Water treatment is an important concern of human societies. Using magnetic nanoparticles as adsorbents for metal removal has been greatly considered due to their particular characteristics such as small sizes, high surface area to volume ratios, and good magnetic properties. In the present study, a modification was implemented in magnetite particles by functionalized carbon nanotubes and carboxylic groups to enhance the performance of magnetite particles in removing hexavalent chromium from water using the adsorption method. The applicability of the nanoadsorbent and magnetic nanoparticles was compared based on adsorption factors affecting the chromium removal including pH, contact time, pollutant concentration, and the adsorbent amount. Properties of the nanocomposites were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the highest percentage of Cr (VI) removal for both adsorbents was under acidic ambient conditions and lasted less than 45 minutes. The study of Langmuir, Freundlich, and Temkin isotherms in the prediction of adsorption behavior revealed that the Langmuir model better fitted the adsorption equilibrium data. The kinetic analysis of pseudo-first and second-order equations showed that the pseudo-second-order equation was more suitable for describing the kinetic behavior of data. Moreover, the obtained nanocomposite had a better performance in Cr (VI) removal from water in comparison to magnetite nanoparticles. 相似文献
In this work, the carbon paste electrode was modified with a composite of a metal-organic framework, nitrogen-doped graphite, and gold nanoparticles and used as an electrochemical sensor for dihydroxybenzene isomers. The morphology and characteristics of the modifiers were found by SEM and FT-IR. Electrochemical techniques showed the specific surface of the electrode to be significantly enhanced. The outcome achieved shows that this novel sensor displays an excellent electro-catalytic activity towards the oxidation of these isomers. The sensor was applied to the simultaneous determination of each three isomers using DPV with a linear response in the concentration range of 5–105 nM. 相似文献
JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) has been used for separation and quantitation of components of high explosives... 相似文献
We define complete order amenability and first complete order cohomology groups for quantized Banach ordered algebras and
show that the vanishing of the latter is equivalent to the operator amenability for the Fourier algebra. 相似文献
CMK-3 nanoporous carbon was prepared and used as an efficient sorbent for microextraction in packed syringe of rosmarinic acid in Rosmarinus officinalis L. (rosemary). In the proposed method, only 2 mg of the nanoporous material, inserted between a syringe’s barrel and needle, was sufficient for the extraction with minimum consumption of organic solvents. Sample preparation was performed on the packed bed using a laboratory-made programmable apparatus. The apparatus was designed and used for automation of the conditioning, sampling, washing and elution steps of the method, and increasing the reproducibility of the experiments. For optimization of the experimental parameters, a central composite design method was used. Under the optimized conditions (i.e., number of adsorption cycles 14 times, number of elution cycles ten times and volume of elution 100 μL), an extraction recovery of 90 (±4.5) % was obtained for rosmarinic acid. The same packing bed could be used for at least 80 extractions without significant changes in its properties. The efficiency of the nanoporous sorbent was found to be superior to that of activated carbon, by a factor of about 17. The proposed method was successfully applied to the extraction of three rosemary samples before analysis by HPLC.
Two novel cationic mono‐s‐chloro triazinyl (MCT) reactive dyes together with their analogues were synthesized via reacting an N,N‐dimethyl dodecylamine with p‐nitrobenzyl bromide. The resultant was reduced using stannous chloride and hydrochloric acid to produce the primary amine. The quaternary ammonium salt containing primary amine was then diazotized and coupled to H‐acid/J‐acid reacted with cyanuric chloride and sulfanilic acid. The analogue dyes were prepared via the same route without quaternary ammonium salt making stage. The dyes were characterized using FTIR, 1H NMR, UV‐Vis spectroscopy and elemental analysis. The substantivity, exhaustion and fixation of the dyes were investigated on cotton fabric. It was found that these functional dyes could be effectively introduced to cotton for achieving simultaneous coloration and functional finishing effects. All the dyed fabrics exhibited softening efficacy. The washing and light fastness of the dyed samples were further studied. 相似文献
A new chemically modified carbon paste electrode for Cd(II) ions based on 3,5-dinitro-N-(tri-2-pyridyl methyl) benzamide (DNTPMBA) as an ionophore was prepared. The electrode exhibits a Nernstian response for Cd(II) ions over a wide concentration range (2.16 × 10?7–1.00 × 10?1 mol L?1) with a slope of 30 ± 1 mV per decade. It has a response time of about 50 s and can be used for a period of 3 months with good reproducibility. Detection limit obtained in the optimal conditions was 1.82 × 10?7 mol L?1. The electrode was successfully used for potentiometric determination of Cd(II) in well water. The pH influence and interference of some cations were also studied. 相似文献
Successful industrial use of amylases requires that they are sufficiently stable and active at application conditions, e.g.,
at high temperature in starch-liquefaction process. In the present study, site-directed mutagenesis was used to enhance the
thermal stability and calcium independency of a mesophilic α-amylase from Bacillus megaterium WHO. Mutations (A53S and H58I) were designed at the calcium-binding site based on the sequence alignment. Kinetic and thermostability
parameters of the mutants were analyzed and compared with that of the wild type. In the presence of calcium, the affinity
of the enzymes (wild type and mutants) toward starch was increased. In comparison to the wild type, calcium ion had more effect
on the catalytic efficiency, kcat/Km, and half-life (at 60 °C) of A53S mutant. In A53S, the dependence of half-life on calcium concentration showed that the enhanced
calcium binding is likely to be responsible for the increased stability. In contrast, calcium-independent mutant (H58I) possessed
high thermostability. In addition, thermodynamic parameters of amylolytic reaction exhibited an increase in the activation
energy and the entropy of the system. Kinetics of irreversible thermal inactivation suggests that the activation energy increased
by 1.4-fold in the most stable variant. 相似文献