Study of a liquid soap containing polyethylene microspheres: characterization, quantification, separation and use of Acrocomia aculeata (macaúba) as an alternative abrasive

, De Freitas Raí, Dias Ribeiro Bernardo, Viana Marcelo Mendes.

Microplastics are particles smaller than 5 mm and larger than 1 μm, which became a global alarm only at the end of the 20th century. Due to the increased public and governmental awareness of several countries, microplastics have found restrictions, and new biodegradable alternatives are being suggested for their replacement. As a way to better understand and assist future studies on the subject, this work aims to seek and raise data regarding an industrial liquid soap that contains polyethylene microspheres in its composition, generically called L̈̈, which is used by an aeronautical engine repair company. According to the analyses carried out, it was found that the microplastics resemble microfragments with an average length of 195.2 ± 100.9 μm and an average density of 0.9416 ± 0.0004 g/cm3, being classified as high-density polyethylene (HDPE). By gravimetry, the presence of 4.90% w/w of microplastics was determined in the liquid soap L̈̈. Centrifugation and membrane filtration processes (porosity of 0.2 μm) were also performed to separate the microplastics from the soap, confirming the filtration method as the most efficient, which was visually verified by SEM and confirmed by thermal analysis due to the absence of PE fusion. By comparison of the liquid soap L̈ẅith another liquid industrial soap, generically called Ä̈, it was found that the first one had an effective COD higher than the second soap, impacting more on the aquatic environment. Moreover, by adding macaúba to the filtered liquid soap L̈̈, a soap with 0.53% of renewable carbon was produced, which differentiates it from the conventional liquid soap L̈̈, which has 4.20% of non-renewable carbon, coming from the polyethylene microspheres, which persist, slowly degrade in the environment and are vectors of pollutants.

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