These expensive metal-based catalysts cannot be used on an industrial scale because even though the catalytic poisoning is minimal, the degradation process is not economically viable. Polyethylene has been degraded to useful products by heat treatment at relatively low temperatures, though in this case, Re and Pt-based expensive catalysts have been used.
Mechanical degradation of polyethylene can also be useful but it produces microparticles that contribute to soil and water pollution. Although this is the most commonly used method for waste PE degradation, it can produce harmful gases and VOCs.
Thermal degradation is being used at an industrial scale to degrade PE to obtain useful organic products, but this process requires high temperatures (typically > 400 ☌) which consume a lot of thermal energy. PE degradation can take various routes, e.g., biotic, thermal, chemical, pyrolysis or plasma degradation. ĭegradation of PE is not only a matter of interest because of its ecological impact, but it is also economically beneficial because it generates fuels and useful chemical products. Ingestion of MPs can lead to false satiation, causing biological harm such as clogging or abrasion of the digestive tract and reducing feeding rates. MPs have been found in many small soil invertebrates, such as snails and nematodes, and are transferred to the food chain. In addition, MPs can absorb organic pollutants and heavy metals owing to their large specific surface area. MPs can also cause soil pollution by changing the bulk density and water holding capacity and degrading organic matter in the soil, which leads to abnormal plant growth. Human consumption of MPs through water and food is estimated to range from 203 to 332 particles per person per day.
Microplastics (MPs) may cause growth inhibition, oxidative damage and immune stress furthermore, when accumulated in marine organisms, they may move through the food chain to the higher trophic levels (e.g., humans). Microplastics (1 μm–5 mm) and nanoplastics (1–1000 nm) are continues source of danger for aquatic organisms and have gained scientific and public attention worldwide. It has recently been estimated that because of the huge industrial growth in China and fellow Asian countries, plastic waste generation has tripled from 2005 to 2020. Total global PE waste generation is expected to increase up to 900 million tonnes per year by the end of this decade. Polyethylene (PE) waste has inflicted adverse impacts on land and water and is one of the most important challenges to be solved for a green and clean Earth. Poor shielding effect, smaller atomic size and greater ionization energy made Ga a stronger Lewis acid compared to Al hence, Ga-doped γ-Al 2O 3 catalyzed the degradation process even more effectively. Lewis acid (Al) and Lewis base (oxygen) in the γ-Al 2O 3 induced ionic character of the C-C bond chain, which led to the efficient cracking of the C-C bond. γ-Al 2O 3 nanorods effectively catalyzed the degradation process by enhancing the C-C chain length in the products. FT-IR analysis further confirmed the presence of carboxylic acid derivatives and double bonds in the degradation products. In the trace amount of wax, complicated carboxylic acids and hydrocarbons with carbon number C-22 to C-58 were also identified. ESI-MS analysis revealed that mixed oil consisted of low carbon number hydrocarbons and their derivatives of carboxylic acids, with the carbon number ranging from C-6 to C-18.
#Ionic character series
A series of reactions resulted in cracking, dehydrogenation and oxidation, hence producing polycarboxylic acids and saturated and unsaturated hydrocarbons. Finally, it was converted to a mixture of the precursors of gasoline and diesel oil with a trace amount of wax. Our study mainly describes the cleavage of C-C and C-H bonds when polyethylene (dispersed in 1-octadecene) was low-temperature heat-treated in two steps, at 180 and 250 ☌, for 24 h for each step. Polyethylene degradation has a significant ecological impact but is also economically beneficial because it generates fuels and useful chemical products.
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