Adsorption of highly toxic chlorophenylacetonitriles on typical microplastics in aqueous solutions: Kinetics, isotherm, impact factors and mechanism

Coagulation performance and mechanism of different hydrolyzed aluminum species for the removal of composite pollutants of polyethylene and humic acid

Microplastics (MPs) and natural organic matter (NOM) composite pollutants have become emerging contaminants with potential threats. Coagulation has been widely used to remove MPs and NOM, but the underlying mechanisms for the removal of MPs-NOM composite pollutants by hydrolyzed Al species remain unclear. Therefore, the coagulation performance and mechanism of AlCl3, polyaluminum chloride with basicity of 2.2 (PAC22), and PAC25 in treating polyethylene (PE), humic acid (HA), and PE-HA composite systems were systematically investigated. The results showed that in the single PE system, PAC25 with hexagonal clusters achieved the maximum removal (68.09 %) (pH: 5, dosage: 0.5 mM) since adsorption bridging and sweeping effect were the main mechanisms for PE removal. The adsorption of HA on the PE surface enhanced its hydrophilicity and electrostatic repulsion, resulting in decreased PE removal. In the AlCl3-PE-HA system, the oligomeric Al first interacted with the -COOH and C-OH of HA through complexation, followed by the meso- and polymers of Al interacted with PE by electrostatic adsorption. The pre-formed medium polymeric Al species (Alb) and colloidal or solid Al species (Alc) in PAC22 and PAC25 formed complexes with the -OH and -COOH groups of HA, respectively, and then removed PE by adsorption bridging and sweeping effect.

Adsorption of azoxystrobin and pyraclostrobin onto degradable and non-degradable microplastics: Performance and mechanism

Microplastics (MPs) exist after agricultural operations and thus present potential hazards to the environment and human health. However, the ecological risks posed by MPs carrying pesticides remain unclear. In this study, the adsorption and desorption behaviors of two pesticides, azoxystrobin and pyraclostrobin, on degradable and non-degradable MPs of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene (PE) were compared before and after UV aging. Additionally, the bioaccessibility of MPs carrying pesticides within a condition simulating gastrointestinal fluids was evaluated. The results showed that, after UV aging, the adsorption capacity of PBAT for pesticides decreased, while that of PE increased. Moreover, PBAT possessed higher adsorption ability towards both the pesticides due to its higher specific surface area, pore volume, contact angle, and lower crystallinity, as well as stronger van der Waals forces, electrostatic interactions, and hydrogen bonding indicated by theoretical calculation. Bioaccessibility experiments showed that azoxystrobin and pyraclostrobin had a higher risk of desorption from PBAT than PE, which is mainly dependent on the LogKow of pesticides according to the random forest analysis. In brief, the study highlights the potential risks of degradable MPs carrying pesticides to human health and the ecosystem, especially when compared to their non-degradable counterparts, manifesting that the ecological risk posed by degradable MPs should not be ignored.