Removal of divalent nickel cations from aqueous solution by multi-walled carbon nano tubes: equilibrium and kinetic processes

Release of heavy metals into water as a result of industrial activity may pose a serious threat to the environment. In this study, the potential of multi-walled carbon nano tubes (MWCNT) to remove Ni²⁺ cations from aqueous solutions was investigated in a batch reactor under different experimental conditions. The effects on the removal process of conditions such as initial concentration of Ni²⁺ ions, temperature, and adsorbent mass were investigated. Nickel uptake was quantitatively evaluated by use of the Langmuir, Freundlich, and Dubinin?CKaganer?CRadushkevich isotherm models. For 20?mg/L initial Ni²⁺ cation concentration, adsorption capacity increased from 8.12 to 11.75?mg/g when the temperature was increased from 25 to 65?°C, an indication of the endothermic nature of adsorption process. In addition, the adsorption equilibrium was well described by the Langmuir isotherm model; maximum adsorption capacity was 17.86?mg/g Ni²⁺ cations on HNO₃-treated MWCNT (t-MWCNT). The results obtained in this study show that adsorption of Ni²⁺ on t-MWCNT is a spontaneous and endothermic process. By use of second-order kinetic constants and the Arrhenius equation, the activation energy of adsorption (E _a) was determined as 5.56?kJ?mol^?1.     

Synthesis of novel β-lactams bearing an anthraquinone moiety,and evaluation of their antimalarial activities

A novel series of β-lactams bearing an anthraquinone moiety have been synthesized from imines derived from anthraquinone-2-carbaldehyde and ketenes by a [2+2] cycloaddition reaction. The cycloadducts were fully characterized and evaluated for their antimalarial activities against Plasmodium falciparum K14 resistant strain and showed moderate to excellent EC₅₀ values varying from 9 to 50 μM.     

Regioselective Synthesis of New Bibracchial Lariat Ethers

A practical and regioselective synthetic method for the synthesis of cis‐diastereomers of bibracchial lariat ethers (BiBLEs) bearing ester and amide groups is reported. The novel BiBLEs 3a and 4a–e with neutral side arms were prepared by reaction of the corresponding aza‐crown macrocycles 1a – c with ethylchlroacetate and chloroacetamide. The structures of the new compounds have been confirmed by FTIR, ¹H, ¹³C, DEPT, and MS spectroscopy.     

Numerical modelling of film cooling with and without mist injection

Two-phase CFD calculations, using a Lagrangian model and commercial code Fluent 6.2.16, were employed to calculate the gas and droplet flows and film cooling effectiveness with and without mist on a flat plate. Two different three dimensional geometries are generated and the effects of the geometrical shape, size of droplets, mist concentration in the coolant flow and temperature of mainstream flow for different blowing ratios are studied. A cylindrical and laterally diffused hole with a streamwise angle of 30° and spanwise angle of 0° are used. The diameter of film cooling (d) hole, and the hole length to diameter ratio (L/d) for both of geometries are 10 mm and 4, respectively. Also the blowing ratio ranges from 1.0 to 2.0, and the mainstream Reynolds number based on the mainstream velocity and hole diameter (Re _d) is 6,219. The results are shown for different droplets diameters (1–10 μm), concentrations (1–5%) and mainstream temperatures (350–500 K). The centreline effectiveness and distribution of effectiveness on the surface of cooling wall are presented.     

Purification of L-Lysine in Simulated Moving Bed and Fixed-Bed Chromatography

 L-Lysine was produced by a microbial process utilizing a Corynebacterium glutamicum (ATCC 21799) strain. L-Lysine was purified from the cultivated medium by fixed-bed and simulated moving bed （SMB） chromatography. The separation conditions including pH, eluent concentration and Lys+ and Lys2+ adsorption isotherms were studied in batch adsorption. The column capacity, eluent flow rate and eluent concentration have been studied in fixed-bed chromatography. Maximum purification rate of lysine was obtained as 0.066 g/(g·h) (per gram resin and per hour) at an eluent flow rate of 10 mL/min in fixed-bed chromatography. The results obtained from SMB were 0.11 g/(g·h) for L-lysine purification rate and 96% for L-lysine recovery.     

Testing whether survival function is harmonic new better than used in expectation

Summary Statistical procedures to test that a life distribution is exponential against the alternative that it is harmonic new better than used in expectation (HNBUE) are considered.     

Application of 1,4-Diaminoanthraquinone as a New Sensing Material for Fabrication of a Iron(III)-Selective Modified Carbon Paste Electrode

In the present work, a novel sensitive electrochemical potentiometric sensor for sensing Fe³⁺ ions based on 1,4-diaminoanthraquinone (DAQ) as a hydrophobic selector element was prepared to implement as an ion selective carbon paste electrode in the aqueous solutions. The adequate amounts of ionophore (5%), paraffin oil (25%) as a binder, Nanosilica (NS: 0.5%) multi-wall carbon nanotubes (MWCNTs: 1%) as a modifier, and graphite powder (68.5%) as an inert matrix was occupied to form the paste. This new FeCP sensor demonstrated a Nernstian slope of 19.7 ± 0.7 mV per decade over widish linear range between 1.0 × 10^–8 to 1.0 × 10^–2 mol L^–1 at working pH range of 1.9–5.0 in the optimized conditions. The average elapsed time to response of electrode was about ~6 s for concentrations from lower (1.0 × 10^?8 mol L^–1) to higher (1.0 × 10^?2 mol L^–1) of Fe³⁺ ion solution. The selectivity of electrode toward Fe³⁺ ions in comparison with other cations was studied by matched potential method. The making FeCP sensor has been put to use successfully as an indicator electrode in analytical applications such as the potentiometric titration and determination of iron(III) ion in blend of different ions.     

Arrangement and nature of intermolecular hydrogen bonding in complex biomolecular systems: modeling the vitamin C---L-alanine interaction

Vitamin C is known as an essential dietary supplement and implicated in diverse biological processes. We present here a theoretical study on the nature of hydrogen bonding of vitamin C in biological systems. For this reason, the complexes of vitamin C (VC) with neutral and zwitterionic L-alanine (as the simplest chiral amino acid) were studied at the MP2/6-311++G(d,p) level of theory. In the gas phase, neutral L-alanine leads to more stable complexes than the zwitterionic forms while the reverse is true in the aqueous phase. The complexes are formed via two hydrogen bond interactions, which result in a ring-like hydrogen-bonded networks. The nature of H-bonds was characterized in terms of natural bond orbital and quantum theory of atoms in molecule analyses (QTAIM). The H-bonds in the studied complexes were electrostatic in nature; however, in the case of shorter and directional H-bonds and ionic interactions, contributions of covalent character were also non-negligible. Natural energy decomposition analysis of hydrogen-bonded complexes reveals that the charge transfer and electrical components are the largest contributors for the interaction energies of complexes. Natural resonance theory analysis suggests higher resonance weight for charge-assisted interactions of vitamin C---alanine (zwitterionic) complexes, where the total interaction energy is considerably higher than that of neutral alanine.     

Antioxidant potential assessment of phenolic and flavonoid rich fractions of Clematis orientalis and Clematis ispahanica (Ranunculaceae)

The antioxidant activities of crude extract fractions using Hexane, Chloroform, Ethyl Acetate, Butanol and Water of Clematis orientalis and Clematis ispahanica were investigated. 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay and the ferric reducing/antioxidant potential (FRAP) were used to evaluate the antioxidant capacity. The total phenolics were found to be 4.37–9.38 and 1.32–11.37 mg gallic acid equivalents (GAE)/g in different fractions for C. orientalis and C. ispahanica, respectively. The ethyl acetate fraction of C. orientalis and chloroform fraction of C. ispahanica showed the highest DPPH and FRAP activities at a concentration of 300 μg/mL. The predominant phenolic compounds identified by HPLC in C. orientalis were Resorcinol (603.5 μg/g DW) in chloroform fraction and Ellagic acid (811.7 μg/g DW) in chloroform fraction of C. ispahanica.