Polycyclic aromatic hydrocarbons (PAHs) are hazardous toxic contaminants and considered as primary pollutants due to their persistent nature and most of them are carcinogenic and mutagenic. The key challenge in PAHs degradation is their hydrophobic nature, which makes them one of the most complex materials and inaccessible by a broad range of microorganisms. This bioavailability can be increased by using a biosurfactant. In the present study mixed PAHs were degraded using the biosurfactant producing bacterial strains. In addition, iron nanoparticles were synthesized and the impact of iron nanoparticles on the growth of the mixed bacterial strains (Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3) was optimized. The mixed PAHs (anthracene, pyrene, and benzo(a)pyrene) degradation was enhanced by addition of biosurfactant (produced by Bacillus subtilis A1) and iron nanoparticles, resulting in 85% of degradation efficiency. The addition of the biosurfactant increased the bioavailability of the PAHs in the aqueous environment, which might help bacterial cells for the initial settlement and development. The addition of iron nanoparticles increased both bacterial biomass and PAHs adsorption over their surface. These overall interactions assisted in the utilization of PAHs by the mixed bacterial consortia. This study illustrates that this integrated approach can be elaborated for the removal of the complex PAHs pollutants from soil and aqueous environments.

Recalcitrant plastics in the environment are gradually fragmented into weathered debris distinguished from their original state by the integrative action of influencing factors, such as UV light, heating and physical abrasion. As new artificial carbon-source substrates in aquatic ecosystems, plastic products can be colonized by biofilms and even utilized by microorganisms. To investigate the influences of weathering of plastics on the colonized biofilms, freshwater samples from the Yangtze River (Nanjing, China) were collected for biofilm incubation. Based on the characterization of plastics and biofilms, the effects of plastic surface properties on biofilm characteristics were revealed by the analysis of partial least squares regression (PLSR). Roughness was the principal influencing factor, while rigidity had the opposite effect to it. 16S rRNA gene high-throughput sequencing results indicated the high relative abundance of Cyanobacteria and rising proportion of harmful components (e.g., Flavobacterium) on photoaged polyethylene plastics. The microbial functional profiles (KEGG) predicted by Tax4Fun showed that the functions (e.g., membrane transport, energy metabolism, etc.) of biofilm on photoaged plastics were dissimilar with those on original ones. These findings suggested that the distinct microbial community and the adverse functional changes in biofilms on photoaged plastics potentially enhanced their environmental risks. On the other hand, 28-day cultured biofilms on original low-density polyethylene (LDPE) films were dominated by Exiguobacterium. The previously ignored potentials of this microorganism in rapidly accommodating to a hydrophobic substrate and its plastic degrading ability were both worthy of attention. Therefore, it is necessary to consider the weathering process of plastics in exploring the “plastisphere”, and to give further insights into the double-edged nature of the “plastisphere".

Multiwalled carbon nanotubes (MWCNTs) were oxidized using a mixture of H₂SO₄ and HNO₃, and the oxidized MWCNTS were decorated with magnetite (Fe₃O₄). Finally, poly-N-isopropyl acrylamide-co-butyl acrylate (P-NIPAM) was added to obtain P-NIPAM/Fe/MWCNT nanocomposites. The nanosorbents were characterized by various techniques, including X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller analysis. The P-NIPAM/Fe/MWCNT nanocomposites exhibited increased surface hydrophobicity. Owing to their higher adsorption capacity, their kerosene removal efficiency was 95%; by contrast, the as-prepared, oxidized, and magnetite-decorated MWCNTs had removal efficiencies of 45%, 55%, and 68%, respectively. The P-NIPAM/Fe/MWCNT nanocomposites exhibited a sorbent capacity of 8.1 g/g for kerosene removal from water. The highest kerosene removal efficiency from water was obtained at a process time of 45 min, sorbent dose of 0.005 g, solution temperature of 40 °C, and pH 3.5. The P-NIPAM/Fe/MWCNTs showed excellent stability after four cycles of kerosene removal from water followed by regeneration. The reason may be the increase in the positive charge of the polymer at pH 3.5 and the increased adsorption affinity of the adsorbent toward the kerosene contaminant. The pseudo second-order model was found to be the most suitable model for studying the kinetics of the adsorption reaction.

The adsorption of hydrophobic organic compounds (HOCs) by microplastics (MPs) has attracted great attention in recent years. However, the ultimate environmental fate of the HOCs sorbed on MPs (HOCs-MPs) is poorly understood. In this work, we investigated the potential influence of the biotransformation process on the environmental fate of phenanthrene (PHE, a model HOC) sorbed on MPs (PHE-MPs) under the existence of humic acid (HA, the main ingredient of dissolved organic matter (DOM)) in the aquatic environment. The results indicated that the adsorption behavior of PHE on MPs decreased its bioavailability and thus inhibited its biotransformation efficiency. However, HA significantly promoted the biodegradation rate and percentage of PHE-MPs. This was probably because HA improved the desorption of PHE from MPs, which promoted the acquisition of PHE by bacteria from the aqueous phase. Further, HA dramatically increased the bacterial community diversity and richness and altered the community composition. The richness of some PHE-degrading bacteria, such as Methylobacillus and Sphingomonas, significantly increased, which may also be an important factor for promoting PHE biodegradation. Molecular ecological network analysis implied that HA enhanced the modularity and complexity of bacterial interaction networks, which was beneficial to maintaining the functional stability of the consortium QY1. Besides, HA decreased the cytotoxicity of functional microbes induced by HOCs-MPs. This work broadens our knowledge of the environmental fate of HOCs-MPs and interactions of MPs, HOCs, DOMs and functional microbial consortiums in aqueous environments.

Considerable efforts on exposure assessment of microplastics (MPs) as an agent in transport of toxic contaminants have been performed in organisms. However, chemical diffusion of inherent hydrophobic organic contaminants from MPs under simulated gut conditions is poorly examined. The present study examined the transfer kinetics of polybrominated diphenyl ethers (PBDEs) from polystyrene (PS), acrylonitrile butadiene styrene (ABS), and polypropylene (PP) MPs under gut surfactants (sodium taurocholate) at two relevant body temperatures of marine organisms, and evaluated the importance of MP ingestion in bioaccumulation of PBDEs in lugworm by a biodynamic model. Diffusion coefficients of PBDEs range from 5.82 × 10⁻²³ to 7.96 × 10⁻²⁰ m² s⁻¹ in PS, 5.49 × 10⁻²³ to 3.45 × 10⁻²⁰ m² s⁻¹ in ABS, and 5.58 × 10⁻²¹ to 5.79 × 10⁻¹⁷ m² s⁻¹ in PP, with apparent activation energies in the range of 33–148 kJ mol⁻¹. The biota–plastic accumulation factors of PBDEs leached from these plastics range from 1.44 × 10⁻⁸ to 7.15 × 10⁻⁵. Although ingestion of MPs with the common size (>0.5 mm) showed the negligible contribution to bioaccumulation of PBDEs in lugworm, their contribution in PBDEs transfer can be increased with gradual breakdown of MPs.

The quality and quantity of dissolved organic matter (DOM) greatly controls the fate of heavy metals. The characteristics of DOM and its interaction with metals are essential for the metal ecological risk assessment of soils. In this study, the DOM spectral characteristics of representative forest soils and the complex capacities between fluorescent DOM components and cadmium (Cd) were analyzed. Functional groups, such as carboxylic acids, alcohols and phenols, were determined by FT-IR analysis. Chromophoric DOM, fluorescent DOM and dissolved organic carbon (DOC) concentrations exhibited strong correlations with each other, indicating that variations of DOC could be well explained by Chromophoric DOM or fluorescent DOM due to high correlation coefficients. The spectral slope ratio was in the range of 0.85–5.90, implying an abundance of heavy macromolecular humic acids, peptides, and polycondensates. The absorbance spectral at 254 nm (SUVA₂₅₄) strongly correlated with SUVA₂₆₀ (r = 0.992, P < 0.01), indicating that hydrophobicity closely related with aromatic structure, and aromatic groups could be broadly hydrophobic. Fluorescence indices were from 1.62 to 2.21 and biological index values ranged from 0.54 to 1.14, where the DOM was mainly sourced from mixed terrestrial and autogenous inputs in most sites. Four universal fluorescence components were identified and characterized by fluorescence EEM-PARAFAC, including two humic-like (components 1 and 2), one tyrosine-like (components 3) and one fulvic-like (components 4) component. Both components 3 and 4 showed fluorescence quenching with increasing Cd concentrations, while components 1 and 2 had no evident change in fluorescence intensity. The logK₃ and logK₄ values ranged from 4.41 to 5.29 and 4.71 to 5.54, respectively, with most logK values of component 3 for Cd binding being smaller than that of component 4, thus, indicating that the fulvic acid substances exhibited stronger and more stable interactions with Cd than protein-like components.

The synthesis of clay-biochar composite has been recognized as an effective way to enhance the removal of pollutants. The interaction between clay mineral and biomass during thermal pyrolysis and the sorption capacity for ionic/nonionic organic containments have not been elaborated. In this study, two types of biochar were obtained from pyrolytic carbonization of the cellulosic-rich corn straw (C) and lignin-rich pine wood (P) at 500 or 700 °C. Typical clay minerals kaolinite and montmorillonite were selected to prepare clay-biochar composite. The results showed that the addition of clay mineral could strengthen dehydration reaction of corn straw biomass and reinforce its carbon structure. Montmorillonite-biochar composite owned more CC functional groups and porous structure than kaolinite-biochar composite. The addition of clay minerals could promote electrostatic attraction of ionic formed norfloxacin (NOR) on clay-pine wood biochar. However, the sorption capacity of nonionic diethyl phthalate (DEP) adsorption on clay-corn straw biochar decreased, owing to that clay increased the compactness of the biochar carbon structure, thus inhabited hydrophobic partition of nonionic organic compounds on disordered carbon fraction. The results from this study provide insights into the suitable contaminated site remediation by clay-biochar composite.

Per-and polyfluoroalkyl substances (PFASs) have attracted extensive attention since this century due to their wide distribution, persistence, bioaccumulation/biomagnification potential, and (eco)toxicity. In the present study, we investigated the sorption kinetics, sorption isotherms and desorption behaviors of legacy and emerging PFASs with different chain lengths and functional end groups onto marine sediments at four different salinities (0, 10, 20, and 30 practical salinity units (psu)). Results revealed that the sorption of PFASs onto sediment can be well described by the pseudo-second-order kinetic model. PFASs sorption was influenced by both compound-specific and solution-specific parameters. The distribution coefficient (Kd) for PFASs were increased with the increase of perfluorocarbon chain length and salinity, suggesting that hydrophobic and electrostatic interactions were involved in the adsorption process. 6:2 FTSA showed the lowest adsorption among PFASs with eight carbon atoms (6:2 FTSA, PFOA and PFOS). The increase of perfluorocarbon chain length of PFASs and salinity would result in the decrease of desorption rate of PFASs from sediment. In addition, PFCAs were desorbed more easily from the sediment than the PFSAs with the same perfluorocarbon chain length at all salinity groups. The present study demonstrated that salinity can apparently influence the fate of PFASs in aquatic environment and provided valuable data for modeling the fate of PFASs in real environment.

Presently, graphenic nanomaterials are being studied as candidates for wastewater pollutant removal. In this study, two graphite oxides produced from natural graphite with different grain sizes (325 and 10 mesh), their respective reduced graphene oxides and one reduced graphene oxide with nitrogen functional groups were synthesized and tested to remove a surfactant model substrate, Triton X-100, from an aqueous solution. Kinetic experiments were carried out and adjusted to pseudo-first order equation, pseudo-second order equation, Elovich, Chain-Clayton and intra-particle diffusion models. Reduced graphene oxides displayed an instantaneous adsorption due to their accessible and hydrophobic surfaces, while graphite oxides hindered the TX100 adsorption rate due to their highly superficial oxygen content. Results from the adsorption isotherms showed that the Sips model perfectly described the TX100 adsorption behavior of these materials. Higher adsorption capacities were developed with reduced graphene oxides, being maximum for the material produced from the lower graphite grain size (qₑ = 3.55·10⁻⁶ mol/m²), which could be explained by a higher surface area (600 m²/g), a lower amount of superficial oxygen (O/C = 0.04) and a more defected structure (ID/IG = 0.85). Additionally, three commercial high surface area graphites in the range of 100–500 m²/g were evaluated for comparison purposes. In this case, better adsorption results were obtained with a more graphitic material, HSAG100 (qₑ = 1.72·10⁻⁶ mol/m²). However, the best experimental results of this study were obtained using synthesized graphenic materials.

This study investigated the competitive adsorption mechanisms of pharmaceuticals (i.e., naproxen, diclofenac, and ibuprofen) toward the pristine and NaOH-activated biochars from spent coffee wastes (SCW) in lake water and wastewater effluent. The kinetic and isotherm studies revealed that the improved physicochemical characteristics and physically homogenized surfaces of the pristine SCW biochar through the chemical activation with NaOH were beneficial to the adsorption of pharmaceuticals (competitive equilibrium adsorption capacity (Qₑ, ₑₓₚ): NaOH-activated SCW biochar (61.25–192.07 μmol/g) > pristine SCW biochar (14.81–20.65 μmol/g)). The adsorptive removal of naproxen (Qₑ, ₑₓₚ = 14.81–18.81 μmol/g), diclofenac (Qₑ, ₑₓₚ = 15.73–20.00 μmol/g), and ibuprofen (Qₑ, ₑₓₚ = 16.20–20.65 μmol/g) for the pristine SCW biochar showed linear correlations with their hydrophobicity (log D at pH 7.0: ibuprofen (1.71) > diclofenac (1.37) > naproxen (0.25)). However, their Qₑ, ₑₓₚ values for the NaOH-activated SCW biochar (naproxen (176.39–192.07 μmol/g) > diclofenac (78.44–98.74 μmol/g) > ibuprofen (61.25–80.02 μmol/g)) were inversely correlated to the order of their log D values. These results suggest that the reinforced aromatic structure of the NaOH-activated SCW biochar facilitated the π-π interaction. The calculated thermodynamic parameters demonstrated that the competitive adsorption of pharmaceuticals on the NaOH-activated SCW biochar compared to pristine SCW biochar occurred more spontaneously over the entire pH (5.0–11.0) and ionic strength (NaCl: 0–0.125 M) ranges. These observations imply that the NaOH-activated SCW biochar might be potentially applicable for the removal of pharmaceuticals in lake water and wastewater effluent.