Dissolved organic matter derived from biodegradable microplastic promotes photo-aging of coexisting microplastics and alters microbial metabolism.

Dissolved organic matter (DOM) leaching from biodegradable microplastics (BMPs) and its characteristics and corresponding environmental implication are rarely investigated. In this study, the main component of DOM leachate from the two BMPs (polyadipate/butylene terephthalate (PBAT)/polycaprolactone (PCL)) was verified by using excitation-emission matrix-parallel factor analysis (EEM-PARAFAC). The PBAT-DOM (PBOM) was aromatized and terrestrial. Comparatively, PCL-DOM (PLOM) had low molecular weight. PBOM contained protein-like components while PLOM contained tryptophan and tyrosine components. Interestingly, both PBOM and PLOM could accelerate the decomposition and oxidation of coexisting polystyrene (PS) under light irradiation. Further, the difference in composition and the properties of BMPs-DOM significantly affected its photochemical activity. The high territoriality and protein-like component of PBOM significantly promoted the generation of 1O2 and O2•-, which caused faster disruptions to the backbone of PS. Simultaneously, the microbial community's richness, diversity, and metabolism were obviously improved under the combined pressure of aged PS and BMPs-DOM. This study threw light on the overlooked contribution of DOM derived from BMPs in the aging process of NMPs and their impact on the microbial community and provided a promising strategy for better understanding of combined MPs' fate and environmental risk.

Fast cost-effective synthesis of metal ions/biopolymer/silica composites by supramolecular hydrogels crosslink with superior tetracycline sorption performance.

In this study, a fast one-pot method was developed for the preparation of Cu/CS/Si ternary composites, which can efficiently remove antibiotic tetracycline from aqueous solutions. Our results demonstrated that the Cu and its content in the composites played a significant role in determining the physical properties and internal morphology of the Cu/CS/Si composites, which subsequently affected the efficiency of the composites for the sorptive removal of tetracycline. Among the studied composites, Cu3-CS2-Si materials had the largest sorption capacity for tetracycline (1076.7 mg/g) with a fast sorption kinetics (>99% in 30 min) under a broad working pH range (5-10). The results from the batch sorption experiments, together with spectroscopic and microscopic analyses, collectively indicated that Cu-tetracycline inner-sphere surface complexation through Cu-O bond was responsible for the tetracycline sorption on Cu3-CS2-Si. In addition, the Cu3-CS2-Si showed an excellent reusability in removing tetracycline. The desired sorption and reuse properties, coupled with the facile and cost-effective synthesis method, indicated that Cu/CS/Si composites have a promising potential for the efficient removal of tetracycline from contaminated solutions.

Degradation mechanism of magnesium alloy stent under simulated human micro-stress environment.

In this study, a vascular stent made of WE43 magnesium alloy was used as a research object and placed in a special physical simulation device constructed independently. This device provided a platform for the study of the degradation of the stent in a dynamic environment. The simulated body fluid of Hank's buffered salt solution flowing inside it would not only make the stent corroded but also apply cyclic shear stress to it, which get closer to the micro-stress environment in human blood vessels. In addition, by means of computer numerical simulation software, ANSYS Fluent 15.0, the fluid-structure interaction (FSI) model was established to simulate the wall shear stress (WSS) exerted by the flowing blood on stent in the blood vessel. Combined with the results of numerical simulation and physical simulation experiments, the degradation mechanism of magnesium alloy sent in an environment similar to the human blood vessels was studied.