Totally found 1795 items.

  • [期刊] Broad spectrum detection of veterinary drugs with a highly stable metal-organic framework
    The broad spectrum detection of veterinary drugs is very important for rapid and large-scale safe screen of animal-derived foods. Metal-organic frameworks (MOFs), as a kind of emerged functional porous materials are quite promising in the chemical sensing and molecular detection. In this work, we report the high-performance broad spectrum detection of 15 commonly-used veterinary drugs through the fluorescence quenching in a newly-designed chemically stable Al-based MOF, Al-3(mu(3)-O)(OH)(H2O)(2)(PPTTA)(3/2) (BUT-22). To the best of our knowledge, this is the first systematic investigation for the application of MOFs in the detection/sensing of veterinary drugs through fluorescence quenching method. The quenching efficiencies of the tested veterinary drugs on BUT-22 are all beyond 82%, and the limits of detection (LOD) are low at parts per billion (ppb) levels. Interestingly, BUT-22 also enables the selective detection of nicarbazin (NIC) through the clearly-observed red shift of its maximum fluorescence emission wavelength. Moreover, the fluorescence quenching mechanism was explored with the help of theoretical calculations. Our work indicates that MOFs are favorable materials for the detection of veterinary drugs, being potentially useful in monitoring drug residues of animal-derived foods.
  • [期刊] Sorption of ionized dyes on high-salinity microalgal residue derived biochar: Electron acceptor-donor and metal-organic bridging mechanisms
    Biochar (BC) has attracted much attention owing to its superior sorption capacity towards ionized organic contaminants. However, the mechanism of ionized organics sorption occurring within BC containing large amounts of minerals is still controversial. In this study, we demonstrate the physicochemical structure of high-salinity microalgal residue derived biochar (HSBC) and elucidate the corresponding sorption mechanisms for four ionized dyes along with determining the crucial role of involved minerals. The results indicate that sodium and calcium minerals mainly exist within HSBCs, and the pyrolysis temperature can dramatically regulate the phases and interfacial property of both carbon matrix and minerals. As a result, the HSBC shows a higher sorption potential, benefiting from abundant functional groups and high content of inorganic minerals. Using theoretical calculations, the activities of electron donor-acceptor interaction between HSBCs and different dyes are clearly illustrated, thereby identifying the critical role of Ca2+ in enhancing the removal of ionized dyes in HSBCs. In addition, Ca-containing minerals facilitate the sorption of ionized dyes in HSBCs by forming ternary complexes through metal-bridging mechanism. These results of mineral-induced dye sorption mechanisms help to better understand the sorption of ionized organics in high-salt containing BC and provide a new disposal strategy for hazardous microalgal residue, as well as provide a breakthrough in making the remediation of ionized organic contaminated microalgal residue derived absorbent feasible.
  • [期刊] Studying the toxicity of SLE_nS-LAS micelles to collembolans and plants: Influence of ethylene oxide units in the head groups
    Mixed micelles of linear alkylbenzene sulfonic acid (LAS) and ether sulfate-based surfactants (SLEnS) can be added in household products and cleaning agents. SLEnS with higher ethylene oxide (EO) units in the head groups have economic and environmental advantages. This work aims to assess the influence of the number of EO units in the ecotoxicity of seven variants of SLEnS-LAS micelles (0-50 EO units) in soils. Ecotoxicological tests were carried out to assess emergence and growth of four plants species and reproduction of collembolans. Most of the variants inhibited plants growth at the highest concentrations (1237.5 mu g SLEnS kg(-1) of soil(dw)). For reproduction, lower number of EO units resulted in EC50 from 924.2 (95 % CL: 760.7-1063.4) to 963.2 (95 % CL: 676.9-1249.6) mu g SLEnS kg(-1) of soil(dw), whereas for higher number of EO units (50 and 30) no inhibition was reported. Based on these results, we suggest that a higher number of EO units contribute to less hazardous formulations, confirming that different designs of surfactants may contribute to changes in the responses of terrestrial organisms. Therefore, we demonstrate that standardized ecotoxicological assays may contribute to more sustainable and effective formulations, when used upstream, prior to manufacture and marketing.
  • [期刊] Measuring bioconcentration factors of sediment-associated fipronil in Lumbriculus variegatus using passive sampling techniques
    Fipronil and its degradates have been detected ubiquitously in aquatic environment worldwide, yet little is known about its bioaccumulation potential. The goal of the present study was to measure bioconcentration factor (BCF) of sediment-associated fipronil in a benthic invertebrate, Lumbriculus variegatus using passive sampling techniques. Three passive samplers including polymethyl methacrylate (PMMA) film, poly(dimethylsiloxane) fiber and polyacrylate fiber were evaluated. PMMA film was identified as the preferred method and was applied to determine fipronil log K-OC (3.77 +/- 0.04). BCF of sediment-associated fipronil in L. variegatus was obtained through measuring freely dissolved concentration (C-free). Because fipronil degraded in sediment, time weighted average (TWA) C-free was estimated for calculating BCFTWA (1855 +/- 293 mL/g lipid). Fipronil BCF was also measured in a water-only bioaccumulation test of L. variegatus under constant exposure condition. This BCF value (1892 +/- 76 mL/g lipid) was comparable with the BCFTWA, validating effectiveness of the passive sampling method for the measurement of sediment C-free. Fipronil was bioaccumulative in L. variegatus according to the USEPA's criteria. The combination of C-free and TWA concentration measurements was demonstrated to properly determine BCF value for moderately hydrophobic and degradable chemicals in sediment.
  • [期刊] Moderation of Al dust explosions by micro- and nano-sized Al_2O_3powder
    Adding solid inertants to combustible dust is one measure to prevent and mitigate dust explosions. Al2O3 at four particle size distributions was used to determine the minimum ignition energy (MIE) and maximum explosion pressure (P-max) of aluminum dust and thus examine the effect of particle size on the inerting efficiency. It was interesting to observe that nano-sized Al2O3 powder showed excellent promise as a solid inertant, having inerting efficacy superior to that of micro-sized Al2O3. In addition to thermal inhibition, nano Al2O3 contributed to explosion moderation by binding Al particles together forming larger-sized aggregates that reduce dispersion in the dust clouds, and thus alleviate explosion hazards. Ignition sensitivity increased when micro-sized Al2O3 was admixed at 5 or 10% with 1000-1500 g/m(3) Al mixtures, an effect apparently caused by a 20% decrease in effective particle size distribution brought on by the Al2O3 addition. Generally, increasing the amount of admixed Al2O3 increased MIE and decreased P, of Al dust clouds, and decreasing the particle size of Al2O3 resulted in better inerting performance on moderating both the likelihood of the ignition and the consequence of the explosion.
  • [期刊] Mechanistic insights into simultaneous removal of copper, cadmium and arsenic from water by iron oxide-functionalized magnetic imogolite nanocomposites
    Imogolite and magnetic imogolite-Fe oxide nanocomposites (Imo-Fe-50 and Imo-Fe-25, at 50 and 25 % Fe loading (w/w), respectively) were synthesized and tested for the removal of aqueous copper (Cu), cadmium (Cd), and arsenic (As) pollutants. The materials were characterized by transmission electron microscopy, and specific surface area and isoelectric point measurements. The Fe-containing samples were additionally characterized by Mossbauer spectroscopy and vibrating-sample magnetometry. Significant differences were found in the morphological, electrophoretic, and magnetic characteristics between imogolite and the nanocomposites. The in-situ Fe-oxide precipitation process modified the active surface sites of the imogolite. The Fe-oxide, mainly magnetite, favored the contaminants' adsorption over the pristine imogolite. The adsorption kinetics of these pollutants were adequately described by the pseudo-second order and intraparticle diffusion models. The kinetic models showed that surface adsorption was more important than intraparticle diffusion in the removal of the pollutants by all the adsorbents. The Langmuir-Freundlich model described the experimental adsorption data, and both nanocomposites showed greater adsorption capacity than the imogolite. The adsorption of Cu and Cd was sensitive to cationic competition, showing a decrease of the adsorption capacity when the two cations coexisted, while their adsorption increased in the presence of arsenate.
  • [期刊] Multifunctional molybdenum disulfide-copper nanocomposite that enhances the antibacterial activity, promotes rice growth and induces rice resistance
    Molybdenum disulfide sheets loaded with copper nanoparticles (MoS2-CuNPs) was prepared and its antibacterial activity against phytopathogen Xanthomonas oryzae pv. oryzae (Xoo) was investigated in vitro and in vivo for the first time. In a 2 h co-incubation, MoS2-CuNPs exhibited 19.2 times higher antibacterial activity against Xoo cells than a commercial copper bactericide (Kocide 3000). In the detached leaf experiment, the disease severity decreased from 86.25 % to 7.5 % in the MoS2-CuNPs treated rice leaves. The results further demonstrated that foliar application of MoS2-CuNPs could form a protective film and increase the density of trichome on the surface of rice leaves, finally prevent the infection of Xoo cells. This was probably due to the synergistic effect of MoS2-CuNPs. Additionally, foliar application of MoS2-CuNPs (4 - 32 mu g/ mL) increased obviously the content of Mo and chlorophyll (up 30.85 %), and then improved the growth of rice seedlings. Furthermore, the obtained MoS2-CuNPs could activate the activities of the antioxidant enzymes in rice, indicating higher resistance of rice under abiotic/biotic stresses. The multifunctional MoS2-CuNPs with superior antibacterial activity provided a promising alternative to the traditional antibacterial agents and had great potential in plant protection.
  • [期刊] Removal of antibiotic resistant bacteria and antibiotic resistance genes in wastewater effluent by UV-activated persulfate
    The emerging antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are increasingly appreciated to be as important as microbial contaminants. This paper focused on UV-activated persulfate (UV/PS), an advanced oxidation process, in removing ARB and ARGs from secondary wastewater effluent. Results showed that the inactivation efficiency of macrolides-resistant bacteria (MRB), sulfonamides-resistant bacteria (SRB), tetracyclines-resistant bacteria (TRB) and quinolones-resistant bacteria (QRB) by UV/PS reached 96.6 %, 94.7 %, 98.0 % and 99.9 % in 10 min, respectively. UV/PS also showed significant removal efficiency on ARGs. The reduction of total ARGs reached 3.84 orders of magnitude in UV/PS which is more than that in UV by 0.56 log. Particularly, the removal of mobile genetic elements (MGE) which might favor the horizontal gene transfer of ARGs among different microbial achieved 76.09 % by UV/PS. High-throughput sequencing revealed that UV/PS changed the microbial community. The proportions of Proteobacteria and Actinobacteria that pose human health risks were 4.25 % and 1.6 % less than UV, respectively. Co-occurrence analyzes indicated that ARGs were differentially contributed by bacterial taxa. In UV/PS system, hydroxyl radical and sulfate radical contributed to the removal of bacteria and ARGs. Our study provided a new method of UV/PS to remove ARGs and ARB for wastewater treatment.
  • [期刊] The decomposition of N-chloro amino acids of essential branched-chain amino acids: Kinetics and mechanism
    The formation of N-chloro-amino acids is of outmost importance in water treatment technologies and also in vivo processes. These compounds are considered as secondary disinfectants and play important role in the defense mechanism against invading pathogens in biological systems. Adversary effects, such as apoptosis or necrosis are also associated with these compounds and the intermediates and final products formed during their decomposition. In the present study, the decomposition kinetics of the N-chloro derivatives of branched chain amino acids (BCAAs) - leucine, isoleucine, valine - were studied. On the basis of spectrophotometric measurements, it was confirmed that the decomposition proceeds via a spontaneous and an OH - assisted path in each case: k(obs) = k + k(OH) [OH-]. H-1, C-13 NMR and MS experiments were also performed to identify the products and to monitor the progress of the reactions. It was established that the pH independent and the [OH-] dependent paths lead to the formation of the same aldehyde in each system (isovaleraldehyde, 2-methyl-butyraldehyde, and isobutyraldehyde) as a primary product. Under alkaline conditions, a portion of the aldehydes are converted into the corresponding Schiff-bases by the excess amino acid in a reversible process. A common mechanism was proposed for these reactions which postulates the formation of imines and hemiaminals as reactive intermediates.
  • [期刊] Integrating cationic metal-organic frameworks with ultrafiltration membrane for selective removal of perchlorate from Water
    We design a novel cationic metal-organic framework hybrid ultrafiltration polyvinylidene fluoride membrane (PVA/Cu-iMOFs/PVDF-0.05) and report its unique capture of aqueous perchlorate (ClO4-) at ppm-level. This membrane outperformed traditional adsorption materials and exhibited a specific affinity toward ClO4- in the presence of various competing anions at greater levels (up to a concentration ratio of 20). In the batch experiment, the ClO4- removal ratio reached 99.6% over a wide pH range (3(similar to)10). Membrane filtration by using a 12.56 cm(2) PVA/Cu-iMOFs/PVDF-0.05 membrane could effectively treat 4.71 L of ClO4--contaminated water before breakthrough occurred, while maintaining a satisfactory permeability ((similar to)627.32 L/(m(2)/h/bar)) and antifouling property. The exhausted membrane could easily be regenerated in aminoethanesulfonic acid solution for repeated use with a negligible decrease in capacity. Moreover, the membrane showed excellent long-term stability in a cross-flow filtration process due to the amido bond between the Cu-iMOFs and membrane surface as well as the "protection" of polyvinyl alcohol. Selective and reversible ion-exchange between the sulfonic acid (R-SO3) ligands of Cu-iMOFs and tetrahedral oxo-anionic species was verified to be the pathway for ClO4- trapping. Thus, other problematic elements that also occur in tetrahedral form in water can be removed by this method.