Kinetic Modeling for Photo-Assisted Penicillin G Degradation of (Mn0.5Zn0.5)[CdxFe2-x]O4 (x ≤ 0.05) Nanospinel Ferrites

Penicillin G is an old and widely used antibiotic. Its persistence in the environment started to appear in many environmental samples and food chains. The removal of these emerging pollutants has been a challenging task for scientists in the last decades. The photocatalytic properties of Cd2+ doped Manganese- Zinc NSFs with chemical formula (Mn0.5Zn0.5)[CdxFe2−x]O4 (0.0 ≤ x ≤ 0.05) NSFs are herein evaluated. The Manganese- Zinc N.S.F.s nanomaterials were deeply characterized, utilizing UV-Vis (reflectance) spectroscopy, X-ray diffraction, N2 adsorption isotherm measurements, and S.E.M., SEM-EDX mapping, and T.E.M. The Kinetic model for the photodegradation of penicillin G (as a model molecule) is investigated using visible light as a source of energy. The kinetic study shows that our results fit well with the modified pseudo-first-order model. The Pen G degradation are 88.73%, 66.65%, 44.70%, 37.62% and 24.68% for x = 0.5, 0.4, 0.3, 0.2 and 0.1, respectively, against 14.68% for the free Cd spinel sample. The pseudo-rate constant is bandgap dependent. From the intra-diffusion rate constant (Kd), we developed an intra-diffusion time (τ) model, which decreases exponentially as a function of (x) and mainly shows the existence of three different domains versus cadmium coordination in spinel ferrite samples. Hence, Cadmium’s presence generates spontaneous polarization with a strong opportunity to monitor the charge separation and then open the route to a new generation of “assisted” photocatalysts under visible light.

Influence of Ultrasound on the Adsorption, Diffusion and Kinetics of Leather Dyeing Process: Mechanistic Insight

Leather is a natural porous material, which is composed of a three-dimensional weave of tanned collagen fibre bundles. This paper studies the influence of power ultrasound on the adsorption and kinetics of leather dyeing process. Dyeing experiments have been carried out using ultrasound (150 W, 33 kHz) and compared with that of static control dyeing process. The data of dye uptake in leather have been analysed using Freundlich and Langmuir adsorption isotherms. Intra Particle diffusion model has been employed to calculate Intra particle diffusion rate constant and Boundary Layer effect. Diffusion coefficient (D) of dye through leather matrix has also been calculated. Kinetics of leather dyeing process has been studied through pseudo first and second order rate equation. The Freundlich constant (Kf), Langmuir parameter (Qm), Intra Particle diffusion rate constant (Kd) Apparent Diffusion coefficient (D) and Pseudo First order kinetic constant, K1 have been calculated to be 18.67 mg/g, 50 mg/g, 0.006 min-1, 1.89 * 10-6 cm2/s and 1.7 mg/g min0.5 respectively for ultrasound assisted leather dyeing as compared to that of 0.1 mg/g, 26.67 mg/g, 0.733 min-1, 0.19 * 10-6 cm2/s and 0.003 mg/g min0.5 respectively for control process. The results indicate that significant enhancement in adsorption capacity with more favorable dye adsorption as well as about 10- fold increase in Apparent Diffusion coefficient with significant reduction in boundary layer effect, improved kinetic parameters due to the use of ultrasound in leather dyeing as compared to control. Mechanisms for enhancement in Adsorption and Kinetic Parameters in leather dyeing due to the use of ultrasound have been presented and corroborate well with better dye penetration, color value and fastness properties. Therefore, the present study demonstrates that the use of ultrasound in leather dyeing helps both in adsorption of dyes as well as diffusion process through the leather matrix.

Examination of 2-Phenoxyaniline Fluorescence Quenching by Chloromethanes

The fluorescence quenching of 2-phenoxyaniline (2PAN) by chloromethanes were studied in hexane, dioxane, acetonitrile and methanol. The quenching rate constants (kq) are large with CCl4 and CHCl3 and close to diffusion rate constant (kdiff) and viscosity dependent, where with CH2Cl2 they are less. No clear cut variation of solvent polarity or viscosity is observed for CH2Cl2. Intermediate donor-acceptor complex formation is suggested for CH2Cl2 quenching. kq varies with electron affinity of quenchers suggesting the formation of non-emissive exciplex in quenching.

ELEMENTARY ACTS OF PHOTOREACTIONS OF 2,6-DIPHENYL-1,4-BENZOQUINONE IN VARIOUS SOLVENTS

In order to determine the effect of the polarity of solvents on the reactivity and the course of the reactions of semihinone radicals, their complexes, this study of 2,6-diphenyl-1,4-benzoquinone, (class of substituted benzoquinones) and its dimer D was carried out. It was found that in the NMR spectrum of the dimer solution, with increasing temperature, the lines widen, and there is one wide line close to the chemical shift to the protons of the meta-groups of quinone. The NMR spectrum of a solution D in deuterochloroform at low temperatures contains lines corresponding to the aromatic part of the protons in the meta position, respectively (7.05 M.d, 6.89 M.d.). That is, the exchange process between the non-equivalent parts of the diamagnetic dimer molecule of the preceding dissociation takes place with the constant of the velocity k-1, coinciding in order of the inverse spin-spin relaxation time. The value of k-1 increases by more than an order of magnitude with the increasing polarity of the solvent. This effect is due to the stronger solvent solvation of the activated complex in the transition state compared to the molecule. The reaction of dimerization of semiquinone radicals is diffusion-controlled, since the values of ∆H1≠ in all solvents differ from the activation energy of viscosity by no more than 1 kcal/M and the values of the velocity constant in 5-8 times differ from the diffusion rate constant calculated by Debye. The solvation of radicals leads to a decrease in the diffusion coefficients of radicals and, possibly, to the shielding of the reaction center, which causes a decrease in k1. With the decrease of the constant in the specified number of solvents, the stability of the radical increases, which is manifested in a symbiotic increase in the equilibrium constant K. The reason for the increase of the direct constant k1 in solvents with high permittivity is explained.

Comparison of methylene blue adsorption from aqueous solution using spent tea dust and raw coir pith

<div> <p>The purpose of the present work is to test the possibility of using the spent tea dust and raw coir pith for the removal of methylene blue (MB) from aqueous solution. The effects of the contact time, adsorbent dosage and solution pH were studied in batch experiments at 27 &deg;C. Results showed that a pH of 7 is favourable for the adsorption of dye. The isothermal data could be well described by the Langmuir equations. Kinetic parameters of adsorption such as the Langergen pseudo-first-order, pseudo-second-order rate constant and the intraparticle diffusion rate constant were determined. The adsorption capacities of Spent Tea Dust (STD) and Raw Coir Pith (RCP) were found to be 86.21 mg and 142.86 mg g^-1 of the adsorbent respectively. The results indicate that STD and RCP could be employed as low-cost alternatives to commercial activated carbon for the removal of dyes from aqueous solution.</p> </div> <p>&nbsp;</p>

Characterization of hydroxybenzoic acid chelating resins: Equilibrium, kinetics, and isotherm profiles for Cd(II) and Pb(II) uptake

Chelating ion-exchange resins were synthesized by polycondensation of ortho/para hydroxybenzoic acid with resorcinol/catechol employing formaldehyde as cross-linking agent at 80?5?C in DMF. The resins were characterized by FTIR and XRD. The uptake behaviour of synthesized resins for Cd(II) and Pb(II) ions have been studied depending on contact time, pH, metal ion concentration and temperature. The sorption data obtained at optimized conditions were analyzed by the Langmuir and Freundlich isotherms. Experimental data of all metal-resin system were best represented by the Freundlich isotherm. The maximum obtained sorption capacity for cadmium was 69.53 mg g-1 and 169.32 mg g-1 for Lead. The adsorption process follows first order kinetics and the specific rate constant Kr was obtained by the application of the Lagergan equation. Thermodynamic parameters ?Gads, ?Sads and ?Hads were calculated for the metal-resin systems. The external diffusion rate constant (Ks) and the intra-particle diffusion rate constant (Kid) were calculated by the Spahn-Schlunder and Weber-Morris models, respectively. The sorption process was found to follow an intra-particle diffusion phenomenon.

Removal of Grey BL from Dye Wastewater by Derris (Pongamia Glabra) Leaf Powder by Adsorption

The dye, Grey BL was adsorbed on an adsorbent prepared from mature leaves of the Pungan tree (Pongamia glabra). A batch adsorption study was carried out with variable adsorbate concentration, adsorbent amount and pH. Ninety three percent of the dye could be removed by 2 g of the derris leaf powder from 1 L of an aqueous solution containing 25 mg of the dye at 300 K. The adsorption followed pseudo first order kinetics with a mean rate constant of 3.73 ×10-3min-1and an intraparticle diffusion rate constant of 6.36 x10-2mg g-1min-0.5. A possible mechanism of adsorption was suggested on the basis of concurrently operating surface adsorption and pore diffusion. The experimental data yielded excellent fits with Langmuir and Freundlich isotherm equations. The Langmuir monolayer capacity had a mean value of 8.27 mg g-1. The results indicated that the dye, Grey BL, strongly interacts with a biomass-based adsorbent, the Derris (Pongamia glabra) leaf powder.

Diffusional Fluorescence Quenching of Aromatic Hydrocarbons

The quenching of the fluorescence of five aromatic hydrocarbons by three halogenated organics and by molecular oxygen has been measured. Both fluorescence intensity and fluorescence lifetime measurements have been employed to validate results and interpretation; linear Stern–Volmer analyses are shown to apply throughout. The fluorescence quenching rate constant of molecular oxygen for the five aromatic hydrocarbons is essentially equivalent to the diffusion rate constant independent of the fluorophore excitation energy. The halogenated organic–fluorophore rate constants vary by a factor of 965 and are shown to correlate roughly with the energy difference between the quencher and fluorophore excited electronic states in accord with a standard model of quantum two-level mixing. The value of the coupling interaction energy is ∼2500 cm−1.