Showing papers by "Tawfik A. Saleh published in 2023"

Optimization of alkali-activated binders using natural minerals and industrial waste materials as precursor materials

Abstract: This paper presents the results of a study on developing optimized alkali-activated binders (AABs) utilizing selected natural minerals and industrial byproducts as precursor materials in addition to sodium hydroxide and sodium silicate as activators. Four selected precursor materials (natural pozzolana, limestone powder, red mud, and silicomanganese fume) were characterized in terms of their physical and chemical properties. The proportioning of the four precursor materials was optimized based on the results of flow, setting time, and compressive strength tests conducted on trial mortars. After reaching an optimal proportioning of the four precursor materials, the natural pozzolan was partially replaced by ordinary Portland cement (maximum 30% by wt.) to significantly enhance the properties of the AABs. The activator to precursor (A/P) ratio, sodium silicate to sodium hydroxide (NS/NH) ratio, sodium hydroxide (NH) molarity, and water to precursor (W/P) ratio, were varied from 0.3 to 0.6, 1 to 2.5, 8 to14 M, and 0.35 to 0.55, respectively. The influence of these activation parameters (at the optimally selected proportioning of precursor materials) on the physical and mechanical properties of AABs besides their mineral composition and morphology was investigated leading towards selecting the optimum AABs. The compressive strength at 28 days ranged from 28.5 to 32 MPa, 24.15 to 31.8 MPa, 24.2 to 33.1 MPa, 15.33 to 31.16 MPa, and 19.7 to 34.1 MPa, as A/P ratio, NS/NH ratio, NH molarity, W/P ratio, and curing method and duration were varied, respectively. XRD, FTIR, and SEM analyses of the AABs were conducted to validate the trends observed in the compressive strength results with variation in the activation parameters. The main phases detected by XRD included CSH, CASH, Mn-SH, KASH, and NASH. FTIR analysis showed bands that coincide with reported vibration and stretching of Si–O-M (M → Al, Si, or Mn) that are associated with geopolymerization, while SEM imaging showed dense microstructure with a homogenous distribution of polymerization gels that filled the microcracks and voids. Additionally, the effect of curing regimes (oven, steam and ambient-air curing) on the performance of AABs was also examined. The results of the present work enabled to identify the optimum proportioning of the selected precursor materials, optimum combination of A/P ratio, NS/NH ratio, NH molarity, and W/P ratio for producing the AABs with enhanced performance.

Removal of Lead from Wastewater Using Synthesized Polyethyleneimine-Grafted Graphene Oxide

Abstract: In this work, polyethyleneimine-grafted graphene oxide (PEI/GO) is synthesized using graphene, polyethyleneimine, and trimesoyl chloride. Both graphene oxide and PEI/GO are characterized by a Fourier-transform infrared (FTIR) spectrometer, a scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Characterization results confirm that polyethyleneimine is uniformly grafted on the graphene oxide nanosheets and, thus, also confirm the successful synthesis of PEI/GO. PEI/GO adsorbent is then evaluated for the removal of lead (Pb2+) from aqueous solutions, and the optimum adsorption is attained at pH 6, contact time of 120 min, and PEI/GO dose of 0.1 g. While chemosorption is dominating at low Pb2+ concentrations, physisorption is dominating at high concentrations and the adsorption rate is controlled by the boundary-layer diffusion step. In addition, the isotherm study confirms the strong interaction between Pb2+ ions and PEI/GO and reveals that the adsorption process obeys well the Freundlich isotherm model (R2 = 0.9932) and the maximum adsorption capacity (qm) is 64.94 mg/g, which is quite high compared to some of the reported adsorbents. Furthermore, the thermodynamic study confirms the spontaneity (negative ΔG° and positive ΔS°) and the endothermic nature (ΔH° = 19.73 kJ/mol) of the adsorption process. The prepared adsorbent (PEI/GO) offers a potential promise for wastewater treatment because of its fast and high uptake removal capacity and could be used as an effective adsorbent for the removal of Pb2+-ions and other heavy metals from industrial wastewater.

Synthesis of polyacrylic-melamine grafted graphene as efficient inhibitor for shale stabilization in water-based drilling fluid

Abstract: The penetration of water-based drilling mud into the formation in the drilling is a serious issue that causes wellbore instability. Here, a polymer-grafted graphene nanosheets (Gr-AM) was prepared as an inhibitor in water-based drilling mud. The polymer was prepared via free radical polymerization using precursors of acrylic acid, melamine, and graphene. Fourier transform infrared spectroscope (FT-IR) and transmission electron microscopy (TEM) were utilized to characterize the prepared polymer. Thermogravimetric analysis (TGA) was employed to evaluate the material's thermal stability. Several inhibition tests were carried out such as shale recovery test, anti-swelling parameter, and immersion analysis. The results showed that the Gr-AM could be stable up to 240 °C. The low concentration of Gr-AM achieved good inhibition performance compared to AM and KCl as common inhibitors. The results of this work offer some technical ideas for developing of high-performance shale inhibitors..

Trends in bimetallic nanomaterials and methods for fourth-generation glucose sensors

Abstract: Diabetes mellitus is one of the most rapidly rising chronic diseases around the globe. To combat these rising numbers, active research has been done in recent years to enhance the sensitivity, selectivity, and specificity of glucose biosensors. Despite the easy availability of these enzymatic glucose sensors, these have demonstrated limitations like low stability, short shelf-life, and being easily altered by physical and chemical environmental factors. To overcome these limitations, non-enzymatic sensors, also called fourth-generation glucose sensors, have been developed. These sensors use nanomaterials and do not employ any enzymes therefore exhibit better shelf life, improved sensitivity, and allow for quick detection of glucose without needing additional steps. In recent years, bimetallic nanocomposite-based fourth-generation glucose sensors have gained widespread attention from the scientific community. Owing to the synergistic effect of two distinct metal nanomaterials, these sensors show enhanced reproducibility and excellent stability as compared to monometallic nanomaterials. In this review, we aim to represent a comprehensive overview of the recent developments in the development of bimetallic nanocomposite-based glucose sensors for rapid and accurate glucose detection. After a brief introduction, we discussed the various bimetallic nanomaterials developed in recent years, followed by a discussion on the mechanism of action of such sensors. We then briefly discussed the industrial challenges of developing such sensors and discussed the advantages and disadvantages of bimetallic nanomaterial-based sensors. We finally concluded the review by highlighting the future perspectives of this new and upcoming field.

Synthesis of Magnetic Manganese-based Adsorbent for Rapid Adsorption of Selenium ions from water

Abstract: Selenium (Se) is one of the natural elements, and it is widely studied because of its complex behavior, especially in its involvement in the metabolism of organisms. In addition, Se contamination at high concentrations has been reported to affect human health. In this study, an adsorbent material based on manganese-magnetic (Mn-Fe3O4) has been developed, which was prepared by impregnation methods. The developed material was characterized by spectroscopy, microscopy, magnetometry, and N2 gas adsorption to investigate its surface and paramagnetic properties. A batch adsorption test was used to investigate the removing Se ions in an aqueous medium. The experimental result showed that the Se equilibrium adsorption onto Mn-Fe3O4 material could be reached within 120 min at pH 7.0 with a maximum adsorption capacity (qe) of 12.50 mg g-1 and %removal of Se at 99% at room temperature conditions. In addition, the material is easy to regenerate under alkaline conditions. This study provides strategies for fabricating magnetic materials to separate rare earth metals efficiently and rapidly.

Colorimetric detection of phosphate-based on iron complexing catechol-displacement assay in eutrophicated water bodies

Abstract: A simple, sensitive, and inexpensive colorimetric indicator-displacement assay based on Fe3+-catechol complex has been developed to determine PO43-. The Fe3+ and catechol formed a greenish color complex, upon the addition of PO43- to the complex, it exhibited a visual color change immediately from greenish to colorless along with UV-Vis spectral change. This change was mainly attributed to the high binding affinity of PO43- with Fe3+ by displacing catechol from the Fe3+-catechol complex. The developed sensor showed good sensitivity for the determination of PO43- in a wide linear range from 2 - 1000 µM with a limit of detection (LOD) of 0.5 µM which was found to be lower than the permissible limit. The sensor presented good selectivity towards the detection of PO43- in the existence of other potential interfering anions. Furthermore, the method was successfully applied to determine PO43- in eutrophicated water bodies (river and lake water) with good recoveries and without showing any significant matrix effect.