Search

Biodegradable plastics (BPs) are widely used as alternatives to non-BPs due to their inherent ability to undergo facile degradation. However, the ecotoxicological impact of biodegradable microplastics (MPs) rarely remains scientific documented especially to aquatic ecosystem and organisms compared to conventional microplastics. Therefore, this study aimed to investigate the ecotoxicity of biodegradable polylactic acid (PLA) MPs to Daphnia magna with that of conventional polyethylene (PE) MPs with and without ultraviolet (UV) treatment (4 weeks). The acute toxicity (48 h) of PLA MPs was significantly higher than that of PE MPs, potentially attributable to their elevated bioconcentration resulting from their higher density. UV treatment notably reduced the particle size of PLA MPs and induced new hydrophilic functional groups containing oxygen. Thus, the acute lethal toxicity of PLA MPs exhibited noteworthy increase, compared to before UV treatment after UV treatment, which was greater than that of UV-PE MPs. In addition, UV-PLA MPs showed markedly elevated reactive oxygen species concentration in D. magna compared to positive control. However, there was no significant increase in the level of lipid peroxidation, possibly due to successful defense by antioxidant enzymes (superoxide dismutase and catalase). These findings highlight the ecotoxicological risks of biodegradable MPs to aquatic organisms, which require comprehensive long-term studies.

In this study, we synthesized La-incorporated O-rich defective MoS2 nanosheets by a simple, inexpensive, in situ hydrothermal reaction to self-exfoliate the bulky MoS2 layers themselves so that they can readily trap hard base anions, arsenic (arsenite and arsenate), from water. Attempting to modify MoS2 surfaces by incorporating O allows for more active sites, which is confirmed by powder XRD patterns where the exfoliated layers have a d-spacing of 0.63 nm, while the spacing for the bulky layers is 0.60 nm. The substitution of La at different equivalent ratios on the interlayer/surface improves the adsorption properties of arsenite and arsenate in simple solutions, as shown by the Langmuir adsorption density values of 0.7760 and 1.4363 mmol g–1, respectively. When the O-rich MoS2 layers were loaded with La, the adsorption densities improved, with La1.0 equiv showing the best values among the materials studied. The presence of O and S was more responsible for the removal of arsenite ions, and La and O, together with a small amount of N, were able to remove arsenate ions from water according to the well-known Pearson's Lewis acid−base principle. The stability of the materials was characterized after the experiments, and it was found that there was no leaching of the materials by ICP-OES and the stability was maintained after 6 regeneration cycles. With the exception of phosphate, which behaves chemically similar to arsenic, the adsorption densities were not significantly affected by the mono- and divalent anions, indicating the selectivity of the prepared materials. The synthesis cost of MoOxS2–x was 2 times lower than that of bulky MoS2, and its adsorption properties were 10 times higher than those of the latter. The results suggest that La-substituted O-rich MoS2 is a potential candidate for the removal of soft and hard base metals from water. [ABSTRACT FROM AUTHOR]

This research work deals with the defluoridation studies of magnetic iron oxide (Fe3O4) fabricated nano-hydroxyapatite (n-HAp) gelatin (Gel) eco-polymeric composite. The developed hybrid Fe3O4@n-HApGel composite displays a high defluoridation capacity (DC) of 5009 mgF-•kg-1. Batch sorption experiments were performed to find the effect of various influencing parameters such as pH, contact time, competitor co-anions, initial fluoride concentration, and temperature. The structural, surface morphological changes, and elements present in the sorbent were studied using FTIR, XRD, and SEM with EDAX techniques. The equilibrium isotherm study was fitted with Langmuir isotherm model. The thermodynamic parameter values indicate the spontaneous and endothermic nature of fluoride sorption. The proposed mechanism indicates that the enhanced DC of magnetic composite is mainly due to electrostatic adsorption and complexation between fluoride ion and composite in addition to ion-exchange. The regeneration and reusability studies were performed for the effective utilization of the magnetic composite. The performance of Fe3O4@n-HApGel nanocomposite at field conditions was checked with the water sample collected from a nearby fluoride prevalent area. [ABSTRACT FROM AUTHOR]