Degradation of chlortetracycline in wastewater sludge by ultrasonication,Fenton oxidation,and ferro-sonication

Residual emerging contaminants in wastewater sludge remain an obstacle for its wide and safe applications such as landfilling and bio-fertilizer. In this study, the feasibility of individual ultrasonication (UlS) and Fenton oxidation (FO) and combined, Ferro-sonication processes (FO) on the degradation of chlortetracycline (CTC) in wastewater sludge was investigated. UlS parameters such as amplitude and sonication time were optimized by response surface methodology (RSM) for further optimization of FS process. Generation of highly reactive hydroxyl radicals in FO and FS processes were compared to evaluate the degradation efficiency of CTC. Increasing in the ratio of hydrogen peroxide and iron concentration showed increased CTC degradation in FO process; whereas in FS, an increase in iron concentration did not show any significant effect (p > 0.05) on CTC degradation in sludge. The estimated iron concentration in sludge (115 mg/kg) was enough to degrade CTC without the addition of external iron. The only adjustment of sludge pH to 3 was enough to generate in-situ hydroxyl radicals by utilizing iron which is already present in the sludge. This observation was further supported by hydroxyl radical estimation with adjustment of water pH to 3 and with and without the addition of iron. The optimum operating UlS conditions were found to be 60% amplitude for 106 min by using RSM. Compared to standalone UlS and FO at 1:1 ratio, FS showed 15% and 8% increased CTC degradation respectively. In addition, UlS of sludge increased estrogenic activity 1.5 times higher compared to FO. FS treated samples did not show any estrogenic activity.     

Fluorescence Characteristics of Schiff Bases Derived from Amino- and Aminoalkylpyridines

The fluorescence characteristics of the Schiff bases 2-(3-pyridylmethyliminornethyl)phenol (1), 2-(2 pyridyliminomethyl)phenol (2), N.N-bis(salicylidene)-2,3-pyridinediamine (3), N,N'-bis(salicylidene)-2,6-pyridinediamine (4) and 2-(2-amino-4-methoxymethyl-6-methyl-3-pyridylmethyliminomethyl)phenol (5) were studied in various solvents at different pH values. Corresponding quantum efficiencies were determined. Compound 1, which showed a tendency towards tautomeric mterconversion to ketoamine in polar protic solvents, was not fluorescent at pH < 8. The fluorescence of other compounds was very sensitive to solvent polarity and the pH of the medium. Compounds 2-4, preferably present as enolimines in all solvents, were not fluorescent in non-polar and moderately polar solvents, whereas weak emission was observed in polar solvents, like methanol, dimethylformamide and dioxane/water 1/1 (0.001 < Q < 0.072). A significant increase in Stokes shifts and in quantum efficiencies was noted as a result of increasing polarity of dioxane/water mixtures, indicating specific interactions with polar water molecules. The emission was promoted at acidic pH values where a pyridinium cation was formed (0.061 < Q < 0.519, in dioxane/water 1/1 at pH 3.4). Compound 5, which was a tautomeric mixture of enoiimine and cyclic diamine in all solvents, was fluorescent in polar as well as in non-polar media. The quantum efficiency varied dependent on the solvent and pH (0.023 <Q< 0.435). The cyclic diamine, i. e. the more rigid structure was supposed to be responsible for the fluorescence in non-polar and aprotic solvents as well as at neutral, and weakly basic pH values.     

Surface-dependent cytotoxicity on bacteria as a model for environmental stress of halloysite nanotubes

Nanoparticles of CoDy_0.1Fe_1.9O₄ were synthesized by sol–gel auto-combustion method. Four samples were synthesized from precursor solutions having different pH values in the range of 2.5–10. X-ray diffraction patterns were analyzed to determine the crystal phase of CoDy_0.1Fe_1.9O₄ nanoparticles synthesized at different pH. The XRD patterns confirm the formation of cubic spinel structure for CoDy_0.1Fe_1.9O₄ nanoparticles synthesized at different pH values. However the single phase is obtained only at pH 7.5, while γ and α-Fe₂O₃ phases appeared at pH 2.5, 5.0, and 10.0. Transmission electron microscopy shows that the structural morphology of the nanoparticles is highly dependent on the pH concentration. Particle size varies in between 24 and 36 nm with respect to change in pH concentration of the sample. Particle size increases to 36 nm with increase in pH up to 7.5 followed by a decrease in particle size for further increase in pH value. Magnetic properties were explored by vibrating sample magnetometry. The variation in pH during the synthesis process changes the size and structural morphology of the nanoparticles, which ultimately causes the variation in the values of the magnetic parameters such as saturation magnetization and coercivity. Infrared spectroscopy is employed to determine the local symmetry in the crystalline solids and to shed light on the ordering phenomenon under the influence of different pH values.     

Agglomeration,isolation and dissolution of commercially manufactured silver nanoparticles in aqueous environments

The increasing use of manufactured nanoparticles ensures these materials will make their way into the environment. Silver nanoparticles in particular, due to use in a wide range of applications, have the potential to get into water systems, e.g., drinking water systems, ground water systems, estuaries, and/or lakes. One important question is what is the chemical and physical state of these nanoparticles in water? Are they present as isolated particles, agglomerates or dissolved ions, as this will dictate their fate and transport. Furthermore, does the chemical and physical state of the nanoparticles change as a function of size or differ from micron-sized particles of similar composition? In this study, an electrospray atomizer coupled to a scanning mobility particle sizer (ES-SMPS) is used to investigate the state of silver nanoparticles in water and aqueous nitric acid environments. Over the range of pH values investigated, 0.5–6.5, silver nanoparticles with a bimodal primary particle size distribution with the most intense peak at 5.0 ± 7.4 nm, as determined from transmission electron microscopy (TEM), show distinct size distributions indicating agglomeration between pH 6.5 and 3 and isolated nanoparticles at pH values from 2.5 to 1. At the lowest pH investigated, pH 0.5, there are no peaks detected by the SMPS, indicating complete nanoparticle dissolution. Further analysis of the solution shows dissolved Ag ions at a pH of 0.5. Interestingly, silver nanoparticle dissolution shows size dependent behavior as larger, micron-sized silver particles show no dissolution at this pH. Environmental implications of these results are discussed.     

TCs-Fe(Ⅲ)体系离子液体气浮浮选荧光光谱法分离/富集四环素类抗生素残留的研究

将离子液体应用于气浮溶剂浮选,建立了一种分离/富集四环素类(tetracyclines, TCs)抗生素的新方法——离子液体气浮溶剂浮选。最优化浮选条件为：以1-己基-3-甲基咪唑六氟磷酸盐([Hmim]PF₆)和乙酸乙酯(EA)的混合溶剂(φ=1/0.9)为浮选剂,以Fe(Ⅲ)为捕集剂,pH值为7.6,气体流速为40 mL·min-1,浮选时间为50 min。富集TCs-Fe(Ⅲ)配合物的[Hmim]PF₆-EA相用荧光光谱法直接测定,其线性回归方程为F=246.5c+4.32(c: μg·10 mL-1),相关系数r=0.999 1。实测了鱼塘表面水体和沉积物中四环素类抗生素的含量,加标回收率达到94.2%～100.4%,RSD＜3.2%(n=5)。红外光谱分析显示TCs-Fe(Ⅲ)配合物没有和离子液体发生反应,离子液体在气浮溶剂浮选中只起到溶剂作用。该方法适合于环境水样中痕量四环素类抗生素的分离/富集及分析。     

On the study of pH effects in the microwave enhanced rapid synthesis of nano-ZnO

The rapid synthesis of ZnO nanostructures by microwave treatment of aqueous solutions of different pH values is reported for the first time. Microwave in various wattages was used as the source of heating or energy feeding the aqueous precursors. The pH of the zinc metal source was altered by a suitable amount of mineralisers. The considered pH values are 8, 10, 12 and 13.5. Microwave dielectric heating is dependent on the ability of the material to absorb microwave. This is responsible for molecular friction and dielectric loss, which as a result produce internal heating of the dielectric medium, in this case the solution. In typical microwave assisted synthesis, the total exposure to the microwave treatment was near about 25 to 35 minutes. The ZnO nanostructures obtained were studied by XRD, SEM and TEM characterisations. From the XRD pattern and the full width half maximum of the dominant reflections, microstructural parameters of the nanostructures are calculated and compared for the different pH values. Flower petal like flakes and hexagonal nanorods are formed for the lower and higher pH solutions, respectively. From the SEM images, the size distributions for the pH 12 and 13.5 cases are compared by drawing a histogram.     

NO Fluorescence Sensing by Europium Tetracyclines Complexes in the Presence of H2O2

The effect on the fluorescence of the europium:tetracycline (Eu:Tc), europium:oxytetracycline (Eu:OxyTc) and europium:chlortetracycline (Eu:ClTc) complexes in approximately 2:1 ratio of nitric oxide (NO), peroxynitrite (ONOO^?), hydrogen peroxide (H₂O₂) and superoxide (O₂ ^·?) was assessed at three ROS/RNS concentrations levels, 30 °C and pH 6.00, 7.00 and 8.00. Except for the NO, an enhancement of fluorescence intensity was observed at pH 7.00 for all the europium tetracyclines complexes—the high enhancement was observed for H₂O₂. The quenching of the fluorescence of the Tc complexes, without and with the presence of other ROS/RNS species, provoked by NO constituted the bases for an analytical strategy for NO detection. The quantification capability was evaluated in a NO donor and in a standard solution. Good quantification results were obtained with the Eu:Tc (3:1) and Eu:OxyTc (4:1) complexes in the presence of H₂O₂ 200 μM with a detection limit of about 3 μM (Eu:OxyTc).     

Thermal and structural characterization of Cu–Al–Mn–X (Ti,Ni) shape memory alloys

In this study, the Cu–Al–Mn–X (X = Ni, Ti) shape memory alloys at the range of 10–12 at.% of aluminum and 4–5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu–Al–Mn–X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu–Al–Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu–Al–Mn–Ni sample is martensite, and due to the low solubility of the Ti, the Cu–Al–Mn–Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu–Al–Mn, Cu–Al–Mn–Ni and Cu–Al–Mn–Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.     

固体废弃物的酸碱度与浸提剂pH值的相关性研究

本文对固体废弃物的酸碱度与浸提剂pH值的相关性进行了初步的研究。研究结果表明：不同酸碱度的固体废弃物在不同pH值的浸提剂浸提下，金属元素的溶出量大为不同。酸性固体废弃物在pH值较低（pH=2-4)的浸提剂浸提时，金属元素的溶出量较大，在pH=4-8时，其重金属元素的溶出量趋于恒值，中性固体废弃物浸提剂的pH值对其金属元素的溶出量变化不大。碱性固体废弃物不受浸提剂pH值的影响，金属元素几乎没有溶出。另外，固体废弃物中，金属元素以不同化合物形态的存在也直接影响到浸提率。提出了固体废弃物的任意堆放和填埋，会在酸雨的冲淋浸泡下，对环境造成极大的危害，并根据当地降水的pH值制定出相应的地方监测标准。     

Study of Salinity and pH Effects on Gelation Time of a Polymer Gel Using Central Composite Design Method

Experiments were conducted to investigate the main effects of salinity (NaCl) concentrations and pH factors and their interactions on the gelation time response of a polymer gel used in a water shutoff system in oil field reservoirs. Central composite design (CCD) was used to design experiments and a mathematical model building. The main advantage of CCD was to generate the quadratic mathematical model for the gelation time as functions of salinity and pH factors. Tests were limited and optimized by CCD points including low star (axial), low factorial, central, high factorial, and high star points. The evaluation of the data and the developed model were performed through the examination of graphical trend of residuals and a numerical approach. Analysis of variance (ANOVA) was used to estimate the amount of data variations from the model predictions. It was found that the model was significant at the 99% confidence against test data. The results showed that the gelation time was dependent more on pH than salinity. For low pH, the gelation time increased with increasing of the salinity, while for a high pH (>4) the relationship was inversed. The research shows that CCD can effectively be applied for the modeling of gelation time and finding an optimum condition to achieve maximum or minimum gelation time for different salinity and pH factors.     

Optimization of Release Conditions of Alzheimer's Drug Donepezil Hydrochloride from Sodium Alginate/Sodium Carboxymethyl Cellulose Blend Microspheres

Microspheres of blends of sodium alginate (NaAlg) and sodium carboxymethyl cellulose (NaCMC) were prepared by a water-in-oil (w/o) emulsion crosslinking method and used for the release of donepezil hydrochloride (DP), which is an Alzheimer's drug. The microspheres were characterized with Fourier transform infrared spectroscopy (FTIR), differantial scanning calorimetry (DSC), and scanning electron microscopy (SEM). The microsphere characteristics, including DP entrapment efficiency, particle size, equilibrium swelling degree (ESD), and DP release kinetics, were determined. The effects of the preparation conditions, including the NaAlg/NaCMC (w/w) ratio, drug/polymer (w/w) ratio, cross-linker concentration and time of exposure to the cross-linker, on the release of DP were investigated for successive gastrointestinal tract pH values of 1.2, 6.8, and 7.4 at 37°C. The release of DP increased with the increase in NaAlg/NaCMC (w/w) ratio and drug/polymer (d/p) ratio, while it decreased with increasing extent of cross-linking. The optimum DP release was obtained as 99.13% for a NaAlg/NaCMC (w/w) ratio of 2/1, d/p ratio of 1/4, CaCl₂ concentration of 5% and crosslinking time of 30 min. It was also observed from release results that DP release from the microspheres through the external medium was higher at low pH (1.2) values than that at high pH (6.8 and 7.4) values. The DP release of the microspheres followed either Fickian transport below a value of n < 0.5 or anomalous transport (n = 0.5–1.0).     

Plastic deformation properties of Zr–Nb–Ti–Ta–Hf high-entropy alloys

We have investigated the plastic deformation properties of single-phase Zr–Nb–Ti–Ta–Hf high-entropy alloys from room temperature (RT) up to 300 °C. Uniaxial deformation tests at a constant strain rate of 10^?4?s^?1 were performed, including incremental tests such as stress relaxations, strain-rate changes, and temperature changes in order to determine the thermodynamic activation parameters of the deformation process. The microstructure of deformed samples was characterized by transmission electron microscopy. The strength of the investigated Zr–Nb–Ti–Ta–Hf phase is not as high as the values frequently reported for high-entropy alloys in other systems. At RT we measure a flow stress of about 850 °C. We find an activation enthalpy of about 1 eV and a stress dependent activation volume between 0.5 and 2 nm³. The measurement of the activation parameters at higher temperatures is affected by structural changes evolving in the material during plastic deformation.     

溶胶-凝胶法制备的纳米TiO2结构相变及晶体生长动力学

讨论了采用溶胶-凝胶法经由先驱物钛酸四异丙脂水解而制备的纳米TiO₂粉末的 结构相变 ，并讨论了该纳米粉末的生长动力学机理.结果表明，水解pH值为0.9，当高压釜热处理温度 ＜503K时，粉末晶粒度增长较为缓慢，而当热处理温度＞503K时，粉末粒度明显长大.应用 相变理论计算出了纳米TiO₂颗粒的两阶段的生长激活能，分别是18.5kJ/mol和5 9.7kJ/mol .XRD物相分析表明，高压釜热处理温度达到503K时，样品就开始发生锐钛矿到金红石相的结 构相变，到543K就基本实现了这一结构相变，使得这一相变温度比其他文献中报道的又降低 了许多. 关键词： 2')" href="#">纳米TiO₂ 溶胶_凝胶法 结构相变 晶粒生长动力学     

Positron annihilation spectroscopic studies of Mn substitution-induced cubic to tetragonal transformation in ZnFe2–xMnxO4 (x = 0.0–2.0) spinel nanocrystallites

The replacement of cations at the B-sites in the spinel ferrite ZnFe₂O₄ by Mn³⁺ ions brings in several interesting changes, the most striking among them being a transformation from the spinel cubic structure to a body-centered tetragonal one. Concomitantly, there are variations in the nanocrystallite sizes and also in the lattice parameters. These are examined through high-precision X-ray diffraction measurements and transmission electron microscopic analysis. A more interesting aspect is the success of positron annihilation spectroscopy comprising of the measurements of positron lifetime and coincidence Doppler broadening measurements in understanding the effects of cation replacement and the resultant generation of vacancy-type defects. There are definite changes in the positron lifetimes and intensities which show positron trapping in trivacancy-type defect clusters and the nanocrystallite surfaces. The presence of ortho-positronium atoms within the extended intercrystallite region is also identified, although in small concentrations. The cubic to tetragonal transformation is indicated through definite decrease in the values of the positron lifetimes. We also performed a model analysis to predict the expected effect of substitution on the positron lifetime in the bulk of the sample and the experimentally obtained positron lifetimes significantly differed, indirectly hinting at the possibility of a structural transformation. Finally, Mössbauer spectroscopic studies have indicated a ferromagnetic nature for one of the samples, i.e. the one with Mn³⁺ doping concentration x = 0.4, which incidentally had the lowest crystallite size ~10 nm.     

Relationship between acoustic emission energy and the kinetics of martensite formation in plain carbon steels

The kinetics of the martensitic transformation in Fe-0.80C determined on the basis of dilatometry data is compared to the acoustic emission (AE) energy accompanying the transformation in the same steel reported in a previous study. The discrepancy between the AE energy and the volume fraction of martensite indicates that the mechanism for the generation of AE during the martensitic transformation is not solely dependent on the kinetics and the associated moving interfaces as suggested in previous studies. During the growth of martensite, slip takes place in order to relieve internal stresses, and dislocations are thought to be mainly introduced in the relatively soft austenite matrix. The quantitative analysis in this study demonstrates that the AE energy generated per unit time is a function of both the transformation kinetics and the volume fraction of remaining austenite. This strongly indicates that the moving dislocations associated with the plastic deformation of the austenite surrounding the as-formed martensite are the dominant sources of the generated acoustic waves. This improved AE source model is consistent with the well-accepted mechanism of AE during conventional plastic deformation due to an external load.     

电子束辐照改性铀吸附材料中官能团的性能研究

探讨了带有肟胺基官能团材料的制备、 吸附铀的机理及其对盐湖卤水中铀的吸附效果。 利用电子束辐照法制备肟胺化无纺布, 红外光谱显示材料中含有肟胺基存在, 表明肟胺基成功的接枝在无纺布基体上。 研究了铀溶液的初始pH、 吸附时间和固液比等因素对铀吸附效果的影响, 吸附过程中络合反应为控速步骤。 肟胺化纤维和肟胺化无纺布对盐湖卤水样品具有较高的吸附效率, 可以作为盐湖提铀的备选材料。 Amidoximed fiber and fabric were synthesized with the purpose of adsorbing U in salt lake and the adsorption mechanism was discussed. IR indicated that amidoxime was graft to the fabric which was irradiated by electron beam. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time on uranium sorption efficiency. The sorption of uranium on amidoxime was dependent on the pH value of the solution, and the optimal pH was 4.0. Uranyl was taken out from solution in the form of complex with amidoxime. Uranium recovery efficiency from salt lake was more than 50% with amidoximed fiber and fabric which can be used as uranium extraction material.     

Biomass waste-derived activated carbon for the removal of arsenic and manganese ions from aqueous solutions

The goal of this study is to investigate the preparation of low-cost activated carbon from bean pods waste and to explore their potential application for the removal of heavy metals from aqueous solutions. Conventional physical (water vapor) activation was used for synthesizing the adsorbent. The obtained carbon was employed for the removal of As (III) and Mn (II) from aqueous solutions at different initial concentrations and pH values. Adsorption for both ions follows Langmuir-type isotherm, the maximum loading capacities for arsenic (III) and Mn (II) ions being 1.01 and 23.4 mg g⁻¹, respectively. According to the experimental data, it can be inferred that the basic character of the surface, i.e. the high content of basic groups, favors adsorption of ions. Arsenic adsorption capacity on the carbon obtained from agricultural waste was found to be similar to this of more expensive commercial carbons showing high adsorption capability. Regarding manganese adsorption, herein obtained carbon presented higher uptake adsorption than that of activated carbons reported in the literature.     

Current–time characteristic of the transient regime of electrohydrodynamic flow formation

The paper presents the results of computer simulation of the current–time characteristic (CTC) of a cell with low-conducting liquid. The basis of simulation is the complete set of electrohydrodynamic (EHD) equations. The injection and dissociation mechanisms of charge formation as well as field-enhanced dissociation are considered. The simulation is carried out in the needle–plane electrode system. The relation between sections of CTC and stages of EHD flow formation is revealed. The shape of CTC is shown to be dependent on mechanisms of charge formation, the ratio of the initial and steady-state ion concentrations and the mechanisms of charge transport.     

Size and temperature dependent stability and phase transformation in single-crystal zirconium nanowire

A novel size dependent FCC (face-centered-cubic) → HCP (hexagonally-closed-pack) phase transformation and stability of an initial FCC zirconium nanowire are studied. FCC zirconium nanowires with cross-sectional dimensions <20 Å are found unstable in nature, and they undergo a FCC → HCP phase transformation, which is driven by tensile surface stress induced high internal compressive stresses. FCC nanowire with cross-sectional dimensions >20 Å, in which surface stresses are not enough to drive the phase transformation, show meta-stability. In such a case, an external kinetic energy in the form of thermal heating is required to overcome the energy barrier and achieve FCC → HCP phase transformation. The FCC-HCP transition pathway is also studied using Nudged Elastic Band (NEB) method, to further confirm the size dependent stability/metastability of Zr nanowires. We also show size dependent critical temperature, which is required for complete phase transformation of a metastable-FCC nanowire.     

Adsorption of Cr(VI) from Aqueous Solutions Onto Raw and Acid-Activated Reşadiye and Hançılı Clays

ABSTRACT

The adsorption of Cr(VI) from aqueous solutions onto raw and acid-activated clays—namely, Re?adiye region clay (R, raw Re?adiye region clay; R-H₂SO₄, acid-activated with H₂SO₄ Re?adiye region clay; R-HCl, acid-activated with HCl Re?adiye region clay) and Hanç?l? region clay (H, raw Hanç?l? region clay; H-H₂SO₄, acid-activated with H₂SO₄ Hanç?l? region clay; H-HCl, acid-activated with HCl Hanç?l? region clay)—was studied in a batch system. For optimization of the Cr(VI) adsorption on raw clays and acid-activated clays, the effect of pH, temperature, initial Cr(VI) concentration, time, and adsorbent dosage were investigated. X-ray diffraction analyses of raw and acid-activated clays were used to determine the effects of acid-activating on the layer structure of the clays. The surface characterizations of clays and modified clays were performed by using FT-IR spectroscopy. The Langmuir and Freundlich adsorption models were employed to describe the equilibrium isotherms, and thus the isotherm constants were determined. The data obtained from our investigations were well described by the Langmuir model. The adsorption capacity of the adsorbents Re?adiye and Hanç?l? clays were found to be 0.0269, 0.0144, and 0.0170 mmol/g for H, H-HCl, and H-H₂SO₄ and 0.0356, 0.0276, and 0.0422 mmol/g for R, R-HCl, and R-H₂SO₄, respectively. The results show that the adsorption was strongly dependent on pH of the medium, initial Cr(VI) concentration and temperature. The removal of Cr(VI) reached saturation in about 120 min, and the adsorption process of Cr(VI) was observed as exothermic. A maximum removal of 73% was noted at 1.0 × 10^?4 M concentration of Cr(VI) in solution for H-HCl. Furthermore the enhancement of removal of Cr(VI) was observed from pH 3 to 4. The results are discussed to highlight the influence of acid activation on Cr(VI) adsorption characteristics of the clays.