Jafar Fathi

Landfilling remains the dominant waste disposal method worldwide, particularly in developing countries, posing serious environmental, health, and climate challenges. Inefficient practices, weak regulations, and un-engineered sites contribute to massive greenhouse gas (GHG) emissions and resource loss. Transitioning to a circular economy (CE) offers a transformative path for sustainable waste management. By closing material loops, recovering energy, urban mining, controlling emissions and CE strategies can convert traditional landfills into eco-efficient systems. The integration of artificial intelligence (AI) further enhances this transition, enabling real-time monitoring, predictive management, and optimized resource recovery, thereby maximizing environmental and economic benefits. This review presents a three-level CE framework at micro (individual organizations), meso (industrial networks), and macro (national and international) levels designed to extract maximum value from waste streams and mitigate climate impacts. The proposed strategies demonstrate the potential to drastically reduce GHG emissions, promote clean energy via waste-to-energy routes, and contribute to SDGs 7, 11, 12, 13 and 15. By combining technology, innovation, and strategic management, this work highlights how AI-driven CE approaches can transform landfills from environmental liabilities into engines of sustainability and climate action. In implementing CE strategies at various levels, various challenges including technological, socio-economic, ethical, policy-based, and unintended consequences are encountered which impact sustainability initiatives. This review comprehensively discusses challenges associated with CE implementation and identifies technological advancement, social awareness and data-driven AI/ML-based modeling which could ensure success in circularity and ultimately curb climate change impacts in the long term.

In this study, a high-power 915 MHz air microwave atmospheric-pressure plasma torch with input power up to 100 kW was investigated using optical emission spectroscopy (OES) and imaging characterization. Emission spectra were acquired from both the post-core plasma region and directly from the plasma core inside the resonator through an axial rear-view access. Molecular emission bands of OH, NO, and N₂ were identified in the UV region, while strong broadband continuous radiation dominated the visible and near infrared wavelengths, with intensity increasing systematically with power. Front-view imaging revealed significant changes in the spatial emission structure of the plasma core as a function of tangential gas flow and input power, including transitions between volume-filling and ring-shaped radiation patterns. The formation of an annular emission region was promoted by increased tangential flow and intermediate power levels, whereas lower flow rates or sufficiently high power resulted in a more homogeneous luminous zone. Side-view post-core microwave plasma OES measurements, combined with fitting to a temperature dependent simulated spectrum based on the OH transition band (X ² Π → A ² Σ ⁺ ), yielded a post core plasma temperature of approximately 4100 K. By smoothing the continuous radiation spectrum and assuming approximate black body behavior, Wien’s displacement law was applied to estimate the maximum plasma core temperature, yielding a value in the range of 5520–5750 K. The combined spectroscopic and imaging results provide insight into the excitation behavior, thermal characteristics, and spatial structure of high-power 915 MHz microwave air plasmas.

The development of efficient and sustainable materials for water remediation is essential to address the growing contamination of aquatic environments by potentially toxic metal(loid)s, while simultaneously reducing the environmental impact of material synthesis. In this work, carbon nanotubes-nano zerovalent iron (CNTs-nZVI) composites were produced via methane Plasma-Catalytic pyrolysis, a single-step, electrified, and solvent-free process that simultaneously converts methane into syngas and carbon nanomaterials. Produced syngas contained 79.6 ±3.7 vol.% hydrogen, 19.9 ±3.9 vol.% carbon monoxide, and 0.5 ±0.2 vol.% methane, which confirms more than 99% conversion. The CNTs-nZVI composite structure, consisting of single-walled CNTs and core-shell, iron-carbon nanoparticles with a metallic iron core, was confirmed by comprehensive microstructural, chemical, and textural characterization using TEM, STEM, EDS, BET, XRD, STA, XPS, and Raman spectroscopy. The remediation performance of the CNTs-nZVI composite was evaluated with nine metal(loid)s in water. The as-synthesized material showed rapid and highly selective removal of Pb(II) exceeding 96% within 24 hours. Thermal activation at 450 °C significantly enhanced long-term adsorption, achieving removal efficiencies of approximately 55% for Cr(VI) and Cu(II) and ~30% Cd(II) and As(V) after 48 days. Thermal activation also completely eliminates the volatile organic compounds present in as-synthesized CNTs-nZVI, as confirmed by GC-MS analysis. These results demonstrate the potential of the plasma-catalytic pyrolysis process to valorize methane and iron oxide into hydrogen-rich syngas and CNTs-nZVI composites, which can be used as sustainable water-treatment materials.

Synthesis of small-diameter (ca. 1 nm) single-walled carbon nanotubes (SWCNTs) is rare due to the difficulty in establishing appropriate catalysts and environments that favor the generation of such species. However, because of their auspicious and structure-tunable electrical and optical properties, this goal remains at the focal point of numerous researchers. The development of a low-cost technique to create such materials could eliminate the main bottleneck hindering their widespread application. In this work, this objective was ultimately achieved by means of the Plasma-Catalytic Pyrolysis (PCP) process. The application of a DC water-stabilized plasma hybrid (WSP-H) torch within an entrained-flow reactor facilitated the breakdown of methane in the presence of an FeO micropowder (50 µm) catalyst. Consequently, high-quality SWCNTs and hydrogen were produced at a relatively large scale. Characterization of the resulting SWCNTs by microscopy and spectroscopy confirmed that the produced SWCNTs exhibited a large degree of structural perfection.