Hafiz Muhammad Abd Ur Rahman

Hydration of formate and acetate ions by dielectric relaxation spectroscopy.

Dielectric relaxation (DR) spectra have been measured for aqueous solutions of sodium formate (NaOFm) and sodium acetate (NaOAc) over a wide range of frequencies (0.2 ≤ ν/GHz ≤ 89) up to solute concentrations c is less or approximately equal to 3.2 M and is less or approximately equal to 3.7 M, respectively, at 25 °C. Measurements were also made on NaOAc(aq) at 15 ≤ T/°C ≤ 35. In addition to the usual dominant bulk-water relaxation process at ~20 GHz, one or two further relaxation modes were detected. One process, centered at ~8 GHz and observed for both NaOFm(aq) and NaOAc(aq), was attributed to the presence of slow water in the hydration shells of the anions. A lower-frequency process at ~0.6 GHz, observed only for NaOAc(aq) at c is less or approximately equal to 1 M, was thought to be due to the presence of very small concentrations of ion pairs. Detailed analysis of the spectra indicated that very few (<2 per anion) water molecules were irrotationally bound (frozen) on the DR time scale. Nevertheless, both anions are strongly hydrated, as evidenced by the significant amounts of slow water detected. Such H(2)O molecules with reduced dynamics result from two distinct effects. The first is the relatively strong hydrophilic interaction of water with the -COO(-) moiety, which is similar for the two anions and little affected by increasing solute concentration. The second (for OAc(-) only) is the hydrophobic hydration of the -CH(3) group, which is fragile, decreasing markedly with increasing solute concentration and temperature. The activation parameters for bulk-water relaxation in NaOAc(aq) indicated a breakdown of the bulk water structure at high solute concentrations.

Dielectric Relaxation Study of the Ion Solvation and Association of NaCF3SO3, Mg(CF3SO3)2, and Ba(ClO4)2 in N,N-Dimethylformamide

Solutions of sodium trifluoromethanesulfonate, magnesium trifluoromethanesulfonate, and barium perchlorate in N,N-dimethylformamide (DMF) have been investigated using broadband dielectric relaxation spectroscopy at 25 °C. All spectra were dominated by a solvent relaxation process centered at ∼15 GHz but also exhibited one (for NaCF(3)SO(3)) or two (for the 2:1 salts) low-amplitude processes, centered at frequencies below 2 GHz, that could be attributed to the presence of ion pairs. Effective solvation numbers calculated from the solvent relaxation amplitudes indicated strong solvation of all three cations, with evidence for the formation of a second solvation sheath for Mg(2+) and possibly Ba(2+). Detailed analysis of the solute-related processes showed that solvent-shared ion pairs (SIPs) were formed in NaCF(3)SO(3) solutions in DMF. The data for Mg(CF(3)SO(3))(2) and Ba(ClO(4))(2) solutions were not definitive but, consistent with the solvation evidence, favored the presence of double solvent-separated ion pairs and SIPs. Overall association constants, K(A), were small for all three salts in DMF and increased in the order: NaCF(3)SO(3)

Rose biomass as a potential biosorbent to remove chromium, mercury and zinc from contaminated waters

Abstract Rose flowers are used for the extraction of essential oil or rose water. The vast majority of the leftover biomass is generally wasted. The aim of the present study was to analyse the rose flower biomass as a potential biosorbent for metals chromium(III), mercury(II) and zinc(II), to remove them from industrial effluents. A number of variables were analysed, including untreated, acid-treated and base-treated biomass, biomass dosage, metal ion concentration, contact time, and pH. Increase in biomass dosage and metal ion concentration increased biosorption. The pH proved to be a very important factor and all the metals showed high adsorption at slightly acidic to moderately basic pH 6–10. They showed very low uptake at low pH. Contact time had little effect on the adsorption capacity of zinc, but was very crucial in the case of mercury. Base treatment favoured adsorption of mercury and zinc. The adsorption of Cr3+, Hg2+ and Zn2+ on rose biomass can be explained by Langmuir and Freundlich isotherms equally well, and the adsorption process followed pseudo second order kinetics. The study suggests that the rose flower biomass can be used in the removal of these metals from contaminated waters employing optimum conditions indicated by the present work.

Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics

To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.