Sarah I. Othman

Water microbial contamination is a serious issue that poses a risk to both animal and human health. 120 water samples collected from main water source and drinkers from a poultry farm. Different bacterial pathogens were isolated from water sources. Escherichia (E.) coli, Pseudomonas (P.) aureoginosa, (Salmonella) S. Typhimurim, Aeromonas (A.) hydrophila at different percentages. Variable degree of bacterial resistance to some commercial disinfectants commonly used to disinfect water system (iodine, terminator and H2O2). Nanoparticles were used to control bacteria in water. About the safety investigation for the prepared nanomaterials, the work results demonstrated that zinc oxide (ZnO) nanoparticles (NPs) exhibit the highest safety profile among the manufactured materials. The median fatal dose (LD50) for ZnO NPs was determined to be 3709 mg/kg body weight. In comparison, the LD50 values for zeolites and nanocomposites were 3251 mg/kg and 2658 mg/kg, respectively. Therapeutic dosages were estimated based on the LD50. Zeolite NPs, ZnO NPs and ZnO/zeolite NPs showing promising results in control of those bacteria. It was concluded that the escalating resistance of bacteria to disinfectants have led to a need to find alternative such as nanoparticles that proved promising results in control of pathogens, particularly it showed a safe effect on laboratory animals.

Two sodalite phases (potassium sodalite (K.SD) and sodium sodalite (Na.SD)) were prepared using alkali fusion of kaolinite followed by a hydrothermal treatment step for 4 h at 90 °C. The synthetic phases were characterized as potential adsorbents for PO₄³⁻ from the aqueous solutions and real water from the Rákos stream (0.52 mg/L) taking into consideration the impact of the structural alkali ions (K⁺ and Na⁺). The synthetic Na.SD phase exhibited enhanced surface area (232.4 m²/g) and ion-exchange capacity (126.4 meq/100 g) as compared to the K.SD phase. Moreover, the Na.SD phase exhibited higher PO₄³⁻ sequestration capacity (Q_max = 261.6 mg g⁻¹ and Q_sat = 175.3 mg g⁻¹) than K.SD phase (Q_max = 201.9 mg g⁻¹ and Q_sat = 127.4 mg g⁻¹). The PO₄³⁻ sequestration processes of both Na.SD and K.SD are spontaneous, homogenous, and exothermic reactions that follow the Langmuir isotherm and pseudo-first-order kinetics. Estimation of the occupied active site density validates the enrichment of the Na.SD phase with high quantities of active sites (Nm = 86.1 mg g⁻¹) as compared to K.SD particles (Nm = 44.4 mg g⁻¹). Moreover, the sequestration and Gaussian energies validate the cooperation of physisorption and weak chemisorption processes including zeolitic ion exchange reactions. Both Na.SD and K.SD exhibit significant selectivity for PO₄³⁻ in the coexisting of other common anions (Cl⁻, SO₄²⁻, HCO₃⁻, and NO₃⁻) and strong stability properties. Their realistic application results in the complete adsorption of PO₄^3- from Rákos stream water after 20 min (Na. SD) and 60 min (K.SD).

Egyptian kaolinite was applied in the synthesis of zeolite-A by conventional hydrothermal and alkali fusion methods, resulting in two forms of zeolite-A: the hydrated phase (H.ZA) and the dehydrated phase (DH.ZA). The DH.ZA phase exhibits an enhanced surface area (488 m²/g), total basicity (7.73 mmol OH/g), high sodium content (20.2%), and a narrow particle size distribution (5 to 25 µm) as compared to the H.ZA phase (423 m²/g surface area, 5.88 mmol OH/g total basicity, 13.3% sodium content, and 10 to 45 µm particle size distribution). DH.ZA exhibits enhanced catalytic activity, achieving a biodiesel yield of 96.8% after 60 min at 60 °C, while the application of H.ZA resulted in a 95.8% yield after 120 min at 80 °C. The controlled transesterification mechanism in the presence of H.ZA and DH.ZA involved robust base-catalyzed reactions. The reactions follow the pseudo-first-order kinetics, and the rate constants (K_c) were determined at three different temperature values (40, 50 and 60 °C). The activation energies using H.ZA (35.9 kJ·mol⁻¹) and DH.ZA (32.714 kJ·mol⁻¹) demonstrates their efficiencies in mild conditions. The thermodynamic parameters of enthalpy (33.23 kJ·mol⁻¹ (H.ZA) and 30.03 kJ·mol⁻¹ (DH.ZA)), Gibb’s free energy (65.164 kJ·mol⁻¹ (H.ZA) and 65.268 kJ·mol⁻¹ (DH.ZA)), and entropy (−195.59 J·K⁻¹·mol⁻¹ (H.ZA) and −195.91 J·K⁻¹·mol⁻¹ (DH.ZA)) demonstrate the spontaneous and endothermic behaviours of these reactions. The obtained biodiesel matches the physical properties of the international standards, and the recyclability properties of the two zeolite phases demonstrate their suitability for commercial-scale applications.