ABSTRACT
A macromolecule, CML, was obtained by purifying and carboxy-methylating the lignin generated from acid hydrolysis of sugarcane bagasse during bioethanol production from biomass. The CMLs complexed with Al(3+) (CML-Al) and Mn(2+) (CML-Mn) were utilised for the removal of a textile dye, Procion Blue MX-R (PB), from aqueous solutions. CML-Al and CML-Mn were characterised using Fourier transform infrared spectroscopy (FTIR), scanning differential calorimetry (SDC), scanning electron microscopy (SEM) and pHPZC. The established optimum pH and contact time were 2.0 and 5h, respectively. The kinetic and equilibrium data fit into the general order kinetic model and Liu isotherm model, respectively. The CML-Al and CML-Mn have respective values of maximum adsorption capacities of 73.52 and 55.16mgg(-1) at 298K. Four cycles of adsorption/desorption experiments were performed attaining regenerations of up to 98.33% (CML-Al) and 98.08% (CML-Mn) from dye-loaded adsorbents, using 50% acetone+50% of 0.05molL(-1) NaOH. The CML-Al removed ca. 93.97% while CML-Mn removed ca. 75.91% of simulated dye house effluents.
Subject(s)
Aluminum/chemistry , Lignin/chemistry , Manganese/chemistry , Triazines/isolation & purification , Water Pollutants, Chemical/isolation & purification , Water Purification/methods , Adsorption , Calorimetry, Differential Scanning , Hydrogen-Ion Concentration , Industrial Waste , Kinetics , Microscopy, Electron, Scanning , Models, Chemical , Molecular Structure , Solutions , Spectroscopy, Fourier Transform Infrared , Surface PropertiesABSTRACT
We study the theoretical van der Waals interaction of parallel gold nanowires (GNs) in matrix form with free extremities using molecular mechanics. It was calculated force, velocity, efficiency, thermodynamics properties like molar heat capacity, molar entropy variation and the relation between kinetic energy and temperature in situ of the GNs. We found new information about the nanowire behavior due to the matrix form. Each nanowire has 20 atoms and distant 27.78 angstroms from each one.
ABSTRACT
The direct amperometric determination of tert-butylhydroquinone (TBHQ) in biodiesel at an unmodified glassy carbon electrode is reported. A biodiesel aliquot was added into an electrochemical cell containing a 75% (v/v) ethanol-water solution under stirring (with final concentration of 50 mmol L(-1) HClO(4)). The amperometric method involved the continuous application of three sequential potential pulses to the working electrode (700 mV for 300 ms, 0 mV for 100 ms and -50 mV for 1s). TBHQ was continuously monitored at the first (direct oxidation) and optionally at the second (reduction) potential pulse while the third potential pulse was applied for cleaning of the electrode surface. For comparison, the samples were also analyzed by high-performance liquid-chromatography and a good agreement between the results was verified. Recovery values for spiked samples were between 90% and 95% and the reproducibility of the proposed method was around 5% (n=5). The proposed method can be easily adapted for on-site analysis.
Subject(s)
Biofuels/analysis , Electrochemistry/methods , Hydroquinones/analysis , Chromatography, High Pressure LiquidABSTRACT
To probe the volume changes of the voltage-dependent anion-selective channel (VDAC), the nonelectrolyte exclusion technique was taken because it is one of the few existing methods that may define quite accurately the rough geometry of lumen of ion channels (in membranes) for which there is no structural data.Here, we corroborate the data from our previous study [FEBS Lett. 416 (1997) 187] that the gross structural features of VDAC in its highest conductance state are asymmetric with respect to the plane of the membrane, and state that this asymmetry is not dependent on sign of voltage applied. Hence, the plasticity of VDAC does not play a role in the determination of lumen geometry at this state and the asymmetry is an internal property of the channel. We also show that the apparent diameter of the cis segment of the pore decreases slightly from 2 to 1.8 nm when the channel's conductance decreases from its high to low state. However, the trans funnel segment undergoes a more marked change in polymer accessible volume. Specifically, its larger diameter decreases from approximately 4 to 2.4 nm. Supposing the channel's total length is 4.6 nm, the apparent change in channel volume during this transition is estimated to be about 10 nm(3), i.e. about 40% of the channel's volume in the high conductance state.
