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1.
In natural waters, fluoride ions are necessary and beneficial for the human being. At higher level of F− in water, it is toxic and detrimental to human health, leading to serious problems such as dental and skeleton fluorosis.
According to the World Health Organization, the acceptable concentrations of fluoride in potable water are in the range of
0.7–1.5 mg L−1. Various treatment technologies for fluoride removal from water have been used such as ion exchange, adsorption and membrane
processes. In the present study, removal of fluoride ions from aqueous solutions was investigated using a polyamide thin film
composite nanofiltration membrane denoted as HL 2514 T from Osmonics Company. Through this membrane, the mechanism of transport
was investigated. The Kedem–Katchelsky model was applied in order to determine phenomenological parameters σ and P
s, respectively, the reflection coefficient of the membrane and the solute permeability of ions. The convective and diffusive
parts of the mass transfer were quantified. The retention of monovalent and bivalent salts by this membrane shows that it
is negatively charged. In the second part, retention of fluoride anions was investigated. Results show that the retention
of fluoride by HL membrane exceeds 80%. The influence of the chemical parameters (feed concentration and ionic strength) and
the physical parameters (applied pressure and recovery) on the elimination of fluoride was studied. 相似文献
2.
A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of
chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The
chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel
matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration
of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone
or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10−9–1 × 10−4 and 1 × 10−8–7 × 10−5 mol L−1, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10−10 , 9.6 × 10−10 and 5.6 × 10−10, 1.7 × 10−9 mol L−1, respectively. 相似文献
3.
Adriana Faria Azevedo F. A. Souza P. Hammer M. R. Baldan N. G. Ferreira 《Journal of nanoparticle research》2011,13(11):6133-6139
The surface properties of boron-doped nanocrystalline diamond films treated with H2 plasma was investigated in regard to their electrochemical response for phenol oxidation. The surface of these films is relatively
flat formed by crystallites with sizes of about 40 nm. X-ray photoelectron spectroscopy analyses showed that electrode surface
has a high amount of C–H bonds. This behavior is in agreement with Mott-Schottky plot measurements concerning the flat band
potential that presented a value as expected for hydrogenated diamond surface. This electrode presented the phenol detection
limit of 0.08 mg L−1 for low phenol concentrations from 40 to 250 μmol L−1. 相似文献
4.
《Ultrasonics sonochemistry》2014,21(2):790-801
A highly porous calcium carbonate (calcite; sorbent 1) was used as a support for modification with α-FeOOH (calcite/goethite; sorbent 2), α-MnO2 (calcite/α-MnO2; sorbent 3) and α-FeOOH/α-MnO2 (calcite/goethite/α-MnO2; sorbent 4) in order to obtain a cheap hybrid materials for simple and effective arsenate removal from aqueous solutions. The adsorption ability of synthesized adsorbents was studied as a function of functionalization methods, pH, contact time, temperature and ultrasonic treatment. Comparison of the adsorptive effectiveness of synthesized adsorbents for arsenate removal, under ultrasound treatment and classical stirring method, has shown better performance of the former one reaching maximum adsorption capacities of 1.73, 21.00, 10.36 and 41.94 mg g−1, for sorbents 1–4, respectively. Visual MINTEQ equilibrium speciation modeling was used for prediction of pH and interfering ion influences on arsenate adsorption. 相似文献
5.
The efficiency of excited-state interaction between Tb3+ and the industrial product Cilostazol (CIL) has been studied in different solvents. High luminescence intensity peak at 545 nm
of terbium complex in acetonitrile was obtained. The photophysical properties of the green emissive Tb3+ complex have been elucidated, the terbium was used as optical sensor for the assessment of CIL in the pharmaceutical tablets
and body fluids at pH 3.1 and λex = 320 nm with a concentration range 1.0 × 10−9–1.0 × 10−6 mol L−1 of CIL, correlation coefficient of 0.998 and detection limit of 7.5 × 10−10 mol L−1. 相似文献
6.
In this study, amino-modified titanate nanotubes (NH2-TNs) were prepared and used to adsorb duplex DNA. Macroscopic complexes between DNA and NH2-TNs were observed. The uptake of DNA by NH2-TNs was very fast; equilibrium was reached within 10 min at pH 3.6–5.0. The equilibrium capacity in the adsorption isotherm
of NH2-TNs was 240 mg g−1, and further increase of the adsorption capacity was obtained with the addition of Ca2+ in solution. The adsorbed DNA could be released with phosphate buffer saline (PBS) solution without damage of the DNA strands.
NH2-TNs could protect DNA from cleavage efficiently in the presence of DNase I. 相似文献
7.
Attia MS Mahmoud WH Ramsis MN Khalil LH Othman AM Hashem SG Mostafa MS 《Journal of fluorescence》2011,21(4):1739-1748
A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical
tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably
enhance the luminescence intensity of the Sm3+ ion in Sm3+- DC complex at λex = 400 nm. The produced luminescence intensity of Sm3+- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic
range for the determination of DC is 1 × 10−8 – 5 × 10−6 mol L−1 and in case of quantum yield calculations is 7 × 10−9 – 5 × 10−6 mol L−1 with detection limit of 6.5 × 10−10 mol L−1. The enhancement mechanism of the luminescence intensity in the Sm3+- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which
Eu3+ ion is used instead of Sm3+ ion is also studied. 相似文献
8.
Synthesis,characterization and role of zero-valent iron nanoparticle in removal of hexavalent chromium from chromium-spiked soil 总被引:3,自引:0,他引:3
Chromium is an important industrial metal used in various products/processes. Remediation of Cr contaminated sites present
both technological and economic challenges, as conventional methods are often too expensive and difficult to operate. In the
present investigation, Zero-valent iron (Fe0) nanoparticles were synthesized, characterized, and were tested for removal of Cr(VI) from the soil spiked with Cr(VI). Fe0 nanoparticles were synthesized by the reduction of ferric chloride with sodium borohydride and were characterized by UV–Vis
(Ultra violet–Visible) and FTIR (Fourier transform infrared) spectroscopy. The UV–Vis spectrum of Fe0 nanoparticles suspended in 0.8% Carboxymethyl cellulose showed its absorption maxima at 235 nm. The presence of one band
at 3,421 cm−1 ascribed to OH stretching vibration and the second at 1,641 cm−1 to OH bending vibration of surface-adsorbed water indicates the formation of ferrioxyhydroxide (FeOOH) layer on Fe0 nanoparticles. The mean crystalline dimension of Fe0 nanoparticles calculated by XRD (X-ray diffraction) using Scherer equation was 15.9 nm. Average size of Fe0 nanoparticles calculated from TEM (Transmission electron microscopy) images was found around 26 nm. Dynamic Light Scattering
(DLS) also showed approximately the same size. Batch experiments were performed using various concentration of Fe0 nanoparticles for reduction of soil spiked with 100 mg kg−1 Cr(VI). The reduction potential of Fe0 nanoparticles at a concentration of 0.27 g L−1 was found to be 100% in 3 h. Reaction kinetics revealed a pseudo-first order kinetics. Factors like pH, contact time, stabilizer,
and humic acid facilitates the reduction of Cr(VI). 相似文献
9.
Youssef AO 《Journal of fluorescence》2012,22(3):827-834
A new, simple, sensitive and selective spectrofluorimetric method for the determination of Hydrochlorothiazide was developed
in acetonitrile at pH 6.2. The Hydrochlorothiazide can remarkably enhance the luminescence intensity of the Tb3+ ion doped in sol–gel matrix at λex = 370 nm. The intensity of the emission band of Tb3+ ion doped in sol–gel matrix was increased due to the energy transfer from the triplet excited state of Hydrochlorothiazide
to (5D4) excited energy state of Tb3 ion. The enhancement of the emission band of Tb3+ ion doped in sol–gel matrix at (5D4→7 F5) 545 nm was directly proportion to the concentration of Hydrochlorothiazide with a dynamic ranges of 5.0 × 10−10—5.0 × 10−6 mol L−1 and detection limit of 2.2 × 10−11 mol L−1. 相似文献
10.
The composition of surface-functionalized gold nanoparticles (diameter of the metallic core: 17–20 nm) was determined by elemental
analysis (C, H, N, S, Au, Na) after preparation of a larger batch. Gold nanoparticles were prepared and functionalized with
citrate according to the classical Turkevich method. The citrate-functionalized nanoparticles contained about 3.1 wt% of organic
material (135 ng cm−2 or 3.1 molecules nm−2). A partial exchange of citrate was accomplished by tris(sodium-m-sulfonato-phenyl)phosphine (TPPTS) which led to 2.1 wt% of citrate (90 ng cm−2 or 2.1 molecules nm−2) and 1.4 wt% TPPTS (61 ng cm−2 or 0.6 molecules nm−2). The citrate coating was quantitatively exchanged by poly(N-vinyl pyrrolidone) (PVP) after immersion in solutions with concentrations of 33, 66 and 128 mg L-1, respectively, leading to contents of 4 to 6 wt% of PVP (171–271 ng cm−2 or 9–15 PVP monomer units nm−2). 相似文献
11.
In this paper, data concerning the effect of pH on the morphology of Ag–TiO2 nanocomposite during photodeposition of Ag on TiO2 nanoparticles is reported. TiO2 nanoparticles prepared by sol–gel method were coated with Ag by photodeposition from an aqueous solution of AgNO3 at various pH levels ranging from 1 to 10 in a titania sol, under UV light. The as-prepared nanocomposite particles were
characterized by UV–vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2 adsorption/desorption method at liquid nitrogen temperature (−196 °C) from Brunauer–Emmett–Teller (BET) measurements. It
is shown that at a Ag loading of 1.25 wt.% on TiO2, a high-surface area nanocomposite morphology corresponding to an average of one Ag nanoparticle per titania nanoparticle
was achieved. The diameter of the titania crystallites/particles were in the range of 10–20 nm while the size of Ag particles
attached to the larger titania particles were 3 ± 1 nm as deduced from crystallite size by XRD and particle size by TEM. Ag
recovery by photo harvesting from the solution was nearly 100%. TEM micrographs revealed that Ag-coated TiO2 nanoparticles showed a sharp increase in the degree of agglomeration for nanocomposites prepared at basic pH values, with
a corresponding sharp decrease in BET surface area especially at pH > 9. The BET surface area of the Ag–TiO2 nanoparticles was nearly constant at around a value of 140 m2 g−1 at all pH from 1–8 with an anomalous maximum of 164 m2 g−1 when prepared from a sol at pH of 4, and a sharp decrease to 78 m2 g−1 at pH of 10. 相似文献
12.
David?S.?M.?Ribeiro Jo?o?A.?V.?Prior Jo?o?L.?M.?Santos José?L.?F.?C.?Lima 《Journal of fluorescence》2010,20(4):915-922
The present work describes the fully integration in line of a photo-degradation unit, comprising a low pressure UV lamp, in
a Multipumping Flow System (MPFS), for the fluorimetric chemical control of commercially available pharmaceutical formulations
containing diazepam. The utilization of an organized micellar medium provided enhanced fluorescence emission. The results
allowed to obtain a linear working range for diazepam concentrations of up to 40 mg L−1 (r = 0.9998) and the detection limit was about 0.97 mg L−1. The results obtained by the miniaturized and automatic flow system were in agreement with those furnished by the reference
procedure, with relative deviations comprised between −2.09% and 2.13%. 相似文献
13.
A sensitive and selective method for the trace determination of 3, 3’, 4, 4’-tetrachlorobiphenyl (PCB77) by using bovine serum
albumin (BSA) as a fluorescence probe was introduced. Under optimum conditions, the enhanced fluorescence intensity was proportional
to the concentration of polychlorinated biphenyls in the range of 8.9 × 10−8–5.0 × 10−6 mol L−1 for PCB77, and 5.0 × 10−7–5.0 × 10−6 mol L−1 for 2, 2’, 5, 5’-tetrachlorbiphenyl (PCB52). The detection limits (S/N = 3) of PCB77 and PCB52 were 2.6 × 10−8 mol L−1 and 2.9 × 10−7 mol L−1, respectively. Furthermore, the fluorescence enhancement mechanism was discussed in detail. Results indicated that fluorescence
enhancement of the system originated from the formation of BSA-PCBs complexes. In addition, PCBs were mainly bound to the
tyrosine residues in BSA molecules. 相似文献
14.
The nanofibrous membrane of polyacrylonitrile (NMP) was successfully synthesized after NaOH and NaHCO3 treatment aiming its functionalization using electrospinning for cadmium ion (Cd2+) adsorption. Field emission scanning electron microscopy (FE-SEM) revealed that small particles attached to the surface of functionalized PAN nanofibers. Equilibrium was attained after 60 min following a rapid uptake of Cd2+ with maximum adsorption capacity and percentage removal at an optimum solution pH of 7.0. The adsorbent dose of 0.3 g and 90 mg L−1 of initial Cd2+ concentration yielded the maximum adsorption capacity. The pseudo-second-order kinetic model was the best fitted to the adsorption data, indicating that the chemisorption is the controlling mechanism of adsorption. The physisorption was proposed based on the calculated values of the mean free energy of adsorption from the D–R isotherm (E < 8 kJ mol−1). Furthermore, three-parameter isotherm models indicated the homogeneous and heterogeneous Cd2+ adsorption onto NMP adsorbent. 相似文献
15.
A highly sensitive and selective fluorogenic probe for fluoride ion, fluorescein di-tert-butyldimethylsilyl ether (FTBS), was designed and synthesized. FTBS was a colorless, non-fluorescent compound and was synthesized
via the one-step reaction of fluorescein with tert-butyldimethylsilyl chloride. Upon incubation with fluoride ion in DMF-water solution (7 : 3, V/V), the Si-O bond of FTBS
was cleaved, causing a large increase in fluorescence intensity and thereby allowing a selective detection of fluoride ion.
The fluorescence increase is linearly with fluoride concentration in the range 0.1–2.0 μmol L−1 with a detection limit of 0.041 μmol L−1 (3σ). The excellent selective signaling behavior of the proposed probe was found to originate from the high affinity of silicon
toward fluoride ion. The method has been successfully applied to the fluoride determination in multi-trace elements injection
and toothpaste samples, and the results are agreed well with those obtained by the fluoride-ion selective electrode method. 相似文献
16.
31P nuclear magnetic resonance (NMR) was used as a highly selective, rapid and suitable analytical tool for the simultaneous
identification and determination of five important organophosphorus pesticides (OPPs), without any sample preparation, in
technical and formulation samples. The quantitative works of 31P-NMR spectroscopy were performed in the presence of phosphoric acid as a suitable internal standard. Linear working range
for the analysis of trichlorfon, chlorpyrofos, fenithrothion, diazinon and glyphosate was 25–300 mg L−1. Limit of detection (at S/N = 3) for the proposed method, under the optimized experimental conditions, was found to be about 3 mg L−1 for the first four OPPs and 16.3 for the last one. The proposed method was applied to the analysis of a glyphosate formulation
and two trichlorfon and chlorpyrofos technical samples. There was excellent agreement between the results by 31P-NMR and those by the standard methods. The proposed method is rapid, simple and safe, as toxic samples are analyzed ‘as
received’ without sample pre-treatment, permitting the routine analysis of pesticides in real samples. 相似文献
17.
A method based on pre-concentration, using electrolysis, has been proposed and used for the improvement of detection sensitivity
of mercury ions at ultra-trace level of concentration in an aqueous matrix by laser-induced breakdown spectroscopy (LIBS).
The experimental evaluation of this method was carried out on mercury chloride (HgCl2) in triple-distilled water for a concentration range of the element of 0.01–10 mg l−1. A pre-concentration factor of ∼180 was obtained for LIBS detection of mercury emission line at 253.65 nm. The limit of detection
(LoD) of ∼0.011 mg l−1 (or ∼11 ppb) for mercury in the water sample was achieved. 相似文献
18.
Encapsulation of iron nanoparticles in alginate biopolymer for trichloroethylene remediation 总被引:2,自引:0,他引:2
Achintya N. Bezbaruah Sai Sharanya Shanbhogue Senay Simsek Eakalak Khan 《Journal of nanoparticle research》2011,13(12):6673-6681
Nanoscale zero-valent iron (NZVI) particles (10–90 nm) were encapsulated in biodegradable calcium-alginate capsules for the
first time for application in environmental remediation. Encapsulation is expected to offers distinct advances over entrapment.
Trichloroethylene (TCE) degradation was 89–91% in 2 h, and the reaction followed pseudo first order kinetics for encapsulated
NZVI systems with an observed reaction rate constant (k
obs) of 1.92–3.23 × 10−2 min−1 and a surface normalized reaction rate constant (k
sa) of 1.02–1.72 × 10−3 L m−2 min−1. TCE degradation reaction rates for encapsulated and bare NZVI were similar indicating no adverse affects of encapsulation
on degradation kinetics. The shelf-life of encapsulated NZVI was found to be four months with little decrease in TCE removal
efficiency. 相似文献
19.
In the paper, a chemiluminescence (CL) system was developed based on the catalytical effect of diperiodatocuprate (III) (DPC)
on the 1,10-phenanthroline (phen)/hydrogen peroxide (H2O2) in the presence of cetyltrimethylammonium bromide (CTAB). The effects of experimental conditions were investigated. Meanwhile
the increase of CL intensity of the DPC/phen/H2O2/CTAB system is proportional to the concentration of phen in the range of low concentration. The linear range of the calibration
curve is 5.0 × 10−9–1.0 × 10−6 mol L−1, and the corresponding detection limit is 1.9 × 10−9 mol L−1. The effects of phenolic compounds (PCs) on the system were investigated. Hydroquinone was used as an example to investigate
the application of the CL system to the determination of PCs. The quenched CL intensity is linearly related to the logarithm
of concentration of hydroquinone. The linear range of the calibration curve is 2.5 × 10−9–1.0 × 10−5 g mL−1, and the corresponding detection limit is 1.8 × 10−9 g mL−1. This phen and hydroquinone can be synchronously determined. The method was applied to the determination of hydroquinone
in water samples and the recoveries were from 92% to 106%. 相似文献
20.
Osamu Yamashita Hirotaka Odahara Takahiro Ochi Jun-ichi Shigeto 《Applied Physics A: Materials Science & Processing》2009,97(1):133-141
The local Seebeck coefficient α
L
and the resultant Seebeck coefficient α
R
of M/Bi0.88Sb0.12/M (M = Cu and Ni) composites with different thicknesses t
Bi–Sb of Bi–Sb alloy were measured as functions of z and T, where T is the absolute temperature, z is the distance from a center of Bi–Sb alloy to the middle point of two probes and α
L
and α
R
were measured using two probes separated by s=1.0 mm and s=t
Bi−Sb+0.1 mm, respectively. As a result, α
L
was enhanced extremely at the position of 0.2–0.3 mm away from the interfaces, while the local temperature along a composite
varies linearly with changes in z within Bi–Sb alloy. The local maximum of α
R
at 344 K appeared at t
Bi−Sb≈0.9 mm, so that it is expected to increase up to −167 μV/K at t
Bi−Sb=0.87 mm from the expression fitted well to the experimental data, which is 2.1 times as large as the intrinsic α at 344 K of Bi–Sb alloy. Such a local enhancement in α
L
would probably be caused by a temperature gradient across the depletion layer formed at the interface. The thermoelectric
figure of merit ZT of a composite with an optimum t
Bi−Sb of 0.87 mm is expected to reach the large value of 0.98 at 344 K, which corresponds to 4.5 times as high a value as ZT=0.22 at 344 K of Bi–Sb alloy. It is thus considered that the increase in α
L
at the interface is available as a useful mean of further increase in ZT of thermoelectric devices. 相似文献