Zhanghong Wang

Biodegradable mulch films, primarily poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends, are increasingly applied as eco-friendly alternatives to conventional polyethylene (PE) films. However, the interfacial interactions and vector potential of commercial biodegradable mulch-derived microplastics toward typical agricultural antibiotics remain insufficiently understood. In this study, the adsorption thermodynamics, kinetics, and interfacial binding mechanisms of tetracycline (TC) and chlortetracycline (CTC) onto microplastics derived from two commercial biodegradable films (WHMPs and RAMPs) and a conventional PE film (PEMPs) were systematically investigated under controlled laboratory conditions. The results demonstrated that biodegradable microplastics exhibited markedly higher saturated adsorption capacities for both TC (5.20 mg/g for WHMPs and 6.18 mg/g for RAMPs) and CTC (11.46 mg/g for WHMPs and 15.01 mg/g for RAMPs) than those of PEMPs (1.22 mg/g for TC and 5.43 mg/g for CTC). Adsorption isotherms adhered closely to the Langmuir model, indicating a monolayer interfacial coverage. Thermodynamic analyses revealed that the adsorption was spontaneous and endothermic, driven predominantly by favorable entropy gain. The significantly higher adsorption affinity for CTC compared to TC was rationalized by its higher octanol–water partition coefficient and the electron-withdrawing induction of the C7–Cl substituent, which enhances localized dipole–dipole attractions with polymer ester carbonyls (C═O). High-resolution X-ray photoelectron spectroscopy and FT-IR analyses revealed that noncovalent physical partitioning, hydrophobic interactions, and dipole–dipole attractions dominated the interfacial binding without irreversible covalent transitions. Multicondition desorption and dynamic leaching assays further revealed that biodegradable microplastics exhibit moderate desorption reversibility and sustained release potential. These findings provide fundamental thermodynamic and kinetic benchmarks for understanding antibiotic retention on commercial mulch-derived microplastics, highlighting the need for future field-scale investigations to evaluate their environmental behaviors under complex soil matrixes and chronic weathering conditions.

The coexistence of microplastics (MPs) and heavy metals (Cd, Pb) in agricultural soils has become a global environmental and ecological risk. In this study, a pot experiment was conducted to investigate the effects of different concentrations of polyethylene (PE) microplastics and combined Cd/Pb contamination on the growth and development, heavy metal accumulation, and antioxidant system of tobacco (Nicotiana tabacum L. cv. Yunyan 87). The results showed that low-dose PE and low concentrations of heavy metals had minor impacts on tobacco growth and the antioxidant system; in contrast, high-dose PE and elevated heavy metal treatments markedly induced increases in malondialdehyde content (MDA) and enhanced the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Under co-contaminated conditions, the addition of low-dose PE reduced the translocation capacity of heavy metals, alleviated heavy metal-induced oxidative stress responses, and promoted tobacco growth. Conversely, high-dose PE promoted the translocation of Cd into tobacco plants and increased Cd contents in tobacco leaves, leading to marked decreases in soluble protein and soluble sugar contents, and causing severe reductions in plant height, number of functional leaves, and biomass. Structural equation modeling (SEM) analysis revealed that the direct effect of PE on tobacco growth was not significant; instead, it primarily acted as a regulatory factor, exerting either promotional or inhibitory effects on tobacco growth at different doses. The impact of Cd/Pb on tobacco growth appeared to involve two potential pathways. On the one hand, Cd/Pb induced direct toxicity through their accumulation within tobacco tissues. On the other hand, they exerted indirect regulation primarily by modulating the activities of the tobacco antioxidant system.

This study synthesized biochar through a one-pot pyrolysis process using IALG as the raw material. The physicochemical properties of the resulting biochar (IALG-BC) were characterized and compared with those of biochar derived from acid-treated lignin with the ash component removed (A-IALG-BC). This study further investigated the adsorption performances and mechanisms of these two lignin-based biochars for Pb(II). The results revealed that the high ash content in IALG, primarily composed of Na, acts as an effective catalyst during pyrolysis, reducing the activation energy and promoting the development of the pore structure in the resulting biochar (IALG-BC). Moreover, after pyrolysis, Na-related minerals transformed into particulate matter sized between 80 and 150 nm, which served as active adsorption sites for the efficient immobilization of Pb(II). Adsorption results demonstrated that IALG-BC exhibited a significantly superior adsorption performance for Pb(II) compared to that of A-IALG-BC. The theoretical maximum adsorption capacity of IALG-BC for Pb(II), derived from the Langmuir model, was determined to be 809.09 mg/g, approximately 40 times that of A-IALG-BC. Additionally, the adsorption equilibrium for Pb(II) with IALG-BC was reached within approximately 0.5 h, whereas A-IALG-BC required more than 2 h. These findings demonstrate that the presence of inorganic mineral components in IALG plays a crucial role in its resource utilization.

Due to its high carbon content, lignin, particularly for lignin-containing solid waste, is considered an excellent raw material for the preparation of carbon materials like biochar. To produce high-quality lignin-based biochar (LGBCs), lignin extracted from black liquor was employed to prepare biochar at various pyrolysis temperatures (300~600 °C). The physicochemical properties of LGBCs were assessed using scanning electron microscopy, N₂ adsorption/desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. Furthermore, the adsorption capability and potential mechanism of LGBCs in removing Cd(II) were investigated as well. The results indicate that LGBCs produced at higher pyrolysis temperatures exhibit rougher surfaces and more developed pore structures, which facilitate the exposure of numerous active adsorption sites. The adsorption of Cd(II) by LGBCs generally follows the order of LG-300C < LG-400C < LG-500C < LG-600C. According to the Langmuir adsorption isotherm model, the theoretical maximum adsorption capacity of LG-600C for Cd(II) is calculated to be 18.54 mg/g. Adsorption mechanism analysis reveals that the complexation interaction, dependent on the surface functional groups, plays a crucial role in the adsorption of Cd(II) by LGBCs prepared at higher pyrolysis temperatures. This study demonstrates that, by controlling the pyrolysis temperature during biochar preparation, high-quality lignin-based biochar can be readily obtained.