Second-order Rate Constants For Reactions Research Articles

Oxidation of 1,3-diphenylguanidine (DPG) by goethite activated persulfate: Mechanisms, products identification and reaction sites prediction

As emerging pollutants continue to be discovered, studies on the degradation behavior of emerging pollutants have proliferated, but few studies have focused on the reactivity of the new pollutants themselves. The work investigated the oxidation of a representative roadway runoff-derived organic contaminant, 1,3-diphenylguanidine (DPG) by goethite activated persulfate (PS). DPG exhibited the highest degradation rate (kd = 0.42 h−1) with present of PS and goethite at pH 5.0, then started to decrease with increasing pH. Chloride ion inhibited DPG degradation by scavenging HO·. Both HO· and SO4−· were generated in goethite activated PS system. Competitive kinetic experiments and flash photolysis experiments were conducted to investigate free radical reaction rate. The second-order reaction rate constants for DPG reacting with HO· and SO4−· were quantified (kDPG + HO·,kDPG + SO4-·), which both reached above 109 M−1 s−1. Chemical structures of five products were identified, four of them were previously detected in DPG photodegradation, bromination and chlorination processes. By density functional theory (DFT) calculations, ortho- and para- C were more easily attacked by both HO· and SO4−·. Abstraction of H on N by HO· and SO4−· were the favorable pathways, and the product TP-210 might be generated by cyclization of DPG radical from abstraction of H on N (3). The results of this study help us to better understand the reactivity of DPG with SO4−· and HO·.

Performance evaluation of the UV activated chlorite process on trimethoprim: Degradation efficiency, energy consumption and disinfection by-products formation

As the primary inorganic by-product species of ClO2, chlorite is believed to have negative toxicological effects on human health and therefrom greatly limits the wide application of ClO2 in water treatment. The synergistic trimethoprim (TMP) removal concerning degradation efficiency, energy consumption and disinfection by-products (DBPs) formation in the UV activated chlorite process accompanied by the simultaneously elimination of chlorite was comprehensively evaluated. UV/chlorite integrated process removed TMP far more rapidly than UV (1.52%) or chlorite (3.20%) alone due to the endogenous radicals (Cl•, ClO• and •OH), the contributing proportions of which were 31.96%, 19.20% and 44.12%. The second-order rate constants of TMP reaction with Cl•, ClO• and •OH were determined to be 1.75 × 1010, 1.30 × 109 and 8.66 × 109 M−1 s−1. The effects of main water parameters including chlorite dosage, UV intensity, pH as well as water matrixes (nature organic matter, Cl− and HCO3−) were examined. kobs obeyed the order as UV/Cl2>UV/H2O2≈UV/chlorite>UV, and the cost ranking via electrical energy per order (EE/O, kWh m−3 order−1) parameter was UV/chlorite (3.7034) > UV/H2O2 (1.1625) >UV/Cl2 (0.1631). The operational scenarios can be optimized to achieve the maximum removal efficiencies and the minimum energy costs. The destruction mechanisms of TMP were proposed by LC-ESI-MS analysis. The overall weighted toxicity in subsequent disinfection was assessed as UV/Cl2>UV/chlorite > UV, the values of which in post-chlorination were 6.2947, 2.5806 and 1.6267, respectively. Owing to the vital roles of reactive chlorine species (RCS), UV/chlorite displayed far higher TMP degradation efficiency than UV, and concurrently presented much less toxicity than UV/Cl2. In an effort to determine the viability of the promising combination technology, this study was devoted to reduce and reuse chlorite and synchronously realize the contaminants degradation efficiently.

Novel activation of sulfite by perovskite CaCu3Ti4O12 for As(III) oxidation: Kinetics and mechanism

A new activation technology for sulfite (S(IV)) using a perovskite CaCu3Ti4O12 (CCTO) catalyst has been proposed to remediate the As(III) polluted water. When 0.05 g·L−1 CCTO and 0.4 mmol·L−1 S(IV) were mixed, 90.6% of As(III) could be removed in 30 min at an initial pH of 8.0. Dissolved oxygen played an indispensable role in the reaction. CCTO can interact with S(IV) via a heterogeneous catalytic route on its surface. Electrochemical characterization indicated that the electron transfer process between the surface Cu/ Ti atoms and S(IV) ions evoked the activation of S(IV), leading to the generation of SO4•−, which played a dominant role in the oxidation of As(III). Density functional theory (DFT) calculations have disclosed the spontaneous adsorption of sulfite on CCTO surface. A kinetics study determined the steady-state concentration of SO4•− to be 4.29 × 10−14mol·L−1, which reacts with As(III) with a second-order reaction rate constant of 3.83 × 1010L·mol−1·s−1. Furthermore, the CCTO catalyst was highly reusable, the structure of which did not significantly alter during the reaction. Therefore, the CCTO/S(IV) system is a promising and efficient advanced oxidation technique for the purification of As(III) in water.

Degradation of antiviral drug acyclovir by thermal activated persulfate process: Kinetics study and modeling

Pharmaceutical and personal care products (PPCPs) pose a great threat to water environment security. In this study, acyclovir (ACV) was efficiently degraded by thermally activated persulfate (TAP) system. The ACV degradation increased with rising reaction temperature and persulfate dosage. With the existence of inorganic anions and humic acid, ACV removal was retarded to varying degrees. Under strong alkaline condition, it was observed that the degradation of ACV was significantly inhibited. In addition, Kintecus software was employed to simulate ACV removal and achieved a good fit with the experimental results. The contribution rates of main reactive radicals under acidic, neutral, and alkaline conditions were investigated, and the contribution of hydroxyl radical (⋅OH) increased significantly under alkaline condition. The main active species were identified as sulfate radical (SO4⋅-) and ⋅OH through quenching experiment, and the second-order reaction rate constants of SO4⋅- and ∙OH reacted with ACV were calculated to be 9.17 × 109 M−1 s−1 and 2.74 × 109 M−1 s−1, respectively. The main degradation pathways included addition of free radicals, oxidation of branch chain and ring opening. The acute and chronic toxicity of intermediates to organisms predicted by ECOSAR were significantly reduced compared with that of ACV.

Washing-free electrogenerated chemiluminescence magnetic microbiosensors based on target assistant proximity hybridization for multiple protein biomarkers

This work reports washing-free electrogenerated chemiluminescence (ECL) magnetic microbiosensors based on target assistant proximity hybridization (TAPH) for multiple protein biomarkers for the first time. As a principle-of-proof, alpha-fetoprotein (AFP) was chosen as a model analyte, and biotin-DNA1 bound streptavidin-coated magnetic microbeads (MMB@SA⋅biotin-DNA1) were designed as the universal capture MMB, while the corresponding two antibodies tagged with DNA2 or DNA3 were utilized as hybrid recognition probes, and ruthenium complex-tagged DNA4-10A was designed as a universal ECL signal probe. When the capture MMB was added into the mixture solution (containing the analyte, hybrid recognition probes, signal probe and tri-n-propylamine), biocomplexes were formed on the MMB. After the resulting MMB was efficiently brought to the surface of a magnetic glassy carbon electrode (MGCE), ECL measurement was performed without a washing step, resulting in an increase in the ECL intensity. A model for ECL measuring the second-order rate constants of hybridization reactions on MMB was derived. It was found that the rate constants for hybridization reactions on MMB in rotating mode are 1.6-fold higher than those in shaking mode, and a suitable DNA length of the signal probe can improve the signal-to-noise ratio. The washing-free ECL method was developed for the determination of AFP with a much lower detection limit (LOD) of 0.04 ng mL−1. The developed flexible strategy has been extended to determine D-dimer with an LOD of 0.1 ng mL−1 and myoglobinglobin with an LOD of 1.1 ng mL−1. This work demonstrated that the proposed strategy of ECL TAPH on MMB at MGCE is a washing-free and flexible promising strategy, and can be extended to qualify other multiple protein biomarkers in real clinical assays.

Impacts of properties of dissolved organic matters on indirect photodegradation of genistein

Excited triplet states of dissolved organic matters (3DOM*) are one of the most important photochemically-produced reactive intermediates leading to transformation of organic contaminants. However, relationships of photodegradation kinetics of different dissociation states of phenolic organic contaminants with chemical components or properties of 3DOM* are largely unknown. In this study, roles of 3DOM* in photodegradation of polyhydroxy phenolic genistein (Gs) at pH 5, 8 and 12 were investigated taking five kinds of DOM from different sources as examples. Relationships between photodegradation kinetics constants and DOM properties were built. Results showed that the contributions of direct 3DOM*-induced reactions to the total indirect photodegradation of Gs and second-order reaction rate constants (kDOM,Gs) of Gs with 3DOM* increased with pH increases. This was mainly attributed to decreases in vertical ionization energy of Gs at higher pH, endowing Gs with stronger electron donating capacities. kDOM,Gs was found to positively correlate with the specific ultraviolet absorbance at 254 nm, reflecting aromaticity of DOM, and negatively correlate with the absorbance ratio at 254 and 365 nm and contents of dissociated acidic functional groups of DOM, representing molecular weights of DOM, antioxidants and the repulsive forces between 3DOM* and Gs. This study provided a new insight into relationship between DOM properties and indirect photodegradation kinetics of phenolic contaminants in aquatic environments.

Reactivity of various brominating agents toward polyamide nanofiltration membranes

Polyamide (PA) membranes, widely used for reverse osmosis and nanofiltration, are prone to bromination under chlorinated bromide-containing water conditions. Conventional wisdom generally assumes HOBr as the only active brominating agent responsible for PA membrane degradation, while some more reactive but less abundant brominating agents (including Br2O, BrOCl, BrCl and Br2) under these conditions are often overlooked. The current study addresses this critical literature gap by systematically evaluating membrane degradation under various [Br−], [Cl−] and [HOCl] conditions. The observed pseudo-first-order rate constant of membrane degradation (kobsm, using change in water flux as a surrogate indicator) was found to be well correlated to [Br−], [Cl−] and [HOCl] (R2 > 0.90). The gradual increase of [Cl−] and [Br−] transforms the predominant brominating agent from HOBr to BrCl and Br2, respectively, under excessive [Br−] conditions. The species-specific second-order reaction rate constants followed a decreasing order of kBrClm(2.6 × 104 M−1·s−1) >kBrOClm (2.0 × 103 M−1·s−1) >kBr2Om(9.6 × 102 M−1·s−1) >kBr2m(1.5 × 101 M−1·s−1) >kHOBrm(5.4 × 10−1 M−1·s−1). Additional decay tests using benzanilide (BA) as a surrogate monomer compound confirmed BrCl as the most reactive species. Under typical seawater conditions (pH 8.0), the more reactive but less abundant BrCl had significantly greater contribution to membrane degradation (85 %) than HOBr (3 %). Under typical neutral wastewater conditions, both BrCl and HOBr contributed equally. The current study developed a novel characterization technique to assess membrane degradation by determining the kinetics of the oxidant-PA reactions.

Probing the reaction kinetics of chlorine radicals (Cl•/Cl2•−) with N-nitrosamines

N-nitrosamines are great concern in potable water reuse. This study investigated the reaction kinetics of chlorine radicals (Cl• and Cl2•−) with N-nitrosamines. The second-order reaction rate constants of Cl• (kCl•) and Cl2•− (kCl2•−) with eight N-nitrosamines at pH 7.0 varied in the range of (5.02 ± 0.41)–(57.1 ± 4.25) × 108 M−1 s−1 and (0.46 ± 0.04)–(10.6 ± 0.73) × 108 M−1 s−1, respectively. The numbers of methylene groups (#−CH2−) showed a good positive correlation with kCl• (R2 = 0.71), but not with kCl2•−. The degradation of eight N-nitrosamines under UV/chlorine advanced oxidation process (AOP) slightly increased by 1–18% in contrast to UV irradiation alone, and Cl− in the AOPs cannot inhibit their removal. The results improved the understanding of the fate of N-nitrosamines in chlorine radical-involved AOPs.

Reducing properties of triplet state organic matter (3DOM*) probed via the transformation from chlorine dioxide to chlorite

The triplet states of dissolved organic matter (3DOM*) have been well known to oxidize various organic contaminants, but evidence of their reducing properties are largely scarce. In this work, chlorine dioxide (ClO2) as a single-electron oxidant was used as a probe to evaluate the reduction property of 3DOM*. The reduction of ClO2 to chlorite was observed in the solutions of model photosensitizers (i.e., 4-carboxybenzophenone, benzophenone, acetophenone, 3-methoxyacetophenone, naphthalene, and xanthone) during UV irradiation with the presence of ClO2, though they are resistant to ClO2 oxidation in the dark. The reducing property of the triplet states of photosensitizers was verified and their second-order reaction rate constants with ClO2 were determined to be in the range of 1.45(± 0.03)× 109 – 2.18(± 0.06) × 109 M−1 s−1 at pH 7.0. The quenching tests excluded the role of other reactive species (e.g., HO•, O(3P), Cl•, ClO• and HOCl/OCl–, O2•– and eaq–) in ClO2 reduction to chlorite when using model photosensitizers and DOM isolates. Chlorite formation was 48.1–90.4% and 4812.8–7721.8% higher during UV irradiation with the presence of ClO2 and DOM than those without UV irradiation or without DOM present, respectively. The enhancement was attributed to the enhanced electron donating capacity (chlorite precursors) of DOM upon UV irradiation and also to 3DOM* acting as an electron donor reducing ClO2 to chlorite. This study highlighted the important role of 3DOM* as a reductant.

Mechanistic Insights into the Markedly Decreased Oxidation Capacity of the Fe(II)/S2O82- Process with Increasing pH.

The poor oxidation capacity of the Fe(II)/S2O82- [Fe(II)/PDS] system at pH > 3.0 has limited its wide application in water treatment. To unravel the underlying mechanism, this study systematically evaluated the possible influencing factors over the pH range of 1.0-8.0 and developed a mathematical model to quantify these effects. Results showed that ∼82% of the generated Fe(IV) could be used for pollutant degradation at pH 1.0, whereas negligible Fe(IV) contribution was observed at pH 7.5. This dramatic decline of Fe(IV) contribution with increasing pH dominantly accounted for the pH-dependent performance of the Fe(II)/PDS process. Unexpectedly, Fe(II) could consume ∼80% of the generated SO4•- non-productively under both acidic and near-neutral conditions, while the larger formation of Fe(III) precipitates at high pH inhibited the SO4•- contribution mildly. Moreover, the strong Fe(II) scavenging effect was difficult to be compensated for by slowing down the Fe(II) dosing rate. The competition of dissolved oxygen with PDS for Fe(II) was insignificant at pH ≤ 7.5, where the second-order rate constants for reactions of Fe(II) with oxygen were much lower than or comparable to that between Fe(II) and PDS. These findings could advance our understanding of the chemistry and application of the Fe(II)/PDS process.

Insight into the performance of UV/chlorine/TiO2 on carbamazepine degradation: The crucial role of chlorine oxide radical (ClO•)

The UV/chlorine (UC) system is a homogeneous advanced oxidation process with increasing attention in water decontamination. The addition of TiO2 is a newly found strategy to enhance the generation of hydroxyl radical (HO•) and chlorine radical (Cl•) in the UC system. However, the crucial role of chlorine oxide radical (ClO•, generated by the reactions of HO• and Cl• with chlorine) on pollutant degradation, has not been noticed in UV/chlorine/TiO2 (UCT), the heterogeneous photocatalytic system for chlorine activation. Herein, the role of ClO• in UCT was clarified through quenching experiments combined with model simulations during carbamazepine degradation. Tert-butyl alcohol completely inhibited while bicarbonate only partly suppressed carbamazepine degradation in UCT, indicating the important role of ClO•. The second-order reaction rate constant between ClO• and carbamazepine (kClO•,carbamazepine) was fitted to be (1.21 ± 0.08) × 107 M−1 s−1 by the kinetic model, which avoided the influence of carbonate radical (CO3•−), whose contribution couldn't be excluded during kClO•,carbamazepine determination in commonly used competitive kinetic methods with bicarbonate. With the obtained kClO•,carbamazepine, model simulation suggested that ClO• contributed about 50 % to carbamazepine degradation in UCT, and its concentration was less affected under varied conditions (solution pH, chlorine, bicarbonate, and chloride concentration) to keep an efficient carbamazepine degradation. On the contrary, pollutant degradation dominated by HO• in UCT was largely inhibited with the increase of pH, chlorine, and bicarbonate concentration. In addition to the promotion of degradation efficiency, less disinfection byproducts and lower energy requirement were found in UCT compared with UC. Furthermore, UCT could maintain satisfactory degradation efficiency and energy saving in ground water and surface water samples. Results of this study unraveled the crucial role of ClO• for pollutant degradation in UCT, and showed bright prospects and great potentials of the system in water treatment.

Photochemical environmental persistence of venlafaxine in an urban water reservoir: A combined experimental and computational investigation

The photochemical behavior of venlafaxine (VNX) in surface water was investigated using a hybrid theoretical-experimental-kinetic modeling approach. In addition to the direct photolysis quantum yield, the rate constants of the reactions between VNX and reactive photo-induced species (hydroxyl radicals, HO·; singlet oxygen, 1O2; and triplet excited states of chromophoric dissolved organic matter, 3CDOM*) in sunlit water were measured under simulated solar radiation using competition kinetics. To elucidate possible degradation products, first-principles calculations were applied, followed by toxicity estimation by quantitative structure-activity relationship (QSAR) calculations. Furthermore, kinetic simulations of VNX persistence in an urban water reservoir of the São Paulo Metropolitan Region, Brazil, were performed. The results indicate low direct photolysis of VNX, with ΦVNX = (1.06 ± 0.18) × 10−2 mol Einstein−1. The measured values of the second-order reaction rate constants are kVNX,3CDOM* = (3.98 ± 0.28) × 109 L mol−1 s−1 and kVNX,1O2 = (2.09 ± 0.17) × 107 L mol−1 s−1, which are lower than kVNX, HO·obs = (6.92 ± 0.37) × 109 L mol−1 s−1 and kVNX, HO·theo = 4.98 × 109 L mol−1 s−1. O-desmethylvenlafaxine, the most thermodynamically stable metabolite predicted by theoretical calculations, revealed potentially greater toxicity and, therefore, higher environmental risk to aquatic ecosystems. The estimated half-lives for VNX range from 9 to 62 days, depending on the season, local weather conditions and water quality parameters, the effects of which can be satisfactorily simulated with the aid of the modified photochemical fate model proposed in this work.

Degradation of three typical hydroxamic acids collectors via UVA-B activated H2O2 and persulfate: Kinetics, transformation pathway, DFT calculation and toxicity evaluation

This work systematically studied the kinetics and mechanism of degradation of salicylhydroxamic acid (SHA), benzhydroxamic acid (BHA) and N-hydroxyphthalimide (NOP) by UVA-B/H2O2 and UVA-B/peroxodisulfate (PDS). UVA-B irradiation could induce a direct photolysis of SHA and dominated SHA destruction in both systems. BHA and NOP were effectively degraded via HO•- and SO4•−-mediated oxidation. UVA-B/PDS displayed a better degradation performance for HAAs investigated than UVA-B/H2O2. An acidic pH was more suitable for three HAAs removal in the UVA-B/H2O2 system. However, basic pH was more efficient for HAAs degradation in the UVA-B/PDS system. The degradation of BHA and NOP was predominantly driven by SO4•− at all pH levels used (5.0–9.0). The second-order rate constants for SHA, BHA and NOP reactions with HO• and SO4•− were calculated to be (4.16–5.22) × 109 M−1·s−1 and (1.19–7.22) × 109 M−1·s−1, respectively. Presence of various water constituents had different influence on HAA removal, with a enhancement in the presence of HCO3–, Fe2+ and Cu2+. When real waters were used as a background, dissolved organic carbon and Cl− were the main factors that consumed radicals and affected the degradation performance of HAAs. Analysis of the transformation products and density functional theory revealed that all of the investigated HAAs first generated amidated products but the formation mechanisms might have been different. HAAs degradation pathways mainly included hydrolysis, hydroxylation, decarboxylation and ring opening processes. Toxicity evaluation showed that the UV/AOP degradation of HAAs generated some transformation products with higher acute toxicity than the parent compounds.

Peracetic Acid Enhances Micropollutant Degradation by Ferrate(VI) through Promotion of Electron Transfer Efficiency.

Ferrate(VI) and peracetic acid (PAA) are two oxidants of growing importance in water treatment. Recently, our group found that simultaneous application of ferrate(VI) and PAA led to much faster degradation of micropollutants compared to that by a single oxidant, and this paper systematically evaluated the underlying mechanisms. First, we used benzoic acid and methyl phenyl sulfoxide as probe compounds and concluded that Fe(IV)/Fe(V) was the main reactive species, while organic radicals [CH3C(O)O•/CH3C(O)OO•] had negligible contribution. Second, we removed the coexistent hydrogen peroxide (H2O2) in PAA stock solution with free chlorine and, to our surprise, found the second-order reaction rate constant between ferrate(VI) and PAA to be only about 1.44 ± 0.12 M-1s-1 while that of H2O2 was as high as (2.01 ± 0.12) × 101 M-1s-1 at pH 9.0. Finally, further experiments on ferrate(VI)-bisulfite and ferrate(VI)-2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic)acid systems confirmed that PAA was not an activator for ferrate(VI). Rather, PAA could enhance the oxidation capacity of Fe(IV)/Fe(V), making their oxidation outcompete self-decay. This study, for the first time, reveals the ability of PAA to promote electron transfer efficiency between high-valent metals and organic contaminants and confirms the benefits of co-application of ferrate(VI) and PAA for alkaline wastewater treatment.

Oxidative degradation of bisphenol A in municipal wastewater reverse osmosis concentrate (ROC) using ferrate(VI)/hydrogen peroxide

The combination of ferrate(VI) with hydrogen peroxide (H2O2) was used for the degradation of bisphenol A (BPA) spiked in municipal wastewater reverse osmosis concentrate (ROC). The results showed that the combined Fe(VI) and H2O2 oxidant provided an additive effect to achieve greater degradation efficiencies of BPA in ROC compared to the use of Fe(VI) or H2O2 alone. The degradation efficiency of BPA was studied in detail by assessing the operating conditions, including Fe(VI) dosage, H2O2 dosage, the dosing strategy of Fe(VI) and H2O2, solution pH, and the initial concentration of BPA. It was found that over 99.0% of BPA was degraded (50 µg L−1) by using [Fe(VI)]/[H2O2] at a ratio of 1050:5000 and at pH 8.0. In addition, the degradation was also accompanied by 37.2% of dissolved organic carbon (DOC) removal and 94.0% of UV254 reduction. However, when the excess amount of H2O2 was added, it was found that H2O2 started to inhibit the degradation and the degradation efficiency of BPA in ROC lowered. It was also found that the simultaneous addition of Fe(VI) and H2O2 provided satisfactory BPA degradation. Similar degradation efficiency could be achieved by injecting the second oxidant into the system 10 min after adding the first oxidant at time zero. The apparent second-order reaction rate constant (kapp) obtained was 67.9 × 103 M−1 s−1 at a [Fe(VI)]/[H2O2] ratio of 1050:5000. The overall ecotoxicity of the treated water samples as measured by the Microtox bioassay technique decreased after the Fe(VI)/H2O2 treatment, which indicated that an insignificant amount, if not none, toxic degradation by-products was formed by the oxidative action of the Fe(VI)/H2O2 combined oxidant. The use of Fe(VI)/H2O2 as an alternative treatment option of cost-effectiveness than Fe(VI) alone in water and wastewater industries.

Clickable Albumin Nanoparticles for Pretargeted Drug Delivery toward PD-L1 Overexpressing Tumors in Combination Immunotherapy.

We present a simple methodology to design a pretargeted drug delivery system, based on clickable anti-programmed death ligand 1 (anti-PD-L1) antibodies (Abs) and clickable bovine serum albumin (BSA) nanoparticles (NPs). Pretargeted drug delivery is based on the decoupling of a targeting moiety and a drug-delivering vector which can then react in vivo after separate injections. This may be key to achieve active targeting of drug-delivering NPs toward cancerous tissue. In pretargeted approaches, drug-delivering NPs were observed to accumulate in a higher amount in the targeted tissue due to shielding-related enhanced blood circulation and size-related enhanced tissue penetration. In this work, BSA NPs were produced using the solvent precipitation methodology that renders colloidally stable NPs, which were subsequently functionalized with a clickable moiety based on chlorosydnone (Cl-Syd). Those reactive groups are able to specifically react with dibenzocyclooctyne (DBCO) groups in a click-type fashion, reaching second-order reaction rate constants as high as 1.9 M–1·s–1, which makes this reaction highly suitable for in vivo applications. The presence of reactive Cl-Syd was demonstrated by reacting the functionalized NPs with a DBCO-modified sulfo-cyanine-5 dye. With this reaction, it was possible to infer the number of reactive moieties per NPs. Finally, and with the aim of demonstrating the suitability of this system to be used in pretargeted strategies, functionalized fluorescent NPs were used to label H358 cells with a clickable anti-PD-L1 Ab, applying the reaction between Cl-Syd and DBCO as corresponding clickable groups. The results of these experiments demonstrate the bio-orthogonality of the system to perform the reaction in vitro, in a period as short as 15 min.

Permanganate Oxidation of Organic Contaminants and Model Compounds.

Permanganate oxidation is an attractive environmental remediation strategy due to its low cost, ease of use, and wide range in reactivity. Here, permanganate reactivity trends are investigated for model organic compounds and organic contaminants. Second-order permanganate reaction rate constants were compiled for 215 compounds from 82 references (journal articles, conference proceedings, master's theses, and dissertations). Additionally, we validated some phenol rate constants and contribute a few additional phenol rate constants. Commonalities between contaminant oxidation products are also discussed, and we tentatively identify several model compound oxidation products. Aromatic rings, alcohols, and ether groups had low reaction rate constants with permanganate. Alkene reaction sites had the highest reaction rate constants, followed by phenols, anilines, and benzylic carbon-hydrogen bonds. Generally, permanganate reactivity follows electrophilic substitution trends at the reaction site where electron donating groups increase the rate of reaction, while electron withdrawing groups decrease the rate of reaction. Solution conditions, specifically, buffer type and concentration, may impact the rate of reaction, which could be due to either an ionic strength effect or the buffer ions acting as ligands. The impact of these solution conditions, unfortunately, precludes the development of a quantitative structure-activity relationship for permanganate reaction rate constants with the currently available data. We note that critical experimental details are often missing in the literature, which posed a challenge when comparing rate constants between studies. Future research directions on permanganate oxidation should seek to improve our understanding of buffer effects and to identify oxidation products for model compounds so that extrapolations can be made to more complex contaminant structures.

Kinetics and Transformations of Diverse Dissolved Organic Matter Fractions with Sulfate Radicals.

Dissolved organic matter (DOM) scavenges sulfate radicals (SO4•-), and SO4•--induced DOM transformations influence disinfection byproduct (DBP) formation when chlorination follows advanced oxidation processes (AOPs) used for pollutant destruction during water and wastewater treatment. Competition kinetics experiments and transient kinetics experiments were conducted in the presence of 19 DOM fractions. Second-order reaction rate constants for DOM reactions with SO4•- (kDOM,SO4•-) ranged from (6.38 ± 0.53) × 106 M-1 s-1 to (3.68 ± 0.34) × 107 MC-1 s-1. kDOM,SO4•- correlated with specific absorbance at 254 nm (SUVA254) (R2 = 0.78) or total antioxidant capacity (R2 = 0.78), suggesting that DOM with more aromatics and antioxidative moieties reacted faster with SO4•-. SO4•- exposure activated DBP precursors and increased carbonaceous DBP (C-DBP) yields (e.g., trichloromethane, chloral hydrate, and 1,1,1-trichloropropanone) in humic acid and fulvic acid DOM fractions despite the great reduction in their organic carbon, chromophores, and fluorophores. Conversely, SO4•--induced reactions reduced nitrogenous DBP yields (e.g., dichloroacetonitrile and trichloronitromethane) in wastewater effluent organic matter and algal organic matter without forming more C-DBP precursors. DBP formation as a function of SO4•- exposure (concentration × time) provides guidance on optimization strategies for SO4•--based AOPs in realistic water matrices.

How does pH influence ferrate(VI) oxidation of fluoroquinolone antibiotics?

• Kinetic model of fluoroquinolones oxidation by Fe(VI) was built at pH 3.0–9.0. • Reactive sites and main reactions were proposed based on theoretical calculation. • Fe VI , Fe V , and Fe IV were primary reactive species at both alkaline and acidic pH. • HO was yielded via Fenton or Fenton-like process at acidic pH in Fe(VI) oxidation. This study investigated the impact of pH on the efficiency of ferrate (Fe(VI), K 2 FeO 4 ) toward fluoroquinolone antibiotics, built kinetic models of Fe(VI) oxidation, and elucidated the involved active species during Fe(VI) oxidation at acidic and alkaline conditions. It was found that the second-order reaction rate constants ( k app , M −1 s −1 ) of Fe(VI) with three fluoroquinolone antibiotics (i.e., enroxacin, ofloxacin, and norfloxacin) were strongly dependent on pH, and k app reached its maximum at pH about 6.5. The reactions between HFeO 4 - /H 2 FeO 4 and neutral/protonated fluoroquinolone antibiotics (X and XH + ) were the major ones. Moreover, the reactive species were identified as high-valent iron species, i.e., Fe(VI), Fe(V), and Fe(IV), in alkaline solution, while hydroxyl radicals was generated through Fenton or Fenton-like processes at acidic condition with limited contribution.

Photodegradation of propranolol in surface waters: An important role of carbonate radical and enhancing toxicity phenomenon

Antihypertensive propranolol (PRO) is frequently detected in surface waters and has adverse effects on aquatic organisms. In this study, its photochemical fate in surface water with the aspect of kinetics, products and toxicity were investigated employing steady-state photochemistry experiments and ecotoxicity tests. The results showed that photodegradation of PRO was enhanced in river water than that in phosphate buffer where dissolved organic matter (DOM), NO3−, and HCO3− played important roles. DOM accelerated the photodegradation mainly through generation of excited triplet-state DOM while NO3− played dual roles in the photodegradation. The reaction between excited triplet-state PRO and HCO3− can generate carbonate radical (CO3·-) to promote the photodegradation. The second-order reaction rate constant between PRO and CO3·- was determined to be (3.4 ± 0.8) × 108 M−1 s−1. Eight photodegradation products were identified in the studied river water sample. Finally, the toxicity evaluated by Vibrio fischeri increased after photodegradation and three photodegradation products were responsible for the increasing toxicity, which was concluded from the significant correlation between toxicity parameters and quantity of the photodegradation products.