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1.
The sorption of Cd(II) from aqueous solution on MnO 2 was investigated under ambient conditions. Experiments were carried out as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid and temperature. The results indicated that the sorption of Cd(II) was strongly dependent on pH and ionic strength. At low pH, the sorption of Cd(II) was dominated by outer-sphere surface complexation and ion exchange with Na +/H + on MnO 2 surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich models were used to simulate the sorption isotherms at three different temperatures. The thermodynamic data (Δ G 0, Δ S 0, Δ H 0) calculated from the temperature dependent sorption isotherms suggested that the sorption of Cd(II) on MnO 2 was an spontaneous and endothermic process. 相似文献
2.
Poly(ortho phenylenediamine) (PoPDA) microrods with ladder-type structure are synthesized in acidic medium (pH?=?0.5) at room temperature based on a developed and facile method. The molecular structure, thermal stability, and surface morphology of the microrods-shaped PoPDA were described by different characterization techniques comprising FTIR, TGA, 1HNMR, and SEM. Optimized thin films of PoPDA were successfully fabricated by thermal deposition method. The thin film was characterized by XRD and AFM. Au/PoPDA/p-Si/Al heterojunction diodes have been successfully fabricated. Dark current–voltage and capacitance–voltage characteristics were applied to get the particular parameters of the devices. Photovoltaic features of Au/PoPDA/p-Si/Al heterojunction at various intensities of white light illumination are studied. Under optimized conditions, the fabricated planar heterojunction solar cells utilizing a 95?±?10 nm of PoPDA film exhibited a power conversion efficiency (PCE) of ~?5.64% ( JSC?=?41.78 A/m 2, VOC?=?0.36 V, and FF?=?28.11%). The relatively small FF (at room temperature with IP) and Rs of the devices designate that by increasing of the absolute temperature, the photovoltaic performance of the solar cells can be improved. 相似文献
3.
A lithium ion-sieve manganese oxide (MO) derived from Li-enriched MO was prepared by the glycolic acid complexation method. The Li adsorption performance in a LiCl–NH 3·H 2O–NH 4Cl buffer solution, simulated a spent lithium-ion battery (LIB) processing solution, and actual spent LIB processing solution were studied. An adsorption capacity of 27.4 mg/g was observed in the LiCl–NH 3·H 2O–NH 4Cl buffer solution (Li concentration of 0.2 mol/L, pH?=?9), and the adsorption behavior conformed to the Langmuir adsorption isotherm equation with a linear correlation coefficient ( R2) of 0.9996. An adsorption capacity of 19 mg/g was observed in the simulated buffer spent battery solution (Li concentration of 0.15 mol/L, pH?=?7), and an adsorption capacity of 17.8 mg/g was observed in the actual spent battery solution (Li concentration of 0.15 mol/L, pH?=?7). X-ray diffraction, scanning electron microscope, and infrared spectrum results revealed that the structure and morphology of MO are stable before and after adsorption, and the adsorption of MO in all of the abovementioned buffer systems conforms to the Li +–H + ion-exchange reaction mechanism. The lithium ion-sieve MO demonstrates promise for the recovery of lithium from spent LIBs. 相似文献
4.
The interaction of HE–Eu(III) complex (HE?=?hematoxylin) with Herring-sperm DNA (hsDNA) has been studied by absorption spectra, fluorescence, and viscosity measurements in physiological buffer (pH?=?7.40). The binding constant of HE–Eu(III) complex to hsDNA was obtained by double reciprocal method at 298 and 310?K and the corresponding thermodynamic parameters (Δ r Hm??=?8.55?×?10 4?J?mol ?1, Δ r Gm??=??3.01?×?10 4?J?mol ?1, Δ r Sm??=?387.95?J?mol ?1?K ?1) were calculated, showing that the interaction between HE–Eu(III) complex and hsDNA was driven mainly by entropy. The value of K indicated that the binding mode of HE–Eu(III) complex with DNA was not classical intercalation. These results were further supported by viscosity method and competitive binding experiment. Scatchard analysis suggests that the interaction mode was a mixed binding, which contains partial intercalation and groove binding. 相似文献
5.
Multiwalled carbon nanotubes chemically functionalized with 2-((3-silylpropylimino) methyl) phenol (SPIMP-MWCNT) and successfully applied for the solid phase extraction (SPE) of some metal ions in food samples. The influences of the analytical parameters including pH, amounts of solid phase, eluent conditions (type, volume and concentrations), sample volume and interference of some metal ions on the recoveries of ions Cu 2+, Pb 2+, Fe 2+, Ni 2+ and Zn 2+ ion were investigated. The metal ions retained on SPIMP-MWCNT was eluted using 6?mL of 4?mol?L ?1 HNO 3 solution and their content was determined by flame atomic absorption spectrometry (FAAS) with recoveries more than 95% and relative standard deviations ( n?=?5) between 2.4–3.4% for both reproducibility and repeatability. The detection limit of this metal ions was between 1.0–2.6?ng?mL ?1 (3 S b , n?=?10) and their preconcentration factor was 100, while their loading capacity was above 32.9?mg?g ?1 of SPIMP-MWCNT. The proposed method was successfully applied for the preconcentration and determination of analytes in different samples. 相似文献
6.
The formation constants of species formed in the systems H +?+?W(VI)?+?nitrilotriacetic acid (NTA) and H +?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm ?3 NaClO 4, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO 3L 3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO 3L 2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm ?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported. 相似文献
7.
Biodegradation of styrene by Exophiala sp. was tested at different initial concentrations (19.3?C170.6?mg?l ?1), pH (2.8?C8.7), and temperatures (19.8?C45.1?°C), for 120?h according to a 2 3 full-factorial central composite design. The specific growth rate (SGR, per hour) and specific styrene utilization rate (SUR, milligrams of styrene per milligram of biomass per hour) values were used as the response variables for optimization purposes. The interactions between concentration and temperature ( P?=?0.022), and pH and temperature ( P?=?0.010) for SGR, and interactions between concentration and temperature ( P?=?0.012) for SUR were found to be statistically significant. The optimal values for achieving high SGR (0.15?h ?1) and SUR (0.3622?mg styrene mg ?1 biomass h ?1) were calculated from the regression model equation. Those values are C o ?=?89.1?mg?l ?1, pH?=?5.4, and T?=?31.5?°C for SGR and C o ?=?69.2?mg?l ?1, pH?=?5.5, and T?=?32.4?°C for SUR. It was also observed that the Exophiala strain degrades styrene via phenylacetic acid, involving initial oxidation of the vinyl side chain. Besides, in the presence of styrene, changes in the fatty acids profile were also observed. It is hypothesized that an increasing amount of linoleic acid (18:2) may be involved in the protection of the fungus against toxic substrate. 相似文献
8.
Coordination equilibria in the Co(II)–Ni(II)–2-aminopropanoic acid (HAla)–EDTA system have been studied spectrophotometrically at different molar ratios of the reagents in a wide pH range. It has been found that, when metal ions are in excess with respect to EDTA at pH 5–9, polyheteronuclear complexonates [(CoAla)Edta(NiAla)] 2–, [(CoAla 2)Edta(NiAla 2)] 4–, [(NiAla 2)Edta(CoAla 2) 2] 4–, [(CoAla 2)Edta(NiAla 2) 2] 4–, and [(NiAla 2) 2Edta(CoAla 2) 2] 4– form in a solution. The equilibrium constants of formation of these complexes and their overall stability constants have been calculated. Possible structures of the polynuclear complexonates are discussed. 相似文献
9.
Novel shellfish waste-derived chitosan (CS) has been developed to adsorb As(V) from simulated wastewater under evaluating adsorption process parameters. The coexistence of some competing ions, like SiO 32-, Cl -, NO 3– and PO 43- as well as the regeneration capacity of the spent adsorbent, was explored. The experimental data were modeled using several kinetics and isotherm models to understand the mechanism related to the uptake process. As(V) uptake was relatively rapid and highly dependent on pH. The Avrami-fractional-order expression supported data best, while the Liu equation described well isotherm data at pH 5.0. The maximum uptake capability (Liu) was 12.32 mg/g, and the highest removal performance (99 %) was obtained at optimum pH 5.0. Molecular dynamics simulations were performed to more clearly illuminate the atomic-level interactions between arsenic species and CS surface in both acidic and basic mediums. After four adsorption–desorption cycles, CS exhibited more than 90 % As(V) removal efficiency. The results of this study indicates that low cost shellfish derived chitosan is promising for efficient removal of As(V) from water body and can be used to remove other pollutants from watewater. 相似文献
10.
Abstract The techniques to purify different components of a typical solvent extraction system, viz., n-hexane/di(2-ethylhexyl)phosphoric acid (HDEHP)/CaCl 2 solution, are described. Data showing how the purity of the different components affects the interfacial tension (γ) are given. The interfacial behavior of the n-hexane/ HDEHP/0.01 mol dm ?3 CaCl 2 solution system was studied as a function of HDEHP concentration and aqueous phase pH. γ-log [HDEHP] curves were also determined at pH 4 when the aqueous phase contained 0.05 mol dm ?3 MgCl 2, CaCl 2, SrCl 2 or BaCl 2. γ-log [HDEHP] curves revealed interaction of the metal ions with the extractant and exhibited a behavior reminiscent of aggregate formation when the aqueous phase contained Ca 2+. 相似文献
11.
Arsenate hydroxyapatite, Ca 10(AsO 4) 6(OH) 2 (AsHA), was synthesized by precipitation at 100°C, and characterized by X-ray studies, IR spectra, electron microscopy, and thermography (TGA, DTA and DTG). The solubility of AsHA was investigated between temperatures of 308 and 323 K, and in the pH range 4.0–8.0. It exhibited a retrograde solubility. The solubility behaviour can be explained on the basis of the chemical potential and free energy in solution. Standard thermodynamic parameters, Δ Hθ, Δ Sθ and Δ Cpθ, are reported. The solubility products of AsHA were found to be 4.0 x 10 −91, 2.7 x 10 −91, 2.1 x 10 −91 and 1.2 x 10 −91 at temperatures of 3.08, 313, 318 and 323 K, respectively. 相似文献
12.
The modification techniques of applying carbon coating on particle surface and doping vanadium at Fe site were applied to make the LiFePO 4 cathode materials achieve high rate performance in lithium ion batteries. To design and synthesize these LiFe (1?x)V x PO 4/C ( x?=?0, 0.02, 0.05, or 0.08) composites, an aqueous solution–evaporation method was taken, in which every kind of raw material was distributed at a high degree of uniformity. The LiFe 0.95V 0.05PO 4/2.57 wt% C composite displayed the best electrochemical performances. At rates of 0.1, 0.5, 2, 5, and 10 C (1 C?=?170 mAg ?1), it delivered a discharge capacity of 157.8, 156.9, 149, 139.6, and 130.1 mAh g ?1, respectively. The composite exhibited perfect cycle stabilities as well, maintaining 100 % (0.5 C), 99.7 % (2 C), 98.9 % (5 C), and 96.6 % (10 C) of the first discharge capacity after 100 cycles at different rates, respectively. 相似文献
13.
应用线性扫描伏安法、循环伏安法、常规脉冲伏安法等电化学手段并结合紫外吸收光谱研究了药物克拉霉素(clarithromycin, CAM)在pH 1.8~9.2 Britton-Robinson缓冲溶液和0.05 mol•L -1 NaOH溶液中的电化学行为. 在所研究的pH范围, CAM分别产生P 1, P 2, P 3, P 4四个还原波, 其中P 1, P 2, P 4三个波均为其药效活性基团C-9位羰基的还原所产生. 实验结果表明: 在pH 1.8~5.7的B-R缓冲溶液条件下所获得的P 1波为两电子不可逆弱吸附还原波; 在6.0<pH<9.2的B-R缓冲溶液中, CAM产生P 2和P 3两个波, 其中P 2为两电子不可逆还原波, P 3为催化氢波. 在0.05 mol• L -1 NaOH溶液中, CAM产生的P 4波是一个单电子的不可逆吸附还原波. 根据P 4波的峰电流 iP与CAM浓度的线性关系, 建立了CAM含量测定的新方法. 相似文献
14.
Single‐, double‐, and multi‐walled carbon nanotubes (SWCNTs, DWCNTs, and MWCNTs), and two oxidized MWCNTs with different oxygen contents (2.51 wt % and 3.5 wt %) were used to study the effect of the wall number and surface functionalization of CNTs on their adsorption capacity and adsorption–desorption hysteresis for heavy metal ions (Ni II, Cd II, and Pb II). Metal ions adsorbed on CNTs could be desorbed by lowering the solution pH. Adsoprtion of heavy metal ions was not completely reversible when the supernatant was replaced with metal ion‐free electrolyte solution. With increasing wall number and amount of surface functional groups, CNTs had more surface defects and exhibited higher adsorption capacity and higher adsorption–desorption hysteresis index (HI) values. The coverage of heavy metal ions on the surface of CNTs, solution pH, and temperature affect the metal ion adsorption–desorption hysteresis. A possible shift in the adsorption mechanism from mainly irreversible to largely reversible processes may take place, as the amount of metal ions adsorbed on CNTs increases. Heavy metal ions may be irreversibly adsorbed on defect sites. 相似文献
15.
Heat effects of the interaction between glycylglycine and nickel (II) nitrate solutions are measured by direct calorimetry at different pH values and metal: ligand ratios in the temperature range of 288.15 to 308.15 K. KNO 3 is used as the background electrolyte. The heat effects of diluting the nickel nitrate solution in solutions of the background electrolyte are determined in order to make the appropriate corrections. The standard thermodynamic characteristics of complex formation by peptides and nickel (II) ions in aqueous solution are calculated. Standard enthalpies of the formation of complex particles NiPep +, NiPep 2, and NiPep 3 ? are determined for the first time. 相似文献
16.
The stability constants (K f) for the complexation reactions of Cr 3+, Mn 2+ and Zn 2+ metal cations with macrocyclic ligand, 15-crown-5 (15C5), in acetonitrile (AN), ethanol (EtOH) and also in their binary solutions (AN–EtOH) were determined at different temperatures, using conductometric method. 15C5 forms 1:1 complexes with Cr 3+, Mn 2+ and Zn 2+ cations in solutions. A non-linear behaviour was observed for changes of logK f of the metal ion complexes versus the composition of the mixed solvent. The order of stability of the metal–ion complexes in pure AN and in a binary solution of AN–EtOH (mol% AN?=?52) at 25?°C was found to be: (15C5Zn) 2+?>?(15C5·Mn) 2+?>?(15C5·Cr) 3+, but in the case of pure EtOH at the same temperature, it changes to: (15C5·Zn) 2+?>?(15C5·Cr) 3+?>?(15C5·Mn) 2+. The results also show that the stability sequence of the complexes in the other binary solutions of AN–EtOH (mol% AN?=?26 and mol% AN?=?76) varies in order: (15C5·Cr) 3+?~?(15C5·Zn) 2+?>?(15C5·Mn) 2+. The values of the standard thermodynamic quantities (ΔH C°, ΔS C°) for formation of (15C15-Cr 3+), (15C5-Mn 2+) and (15C5-Zn 2+) complexes were obtained from the temperature dependence of the stability constants and the results show that the thermodynamics of complexation reactions is affected by nature and composition of the solvent systems and in most solution systems, the complexes are enthalpy stabilized but entropy destabilized. 相似文献
17.
Tridentate Schiff bases (H 2L 1 or H 2L 2) were derived from condensation of acetylacetone and 2-aminophenol or 2-aminobenzoic acid. Binuclear square pyramidal complexes of the type [M 2(L 1) 2]?·? nH 2O (M?=?Fe–Cl, n?=?0; M?=?VO, n?=?1) were accessed from interaction of H 2L 1 with anhydrous FeCl 3 and VOSO 4?·?5H 2O, respectively. A similar reaction with H 2L 2, however, produced mononuclear complexes [ML 2(H 2O) x ]?·? nH 2O (M=Fe–Cl, x?=?0, n?=?0; M=VO, x?=?1, n?=?1). The compounds were characterized using elemental analysis, FT-IR, UV-Vis, and NMR (for ligand only), and mass spectroscopies and solution electrical conductivity studies. Magnetic susceptibility measurements suggest antiferromagnetic exchange in binuclear Fe(III) and VO(IV) complexes. Thermo gravimetric analysis (TGA) provided unambiguous evidence for the presence of coordinated as well as lattice water in [VOL 2(H 2O)]?·?H 2O. Cyclic voltammetric studies showed well-defined redox processes corresponding to Fe(III)/Fe(II) and VO(V)/VO(IV). In vitro antimicrobial activities of the compounds were investigated against Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeroginosa, Escherichia coli, Bacillus subtilis, and Proteus vulgaris. H 2L 1 and its binuclear complexes exhibited pronounced activity against all the microorganisms tested. 相似文献
18.
Ti(OH)4 and TiCl4 modified bentonite (Ti–Na-bent) were applied in the removal of Th(IV) from aqueous solution. Effect of different factors such as pH, contact time, temperature, initial concentration of Th(IV) and efficiency of them for thorium adsorption are investigated. Ti–Na-bent showed high adsorption capacity (qm?=?231.37 mg/g) and quick adsorption kinetics at lower pH. The adsorption mechanisms involved are: (1) Th4+, [Th(OH)4?n]n+ complexed on the outer-sphere of Na-bent and Ti–Na-bent. (2) Ion exchange between Th4+, [Th(OH)4?n]n+ and exchangeable cations of Na-bent and the H on the hydroxyl group of Ti(OH)4. Ti–Na-bent manifested high adsorption capacity for Th(IV), good acid resistance and long-term adsorption stability. 相似文献
20.
Sediment has been considered to be one of the most important mercury methylation sites, but recent studies have demonstrated a new site that is relevant, i.e. the roots of floating aquatic macrophytes, where high methylation is observed. The effects of temperature, pH and electric conductivity on net mercury methylation were studied in the roots of the water‐hyacinth Eichhornia crassipes of a freshwater coastal lagoon (Lagoinha, RJ, Brazil). Root samples were incubated, over three days, with 203HgCl 2 addition, at different temperatures (10–90 °C), pH values (3–8) and different electrolytic solutions (KClO 4, KCl and CaCl 2, at 1, 5, 10, 25 and 50 mM , ranging between 18 and 760 µS cm −1). 203Hg‐labeled methylmercury (Me 203Hg) was extracted in toluene, after acid leaching, and measured by β‐counting. Up to 35% of mercury added was converted to MeHg Methylation increased from 10 to 35 °C, and decreased thereafter. The process was completely inhibited at 90 °C. At pH values of 6 and 7 methylation was stimulated and a significant decrease was verified at pH 8. Increasing KClO 4 concentrations led to a significant decrease in the methylation rates, while for KCl and CaCl 2 solutions only a slight decrease was observed. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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