The photolysis of five frequent emerging contaminants (Benzotriazole, Chlorophene, N,N-diethyl-m-toluamide or DEET, Methylindole, and Nortriptyline HCl) was investigated in ultrapure water under ...monochromatic ultraviolet radiation at 254 nm and by a combination of UV and hydrogen peroxide. The results revealed that the photolysis rates followed first-order kinetics, with rate constant values depending on the nature of the specific compound, the pH, and the presence or absence of the scavenger tert-butanol. Quantum yields were also determined and values in the range of 53.8 × 10−3 − 9.4 × 10−3 mol E−1 for Benzotriazole, 525 × 10−3 − 469 × 10−3 mol E−1 for Chlorophene, 2.8 × 10−3 − 0.9 × 10−3 mol E−1 for DEET, 108 × 10−3 − 165 × 10−3 mol E−1 for Methylindole, and 13.8 × 10−3 − 15.0 × 10−3 mol E−1 for Nortriptyline were obtained. The study also found that the UV/H2O2 process enhanced the oxidation rate in comparison to direct photolysis. High-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS) technique was applied to the concentrations evaluation and further identification of the parent compounds and their by-products, which allowed the proposal of the degradation pathways for each compound. Finally, in order to assess the aquatic toxicity in the photodegradation of these compounds, the Vibrio fischeri acute toxicity test was used, and the results indicated an initial increase of this parameter in all cases, followed by a decrease in the specific case of Benzotriazole, DEET, Methylindole, and Chlorophene.
► Photolysis of five emerging contaminants (EC) was investigated. ► First-order rate constants and quantum yields were determined for each EC. ► The combined UV/H2O2 process provided a significant increase in the reaction rates. ► Intermediates were identified and the degradation pathways were proposed. ► Toxicity measurements showed an initial increase, followed by a decrease.
•The removal of 5 emerging contaminants (ECs) by UV/PS was investigated.•Rate constants of ECs with sulfate radicals were determined by competition kinetics.•The degradation rate of ECs followed ...pseudo-first order kinetics.•The maximum degradation rate was achieved at near neutral pH.•Natural organic matter and radical scavengers inhibited the removal of ECs.
The degradation of five selected emerging contaminants (ECs) including 1H-benzotriazole (BZ), N,N-diethyl-m-toluamide or DEET (DT), chlorophene (CP), 3-methylindole (ML), and nortriptyline hydrochloride (NH) in aqueous solutions by UV-activated persulfate (UV/PS) has been investigated. Selected ECs were not effectively degraded by direct UV photolysis or dark PS. However, their photodegradation efficiency significantly increased with addition of PS due to the generation of SO4− and HO. Second order rate constants for the reaction between SO4− and each EC were determined by competition kinetics, being the values at pH 7 2.0 × 1010, 1.2 × 1010, 1.8 × 109, 1.1 × 109 and 9.5 × 108 M−1 s−1 for NH, ML, CP, BZ and DT, respectively. While the dose of PS exerted a positive influence on the degradation of ECs, the highest degradation rate was observed at near neutral pH. With respect to the influence of background water matrix constituents, bicarbonate showed an inhibition effect on the removal of DT, BZ and NH and promoted the degradation of CP and especially of ML, which can be explained by their high reaction rate with carbonate radicals. The presence of humic acids inhibited the degradation of selected ECs, probably due to light screening and radical scavenging. Both radical species SO4− and HO exert an important role on the oxidation of the ECs investigated by the UV/PS system, being the contribution of SO4− predominant for those compounds that present high reactivity with this radical. Although the presence of inorganic and organic matter in real water matrices decreased the degradation rate of selected ECs, UV/PS process is an efficient option for their removal from contaminated waters.
Apparent rate constants for the reactions of four selected pharmaceutical compounds (metoprolol, naproxen, amoxicillin, and phenacetin) with chlorine in ultra-pure (UP) water were determined as a ...function of the pH. It was found that amoxicillin (in the whole pH range 3–12), and naproxen (in the low pH range 2–4) presented high reaction rates, while naproxen (in the pH range 5–9), and phenacetin and metoprolol (in the pH range 2.5–12 for phenacetin, and 3–10 for metoprolol) followed intermediate and slow reaction rates. A mechanism is proposed for the chlorination reaction, which allowed the evaluation of the intrinsic rate constants for the elementary reactions of the ionized and un-ionized species of each selected pharmaceutical with chlorine. An excellent agreement is obtained between experimental and calculated rate constants by this mechanism.
The elimination of these substances in several waters (a groundwater, a surface water from a public reservoir, and two effluents from municipal wastewater treatment plants) was also investigated at neutral pH. The efficiency of the chlorination process with respect to the pharmaceuticals elimination and the formation THMs was also established. It is generally observed that the increasing presence of organic and inorganic matter in the water matrices demand more oxidant agent (chlorine), and therefore, less chlorine is available for the oxidation of these compounds. Finally, half-life times and oxidant exposures (CT) required for the removal of 99% of the four pharmaceuticals are also evaluated. These parameters are useful for the establishment of safety chlorine doses in oxidation or disinfection stages of pharmaceuticals in treatment plants.
How do small firms learn to develop a social media competence? Braojos-Gomez, Jessica; Benitez-Amado, Jose; Javier Llorens-Montes, F.
International journal of information management,
August 2015, 2015-08-00, 20150801, Letnik:
35, Številka:
4
Journal Article
Recenzirano
•Leveraging social media for marketing activities remains crucial for small firms.•We examine how small firms learn to develop a social media competence.•Empirical study with a unique secondary ...dataset on a sample of 100 U.S. small firms.•We introduce the construct social media competence and a good proxy to measure this construct.•The study shows the mechanisms through which small firms learn to develop a social media competence.
Social media can be leveraged to improve the firm's business activities to create value. Because small firms have a lower portfolio of financial resources to compete more effectively in the market, social media capabilities can become more important for small than large firms. However, prior research has failed in explaining the variables through which small firms can learn to adopt social media. Our study is a first effort to address this research gap. We propose a conceptual model in which social competitor pressure, IT infrastructure capability, two organizational capabilities (marketing management and innovation management) and firm size enable small firms to learn to develop a social media competence. The model is tested using the partial least squares-based structural equation modeling technique employing a unique secondary dataset on a sample composed of the 100 small U.S. firms included in the 2013 Forbes America's Best Small Companies ranking. The empirical analysis suggests that IT infrastructure capability, social competitor pressure, marketing management and innovation management are key mechanisms through which small firms learn to develop a social media competence. The empirical analysis also suggests that social media competence is more important for the smallest manufacturing firms even among a sample of small firms.
•Ozone exhibited better pollutants and UV254 removal than chlorine and permanganate.•0.5mgO3mgDOC−1 led to an important elimination of fast ozone-reacting compounds.•Iron coagulation was more ...efficient than alum and removed high MW compounds.•PAC could effectively eliminate hydrophobic and aromatic contaminants.•Coupling coagulation with ozone significantly improved contaminants and EfOM removal.
One important disadvantage of using ultrafiltration (UF) and nanofiltration (NF) for reclamation of secondary effluents from municipal wastewater treatment plants (WWTPs) is the necessity to dispose of the UF and NF retentates. Different advanced treatments including coagulation (iron and alum), oxidation (chlorine, permanganate and ozone) and powdered activated carbon (PAC) adsorption were compared for their efficiencies in removing 11 selected micropollutants and effluent organic matter (EfOM) from UF and NF retentates generated in the filtration of secondary effluents. Ozone exhibited better micropollutants and UV254 removal efficiencies than chlorine and permanganate. Similar abatement of organics was observed when the same specific oxidant dose was applied to UF and NF retentates. Coagulation preferentially removed high molecular weight compounds, being ineffective for the elimination of most micropollutants. In general terms, iron coagulation was more efficient than alum, since iron achieved higher DOC and UV254 removal at lower molar doses. In addition, PAC was an effective method for removing micropollutants, especially hydrophobic and aromatic compounds. The hybrid coagulation/ozonation process improved micropollutants and EfOM (DOC and UV254) removal. A specific ozone dose of 1mgO3mgDOC−1 was able to almost completely remove selected micropollutants from the UF retentate. The final effluent, which is likely more biodegradable and less toxic, could be recirculated to biological treatment processes in the WWTP, avoiding the continuous discharge of non-biodegradable micropollutants through the WWTP effluents.
Four UF membranes (denoted GH, GK, PT and PW with MWCO of 1000, 2000, 5000 and 20,000
Da, respectively) and four NF membranes (denoted DL, CK, DK and HL, with an approximate MWCO of 150–300
Da in all ...cases) were used for the filtration of an effluent generated in a municipal wastewater plant after a secondary treatment. The influence of the most important operating variables (nature and MWCO of the membranes, transmembrane pressure, tangential velocity, and temperature) on the permeate flux was widely discussed, and the resistances to the permeate flux were determined following the resistances in series model. Rejection coefficients for parameters that measure the global pollutant content of the effluent (chemical oxygen demand, total organic carbon, absorbance at 254
nm, turbidity, total nitrogen and total phosphorus) were also evaluated, and the results revealed that both UF and NF are feasible options for the treatment of this effluent, yielding a permeate stream that can be reused in several applications. Finally, 28 pharmaceutical compounds were initially detected in this effluent, and their respective rejection coefficients were determined, with eliminations higher than 75% in the case of NF with the HL membrane. Therefore, it is concluded that NF is an excellent option for the removal of toxic pharmaceuticals in municipal wastewaters.
The elimination of five selected emerging contaminants (1-H-benzotriazole,
N
,
N
-diethyl-
m
-toluamide (DEET), chlorophene, 3-methylindole, and nortriptyline HCl) dissolved in different water ...matrices (surface water and secondary effluents) was carried out by sequential membrane filtration and chemical oxidation processes. First, a membrane filtration (ultrafiltration (UF) or nanofiltration(NF)) pre-treatment was conducted, and both permeate and retentate were afterwards treated by chemical oxidation, using ozone or chlorine. The application of UF and especially of NF provided a large volume of permeate, whose quality can be improved by a chemical treatment to completely remove residual contaminants except 1-H-benzotriazole. Chlorination and especially ozonation have demonstrated to be effective for the reduction of emerging contaminants in the concentrated stream, thus generating an effluent that might be recycled to the activated sludge treatment in the wastewater treatment plants (WWTP). In a second group of experiments, a chemical oxidation pre-treatment (by using ozone, chlorine, O
3
/H
2
O
2
, ultraviolet (UV) radiation, or UV/H
2
O
2
) was applied followed by a nanofiltration process. Results of removals and rejection coefficients for the emerging contaminants showed that the chemical pre-treatment exerted a positive influence on the subsequent NF process, not only in terms of ECs removal but also of dissolved organic carbon content (DOC) reduction. While global removals higher than 97 % were reached for DEET, chlorophene, 3-methylindole, and nortriptyline HCl, lower values were obtained for 1-H-benzotriazole, especially for chlorine pre-treatment and in those water matrices with high content of natural organic matter. Therefore, both sequential treatments are promising to remove the selected micropollutants while reducing the chlorine doses needed to achieve final water disinfection.
•The ozonation of ECs benzotriazole and methylindole, is investigated.•Apparent second order rate constants are determined in the pH range 3–10.•Eight intermediates for benzotriazole and six ...intermediates for methylindole are identified.•Degradation pathway mechanisms are proposed for the ozonation reactions.•The ozonation reactions in water systems are modeled.
The ozonation of 1H-benzotriazole (BZ) and 3-methylindole (ML), two emerging contaminants that are frequently present in aquatic environments, was investigated. The experiments were performed with the contaminants (1μM) dissolved in ultrapure water. The kinetic study led to the determination of the apparent rate constants for the ozonation reactions. In the case of 1H-benzotriazole, these rate constants varied from 20.1±0.4M−1s−1 at pH=3 to 2143±23M−1s−1 at pH=10. Due to its acidic nature (pKa=8.2), the degree of dissociation of this pollutant was determined at every pH of work, and the specific rate constants of the un-dissociated and dissociated species were evaluated, being the values of these rate constants 20.1±2.0 and 2.0±0.3×103M−1s−1, respectively. On the contrary, 3-methylindole does not present acidic nature, and therefore, it can be proposed an average value for its rate constant of 4.90±0.7×105M−1s−1 in the whole pH range 3–10. Further experiments were performed to identify the main degradation byproducts (10mgL−1 of contaminants, 0.023gh−1 of ozone). Up to 8 intermediates formed in the ozonation of 3-methylindole were identified by LC–TOFMS, while 6 intermediates were identified in the ozonation of 1H-benzotriazole. By considering these intermediate compounds, the reaction mechanisms were proposed and discussed. Finally, evaluated rate constants allowed to predict and modeling the oxidation of these micropollutants in general aquatic systems.
Filtration experiments in batch concentration mode (with recycling of the retentate stream) of the cork processing wastewater were performed in laboratory filtration membrane equipment, by using four ...commercial membranes: two UF membranes with MWCO of 20,000 and 5000
Da, and two NF membranes with an approximate MWCO of 150–300
Da. The filtration experiments of the selected wastewater were performed by modifying the most important operating variables: transmembrane pressure, tangential velocity, temperature, and the nature and MWCO of the membranes. The evolution of the cumulative permeate volumes and permeate fluxes with processing time were analysed, and it was established that the steady-state permeate flux was reached for a volume retention factor of 2. The effect of the mentioned operating conditions on this steady-state permeate flux was discussed. The effectiveness of the filtration treatments was determined by the evaluation of the rejection coefficients for several parameters, which measure the global pollutant content of the effluent: COD, absorbance at 254
nm, tannic content, color, and ellagic acid. Finally, the resistances in series model was used for the evaluation of the resistances to the permeate flux, and it was concluded that the contribution to the total resistance of the fouling resistance (combined external plus internal) was higher than the inherent resistance of the clean membrane.
Primary and secondary alcohols have been converted into 2-amino-1,3-thiazoles under microwave irradiation, employing trichloroisocyanuric acid (TCCA) as a dual oxidant and chlorine source, TEMPO as a ...co-oxidant, and thiourea. Secondary alcohols underwent a single-stage, one-pot conversion process, while primary alcohols required a two-stage, one-pot procedure. Both transformations were completed within minutes (25–45 min). The versatility of this protocol extends to the synthesis of other heterocycles, including 1,3-selenazoles, 2-aminoimidazoles, imidazo1,2-apyridines, quinoxalines, and hydrazino thiazoles by replacing thiourea with the appropriate surrogates.
