Influence of Montmorillonite and Clinoptilolite on the Properties of Starch/Minerals Biocomposites and Their Effect on A

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ORIGINAL PAPER

Influence of Montmorillonite and Clinoptilolite on the Properties of Starch/Minerals Biocomposites and Their Effect on Aquatic Environments Lilian Cristina Soares Silva1 · Raquel Vieira Busto1 · Paulo Henrique Camani1 · Leonardo Zanata1 · Lucia Helena Gomes Coelho1 · Roseli Frederigi Benassi1 · Derval dos Santos Rosa1 

© Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract This work has analyzed the properties of thermoplastic starch (TPS)-minerals biocomposites and their degradation on water bodies. The TPS-minerals biocomposites were prepared from cassava peels, residual glycerin, and minerals [montmorillonite (MMT) and clinoptilolite (CLI)]. The TPS and TPS-minerals biocomposites were characterized by scanning electron microscopy (SEM), tensile tests, and contact angle measurements. Moreover, microcosm degradation tests evaluated the release of dissolved organic carbon content (DOC) and total nitrogen (TN), carbon/nitrogen ratio (C/N), and heterotrophic bacteria count (HBC) in order to simulate the environmental effects of these biocomposites disposal. The SEM results showed the appearance of whole starch grains in TPS, which is an indicative of a partial thermo-plasticization. Furthermore, it was observed a surface roughness in all samples, with a possible better dispersion of mineral particles for TPS-MMT. This fact indicates an improvement of the tensile strength and elongation at break, when compared to the TPS-CLI. Both TPS-MMT and TPS-CLI presented lower contact angle values than TPS. These characteristics may assist in the microorganism access to the surface, favoring the degradation and the release of carbon and nitrogen. Microcosm degradation tests revealed an increase in DOC release from 18 to 98 mg ­L−1 for TPS-CLI after 24 h. Besides, there was an increase in TN release to 200% for TPS-MMT and TPS and 500% for TPS-CLI. The HBC presented a high growth after 12 h of contact, especially for TPS (3.4 ± 0.2 log CFU ­mL−1). Therefore, the TPS-minerals (clinoptilolite/montmorillonite) promoted better surface properties to the biocomposites, by making them biodegradable on aquatic environments, without unbalancing the nutrient loads among different environmental compartments. Keywords  Degradation · Dissolved organic carbon · Microcosm · Total nitrogen · TPS-minerals biocomposites

Introduction In the last 50 years, polymers from non-renewable sources (synthetic polymers) have sharply increased their applications due to the high performance and the versatility they present [1]. However, these synthetic polymers have handicaps, such as non–biodegradability and improper disposal in the post-consumer waste [2]. The extensive application of plastic derived from fossil fuel has risen to a point of huge * Derval dos Santos Rosa [email protected]; [email protected] 1



Center for Engineering, Modeling and Applied Social Sciences (CECS), Federal University of ABC (UFABC), Santo André, São Paulo, Brazil

waste production problems, causing environmental pollution