Biomicroplastics versus conventional microplastics: An insight on the toxicity of these polymers in dragonfly larvae

The toxicological safety of products developed as alternative for conventional plastics (i.e., petroleum derivatives) inevitably demands conducting (eco)toxicological studies. Thus, the aim of the current study was to evaluate the biochemical toxicity of polyethylene microplastics (PE MPs) (representative of conventional MPs) and polylactic acid biomicroplastics (PLA BioMPs) in Aphylla williamsoni larvae used as experimental models. Animals subjected to short exposure to both pollutants (48 h), at environmentally relevant concentration (6 mg/L). At the end of the experiment, different toxicity biomarkers were evaluated. To assess the possible impact of pollutants on the nutritional status of the animals, the total protein, total soluble carbohydrate and triglyceride levels were determined. However, we did not observe differences between the groups, which suggests that PE MPs and PLA BioMPs did not affect the animals' energy metabolism, inducing them to a nutritional deficit. However, larvae exposed to PLA BioMPs have shown increased nitrite and lipid peroxidation levels, which supports the hypothesis that these pollutants increase oxidative stress processes in the animals evaluated, which can affect the animals' physiological homeostasis from different changes. In addition, the decrease in superoxide dismutase activity and of total thiols levels, in these same animals, is suggestive of the impact of PLA BioMPs on the antioxidant defenses, causing a REDOX imbalance, never before reported. On the other hand, decreased AChE activity was only observed in larvae exposed to PLA BioMPs, which demonstrates the anticholinergic activity of the tested polymers; the consequences of which include changes in different neurophysiological functions. Thus, the current study has helped improving the scientific knowledge about impacts caused by PLA BioMPs on freshwater ecosystems, as well as corroborated assertions about the risks posed by such biopolymers on these environments.

Preparation of Biocomposite Material with Superhydrophobic Surface by Reinforcing Waste Polypropylene with Sisal (Agave sisalana) Fibers

Nowadays, eco-friendly, renewable, and biodegradable biocomposites are among the most intensely sought materials of choice. Biocomposites have been widely used as substitutes for plastics due to their biodegradability. However, biocomposite materials absorb water and ultimately loss mechanical properties that affect service life. In this work, a biocomposite material with superhydrophobic surface was prepared by reinforcing waste polypropylene with sisal (Agave sisalana) fibers. The biocomposite was prepared by mixing waste polypropylene and sisal fiber with 5%, 10%, 15%, and 20% fiber loading. Based on characterization results, the composite with 15% fiber content is considered as optimum ratio. Physicochemical properties of composites were evaluated using standard American Society of Testing Materials including biodegradability test and chemical resistance test. The biodegradability of the composite before surface modification was determined by calculating weight loss and found to be 0.11%, 4.62%, 7.15%, and 10.97% for 0%, 5%, 10%, and 15% fiber loadings, and their tensile strength was $10.25\pm 0.05$ , $14.47\pm 0.02$ , $14.48\pm 0.02$ , and $19.90\pm 0.09\text{MPa}$ for 0%, 5%, 10%, and 15% fiber content, respectively. The surface of the composite was modified for hydrophobicity by etching the surface with chromic acid followed by treating with stearic acid. The FTIR and the SEM images of unmodified and modified (superhydrophobic) surface of composites clearly state the significant difference in chemical composition and surface structure, respectively. The superhydrophobicity of the surface-modified biocomposite was defined by its self-cleaning and low wet ability properties.

Regeneration and Recovery of Plastics

Plastics are the most essential commodities in the world and are replacing the metals, wood, glass, cements and other materials in some application areas. Plastics are easy handling, resource-saving, non-toxic with esthetically attractive. Oil and gas are the major feedstocks for plastics, besides sugar and corn as renewable feedstocks. Plastics represent a serious waste-handling problem, with only 10%–12% of the plastic waste generated worldwide being regenerated/recycled. After disposal, plastic waste takes very long time to decompose naturally and impact the environment during the degradation process. The above situation has necessitated the invention of efficient technologies for regeneration and recovery of plastics all over the world.