Gomaa A. M. Ali

The role of nanomaterials as effective adsorbents and their applications in wastewater treatment

Nanomaterials have been extensively studied for heavy metal ions and dye removals from wastewater. This article reviews the role of nanomaterials as effective adsorbents for wastewater purification. In recent years, numerous novel nanomaterial adsorbents have been developed for enhancing the efficiency and adsorption capacities of removing contaminants from wastewater. The innovation, forthcoming development, and challenges of cost-effective and environmentally acceptable nanomaterials for water purification are discussed and reviewed in this article. This review concludes that nanomaterials have many unique morphological and structural properties that qualify them to be used as effective adsorbents to solve several environmental problems.Graphical Abstract

High performance supercapacitor using catalysis free porous carbon nanoparticles

Very high supercapacitance values are obtained using catalyst free porous carbon nanoparticles (PCNs). The obtained PCNs have a porous structure with fine particles 35 nm in size. The specific capacitance of PCNs is 343 F g −1 and 309 F g −1 at 5 mV s −1 and 0.06 A g −1 , respectively. PCNs shows a high cyclic stability of about 90% and high columbic efficiency of 95% over 2500 cycles at 1 A g −1 . Impedance spectra show low resistance of PCNs, supporting their suitability for supercapacitor electrode application.

Enhancement of adsorption efficiency of methylene blue on Co3O4/SiO2 nanocomposite

AbstractSingle and well-crystalline Co3O4 phase imbedded in an amorphous SiO2 matrix has been obtained by novel aqueous solution method. The structural and morphological properties are investigated using X-ray diffraction, Fourier transform infrared spectrometer, and N2 adsorption–desorption techniques. The apparent crystallite size for Co3O4 was found to be about 13.5 nm, which elucidates the rule of poly ethylene glycol in preventing particle’s agglomeration; moreover, the pours structure of the composite enhances its adsorption ability. Co3O4/SiO2 has a high ability to absorb methylene blue from an aqueous solution. The removal percent of Methelene blue (MB) by Co3O4/SiO2 has reached 95.7%. The effect of various experimental parameters, such as initial dye concentration, contact time, and dose were investigated. Co3O4/SiO2 nanocomposite shows high adsorption capacity of 53.87 mg g−1, which is larger than the adsorption capacity of MB on other materials. Both of Langmuir and Freundlich models were used ...

HUMIDITY SENSING PROPERTIES OF COBALT OXIDE/SILICA NANOCOMPOSITES PREPARED VIA SOL–GEL AND RELATED ROUTES

Ultrafine Co3O4/SiO2 nanocomposites were obtained via sol–gel (SG) method and related routes. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 adsorption–desorption techniques. The obtained phase, size of crystallites and specific surface area of the composites vary with the Co:SiO2 weight ratio and preparation route. Humidity sensing properties measured by monitoring the DC conductivity for the obtained nanocomposites are reported. Conductivity changes amount to four orders of magnitudes were observed in response to 10–90% relative humidity change in the measuring chamber. Results indicate that humidity sensing properties depend on Co content and specific surface area of the composite.

Hydration characteristics and immobilization of Cr (VI) in slag cement-CKD pastes under hydrothermal treatment

The effect of hydrothermal curing regimes on the hydration characteristics of slag cement containing different ratios of cement kiln dust has been studied. The samples for this study were combination of slag cement and cement kiln dust (5%-25%) without and with immobilization of 5% Cr (VI) by mass. Pastes were hydrothermally treated at 180 °C for different periods (2-24 h) in well closed stainless steel capsule. The hydration characteristics of these pastes were studied by measuring the compressive strength, bulk density, total porosity and combined water content. The findings were further supported by XRD and SEM analysis. The results indicated that the hydration characteristics of slag cement paste containing cement kiln dust 10% by mass were enhanced, especially at later ages (24 h) of hydration. That is due to the hydrothermal curing regimes of immobilized pastes accelerating hydration reactions and precipitation of CaCrO4, indicating that Cr (VI) can be solidified in the cement paste. This precipitation leads to pore formation in hydrated slag cement pastes.

Hydrogen sulfide emission sources, regulations, and removal techniques: a review

Abstract This review highlights the recent technologies of H2S removal from wastewater in the petroleum refinery. H2S is a harmful, putrid, and hazardous gaseous compound. The main processes such as physicochemical, chemical, biological, and electrochemical methods were compared and discussed in detail. The effects of various parameters and adsorbent characteristics were highlighted and correlated with the adsorption capacities. Surface functional groups and porosity surface area play a crucial role in the process of single-phase and composite adsorbents. Composite materials impregnated with some metals showed high removal efficiencies. It was found that the adsorption process is the most relevant way for H2S removal due to its high removal efficiency, low cost, eco-friendly, and operational simplicity. This study serves as a useful guideline for those who are interested in H2S removal.

Flakes Size-Dependent Optical and Electrochemical Properties of MoS2

Background: Molybdenum disulfide (MoS2) is a transition metal dichalcogenides and has some interesting and promising properties. MoS2 has direct and indirect band gaps depending on its crystalline structure. In addition, its sheets morphology makes it a good candidate for supercapacitor applications. Objective: The aim of this work is to study the effect of MoS2 flakes size on its optical and electrochemical properties. Method: MoS2 with different flakes sizes were prepared by exfoliation method. The exfoliation was performed by sonication of MoS2 powder in N,N-Dimethylformamide followed by different centrifugation speeds. UV-Vis spectra illustrated the optical energy gap was inversely proportional to the MoS2 flakes size. Results: Absorption coefficient values indicated that the exfoliation reduced the number of layers. Symmetric supercapacitor was made from two MoS2 electrodes and tested in 6 M KOH electrolyte. The specific capacitance was found to be dramatically increased with decreasing flakes size (9.5 and 4.5 mF/cm2 for 0.26 and 0.98 µm flakes size, respectively). Conclusion: These findings recommend that MoS2 can be the excellent electrode material for supercapacitor.