The widespread utilization of plastic products ineluctably leads to the ubiquity of nanoplastics (NPs), causing potential risks for aquatic environments. Interactions of NPs with mineral surfaces may affect NPs transport, fate and ecotoxicity. This study aims to investigate systematically the deposition and aggregation behaviors of carboxylated polystyrene nanoplastics (COOH-PSNPs) by four types of clay minerals (illite, kaolinite, Na-montmorillonite, and Ca-montmorillonite) under various solution chemistry conditions (pH, temperature, ionic strength and type). Results demonstrate that the deposition process was dominated by electrostatic interactions. Divalent cations (i.e., Ca²⁺, Mg²⁺, Cd²⁺, or Pb²⁺) were more efficient for screening surface negative charges and compressing the electrical double layer (EDL). Hence, there were significant increases in deposition rates of COOH-PSNPs with clay minerals in suspension containing divalent cations, whereas only slight increases in deposition rates of COOH-PSNPs were observed in monovalent cations (Na⁺, K⁺). Negligible deposition occurred in the presence of anions (F^-, Cl^-, NO^3-, CO₃^2-, SO₄^2-, or PO₄^3-). Divalent Ca²⁺ could incrementally facilitate the deposition of COOH-PSNPs through Ca²⁺-assisted bridging with increasing CaCl₂ concentrations (0-100 mM). The weakened deposition of COOH-PSNPs with increasing pH (2.0-10.0) was primarily attributed to the reduce in positive charge density at the edges of clay minerals. In suspensions containing 2 mM CaCl₂, increased Na⁺ ionic strength (0-100 mM) and temperature (15-55 ^◦C) also favored the deposition of COOH-PSNPs. The ability of COOH-PSNPs deposited by four types of clay minerals followed the sequence of kaolinite > Na-montmorillonite > Ca-montmorillonite > illite, which was related to their structural and surface charge properties. This study revealed the deposition behaviors and mechanisms between NPs and clay minerals under environmentally representative conditions, which provided novel insights into the transport and fate of NPs in natural aquatic environments.

The pharmacokinetics, tissue distribution, and elimination of enrofloxacin (ENR) and its metabolite ciprofloxacin (CIP) were investigated to the crucian carp (Carassius auratus gibelio) after single (20 mg/kg b. w.) and multiple oral administration (20 mg/kg b.w. one time daily for 5 days) at 28°C. The concentrations of ENR and CIP in the plasma and tested tissues (muscle/skin, liver, and kidney) were detected simultaneously by high-performance liquid chromatography (HPLC), and the pharmacokinetic data were analyzed with a non-compartmental model using WinNonLin 6.1 PK software (Pharsight Corporation, Mountain View, CA, USA). The pharmacokinetic characteristics of ENR in crucian carp exhibited slow absorption, wide tissue distribution, and long elimination half-life. In the single-dose group, the peak concentrations (Cmax) of ENR in the plasma, muscle/skin, liver, and kidney were 8.93 μg/mL, 13.9 μg/g, 31.2 μg/g, and 27.3 μg/g, respectively, observed at 3 h, 6 h, 1 h, and 3 h after dosing. The elimination half-lives (T_1/2λz) of ENR in plasma, muscle/skin, liver, and kidney were calculated to be 67.4, 82.8, 94.4, and 114 h, respectively. In the multiple-dose group, the C_maxof ENR in the plasma, muscle/skin, liver, and kidney were 18.4 μg/mL, 26.8 μg/g, 82.8 μg/g, and 74.5 μg/g, respectively, achieved at 3 h, 6 h, 1 h, and 1 h after the last dose. The T_1/2λzof ENR in the plasma, muscle/skin, liver, and kidney were calculated to be 76.4 h, 91.5 h, 114 h, and 148 h, respectively. During the multiple-dose administration, significant accumulations of ENR and CIP were observed in the plasma and tissues of crucian carp, possibly due to their long elimination half-lives. In both dose groups, the AUC_0−∞for both ENR and CIP followed the order of liver > kidney > muscle/skin > plasma. The finding suggested that the liver may play an important role in the metabolism of ENR. According to the calculated PK/PD indices of C_max/minimum inhibitory concentrations (MIC) and AUC_24h/MIC, the multiple-dose regimen would be highly effective against pathogenic bacteria with a MIC value of ≤ 1.84 μg/ml. Depletion studies indicated that a withdrawal period of at least 29 or 32 days was necessary to guarantee food security after single or multiple oral gavage administration at 28°C.

Porous activated carbons (AC-AN and AC-AO) for toluene adsorption were prepared starting from brewer’s grain biomass pretreated with microorganisms (Aspergillus niger van Tieghem for AC-AN and Aspergillus oryzae RIB40 for AC-AO). The structures and chemical properties of the three activated carbon materials (AC-AN, AC-AO, and AC that was not pretreated with microorganisms) were characterized by N₂ adsorption–desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The adsorption behavior of the three activated carbons for toluene was studied and correlated with the physical and chemical properties of these materials. The results suggested that the activated carbons prepared by microbial pretreatment had a rougher morphology, higher specific surface area, richer pore structure, fewer oxygen-containing functional groups on the surface, and better adsorption performance for toluene (increased by 31.5% and 18.3% with AC-AN and AC-AO, respectively) compared with the untreated activated carbon (AC). The Thomas model was used to fit the toluene adsorption data, indicating that the rich pore structure accelerated the kinetic process of toluene adsorption. Therefore, appropriate microbial pretreatment of the feedstock that is used to prepare activated carbon can effectively improve its adsorption capacity towards toluene.

The focus of pK_a calculations has primarily been on stable molecules, with limited studies comparing radical cations and stable cations. In this study, we comprehensively investigate models with implicit solvent and explicit water molecules, direct and indirect calculation approaches, as well as methods for calculating free energy, solvation energy, and quasi-harmonic oscillator approximation for para-substituted aniline radical cations (R-PhNH₂^•+) and anilinium cations (R-PhNH₃⁺) in the aqueous phase. Properly including and positioning explicit H₂O molecules in the models is important for reliable pK_a predictions. For R-PhNH₂^•+, precise pK_a values were obtained using models with one or two explicit H₂O molecules, resulting in a root mean square error (RMSE) of 0.563 and 0.384, respectively, for both the CBS-QB3 and M062X(D3)/ma-def2QZVP methods. Further improvement was achieved by adding H₂O near oxygen-containing substituents, leading to the lowest RMSE of 0.310. Predicting pK_a values for R-PhNH₃⁺ was more challenging. CBS-QB3 provided an RMSE of 0.349 and the M062X(D3)/ma-def2QZVP method failed to calculate pK_a accurately (RMSE > 1). However, by adopting the double-hybrid functional method and adding H₂O near the R substituent group, the calculations were significantly improved with an average absolute difference (ΔpK_a) of 0.357 between the calculated and experimental pK_a values. Our study offers efficient and reliable methods for pK_a calculations of R-PhNH₂^•+ (especially) and R-PhNH₃⁺ based on currently mature quantum chemistry software.