Mohannad Mayyas

Preliminary investigation on the thermal conversion of automotive shredder residue into value-added products: Graphitic carbon and nano-ceramics

Large increasing production volumes of automotive shredder residue (ASR) and its hazardous content have raised concerns worldwide. ASR has a desirable calorific value, making its pyrolysis a possible, environmentally friendly and economically viable solution. The present work focuses on the pyrolysis of ASR at temperatures between 950 and 1550°C. Despite the high temperatures, the energy consumption can be minimized as the decomposition of ASR can be completed within a short time. In this study, the composition of ASR was investigated. ASR was found to contain about 3% Ti and plastics of high calorific value such as polypropylene, polyethylene, polycarbonate and polyurethane. Based on thermogravimetric analysis (TGA) of ASR, the non-isothermal degradation kinetic parameters were determined using Coats-Redferns and Freeman and Carroll methods. The evolved gas analysis indicated that the CH4 was consumed by the reduction of some oxides in ASR. The reduction reactions and the presence of Ti, silicates, C and N in ASR at 1550°C favor the formation of specific ceramics such as TiN and SiC. The presence of nano-ceramics along with a highly-crystalline graphitic carbon in the pyrolysis residues obtained at 1550°C was confirmed by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Raman imaging microscope (RIM) analyses.

Nitrogen-doped porous carbon foams prepared from mesophase pitch through graphitic carbon nitride nanosheet templates

A scalable and facile method was developed to synthesize nitrogen-doped porous carbon foams (NDPCFs) using graphitic carbon nitride (g-C3N4) nanosheets as hard templates through the calcination of mesophase pitch. The morphology, structure, chemical composition and electrochemical performance of the as-prepared NDPCFs were characterized and investigated. The results show that NDPCFs are fabricated from crimpled and folded carbon nanosheets and have a three-dimensional interconnected structure. The carbon nanosheets show a certain degree of orientation of graphite crystallites. The specific surface area, wall thickness and nitrogen content are controllable by tuning the mass ratio of g-C3N4 nanosheets to mesophase pitch. The content of nitrogen species, most of which are quaternary-N and pyridinic-N components, significantly decreases from 6.48 to 0.74 at% with raising calcination temperature from 800 to 1600 °C. The NDPCFs prepared at 800 °C have a high specific surface area of 2098 m2 g−1, an ultra-large pore volume of 5.048 cm3 g−1 and a high nitrogen content of 6.48 at%. Furthermore, this material exhibits remarkable electrochemical performance as an electrode material for supercapacitors with a specific capacitance of 125.6 F g−1 even at a high scan rate of 200 mV s−1.

Growth mechanism of ceria nanorods by precipitation at room temperature and morphology-dependent photocatalytic performance

Ceria (CeO2) nanorods have been prepared by simple short-term precipitation at room temperature for the first time using aqueous solutions based on Ce(NO3)3·6H2O and NaOH. TEM showed that (a) the two solutions alone yielded nanooctahedra of cross section ∼10 nm and (b) selective surface modification by isopropanol (IPA) played a significant role in the morphological development of approximately square nanorods of dimensions 4–5 nm width, 15–25 nm length, and [110] growth direction. DFT was used to assess surface energies and the interactions of the H2O and IPA molecules with the {111}, {110}, and {100} ceria surfaces. A growth mechanism on the basis of these adsorption energies and orientations is proposed and it depends on the favorable IPA adsorption energy. Its effect is twofold. First, it facilitates the formation of a {110} prism that alters the morphology from octahedral to spheroidal and then cuboidal. Second, the anisotropic electrostatic field in the electrical double layer, which is established by the oriented adsorption of the IPA molecule, is considered to facilitate the growth of the nanorod morphology. XPS data show that nanorods exhibit a greater concentration of Ce3+ (and associated oxygen vacancies) than do the nanooctahedra. The parameters determining the development of nanoparticle morphology are ranked in the order: packing density ≈ lattice spacing > IPA adsorption > H2O adsorption > surface energy. The present work suggests the applicability of crystallography considerations and DFT modeling to direct the crystal growth of specific morphologies.

Growth of NiO nanorods, SiC nanowires and monolayer graphene via a CVD method

Green approaches for producing high purity advanced materials have always been a challenging task. Conventional methods for converting waste materials into char by heat treatment can have limitations in making defect free and pure materials for practical applications. Herein, we report a Green-Chemical Vapor Deposition (G-CVD) method to transform waste into functional materials in various forms by condensation of gases generated from waste on a chosen substrate. The flow of gases, mainly CO2, CH4 and CO, can be controlled via a regulated flow of a carrier gas and by controlling the temperature, gases can react/recombine on the substrate forming a crystalline lattice of semiconducting materials. Such a versatile green method can be sustainable and at the same time help in reducing the burden of landfill waste. We present how an appropriate control of the gas mixture resulting from the heat-treatment of waste rubber tyres and plastics leads to the growth of various types of functional materials on substrates. The growth mechanism of materials on substrates in this method is similar to the conventional CVD method. However, the utilization of waste to generate these gases adds the green and sustainable feature to this method and its high degree of reproducibility offers practical applicability. Once established for NiO nanorods, we tested the versatility of this technique to grow SiC nanowires, SiC nanoparticles and monolayer graphene. This highly reproducible G-CVD method of making advanced materials solely involves waste materials as the solid carbon source at atmospheric pressure without any other synthetic reagents.

Characterization of Volatiles in Coal Tar Pitch by Gas Chromatography/Mass Spectrometry and Atmospheric Pressure Solid Analysis Probe/Time of Flight-Mass Spectrometry

Volatiles obtained by heating carbon disulfide-extractable portions from coal tar pitch were characterized by gas chromatography/mass spectrometry (GC/MS) and atmospheric pressure solid analysis probe/time of flight-mass spectrometry (ASAP/TOF-MS). The results show that the maximum yield of volatiles was obtained at temperatures from 200 to 300°C. In total, ninety-one compounds were identified by GC/MS, including fifty-eight condensed arenes, nineteen oxygen-containing compounds, thirteen nitrogen-containing compounds, and a sulfur-containing compound. The total relative content of the heteroatom-containing compounds decreased with rising temperature, whereas the content of the condensed arenes increased. According to ASAP/TOF-MS analysis, the molecular masses of the volatiles released at temperatures of 30 to 200°C, 200 to 300°C, and 300 to 410°C are between 110 and 260, 150 and 350, and 280 and 420 u, respectively. ASAP/TOF-MS was shown to be an effective tool for characterizing high-molecular weight species that are difficult to be determined by GC/MS analysis.

Nano-carbons from waste tyre rubber: An insight into structure and morphology

This study reports on the novel and sustainable synthesis of high value carbon nanoparticles (CNPs) from waste tyre rubber (WTR), using an innovative high temperature approach. As waste tyres are composed, primarily, of carbon - accounting for some 81.2wt% - they represent a promising source of carbon for many potential applications. However, cost-effective options for their processing are limited and, consequently, billions of waste tyres have accumulated in landfills and stockpiles, posing a serious global environmental threat. The rapid, high temperature transformation of low value WTR to produce valuable CNPs, reported here, addresses this challenge. In this study, the transformation of WTRs was carried out at 1550°C over different reaction times (5s to 20min). The structure and morphology of the resulting CNPs were investigated using X-ray diffraction (XRD), Raman spectroscopy, X-ray photon spectroscopy (XPS), N2 isothermal adsorption method and scanning electron microscopy (SEM). The formation of CNPs with diameters of 30 and 40nm was confirmed by Field Emission Electron Microscopy (FE-SEM). Longer heating times also resulted in CNPs with regular and uniform spherical shapes and a specific surface area of up to 117.7m2/g, after 20min. A mechanism that describes the formation of CNPs through mesophase nuclei intermediate is suggested.

Planar-dependent oxygen vacancy concentrations in photocatalytic CeO2 nanoparticles

The present work reports the rapid preparation of CeO2 nanorods by surfactant-free precipitation for the first time, which initiates a strategy for the quantitative elucidation of the importance of the exposed crystallographic planes and the oxygen vacancy concentrations of different morphologies of nanoceria. These relations are revealed through comparison of the relative surface areas of the exposed crystallographic planes. The precipitation temperature was critical in that nanooctahedra formed at the three lower temperatures and nanorods formed at the highest. The key feature to differentiate the photocatalytic performance was the morphology that the nanorods exhibit ∼200% superior performance compared to those of the nanooctahedra. The principal reason for this is the presence of exposed {110} planes in the nanorods, which are not present in nanoctahedra. This crystallographic dependence of the improved performance of the nanorods is attributed directly to the greater oxygen vacancy concentration for the calculated surface area of this morphology.

Application of High-Resolution NMR and GC–MS to Study Hydrocarbon Oils Derived from Noncatalytic Thermal Transformation of e-Waste Plastics

The increases in the volumes of electronic waste have become an aggravating environmental, economic, and social health issue in recent times. This study investigates the conversion of e-waste plastics into hydrocarbon oils via noncatalytic thermal transformation followed by an in-depth characterization of these oils using diverse analytical techniques such as gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In particular, NMR spectroscopy is a key analytical tool utilized in this study to gain a comprehensive insight into the chemical nature of the resultant oils along with a semiquantitative investigation of the changes in their composition over a temperature range of 800–1200 °C. The one-dimensional (1D) 1H and two-dimensional (2D) heteronuclear single-quantum correlation spectra were acquired for the oils, wherein the 2D NMR spectrum provided improved resolution of peaks to address the overlaps encountered in the 1D spectrum. The experimental results obtained from GC–MS, FTIR spectroscopy, and NMR spectroscopy were found to align well with each other. The oils produced in this study have a high calorific value of 38.27 MJ/kg and thus may find use in several applications. A detailed mechanism for the thermal degradation of styrene acrylonitrile plastics and the formation of major products is elucidated in this study.