An-Najah Staff

From an environmental engineering point of view, pharmaceuticals such as antibiotics are a group of man-made chemicals of concern entering the environment in concentrations at which, the health effects are unknown. The problem that may be created by the presence of antibiotics at low concentrations in the environment is the development of antibiotic resistant microorganisms. In this study, three pharmaceutical drugs manufactured in Palestine were studied in waste water and their adsorption in agriculture soil was studied using soil columns. During the study of soil columns, it was noted that the concentration of caffeine in leachate was higher than that of ibuprofen and amoxicillin, as caffeine has higher aqueous solubility. Ibuprofen and amoxicillin were present in leachate with very small concentrations, due to their degradation and decomposition into other substances that may be harmful, and affect the natural properties of soil, groundwater and human health. The decomposition percentages of the pharmaceuticals in the soil columns were 97.82, 97.88 and 86.52% for amoxicillin, ibuprofen and caffeine for one year’s study, respectively. For the fifteen years, the decomposition percentages were 94.04, 96.60 and 93.70% for amoxicillin, ibuprofen and caffeine, respectively.

Kinetics of osmium tetroxide catalyzed-oxidation of the studied fluoroquinolones by potassium hexacyanoferrate(III) in alkaline medium were studied. The rate was found to be independent on the concentration of hexacyanoferrate(III), and first order with respect to both fluoroquinolone and OsO4. An empirical rate law was derived for the reaction, and the effect of various variables on the rate of reaction was studied. Thermodynamic parameters (Ea, ΔH*, ΔS*, ΔG*) were also calculated.

Removal of cadmium from aqueous solutions using 20 species of plant leaves and combinations of these leaves have been studied. Several factors affecting the removal efficiency have been studied. The most efficient types of plant leaves for the removal of cadmium are those of styrax, plum, pomegranate and walnut. The interaction effect of the combined leaf samples on the efficiency of removal of cadmium has been found to be additive in combinations involving styrax plant leaves but seems to be antagonistic in all other combinations. The optimum experimental conditions for removal of cadmium have been found to be at pH 4.1, using high concentrations of naturally dried plant leaves, using ground leaves and to remove cadmium from agitated aqueous solutions. The percentage of metal removed at an initial cadmium concentration of 10 mg/l by the most efficient types of leaves have been found to be 85% for styrax leaves, 85% for plum leaves, 80% for pomegranate leaves, 78% for walnut leaves and 77% for meddler leaves. The presence of foreign ions or complexing agents has been found to reduce the efficiency of removal of cadmium by plant leaves. About 80–85% of the cadmium in charged plant leaves has been released under the influence of changing the pH of the solution, addition of competing ions and the addition of EDTA. The results of removal of cadmium by plant leaves have been found to follow the Freundlich adsorption isotherm, first-order reaction with respect to cadmium and to have intra-pore diffusion as the rate-limiting step.

Uptake of cadmium from aqueous solutions by beech leaves has been studied. The effect of several factors on both rate and amount of this uptake has been studied. These factors include concentration of leaves, concentration of cadmium, pH, competing ions and drying leaves. The pattern of the curves showing the loss of cadmium from solution has been explained. Applicability of the Freündlich adsorption isotherm on the present results has been examined and the parameters of this isotherm have been calculated. The order of reaction between cadmium ions and beech leaves has been determined and a mechanism for this reaction has been suggested.

Decaying leaves have been proven capable of partially removing lead from polluted water. Several factors affecting the removal process have been studied. These include the concentration of lead ions, concentration of leaves, drying leaves, degree of crushing of leaves, leaf extracts, pH, agitation and presence of competing and of complexing agents. The relative capability of some common types of leaves for the removal of lead from water has been studied.
The release of lead from leaves saturated with lead ions has been studied under the effect of varying pH, addition of competing ions and the addition of complexing agents.
The results of the present work indicate that the interaction between lead ions and leaves is mainly an adsorption process and fit the Freundlich adsorption isotherm whose parameters have also been calculated. A fractional order of reaction (0.7) has been determined for the reaction between lead ions and leaves using two methods of evaluation. A mechanism in which film diffusion being the most probable limiting step has been suggested.

Thiomorpholine (tetrahydro-1,4-thiazine), in the presence of Os(VIII) as catalyst, is oxidized by alkaline hexacyanoferrate(III) to 2-hydroxythiomorpholine. There is a first-order dependence in [Fe(CN)₆^3-] and [Os(VIII)] and zero-order dependence in [thiomorpholine] and [OH^-]. The observed rate constant was dependent on [Fe(CN)₆^4-] the type of electrolyte and the permitivitty of the reaction medium (10-40% ethanol). The proposed mechanism includes the formation of a transient [OsO₄(OH)₂ ]^2--thiomorpholine complex prior to the rate-determining regeneration of Os^VIII by [Fe(CN)₆^3-]. The values of the enthalpy and entropy of activation are calculated from rate constant values measured at different temperatures (20-40 ° C).

The kinetics of oxidation of L-cysteine by 3-di-2-pyridylketone-2-thiophenylhydrazone-iron(III), [Fe(DPKTH)2]3+ complex in acidic medium was studied spectrophotometrically at 36 C temperature. The molar ratios of DPKTH to iron(III) and iron(II) individually, were found to be [2:1] [DPKTH : iron(III)/(II)]. The reaction was stroked to be first-order with respect to iron(III) and L-cysteine, second-order with respected to DPKTH ligand and reversed second-order with respected to hydrogen ion concentration. Added salts did not affect the rate and no free radical was detected when radical detector was placed in the reaction mixture. Ethanol solvent ratio was found to effect both the initial rate and the maximum absorbance (ʎmax) of [Fe(DPKTH) 2]2+ complex. The initial rate rose when the temperature was increased which empowered to calculate the activation parameters. A suitable reaction mechanism was proposed.