共查询到20条相似文献,搜索用时 31 毫秒
1.
A new electrochemical voltammetric sensor, Langmuir–Blodgett (LB) film of 25,27‐dimethoxy‐26‐(N‐trichloroacetyl)carbamoyloxy‐p‐tert‐butylcalix[4]arene (DCA) modified GCE (LBDCA–GCE), was designed and successfully used for recognition and determination of trace amounts of Ag+ in water. Under the optimum experimental conditions, the lowest detectable concentration of Ag+ reached 1 × 10?9 mol L?1. Moreover, LBDCA–GCE exhibited a well‐defined response relating to the Ag+ with good sensitivity, selectivity, reproducibility, and long stability. The recognizing mechanism of LBDCA–GCE for silver ion in aqueous solution was also discussed. The results show that the size of calixarene cavity may be the predominate factor affecting recognition of calixarene for silver ions. 相似文献
2.
Response surface methodology (RSM) employing the three‐level Box–Behnken factorial design was used to optimize the biosorption of Ag(I) by the macrofungus Pleurotus platypus. The initial Ag(I) concentration (100–300 mg/L), pH (3.0–9.0), and biomass dosage (1.0–5.0 g/L) were chosen as the process variables for the optimization. A coefficient of determination (R2) value (0.99), model F value (234.18), and its low p‐value (F < 0.0001) along with the lower value of coefficient of variation (2.44%) indicated the fitness of response surface quadratic model during the present study. At the optimum pH (6.0), initial metal concentration (220 mg/L), and biomass dosage (3.0 g/L), the model predicted 46.7 mg/g Ag(I) uptake and an experimental 46.77 mg/g Ag(I) uptake by P. platypus was obtained. This is the first report on Ag(I) sorption by P. platypus using statistical experimental design employing RSM which may be helpful towards the treatment of industrial effluent containing silver. 相似文献
3.
A cloud point extraction procedure is presented for the preconcentration and simultaneous determination of Ag+ and Pd2+ in various samples. After complexation with 2‐((2‐((1H‐benzo[d]imidazole‐2‐yl)methoxy)phenoxy)methyl)‐1H‐benzo[d]imidazol (BIMPI), which was used as a new chelating agent, analyte ions were quantitatively extracted to a phase rich in Triton X‐114 following centrifugation, and determination was carried out by flame atomic absorption spectrometry (FAAS). Under the optimum experimental conditions (i. e., pH = 7.0, 15.0·10–5 mol/L BIMPI and 0.036% (w/v) Triton X‐114), calibration graphs were linear in the range of 28.0–430.0 μg/L and 57.0–720.0 μg/L with detection limits of 10.0 and 25.0 μg/L for Ag+ and Pd2+, respectively. The enrichment factors were 35.0 and 28.0 for Ag+ and Pd2+, respectively. The method has been successfully applied to evaluate these metals in some real samples, including waste water, soil and hydrogenation catalyst samples. 相似文献
4.
Dr. Tönnies Frevert 《Aquatic Sciences - Research Across Boundaries》1980,42(2):255-268
The glass/Ag0, Ag2S electrode applicable for in situ determination of H2S was tested in solutions of inert electrolytes. No effects on sensitivity, selectivity and slope were found up to an ionic
strength of ≈0.7 (artificial seawater). In salty brines such as Dead Sea water or NaClsat. solution a positive potential shift and a slope increase was observed. This corresponds, presumably, to salting-out of the
gas. Within the observed precision range of the detection method (+-3%) the electrode allows the measurement of H2Sconcentrations (lower limit of detection: 10−5.5 M Stot). Nevertheless, as a consequence of its half cell combination, the electrode could be a means for the direct detection of
the salting coefficient of H2S in hypersaline media (I≫0.1). 相似文献
5.
The experimental results on adsorption of ions pb2+, Zn2+ and Ag+ onto mineral surfaces in a mix system show that the reaction kinetics of adions adsorbed onto mineral surfaces was mainly
controlled by their diffusion rates in solution. The concentration variations can be fit for the second-order rate equation
with good determined coefficients r = 0.800 5—0.979 7. In the near neutral solution, the concentration of exchanged ions K+ and Na+ related to reaction time can be described by the fint-order rate equation with r = 0.855 7–0.997 7. Meanwhile, the complex
diffusionexchange rate equation is suitable for describing the ca2
+ concentration variation, as ions Pb2
+ and Zn2+ were adions. Experimental data show that the amount of ions K+, Na+and Ca2+ release is much more than that of adion decrement in solution. This fact may suggest that the complexstion reaction of adions
Pb2+, Z2+ and Ag+ with the mineral surfaces was the major reaction process while adions were not entering the phyllosilicate interlayers or
CaCO3 lattice to exchange the ions K+, Na+ and Ca2+ at room temperature.
Project supported by the National Natural Science Foundation of China (Grant No. 49773206) and the Natural Science Foundation
of Guangdong Province (Grant No. 960504) 相似文献
6.
For the direct potentiometric measurement by means of a sulphidselective solidstate membrane electrode (as the reference electrode a calomel electrode with a salt bridge filled with 1M KNO3-solution) there were mixed 25 ml sample with 25 ml sulphide-antioxidant buffer (0.2 M ascorbic acid in 2 M NaOH, Ag2S-saturated). Calibration is done with thioacet-amide in the same buffer. This measuring arrangement determines sulphide concentrations of 1.5.10?6… 10?3 M. If the buffer is added to the samples in the ratio of 1 +1 immediately during sampling, the sulphide content will be stabilized by this for at least 24 h. The measuring method and its calibration are compared with other methods of calibration with Na2S and the potentiometric titration, the iodometric titration and the photometric determination. The method having been developed proves to be very selective and requires a minimum expenditure of time. 相似文献
7.
The amination water (AW) effluent stream from the industrial production of the trifluraline herbicide was submitted to an oxidation‐coagulation treatment with potassium ferrate, combined with advanced oxidation processes. The experimental results obtained by analysis of variance (ANOVA) for the oxidation‐coagulation‐Fenton process, evaluating the variables pH (A), Fe(VI) concentration (B), and H2O2 concentration (C), demonstrated that the regression equation resulting from the Response Surface Methodology (RSM) experimental design, for the quadratic model, was ηAbs (%) = 36.9– 21.58A + 8.37A2 + 1.36B + 0.92B2 + 1.08C + 1.52C2 + 1.27AB – 1.34AC + 1.33BC. The maximum absorptiometric color reduction occurred at pH 3, with corresponding maximum amounts of iron and hydrogen peroxide. The absorptiometric color and COD reduction were 96% and 57%, respectively. For the oxidation‐coagulation‐photo‐Fenton process, the analyzed variables were pH (A), Fe(VI) concentration (B), H2O2 concentration (C), and temperature (D). The regression equation resulting from the quadratic model was ηAbs (%) = 38.3 – 20.2A + 8.12A2 – 0.27B + 3.73B2 + 0.3C + 3.6C2 + 1.67D + 3.1D2 + 1.72AB + 0.51AC – 1.82AD + 0.74BC – 1.11BD + 0.03CD. The ANOVA response showed that the highest absorptiometric color reduction occurred at pH 3, with respective maximum amounts of iron and hydrogen peroxide at 60°C. The maximum efficiencies achieved by the proposed treatment process for the trifluraline effluent stream were 95% and 85%, for absorptiometric color and COD reduction, respectively. 相似文献
8.
Solid‐contacted Potentiometric Electrodes for Measurements of Sulfate Ions in Aqueous Solutions A solid‐contact electrode for potentiometric measurement of sulfate ions in aqueous solutions was developed and examined. The electrode is based on a PVC membrane which contains the ionophore 3‐decyl‐1,5,8‐triazacyclodecan‐2,4‐dione (DTADD). Instead of the usual inner fluid junction, a polypyrrole layer applied on the inner side of the PVC membrane was employed as inner solid contact. The performance of this electrode was compared to solid‐state sulfate‐selective electrodes with the ionophore α,α′‐bis(N′‐phenylthioureylene)‐m‐xylene (BTH) and to electrodes in the coated‐wire configuration. For the parameters sensitivity, selectivity, and long‐term stability, electrodes with the DTADD ionophore show improved properties. In the sulfate concentration range of 5·10–5...10–2 mol L–1 the slope of the response is –(26.8 ± 0.5) mV/decade. The new solid contact sulfate electrodes showed a very low drift of the electrode potential within a period of 150 days when the electrode was stored in 10–2 M Na2SO4. In Na2SO4 solutions of the pH range of 4...9 the electrode potentials were constant. The 95% response time was about 10 s when the sulfate concentration was changed from 10–4 mol L–1 to 10–3 mol L–1. The selectivity with DTADD ionophore relating to the nitrate ions is higher than the selectivity with BTH. Improvements are also made in comparison with sulfate‐selective electrodes described in the literature which contain other ionophores with fluid inner reference electrolytes. 相似文献
9.
Based on satellite observation data, using dynamics equation, the ionospheric O+ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK
p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O+ ion’s density and flux versus longitude in the synchronous altitude region for differentK
p
are given. The main results show that in the synchronous altitude region: (i) The O+ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic
activity indexK
p
is, the higher the O+ ion’s density and flux, and their variation amplitude will be. The O+ ion’s density and flux whenK
p ≥ 6 will be about ten times as great as that whenK
p
= 0. (iii) WhenK
p
= 0 orK
p ≥ 6, the O+ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK
p
= 3−5, the O+ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O+ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK
p
value. 相似文献
10.
Batch sorption technique was carried out for the removal of anionic dye Congo red (CR) from aqueous solution using raw rectorite (R‐REC) and organified rectorite (CTA+‐REC) modified by cetyltrimethylammonium bromide (CTAB) as adsorbents. The effects of organification degree of CTA+‐REC as well as the process parameters including the pH of dye solution, sorption time, and initial dye concentration on adsorption capacity for CR were investigated and the sorption kinetics was also evaluated. The results showed that the sorption behaviors of R‐REC and CTA+‐REC for CR followed pseudo‐second‐order kinetic model and the sorption equilibrium data perfectly obeyed the Langmuir isotherm. The thermodynamic parameters including entropy of sorption (ΔS0), enthalpy of sorption (ΔH0), and Gibbs free energy of sorption (ΔG0) were obtained and analyzed. Fourier transform infrared study revealed that a chemisorption process occurred between CR and CTA+‐REC. REC modified by cationic surfactants showed the higher adsorption capacities for CR compared to R‐REC and in theory would be used as an efficient and promising adsorbent for the removal of anionic dyes in wastewater treatment. 相似文献
11.
P.-F. Cai C.-J. Su W.-T. Chang F.-C. Chang C.-Y. Peng I-W. Sun Y.-L. Wei C.-J. Jou H.Paul Wang 《Marine pollution bulletin》2014
Drinking water shortage has become worse in recent decades. A new capacitive deionization (CDI) method for increasing water supplies through the effective desalination of seawater has been developed. Silver as nano Ag and Ag@C which was prepared by carbonization of the Ag+-β-cyclodextrin complex at 573 K for 30 min can add the antimicrobial function into the CDI process. The Ag@C and Ag nanoparticles dispersed on reduced graphene oxide (Ag@C/rGO and nano Ag/rGO) were used as the CDI electrodes. The nano Ag/rGO and Ag@C/rGO electrodes can reduce the charging resistant, and enhance the electrosorption capability. Better CDI efficiencies with the nano Ag/rGO and Ag@C/rGO electrodes can therefore be obtained. When reversed the voltage, the electrodes can be recovered up to 90% within 5 min. This work presents the feasibility for the nano Ag and Ag@C on rGO electrodes applied in CDI process to produce drinking water from seawater or saline water. 相似文献
12.
Lourdes Vazquez‐Gomez Achille de Battisti Sergio Ferro Monica Cerro Silvia Reyna Carlos A. Martínez‐Huitle Marco A. Quiroz 《洁净——土壤、空气、水》2012,40(4):408-415
The electrochemical oxidation (EO) of diethyl phthalate (DEP) in aqueous solution was studied at Pb/PbO2 and Ti/SnO2 anode materials under galvanostatic‐experimental conditions. Results obtained clearly demonstrated that the anode plays a significant role for the optimization of the oxidation process, deciding the mechanisms and by‐products formed. DEP and by‐products of oxidation were also analyzed during various stages of the electrolysis reaction by HPLC and GC/MS techniques. Before the analysis by GC/MS technique, the samples were treated by solid phase microextraction (SPME) in order to concentrate the compounds from the reaction solution and identify all electrolysis intermediates. Current efficiencies (instantaneous current efficiency; ICE and total current efficiency; TCE) achieved during EO experiments were dependent on anode used and current density (20–40 mA cm?2) at 40°C. The results obtained demonstrated that the environmental electrochemical methods can be a feasible alternative for the wastewater treatment containing hazardous phthalates. 相似文献
13.
In the present work, experiments have been carried out with a focus to reduce the volume requirement of solvent by mixing with imidazolium based ionic liquids (ILs) for the solvent extraction of phenol, p‐chlorophenol, 2,4‐dichlorophenol, 2,4,6‐trichlorophenol, and pentachlorophenol from aqueous solutions. The effect of aqueous phase pH (2–12), agitation speed (100–450 rpm), solute concentration in feed (2–50 mg/L), temperature (303–333 K), treat ratio (1–11), and 1‐butyl‐3‐methyl imidazolium tetrafluoroborate [Bmim]+[BF4]? volume in tributyl phosphate (TBP; 0–0.7% v/v) on extraction of phenols has been studied and optimized. Parameters like strip phase pH (3–13) and stripping agent concentration (0.001–0.009 N) have also been studied for stripping of phenols from solvent phase. It has been found that 0.5% v/v of ionic liquid [Bmim]+[BF4]? in solvent TBP extracts more than 97.5% of phenol and chlorophenols from aqueous solutions with a treat ratio (aqueous to solvent phase ratio) of 5. Transport mechanism for extraction and stripping of phenol and chlorophenols using ionic liquid [Bmim]+[BF4]? has been discussed. The results show that by appropriate selection of extraction and stripping conditions, it is possible to remove nearly all phenols with a treat ratio of 5. 相似文献
14.
Analyses (n = 525) of chloride (Cl−), bromide (Br−), nitrate as nitrogen (NO3-N), sodium (Na+), calcium (Ca2+) and potassium (K+) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl− originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl− concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl− concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl− to Br− (p = .045), to NO3-N (p < .0001), to Ca2+ (p < .0001), and to Na+ (p < .0001) to be significantly different between urban and agricultural waters. While Cl− ratios indicate that road salt was the dominant source of Cl− in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl− dynamics; however, agricultural practices contributed Cl− year-round, elevating stream base flow Cl− concentrations above the background level. 相似文献
15.
Schnelle und einfache Methode zur In-situ-Bestimmung von Schwefelwasserstoff in Gewässern und Sedimenten 总被引:3,自引:0,他引:3
A direct potentiometric measurement chain (pH2S-electrode) for in situ determination of H2S in aquatic habitats is proposed which works like a conventional glass electrode chain but with Ag, Ag2S as reference electrode.
In the pH range ≤6 pStot can be determined irrespective of varying pH values. As there is no liquid junction most of the well-known interferences
in pS-measurement chains with an external reference electrode with liquid junction are diminished or avoided. Four methods
for calibration of the pH2S-electrode are discussed.
相似文献
16.
Hossein Tavallali Shahram Lalehparvar Abdo‐Reza Nekoei Maryam Ghane Jahromi Khodabakhsh Niknam 《洁净——土壤、空气、水》2012,40(6):640-647
A sensitive, reliable, and environmentally friendly method for simple separation and preconcentration of Ag(I) traces in aqueous samples is presented prior to their flame atomic absorption spectrometric determinations. At pH 7.0, Ag(I) was separated with 2‐(2‐methoxyphenyl)benzimidazole (MPBI) as a new complexing agent and floated after adding sodium dodecyl sulfate (SDS) as a foaming reagent. The floated layer was then dissolved in proper amount of concentrated nitric acid in methanol and introduced to the flame atomic absorption spectrometer (FAAS). The effects of pH, concentration of MPBI, type and amount of surfactant as the floating agent, type and amount of eluting agent, and influence of foreign ions on the recovery of the analyte ion were investigated. Also, using a nonlinear curve fitting method, the formation constant of 1.62 × 106 was obtained for Ag(I)–MPBI complex. The analytical curve was linear in the range of 1.8 × 10?7–1.7 × 10?6 mol/L for determination of Ag(I). The relative standard deviation (RSD; N = 10) corresponding to 0.7 × 10?6 mol/L of Ag(I), the limit of detection (10 blanks), and the enrichment factor were obtained as 1.7%, 2.9 × 10?8 mol/L, and 43.0, respectively. The proposed procedure was then applied successfully for determination of silver ions in different water samples. 相似文献
17.
David T. Adamson Thomas E. McHugh Michal W. Rysz Roberto Landazuri Charles J. Newell 《Ground Water Monitoring & Remediation》2012,32(1):59-72
The use of in‐field analysis of vapor‐phase samples to provide real‐time volatile organic compound (VOC) concentrations in groundwater has the potential to streamline monitoring by simplifying the sample collection and analysis process. A field validation program was completed to (1) evaluate methods for collection of vapor samples from monitoring wells and (2) evaluate the accuracy and precision of field‐portable instruments for the analysis of vapor‐phase samples. The field program evaluated three vapor‐phase sample collection methods: (1) headspace samples from two locations within the well, (2) passive vapor diffusion (PVD) samplers placed at the screened interval of the well, and (3) field vapor headspace analysis of groundwater samples. Two types of instruments were tested: a field‐portable gas chromatograph (GC) and a photoionization detector (PID). Field GC analysis of PVD samples showed no bias and good correlation to laboratory analysis of groundwater collected by low‐flow sampling (slope = 0.96, R2 = 0.85) and laboratory analysis of passive water diffusion bag samples from the well screen (slope = 1.03; R2 = 0.96). Field GC analysis of well headspace samples, either from the upper portion of the well or at the water‐vapor interface, resulted in higher variability and much poorer correlation (consistently biased low) relative to laboratory analysis of groundwater samples collected by low‐flow sample or passive diffusion bags (PDBs) (slope = 0.69 to 0.76; R2 = 0.60 to 0.64). These results indicate that field analysis of vapor‐phase samples can be used to obtain accurate measurements of VOC concentrations in groundwater. However, vapor samples collected from the well headspace were not in equilibrium with water collected from the well screen. Instead, PVD samplers placed in the screened interval represent the most promising approach for field‐based measurement of groundwater concentrations using vapor monitoring techniques and will be the focus of further field testing. 相似文献
18.
G. Kremser R. Rasinkangas P. Tanskanen B. Wilken G. Gloeckler 《Annales Geophysicae》1994,12(2-3):152-168
Measurements with the ion charge-energy-mass spectrometer CHEM on the AMPTE/CCE spacecraft were used to investigate the origin of energetic He+ and He++ ions observed in the equatorial plane at 3\leqL\leq9. Special emphasis was laid on the dependence of long-term average distributions on magnetic local time (MLT) and the geomagnetic activity index Kp. The observations are described in terms of the phase space densities f1 (for He+) and f2 (for He++). They confirm preliminary results from a previous study: f1 is independent of MLT, whereas f2 is much larger on the nightside than on the dayside. They show, furthermore, that f1 increases slightly with Kp on intermediate drift shells, but decreases on high drift shells (L\geq7). f2 increases with Kp on all drift shells outside the premidnight sector. Within this sector a decrease is observed on high drift shells. A simple ion tracing code was developed to determine how and from where the ions move into the region of observations. It provides ion trajectories as a function of the ion charge, the magnetic moment and Kp. The ion tracing enables a distinction between regions of closed drift orbits (ring current) and open convection trajectories (plasma sheet). It also indicates how the outer part of the observation region is connected to different parts of the more distant plasma sheet. Observations and tracing show that He++ ions are effectively transported from the plasma sheet on convection trajectories. Their distribution in the observation region corresponds to the distribution of solar wind ions in the plasma sheet. Thus, energetic He++ ions most likely originate in the solar wind. On the other hand, the plasma sheet is not an important source of energetic He+ ions. Convection trajectories more likely constitute a sink for He+ ions, which may diffuse onto them from closed drift orbits and then get lost through the magnetopause. An ionospheric origin of energetic He+ ions is unlikely as well, since the source mechanism should be almost independent of Kp. There is considerable doubt, however, that a plausible mechanism also exists during quiet periods that can accelerate ions to ring current energies, while extracting them from the ionosphere. It is concluded, therefore, that energetic He+ ions are mainly produced by charge exchange processes from He++ ions. This means that most of the energetic He+ ions constituting the average distributions also very likely originate in the solar wind. Additional ionospheric contributions are possible during disturbed periods. 相似文献
19.
Kuppusamy Vijayaraghavan 《洁净——土壤、空气、水》2008,36(3):299-305
The present work investigated the biosorption of nickel from synthetic and electroplating industrial effluents using a green marine algae Ulva reticulata. Preliminary batch results imply that pH 4.5 was optimum for nickel uptake and the isotherm experiments conducted at this pH condition indicated that U. reticulata can biosorb 62.3 mg g–1 nickel ions from synthetic solutions, according to the Langmuir model. Desorption was effective and practical using 0.1 M CaCl2 (pH 2.5, HCl) and the biomass was regenerated and reused for three cycles. Continuous biosorption experiments were performed in an upflow packed column (2 cm I.D and 35 cm height). Among the two electroplating effluents used, effluent‐1 is characterized by excess co‐ions and high nickel ion content. This influenced the column nickel uptake with U. reticulata exhibiting 52.1 mg g–1 in the case of effluent‐1 compared to 56.5 mg g–1 in the case of synthetic solution. On the other hand U. reticulata performed well in effluent‐2 with uptakes of 53.3 and 54.3 mg g–1 for effluent‐2 and synthetic solution, respectively. Mathematical modeling of column experimental data was performed using nonlinear forms of the Thomas‐ and modified dose‐response models, with the latter able to simulate breakthrough curves with high correlation coefficients. 相似文献
20.
Hydrological processes of lowland watersheds of the southern USA are not well understood compared to a hilly landscape due to their unique topography, soil compositions, and climate. This study describes the seasonal relationships between rainfall patterns and runoff (sum of storm flow and base flow) using 13 years (1964–1976) of rainfall and stream flow data for a low‐gradient, third‐order forested watershed. It was hypothesized that runoff–rainfall ratios (R/P) are smaller during the dry periods (summer and fall) and greater during the wet periods (winter and spring). We found a large seasonal variability in event R/P potentially due to differences in forest evapotranspiration that affected seasonal soil moisture conditions. Linear regression analysis results revealed a significant relationship between rainfall and runoff for wet (r2 = 0·68; p < 0·01) and dry (r2 = 0·19; p = 0·02) periods. Rainfall‐runoff relationships based on a 5‐day antecedent precipitation index (API) showed significant (r2 = 0·39; p < 0·01) correspondence for wet but not (r2 = 0·02; p = 0·56) for dry conditions. The same was true for rainfall‐runoff relationships based on 30‐day API (r2 = 0·39; p < 0·01 for wet and r2 = 0·00; p = 0·79 for dry). Stepwise regression analyses suggested that runoff was controlled mainly by rainfall amount and initial soil moisture conditions as represented by the initial flow rate of a storm event. Mean event R/P were higher for the wet period (R/P = 0·33), and the wet antecedent soil moisture condition based on 5‐day (R/P = 0·25) and 30‐day (R/P = 0·26) prior API than those for the dry period conditions. This study suggests that soil water status, i.e. antecedent soil moisture and groundwater table level, is important besides the rainfall to seasonal runoff generation in the coastal plain region with shallow soil argillic horizons. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献