Effect of Ultraviolet Irradiation on Polystyrene Containing Cephalexin Schiff Bases

Photo-induced leaching behaviors and biodegradability of dissolved organic matter from microplastics and terrestrial-sourced particles

Recent studies have increasingly focused on the occurrence of plastic leachate and its impacts on aquatic ecosystems. Nonetheless, the environmental fate of this leachate in the presence of abundant natural organic matter (NOM)-a typical scenario in environments contaminated with plastics-remains underexplored. This study investigates the photo-induced leaching behaviors of dissolved organic matter (DOM) from terrestrial-sourced particles (forest soil and leaf litter) and microplastics (MPs), specifically polystyrene (PS) and polyvinyl chloride (PVC), over a two-week period. We also examined the biodegradability and spectroscopic characteristics of the leached DOM from both sources. Our results reveal that DOM from microplastics (MP-DOM) demonstrates more persistent leaching behavior compared to terrestrial-derived DOM, even with lesser quantities per unit of organic carbon. UV irradiation was found to enhance DOM leaching across all particle types. However, the photo-induced leaching behaviors of fluorescent components varied with the particle type. The MP group exhibited a broader range and higher biodegradability (ranging from 19.7% to 61.6%) compared to the terrestrial-sourced particles (ranging from 3.7% to 16.5%). DOM leached under UV irradiation consistently showed higher biodegradability than that under dark conditions. Furthermore, several fluorescence characteristics of DOM, such as the protein/phenol-like component (%C2), terrestrial humic-like component (%C3), and humification index (HIX)-traditionally used to indicate the biodegradability of natural organic matter-were also effective in assessing MP-DOM (with correlation coefficients R2 = 0.6055 (p = 0.003), R2 = 0.5389 (p = 0.007), and R2 = 0.4640 (p = 0.015), respectively). This study provides new insights into the potential differences in environmental fate between MP-DOM and NOM in aquatic environments heavily contaminated with MPs.

Biodegradation of polystyrene by intestinal symbiotic bacteria isolated from mealworms, the larvae of Tenebrio molitor

Objectives

Polystyrene is a plastic that leads to environmental pollution. In particular, expanded polystyrene is very light and takes up much space, causing additional environmental problems. The aim of this study was to isolate new symbiotic bacteria which degraded polystyrene from mealworms.

Methods

The population of polystyrene degrading bacteria was increased by enrichment culture of intestinal bacteria from mealworms with polystyrene as a sole carbon source. The degradation activity of isolated bacteria was evaluated by morphological change of micro-polystyrene particles and the surface change of polystyrene films.

Results

Eight isolated species (Acinetobacter septicus, Agrobacterium tumefaciens, Klebsiella grimontii, Pseudomonas multiresinivorans, Pseudomonas nitroreducens, Pseudomonas plecoglossicida, Serratia marcescens, and Yokenella regensburgei) were identified that degrade polystyrene.

Conclusion

Bacterial identification shows that a broad spectrum of bacteria decomposing polystyrene coexists in the intestinal tract of mealworms.

Fabrication of Highly Photostable Polystyrene Films Embedded with Organometallic Complexes

Polystyrene is a common thermoplastic and is produced in different shapes and forms. The scale of manufacture of polystyrene has grown over the years because of its numerous applications and low cost of production. However, it is flammable, brittle, has low resistance to chemicals, and is susceptible to photodegradation on exposure to ultraviolet radiation. There is therefore scope to improve the properties of polystyrene and to extend its useful lifetime. The current work reports the synthesis of organometallic complexes and investigates their use as photostabilizers for polystyrene. The reaction of excess ibuprofen sodium salt and appropriate metal chlorides in boiling methanol gave the corresponding complexes excellent yields. The organometallic complexes (0.5% by weight) were added to polystyrene and homogenous thin films were made. The polystyrene films blended with metal complexes were irradiated with ultraviolet light for extended periods of time and the stabilizing effects of the additives were assessed. The infrared spectroscopy, weight loss, depression in molecular weight, and surface morphology of the irradiated blends containing organometallic complexes were investigated. All the synthesized organometallic complexes acted as photostabilizers for polystyrene. The damage (e.g., formation of small polymeric fragments, decrease in weight and molecular weight, and irregularities in the surface) that took place in the polystyrene blends was much lower in comparison to the pure polystyrene film. The manganese-containing complex was very effective in stabilizing polystyrene and was superior to cobalt and nickel complexes.

Modifications of Polymers through the Addition of Ultraviolet Absorbers to Reduce the Aging Effect of Accelerated and Natural Irradiation

The photooxidative degradation process of plastics caused by ultraviolet irradiation leads to bond breaking, crosslinking, the elimination of volatiles, formation of free radicals, and decreases in weight and molecular weight. Photodegradation deteriorates both the mechanical and physical properties of plastics and affects their predicted life use, in particular for applications in harsh environments. Plastics have many benefits, while on the other hand, they have numerous disadvantages, such as photodegradation and photooxidation in harsh environments and the release of toxic substances due to the leaching of some components, which have a negative effect on living organisms. Therefore, attention is paid to the design and use of safe, plastic, ultraviolet stabilizers that do not pose a danger to the environment if released. Plastic ultraviolet photostabilizers act as efficient light screeners (absorbers or pigments), excited-state deactivators (quenchers), hydroperoxide decomposers, and radical scavengers. Ultraviolet absorbers are cheap to produce, can be used in low concentrations, mix well with polymers to produce a homogenous matrix, and do not alter the color of polymers. Recently, polyphosphates, Schiff bases, and organometallic complexes were synthesized and used as potential ultraviolet absorbers for polymeric materials. They reduced the damage caused by accelerated and natural ultraviolet aging, which was confirmed by inspecting the surface morphology of irradiated polymeric films. For example, atomic force microscopy revealed that the roughness factor of polymers' irradiated surfaces was improved significantly in the presence of ultraviolet absorbers. In addition, the investigation of the surface of irradiated polymers using scanning electron microscopy showed a high degree of homogeneity and the appearance of pores that were different in size and shape. The current work surveys for the first time the use of newly synthesized, ultraviolet absorbers as additives to enhance the photostability of polymeric materials and, in particular, polyvinyl chloride and polystyrene, based mainly on our own recent work in the field.