Waste plastics are non‐degradable constituents that can stay in the environment for centuries. Their large land space consumption is unsafe to humans and animals. Concomitantly, the continuous engineering of plastics, which causes depletion of petroleum, poses another problem since they are petroleum‐based materials. Therefore, energy recovering trough pyrolysis is an innovative and sustainable solution since it can be practiced without liberating toxic gases into the atmosphere. The most commonly used plastics, such as HDPE, LDPE (high‐ and low‐density polyethylene), PP (polypropylene), PS (polystyrene), and, to some extent, PC (polycarbonate), PVC (polyvinyl chloride), and PET (polyethylene terephthalate), are used for fuel oil recovery through this process. The oils which are generated from the wastes showed caloric values almost comparable with conventional fuels. The main aim of the present review is to highlight and summarize the trends of thermal and catalytic pyrolysis of waste plastic into valuable fuel products through manipulating the operational parameters that influence the quality or quantity of the recovered results. The properties and product distribution of the pyrolytic fuels and the depolymerization reaction mechanisms of each plastic and their byproduct composition are also discussed.

Nanotechnology has become a promising and emerging field of research in creating and modifying nanomaterials for different applications. Nanoparticles are considered to be the basic element of nanotechnology as they are the primary source of several nanostructured materials. During the last few decades, several metal oxide nanoparticles (NPs) were synthesized and their applications were investigated in various fields of science and technology, including biomedical, environmental, energy and agricultural practices. Moreover, metal oxide NPs have been synthesized by physical and chemical methods, while the chemical method used different chemicals as reducing and stabilizing agents. However, the wet chemical synthesis strategy become responsible for various biological and environmental risks due to the toxicity of used chemicals. Recently, biological synthesis of metal oxide nanoparticles using plants, algae, and microbes as a source of precursor material has emerged as a green and safe method. Additionally, the green synthesized metal oxide nanoparticles have shown a pivotal role in several applications such as nano-adsorbents, nano-membranes, photocatalysts and disinfection of wastewater from microbes. In this review, we present an overview of the biosynthesis of metal oxide nanoparticles such as; ZnO, CeO 2 , TiO 2 , CdO, CuO, Fe 3 O 4 , SnO 2 , NiO etc. Their method of characterization and properties is also discussed. Finally, their applications towards environmental protection is presented with particular attention to water treatment and remediation.

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Designing and building an ideal catalyst for organic reactions is needed to increase the efficiency, reaction conditions, and to reduce its environmental impacts. The growth of nanotechnology is realized in the production of various nano-level catalysts for different applications. The as-synthesized nanocatalysts are easily manipulated to a desired shape and size with a high surface area to volume ratio, which is their critical property of the interaction of the nanomaterials with the substrates. These days, a vast array of catalysts (nanocatalysts) such as metals, metal oxides, magnetic, and alloyed/mixed nanocatalysts are applied in organic reactions to synthesize important chemicals in industries and pharmaceutical sectors with a high yield, selectivity, and reusability via reduction/hydrogenation, oxidation, condensation, C-C coupling, cyclization, and more. Consequently, this present review highlights the application of various nanocatalysts in organic reactions by combining certain proposed reaction mechanisms that have shown the impact of nanoparticles on the reactions. The factors influencing nanocatalyst performances are also discussed. Finally, the conclusion and future prospects are conveyed.