Removal of methyl violet from aqueous solution by perlite

The use of perlite for the removal of methyl violet from aqueous solutions at different concentration, pH, and temperature has been investigated. Adsorption equilibrium is reached within 1 h. The capacity of perlite samples for the adsorption of methyl violet was found to increase with increasing pH and temperature and decrease with expansion and increasing acid-activation. The adsorption isotherms are described by means of the Langmuir and Freundlich isotherms. The adsorption isotherm was measured experimentally at different conditions and the experimental data were correlated reasonably well by the adsorption isotherm of Langmuir. The order of heat of adsorption corresponds to a physical reaction. It is concluded that the methyl violet is physically adsorbed onto the perlite. The removal efficiency (P) and dimensionless separation factor (R) have shown that perlite can be used for removal of methyl violet from aqueous solutions, but unexpanded perlite is more effective.     

Electrokinetic properties of sepiolite suspensions in different electrolyte media

The present paper deals with the electrokinetic characterization of sepiolite. A series of systematic zeta potential measurements have been carried out to determine the isoelectric point (iep) and potential-determining ions (pdi), and the effect of mono-, di-, and trivalent electrolytes such as NaCl, KCl, LiCl, NaNO(3), NaCH(3)COO, MgCl(2), CaCl(2), BaCl(2), CoCl(2), CuCl(2), Pb(NO(3))(2), Na(2)CO(3), Na(2)SO(4), AlCl(3), FeCl(3), and Na(3)PO(4) on the zeta potential of sepiolite. Zeta potential has been calculated with the aid of Smoluchowski's equation. Sepiolite yields an isoelectric point at pH 6.6. The zeta potential for the sepiolite has ranged from +23.3 mV at pH approximately 2 to -22.4 mV at pH approximately 8 at 20 +/- 2 degrees C in water. The valency of the ions have proven to have a great influence on the electrokinetic behavior of the suspension. Monovalent cations were found to have a weak effect, while di- and trivalent cations made the zeta potential positive. Charge reversal was observed for divalent cations at 1 x 10(-2) M and for trivalent cations at 3 x 10(-4) M. As a result, it can be said that monovalent cations are indifferent ions when di- and trivalent cations are potential-determining ions.     

Chloro-Bridged Dimeric Cadmium(II)-Isothiocyanate Complex with a Tridentate NNN Type Ligand: Synthesis,X-ray Structure,Thermal Analysis

Abstract  

The dinuclear cadmium(II) complex with 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine (btmpp) has been synthesized, and characterized by single crystal X-ray diffraction, IR, UV–Vis and TGA–DTA methods. Cd atoms are located in a distorted octahedral environment in the complex. The complex crystalizes in monoclinic space group C 2/c, with unit cell dimensions a = 20.5636(12) Å, b = 14.0167(13) Å, c = 15.6598(11) Å, β = 113.425(5)o, V = 4141.7(5) Å³. There are two intermolecular and a intramolecular hydrogen bonds interactions in crystal.     

Numerical test of Born–Oppenheimer approximation in chaotic systems

We study the validity of the Born–Oppenheimer approximation in chaotic dynamics. Using numerical solutions of autonomous Fermi accelerators, we show that the general adiabatic conditions can be interpreted as the narrowness of the chaotic region in phase space.     

High frequency parallel plate probe for the measurement of the complex viscosity of liquids

In this work an instrument is described which measures the complex shear viscosity of liquids in the kHz frequency range. The instrument is driven electromagnetically and operates in resonant mode. The measurement of the primary data, from which the rheological properties of the fluid sample are inferred, does not include any deflection amplitude measuring step and is purely digital. Models allowing the interpretation of the probe primary data in terms of fluid complex viscosity are presented. The theoretically predicted mechanical behaviour of the probe is compared with the measured one and the rheometric ability of the device is discussed.     

1H and 13CNMR Study of a New Class of Bipyridinium Liquid Crystals

Abstract

¹H and ¹³C NMR, as well as UV and IR, spectra of a new class of bipyridinium salts made by double quaternization of trans?1, 2-bis(4-pyridyl) ethene unit with n-alkyl salts are reported. The effect of quaternization on the ¹ and ¹³C NMR spectra of the salts is discussed.     

Solvent Effect upon Ion-pair Extraction of Different Sodium Dyes Using Some Crown Ethers

Liquid-liquid extractive-spectrophotometric studies of sodium ion complexes of 18-crown-6(18C6), dibenzo-18-crown-6(DB18C6), 15-crown-5(15C5), and 12-crown-4(12C4) and anionic dyes [4-(2-pyridylazo)-resorcinol monosodium salt monohydrate (PAR), Eriochrom Black T (EBT), and methyl orange (MOR)] and sodium picrate (PICRAT) as the counter ion are described. The overall extraction equilibrium constants for the 1 : 1 complexes of the above crown ethers with sodium dyes between different organic solvents and water have been determined at 25deg;C. They were conducted in various solvent-water systems maintaining an identical initial cation concentration in water, [M0+]w, and macrocyclic ligand concentration in the organic phase, [L0]org}, so that in all extractions [M0+]w : [L0]org ratios were 1 : 1, 1 : 10, 1 : 20, 1 : 50, and 1 : 62.5. An ion association complex formed between the sodium-crown ether complex ion and a dye anion was extracted into the organic solvent, and then the dye concentration of the separated aqueous phase was measured with an ultraviolet-visible spectrophotometer. PAR was the best associated dye with all crown ethers sodium-dyes and the extracted dye occurs as the ion-pair complex. Methylene chloride was found to be better than other extractive solvents used in this study.     

Adsorption of polyvinylimidazole onto kaolinite

The adsorption of polyvinylimidazole (PVI) onto kaolinite from aqueous solutions has been investigated systematically as a function of parameters such as calcination temperature of kaolinite, pH, ionic strength, and temperature. According to the experimental results, the adsorption of PVI increases with pH from 8.50 to 11.50, temperature from 25 to 55 degrees C, and ionic strength from 0 to 0.1 mol L(-1). The kaolinite sample calcined at 600 degrees C has a maximum adsorption capacity. Adsorption isotherms of PVI onto kaolinite have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The physical properties of this adsorbent are consistent with the parameters obtained from the isotherm equations. Furthermore, the zeta potentials of kaolinite suspensions have been measured in aqueous solutions of different PVI concentrations and pH. From the experimental results, (i) pH strongly alters the zeta potential of kaolinite; (ii) kaolinite has an isoelectric point at about pH 2.35 in water and about pH 8.75 in 249.9 ppm PVI concentration; (iii) PVI changes the interface charge from negative to positive for kaolinite. The study of temperature effect has been quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (RL) has shown that kaolinite can be used for adsorption of PVI from aqueous solutions.