance upon the UV light irradiation under acid condition, which was superior to those of existing photocatalysts. The photocatalytic performance was not influenced by the presence of inorganic ions, which was affirmed by the introduction real surface water to prepare simulated wastewater. BUC-20 exhibited good water stability, and could be used several runs without significant efficiency decrease.

Removing Humic Acid from Aqueous Solution Using Titanium Dioxide: A Review

Recently, the photocatalytic degradation technique with titanium dioxide (TiO2) has been widely applied for the degradation of humic acid (HA) from aqueous solution due to its ability to achieve complete mineralization of organic contaminants. Because TiO2 is the most commonly used semiconductor photocatalyst, efforts on the modification of TiO2 in order to improve catalyst efficiency were presented in this review manuscript. The key photoreactor operation parameters such as TiO2 loading, pH, temperature, oxygen concentration, concentration and nature of HA, light wavelength, light intensity, the presence of inorganic ions and mechanistic pathway for pollutant removal, and the formation of the intermediates and their effects on the mineralization and disinfection of the photo- process were also assessed. Although we can see an increase in the number of papers that have been published in this area, further progress is needed to improve the understanding of the dynamic interactions between TiO2 photocatalytic oxidation process and HA, as well as to suggest possible future developments in this promising field.

An Amperometric Sensor Based on Tin Dioxide and Cetylpyridinium Bromide Nanoparticles for the Determination of Vanillin

Voltammetric characteristics of vanillin are determined using electrodes modified with tin dioxide nanoparticles dispersed in surfactants of various nature in the Britton–Robinson buffer solution. The best characteristics are observed for a glassy carbon electrode modified by a dispersion of SnO2 nanoparticles in cationic cetylpyridinium bromide (SnO2–CPB/GCE). The electrode is characterized by cyclic voltammetry and electrochemical impedance spectroscopy. A fourfold increase in the effective surface area of SnO2–CPB/GCE and a significant decrease in charge transfer resistance are shown in comparison with a GCE. The electrooxidation of vanillin proceeds irreversibly with the participation of two electrons and two protons and is controlled by the diffusion of the analyte. A sensor based on a SnO2–CPB/GCE was developed to determine vanillin; it functions under conditions of differential pulse voltammetry. The analytical ranges for vanillin are 0.10–100 and 100–500 µM with the limits of detection and quantification 20 and 67 nM, respectively. The developed sensor is selective to vanillin in the presence of inorganic ions, saccharides, ascorbic acid, and a number of phenolic compounds. The sensor is used for the determination of vanillin in perfumes for household chemicals and vanilla essential oils. The results are in good agreement with the data of gas chromatography.

Significance of the examination of the metal element content of herbal extracts in adjuvant therapy

The consumption of herbal teas is becoming more and more popular nowadays both as luxury foods and a complementary part of medical therapy. Beside the organic agents of medicinal plants, the presence of inorganic ions is also relevant in exerting the favorable pharmacological effect. The author briefly summarizes the importance of some essential metal ions and their quantitative values in teas applied in the adjuvant therapy of diabetes and used as diuretics. The common feature of teas used in diabetes is that they contain a measurable amount of chromium and the concentration of most essential elements (such as K, Mg, Mn and Zn) is significant, which can be considered as a mineral source for some metal ions. Diuretic herbs have an outstanding K content, but from the point of view of diuresis, the large K/Na molar ratio above 50 is relevant. Orv Hetil. 2018; 159(18): 713-719.

Degradation kinetics and mechanism of pentoxifylline by ultraviolet activated peroxydisulfate.

Degradation of pentoxifylline (PTX) by sodium peroxydisulfate (SPDS) assisted by UV irradiation has been investigated in deionized water. The treatment was more favorable over direct photolysis or peroxydisulfate oxidation alone. The effects of various parameters, including different dosage of oxidant agent, PTX concentration, initial solution pH levels, and the presence of inorganic ions like chloride, nitrate and carbonate have been evaluated. The rate of PTX decomposition depends on the oxidant agent dose. The highest degradation was determined at pH 10.5, which can be explained by the generation of additional hydroxyl radicals (HO˙) in the reaction between sulfate radicals and hydroxide ions. The presence of inorganic ions, especially the carbonate ions quench valuable sulfate radicals and have successfully retarded the PTX decomposition. Six PTX oxidation products were identified using UPLC-QTOF-MS for trials in a basic environment. The main degradation product (3,7-dimethyl-6-(5-oxohexyloxy)-3,7-dihydro-2H-purin-2-one) was isolated by column chromatography and identified by 1HNMR and LC MS analyzes.

Amicarbazone degradation promoted by ZVI-activated persulfate: study of relevant variables for practical application.

Alarming amounts of organic pollutants are being detected in waterbodies due to their ineffective removal by conventional treatment techniques, which warn of the urgent need of developing new technologies for their remediation. In this context, advanced oxidation processes (AOPs), especially those based on Fenton reactions, have proved to be suitable alternatives, due to their efficacy of removing persistent organic compounds. However, the use of ferrous iron in these processes has several operational constraints; to avoid this, an alternative iron source was here investigated: zero-valent-iron (ZVI). A Fenton-like process based on the activation of a recently explored oxidant-persulfate (PS)-with ZVI was applied to degrade an emerging contaminant: Amicarbazone (AMZ). The influence of ZVI size and source, PS/ZVI ratio, pH, UVA radiation, dissolved O2, and inorganic ions was evaluated in terms of AMZ removal efficiency. So far, this is the first time these parameters are simultaneously investigated, in the same study, to evaluate a ZVI-activated PS process. The radical mechanism was also explored and two radical scavengers were used to determine the identity of major active species taking part in the degradation of AMZ. The degradation efficiency was found to be strongly affected by the ZVI dosage, while positively affected by the PS concentration. The PS/ZVI system enabled AMZ degradation in a wide range of pH, although with a lower efficiency under slightly alkaline conditions. Dissolved O2 revealed to play an important role in reaction kinetics as well as the presence of inorganic ions. UVA radiation seems to improve the degradation kinetics only in the presence of extra O2 content. Radicals quenching experiments indicated that both sulfate (SO4•-) and hydroxyl (•OH) radicals contributed to the overall oxidation performance, but SO4•- was the dominant oxidative species.