Investigation of electrocoagulation reactor design parameters effect on the removal of cadmium from synthetic and phosphate industrial wastewater

This study investigates the effect of reactor design parameters on cadmium removal from industrial wastewater discharged by the Tunisian Chemical Group (TCG) to improve as much as possible efficiency and cost of electrocoagulation (EC) process. Based on an examination of the design parameters one by one, the best cadmium removal was achieved for an inter-electrode distance (d_ie) of 0.5 cm, monopolar connection mode, stirring speed of 300 rev min^?1, surface-area-to-volume ratio (S/V) of 13.6 m^?1, and an initial temperature of 50 °C. These operating conditions are allowed to achieve efficient removal in a relatively short operating time with the lowest energy consumption and cost possible. The present study proved that the parameters that have an effect on the operating cost are the electrode configuration, inter-electrode distance and S/V ratio. The energy consumption, the pH evolution, and the treatment cost were studied. The investigation of the effect of all the selected optimum EC design parameters together on the removal of cadmium from the TCG wastewater proved that the treatment was highly efficient; 100% of cadmium removal was reached in 5 min, with a very low power consumption (1.6 kW h m^?3) and very low cost (0.116 TND m^?3). Moreover, EC was found to be capable of removing cadmium as well as other pollutants at the same time from the case-study industrial wastewater. The investigation carried out in this work explores and proposes a very cost-effective treatment method to remove heavy metals from industrial wastewater if compared to results reported about cost of this treatment process through other widely used technologies such as coagulation (4.36 Tunisian National Dinar (TND) m^?3) and precipitation (9.96 TND m^?3) employed in previous studies.     

High resolution gas phase chromatography-mass spectrometry of polychlorinated biphenyl congener residues in samples of biologic origin

A study is performed on polychlorinated biphenyl (PCB) congener residues in samples of human blood and milk as well as in falcon and pigeon eggs. Most of the PCB congeners found in these biological samples were quantified by high-resolution gas chromatography (HRGC). A PCB technical mixture--namely, DP6 (Phenochlor)--was used for the calibration as its composition was previously determined by HRGC-mass spectrometry. The usefulness of such a congener analysis is outlined. It is the first time to the best of our knowledge that a Phenochlor mixture is used for standardization.     

Photo-oxidation process of indole in aqueous solution with ZnO Catalyst: Study and optimization

The photo-oxidation of indole has been investigated using the catalytically active ZnO in aqueous solution, under various physical and chemical conditions. First of all, a structural analysis with X ray diffraction (XRD) shows that ZnO powder crystallizes in wurtzite with a main grain size estimated to be about 270 nm. An increase in catalyst loading greatly enhances the process efficiency until a certain. limit. Indole photodegradation improves with increasing air flow. The effect of the pH on the photo-oxidation efficiency was carried out from 3.88 to 11.16. The activity exhibits its maximal value around the natural pH (6.68). Photocatalytic degradation showed that the activity of ZnO improved with increasing light intensity. This was ascribed to the fact that there was a more efficient generation of electron-hole pairs used in the degradation process.     

Time-Dependent 2D Harmonic Oscillator in Presence of the Aharanov-Bohm Effect

We use the Lewis-Riesenfeld theory to determine the exact form of the wavefunctions of a two-dimensionnal harmonic oscillator with time-dependent mass and frequency in presence of the Aharonov-Bohm effect (AB). We find that the auxiliary equation is independent of the AB magnetic flux. In the particular case of quantized AB magnetic flux the wavefunctions coincide exactly with the wavefunctions of the 2D time-dependent harmonic oscillator. PACS: 03.65Ge; 03.65Fd; 03.65Bz     

Thermodynamic study of the protonation of dimethyldodecylamine N-oxide micelles in aqueous solution at 298 K. Establishment of a theoretical relationship linking critical micelle concentrations and pH

Dodecyldimethylamine N-oxide (DDAO) is a zwitterionic surfactant with acid-base properties. The proton dissociation constant of this surfactant was determined by a novel potentiometric method at "controlled chemical potential" of the proton using a classical pH-glass electrode. When the DDAO was in its monomeric form, the pKa was about 5, consistent with the value commonly reported in the literature. However, a unique proton dissociation constant specific to the micellar form of this surfactant could not be obtained. We found that the acid-base behavior of the DDAO micelles depended on their environment. Indeed, we were able to establish thermodynamic relations linking the critical micellar concentration to the degree of protonation of the micelles. The experimental values were in good accordance with this model.     

Synthesis of high added value compounds through catalytic oxidation of 2-phenylethanol: A Kinetic study

An effective procedure was developed to produce high-value added phenolic compounds through the conversion of 2-phenylethanol (2-PhEt) by using acid-activated clays KSF for the hydrogen peroxide. Owing to KSF's ability to catalyze a variety of complex oxidations, it was likely to convert 2-PhEt to hydroxytyrosol (HTY) and tyrosol (TY) derivatives. The analyses of catalytic solution revealed that the optimum conditions, giving a higher concentration of oxidation products such as HTY, were as follows: 2-PhEt concentration 10⁻² mol/L, the hydrogen peroxide concentration 5.05 × 10⁻² and 0.6 g L^–1 of KSF clays . The yield during the conversion reaction into HTY was around 25%. All compounds in the reaction mixture were identified by mass spectrophotometry using a LC-MS apparatus. HTY, TY, meta-tyrosol and ortho-tyrosol were the major compounds. The antioxidant activity was realized by 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. In fact, it is revealed that the strongest inhibition percentage (PI = 96) was detected with the increase in the concentration of HTY. The approach proposed in the present work presents an environment friendly method.     

Dark-managed solitons in inhomogeneous cubic–quintic–septimal nonlinear media

Nonlinear Dynamics - We investigate the inhomogeneous higher-order nonlinear Schrödinger (INHLS) equation including cubic–quintic–septic (CQS) nonlinear terms and gain or loss with...     

Elasticity of the B2 phase and the effect of the B1–B2 phase transition on the elasticity of MgO

A study of the high-pressure anisotropy of MgO was conducted using first-principles calculations based on density functional theory within the generalized gradient approximations. The pressure dependence of the elastic stiffness coefficients and the anisotropy parameters, in both B1 and B2 phases, shows that for high-hydrostatic compression the easiest deformation is the shear along (100) plane and the the material's response to deformation and to shearing strains is quite the same. According to the calculations of the velocities of propagation of elastic waves, we deduced that MgO develop an elastic anisotropy, especially, in the B1 phase. We present the B2 phase elastic properties which are not already studied under high pressure.