Khaled Elsaid

Ring-opening metathesis polymerization using polyisobutylene supported Grubbs second-generation catalyst

Olefin metathesis is among the most powerful tools for the formation of regio- and steroselective carbon–carbon double bonds. Applying the principles of Green Chemistry to the syntheses of polymers by developing useful strategies to facilitate catalyst and polymer product separation after a polymerization is vital. In the present study, a phase selectively soluble polymer bound second generation Grubbs catalyst was successfully used to carry out ring-opening metathesis polymerization (ROMP) on norbornene and a variety of different exo-norbornene derivatives. Polymers with low ruthenium contamination levels were achieved in comparison to the non-supported Grubbs catalyst which required multiple precipitations. Furthermore, the bound catalyst exhibits similar catalytic activity to its homogenous counterpart.

Inland Desalination: Potentials and Challenges

Groundwater is the main source of drinking water in many countries all over the world. In absence of surface water supply, the use of groundwater as the main water source for drinking, industrial, and agricultural use becomes essential especially in the case of rural communities. Underground reservoirs constitute a major source of fresh water, in terms of storage capacity; underground aquifers worldwide contain over 95% of the total fresh water available for human use. Typical groundwater supplies have low coliform counts and total bacterial counts, low turbidity, clear color, pleasant taste, and low odor. Accordingly, groundwater has higher quality than surface water, and the quality is quite uniform throughout the year that makes it easy to treat. A disadvantage of groundwater supplies is that many groundwater aquifers have moderate to high dissolved solids such as calcium, magnesium, iron, sulfate, sodium, chloride, and silica. The high concentration of dissolved solids particularly, sodium chloride, makes the water brackish and thus requires to be desalinated before its use for a certain purpose.

Treatment of Pharmaceutical-manufacturing Wastewaters by UV Irradiation/Hydrogen Peroxide Process

Abstract In this study, the treatment of pharmaceutical-manufacturing wastewaters (PMWW) by advanced chemical oxidation using UV irradiation/hydrogen peroxide (H2O2) process has been investigated. Effects of experimental conditions such as H2O2 dose, initial organic matter concentration, temperature and initial pH value on the removal efficiency and kinetics of organic matter were investigated. Results of this study indicated that UV/H2O2 process can be successfully used to completely destroy aromatic compounds, and to remove chemical oxygen demand (COD) and total organic carbon (TOC) with removal efficiencies more than 95% and 90%, respectively. Kinetic experiments have demonstrated that TOC removal rate followed pseudo-second order kinetics. Rate constants of 1.12×10-3 A-1 min-1 and 2×10-5 L mg-1 min-1 were calculated for UV absorbance at 277 nm and TOC decay, respectively. These results indicate that the mechanism of pharmaceuticals degradation involves two main steps: (i) Rapid degradation of aromatic compounds by hydroxylation followed by oxidative opening of benzene rings to form aliphatic derivatives and (ii) subsequent slow fragmentation of aliphatic derivatives into small carboxylic acids which are mineralized into CO2, H2O and other inorganic ions during the final steps of degradation.

Surfactant/organic solvent free single-step engineering of hybrid graphene-Pt/TiO2 nanostructure: Efficient photocatalytic system for the treatment of wastewater coming from textile industries

In this study, hybrid graphene-Pt/TiO2 nanostructure were synthesized by single-step, inexpensive and surfactant/organic solvent free route; hydrothermal technique. The physicochemical properties of hybrid graphene-Pt/TiO2 nanostructure were carefully analyzed by multiple techniques, including X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The synthesized hybrid nanostructures were utilized as photocatalyst for the degradation of methylene blue (MB) dye under natural environment at average ambient temperature and mean daily global solar radiation, of about 22–25 °C and 374.9 mWh/cm2, respectively. The activity performance indicated considerable degradation of methylene blue (MB) dye and was in the following order Gr (13%), TiO2 (60%) and hybrid graphene-Pt/TiO2 nanostructure (90%) over 21 min under the natural light illumination. The physiochemical characterization suggests that, the tightly attached metalized TiO2 nanoparticles (Pt-TiO2) on the high surface area graphene sheets improved utilization of visible light and increased separation and transfer of photo-excited electron (ē) hole (h+) pairs. Notably, the hybrid graphene-Pt/TiO2 nanostructure exhibited an excellent cyclic stability for methylene blue (MB) dye removal. Finally, the kinetic behavior indicated that the photocatalytic degradation reaction of the dye obeyed the pseudo-first order (Langmuir-Hinshelwood) kinetics model.

Validation of Total Mercury in Marine Sediment and Biological Samples, Using Cold Vapour Atomic Absorption Spectrometry

A method for the measurement of total mercury (T-Hg) in environmental samples using cold vapour atomic absorption spectrometry (CV AAS) has been validated yielding a dynamic range (0.04–10.00 μg/kg) and high certified reference material (CRM) recovery (>90%). The validation was carried out according to International Union of Pure and Applied Chemistry (IUPAC) validation and Eurachem Guides. A freeze-dried and homogenised sample was weighed and then digested using Suprapur acids (HNO3, H2SO4, and HF) with potassium dichromate solution in a hot block digestion system. A calibration curve was constructed (R2 > 0.999). Two CRMs (Marine Sediment Reference Material (PACS-3) and Trace Elements in Muscle Tissue (Trace Elements and Methylmercury in Mussel Tissue (NIST2976)) were utilised for quality assurance and control. The limit of quantification (LOQ) calculated as 0.04 µg/kg, and uncertainty (U) calculated as 2%. The obtained results showed the suitability of this method for direct mercury measurement in environmental samples. Additionally, the proficiency of this method was recognised by accreditation under the standard of International Organization for Standardization (ISO/IEC 17025:2017) for competence of testing and calibration laboratories.

Acid-functionalized carbon nanofibers for high stability, thermoelectrical and electrochemical properties of nanofluids

Carbon-based nanofluids are viewed as promising thermal fluids for heat transfer applications. However, other properties, such as electrical conductivity and electrochemical behavior, are usually overlooked and rarely investigated despite their importance for the overall performance characterization of a given application. In this study, we synthesized PAN-based carbon nanofibers (CNF) by electrospinning, and characterized them using electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Thermoelectrical and electrochemical measurements were carried out on nanofluids. We found that, although CNF nanofluids exhibit good thermal and electrical properties with a negligible corrosive effect, the suspensions tend to sediment within a few days. However, acid treatment of CNF (F-CNF), which resulted in the shortening of the fibers and the appearance of surface-oxygenated species, made F-CNF-based nanofluids exhibit superior stability in water that extended for more than 90 days, with consistent and superior thermal and electrical properties.

Synthesis and Physicochemical Studies of Perovskite Manganite La0.8Ca0.2Nn1−xCoxO3 (0 ≤ x ≤ 0.3)

This work has been supported by the Tunisian Ministry of Scientific Research and Technology and Institute Neel at Grenoble.

Utilization of Byproduct Sulfur for Chromium Waste Treatment

Publisher Summary Sulfur-based treatment technologies have been the focus of an increasing number of research studies and commercial applications for treating soils and groundwater contaminated with toxic metals. Calcium polysulfide reduces and precipitates some highly soluble metals such as arsenic, lead, copper, and zinc to form metal sulfides, which often are much less soluble than metal hydroxides and remain insoluble within a wider range of pH values. In addition to their ability to immobilize and degrade hazardous wastes, modified sulfur products can be used as binders in solidification/stabilization treatment of hazardous wastes. One of the modified sulfur products that can be used for that purpose is called plasticized sulfur. Plasticized sulfur is made by heating elemental sulfur to the point where it becomes a viscous fluid. At that point hydrocarbon plasticizers are added to maintain a semi-solid consistency of the sulfur as the temperature returns to normal levels. Plasticized sulfur has recently emerged as a possible alternative binding and stabilizing agent for the solidification and stabilization of hazardous, low-level radioactive and mixed wastes. Plasticized sulfur has been used as a binder for solidification/stabilization of wastes contaminated with heavy metals, elemental mercury waste and a variety of mixed wastes.