Risk associated with microplastics in urban aquatic environments: A critical review.

The presence of microplastics (MPs) has been recognized as a significant environmental threat due to adverse effects spanning from molecular level, organism health, ecosystem services to human health and well-being. MPs are complex environmental contaminants as they bind to a wide range of other contaminants. MPs associated contaminants include toxic chemical substances that are used as additives during the plastic manufacturing process and adsorbed contaminants that co-exist with MPs in aquatic environments. With the transfer between the water column and sediments, and the migration within aquatic systems, such contaminants associated MPs potentially pose high risk to aquatic systems. However, only limited research has been undertaken currently to link the environmental risk associated with MPs occurrence and movement behaviour in aquatic systems. Given the significant environmental risk and current knowledge gaps, this review focuses on the role played by the abundance of different MP species in water and sediment compartments as well as provides the context for assessing and quantifying the multiple risks associated with the occurrence and movement behaviour of different MP types. Based on the review of past literature, it is found that the physicochemical properties of MPs influence the release/sorption of other contaminants and current MPs transport modelling studies have primarily focused on virgin plastics rather than aged plastics. Additionally, risk assessment of contaminants-associated MPs needs significantly more research. This paper consolidates the current state-of-the art knowledge on the source to sink movement behaviour of MPs and methodologies for assessing the risk of different MP species. Moreover, knowledge gaps and emerging trends in the field are also identified for future research endeavours.

Using cellulose, starch and ß-cyclodextrin poly/oligosaccharides as chiral inducers for preparing chiral particles.

Poly/oligosaccharides are renewable natural resources with abundant chirality. Herein, we develop a general route to prepare optically active particles by using poly/oligosaccharides as both chiral inducers and growth templates. By complexing with Cu(NH3)42+ ions, OH groups on C2 and C3 in poly/oligosaccharides can transfer the chirality to Cu(II) and retain it in CuO. At the same time, poly/oligosaccharides direct growth of CuO by in situ transformation of Cu(NH3)42+ ions. Cellulose nanocrystal (CNC) and starch (ST) are used as representative polysaccharides, and ß-cyclodextrin (ß-CD) as a representative oligosaccharide, thus dandelion, duchesnea, and chrysanthemum-like composite particles with chiroptical activity are obtained. Besides, chiral CuO/poly(oligo)saccharide particles (CSP) demonstrate enantioselective ability by differentiating coordination with tryptophan (Trp) enantiomers and form Cu-Trp metal organic framework architectures with different morphologies. The study provides an easily accessible approach to prepare novel functional materials by poly/oligosaccharide-based chiral induction and hold great promise in chiral applications.

Thermal degradation behavior of waste video cards using thermogravimetric analysis and pyrolysis gas chromatography/mass spectrometry techniques.

The thermal degradation characteristics of a printed circuit board assembly (PCBA), specifically video cards from waste computers, was studied using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and thermogravimetric analysis (TGA). The video-card waste was dismantled into substrate, integrated circuits (ICs), and plastic slots for comparable investigation. The results by TGA revealed that the initial temperature at which degradation began was 300 degrees C for substrate, but it was 330 degrees C for ICs and plastic slots. For a given type of scrap, the initial temperature leading to degradation is the same under air and N2 atmosphere. However, the degradation rate was lower using air than N2 during the weight-loss stage. Further Py-GC/MS application revealed that pyrolysis products derived from substrate consisted mainly of acetone, bromotoluene, and phenol that came from the brominated epoxy resins present in substrate. Unlike substrate, the relative amounts of some products (e.g., phenol) were higher in the ICs, and cyclotetrasiloxane was released; these were released from the phenolic resins and Si mixture present in that type of waste. Benzoic acid, rather than acetone or phenol, was the main product released from plastic slots. It was proved that this scrap was a mixture of various polyesters, cracking of which predicatively generated aromatic products. The results will be useful in developing pyrolysis or starved-air incineration systems for thermosetting plastic and PCBA waste and helpful to control pollution during the treatment of this waste.

The recycling of comminuted glass-fiber-reinforced resin from electronic waste.

The reuse of comminuted glass-fiber-reinforced resin with various granularities gathered from printed circuit manufacturing residues was investigated. As fillers, these residues were converted into polymeric composite board by an extrusion and injection process using polypropylene as a bonding agent. The mechanical properties of the reproduced composite board were examined by considering the effects of mass fraction and glass-fiber distribution. Interfacial-layer micrograph analysis of the composite material fracture surface was used to study the fiber reinforcement mechanism. Results showed that using comminuted glass-fiber-reinforced resin as a filler material greatly enhanced the performance properties of the composite board. Although the length and diameter of filler varied, these variations had no appreciable effect on the mechanical properties of the processed board. Maximum values of 48.30 MPa for flexural strength, 31.34 MPa for tensile strength, and 31.34 J/m for impact strength were achieved from a composite board containing mass fractions of 30, 10, and 20% glass-fiber-reinforced resin waste, respectively. It was found that the maximum amount of recyclate that could be added to a composite board was 30% of weight. Beyond these percentages, the materials blend became unmanageable and the mixture less amenable to impregnation with fiber. Presented studies indicated that comminuted glass-fiber-reinforced resin waste-filled polypropylene composites are promising candidates for structural applications where high stiffness and fracture resistance are required.

Toxicity evaluation of E-waste plastics and potential repercussions for human health.

At present, waste mobile phone is considered to be one of the fastest-growing obsolete items in the stream of electronic waste (e-waste). Toxic substances such as heavy metals and brominated flame retardants (BFRs) have been widely added to plastics used in electrical and electronic equipment (EEE). The recent technological revolution in electronic appliances combined with high and growing consumption has caused a huge generation of waste electrical and electronic equipment (WEEE). Therefore, e-waste plastics are considered to be one of the fastest-growing waste streams globally. In this study, we examined the hazardous substances in the plastic components of waste mobile phones and then applied the USEtox life cycle impact assessment (LCIA) model to determine the impacts on human health. Specifically, various plastic parts separated from waste mobile phones (n = 20) were collected and then, we used standard tests to characterize the heavy metals and brominated flame retardants. The mean and range of the results are 2207.7 µg/kg (503.9-11569.9 µg/kg) for Pb, 91.6 µg/kg (8.8-464.4 µg/kg) for Cd, 13.7 µg/kg (1.6-58.9 µg/kg) for Be, 7203.3 µg/kg (117-69813 µg/kg) for Sb, 471.3 µg/kg (143.4-2351.3 µg/kg) for As, 1.5 mg/kg (2.1-12.5 mg/kg) for Hg and 523.7 mg/kg (27.1-3859 mg/kg) for Cr. The BFRs - a sum Polybrominated Biphenyls, Polybrominated Diphenyl Ethers and Hexabromocyclododecane - were not detected except for two samples, which was an average of 234.5 µg/kg for nona-BDE and deca-BDE. The total bromine (Br) concentration varied from 0 to 471 mg/kg (average value of 87.9 mg/kg) , while Tetrabromobisphenol A (TBBP-A) showed an average concentration of 214.3 µg/kg. In the case of potential human health risks, Hg contributed the major risk for carcinogens and non-cancer disease in the plastics, but the contribution of Pb was also significant. In the case of eco-toxicity, Cr posed the most significant risks in the plastics. Overall, the results show that the toxic substances are below the limit values of substances regulated in the RoHS Directive in China and Europe. However, the results of LCIA highlight the growing importance to avoid the open burning practices of e-waste plastics that contain Hg, Pb, Cr ad Sb. Additionally, the results set a new database for the e-waste plastics recycling industry and provide information for ecodesign in EEE production.