Upcycling Polystyrene

Morphology and Thermodynamic Study of a Novel Composite Membrane from Waste Polystyrene/Slag: Experimental Investigation

The development of the membrane surface and cross-sectional morphology is pivotal in influencing the effectiveness of membrane separation. In this study, evaluating the separation rates between the solvent and nonsolvent in the casting solution and the related thermodynamic alteration analysis were illustrated. Additionally, the rheological variations were determined by measuring the viscosity of the resulting dope solutions, providing an initial estimation of the phase separation kinetics. Asymmetric polystyrene (PS)/slag composite membrane, incorporating slag waste as an inorganic additive, was developed. Dimethylformamide (DMF) was utilized as the solvent, and sodium dodecyl sulfate (SDS) was employed as an anionic surfactant to facilitate the casting process. A tertiary system diagram approach involving waste PS, DMF, and water introducing slag as an inorganic additive and SDS as a surfactant was attained to promote the separation of the solvent and nonsolvent in the casting solution. These novel composite mixtures exhibited increased thermodynamic instability within the coagulation bath, facilitating the rapid separation of solid membranes from the dope solutions and forming composite membranes with significantly increased porosity (exceeding a 20% increase) compared to that of plain waste materials. The composite membrane characteristics were assessed with the widely used poly(vinylidene difluoride) (PVDF) membrane, showing comparative features and performance when tested on a membrane distillation (MD) cell; it gave a flux of 1 kg/m2·h. These promising characteristics positioned this novel PS/slag composite membrane as a candidate for various water-related applications.

Performance of Particleboard Made of Agroforestry Residues Bonded with Thermosetting Adhesive Derived from Waste Styrofoam

This paper investigated the upcycling process of thermoplastic waste polystyrene (WPS) into thermosetting particleboard adhesive using two cross-linkers, namely methylene diphenyl diisocyanate (MDI) and maleic anhydride (MA). The WPS was dissolved in an organic co-solvent. The weight ratio of WPS/co-solvent was 1:9, and 10% of cross-linkers based on the WPS solids content were added subsequently at 60 °C under continuous stirring for 30 min. The adhesive properties, cohesion strength, and thermo-mechanical properties of WPS-based adhesives were examined to investigate the change of thermoplastic WPS to thermosetting adhesives. The bonding strength of WPS-based adhesives was evaluated in particleboard made of sengon (Falcataria moluccana (Miq.) Barneby & J.W. Grimes) wood and rice straw particles at different weight ratios according to the Japanese Industrial Standard (JIS) A 5908:2003. Rheology and Dynamic Mechanical Analysis revealed that modification with MDI and MA resulted in thermosetting properties in WPS-based adhesives by increasing the viscosity at a temperature above 72.7 °C and reaching the maximum storage modulus above 90.8 °C. WPS modified with MDI had a lower activation energy (Ea) value (83.4 kJ/mole) compared to the WPS modified with MA (150.8 kJ/mole), indicating the cross-linking with MDI was much faster compared with MA. Particleboard fabricated from 100% sengon wood particles bonded with WPS modified with MDI fulfilled the minimum requirement of JIS A 5908:2003 for interior applications.

E-waste plastic liquefaction using supercritical Toluene: Evaluation of reaction parameters on liquid products

Solvothermal liquefaction (STL) is a thermochemical conversion technique that employs solvents other than water to transform waste plastics into valuable compounds. The objective of this study was to explore the potential use of supercritical toluene, a nonpolar solvent, for the depolymerization of four electrical waste (e-waste) thermoplastics, namely polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), and polyether ether ketone (PEEK), into liquid products. Depolymerization experiments were carried out in batch reactors at three reaction temperatures (325, 350, and 375 °C), and three residence times (1, 3, and 6 h). The findings revealed that increasing STL temperature and extending the reaction time enhances the depolymerization of e-waste thermoplastics. The highest STL conversation (100 %) was observed for POM, and the lowest STL conversation (32.23 %) was observed for PEEK. Additionally, the ultimate analysis showed that the liquid product obtained from STL at 375 °C and 6 h exhibited higher heating values (HHV) within the range of 31.43 to 35.31 MJ/kg. Thermogravimetric analysis (TGA) demonstrated that the boiling point distributions of liquid products are highly dependent on thermoplastic type. Finally, the reaction mechanisms of STL for PA, PC, POM, and PEEK were proposed based on gas chromatography-mass spectrometry (GCMS) analysis.

Micro and Nanoplastic Contamination and Its Effects on Freshwater Mussels Caged in an Urban Area

Plastic-based contamination has become a major cause of concern as it pervades many environments such as air, water, sediments, and soils. This study sought to examine the presence of microplastics (MPs) and nanoplastics (NPs) in freshwater mussels placed at rainfall/street runoff overflows, downstream (15 km) of the city centre of Montréal, and 8 km downstream of a municipal effluent dispersion plume. MPs and NPs were determined using flow cytometry and size exclusion chromatography using fluorescence detection. Following 3 months of exposure during the summer season, mussels contained elevated amounts of both MPs and NPs. The rainfall overflow and downstream of the city centre were the most contaminated sites. Lipid peroxidation, metallothioneins, and protein aggregates (amyloids) were significantly increased at the most contaminated sites and were significantly correlated with NPs in tissues. Based on the levels of MPs and NPs in mussels exposed to municipal effluent, wastewater treatment plants appear to mitigate plastic contamination albeit not completely. In conclusion, the data support the hypothesis that mussels placed in urbanized areas are more contaminated by plastics, which are associated with oxidative damage. The highest responses observed at the overflow site suggest that tire wear and/or asphalt (road) erosion MPs/NPs represent important sources of contamination for the aquatic biota.