Efficient adsorption of short-chain perfluoroalkyl substances by pristine and Fe/Cu-loaded reed straw biochars.

As the substitutes of legacy long-chain per-/polyfluoroalkyl substances (PFASs), short-chain PFASs have been widely detected in the environment. Compared to long-chain PFASs, short-chain PFASs have smaller molecules and are more hydrophilic. Therefore, they are more likely to experience long-distance transport and pose lasting environmental impacts. In this study, Fe-doped (R-Fe) and Cu-doped biochars (R-Cu) were prepared using reed straw biochar (R). The results showed that the PFBA and PFPeA sorption capacities of R-Fe were 25.81 and 43.59 mg g-1, 1.65 and 1.55 times higher than those of R, respectively. The PFBA and PFPeA sorption capacities of R-Cu were 19.34 and 33.69 mg g-1, 1.24 and 1.20 times higher than those of R, respectively. In addition, R, R-Fe, and R-Cu exhibited higher PFBA and PFPeA sorption capacities than the biochars previously reported. The excellent PFAS sorption performances of the biochars were attributed to the highly porous structure of R, which provided rich adsorption sites. Ion-pair sorption, pore filling, electrostatic interaction between the Fe/Cu and cationic groups on biochar and the anionic groups of PFASs, and hydrophobic interaction between the hydrophobic surface of biochar and the fluorinated tails of PFASs were the underlying sorption mechanisms. The biochars presented high removal rates (>86 %) of multiple PFASs (∑PFAS: 350 µg L-1) from synthetic wastewaters, including legacy and emerging PFASs of different chain lengths and with different functional groups. The biochars reported in this study are promising candidate adsorbents for treating waters contaminated with short-chain PFASs.

Adsorption behaviors of chlorpyrifos on UV aged microplastics.

Both non-degradable and biodegradable plastics can act as vectors of diverse organic pollutants. In this study, two types of biodegradable microplastics [poly (butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA)] and one type of non-degradable microplastics [polypropylene (PP)] were selected to investigate the impacts of ultraviolet (UV) irradiation for one month on microplastics surface modification and their adsorption behaviors for chlorpyrifos (CPF). The study revealed that PBAT held the largest adsorption capacity, and PLA held the fastest adsorption rate. The UV irradiation diminished the adsorption capacities on PLA and PP but enhanced the adsorption capacities on PBAT. The adsorption capacity normalized by specific surface area revealed that specific surface area was the dominant factor for affecting the adsorption capacities on PP and PLA after UV irradiation. These findings further clarify the interaction between CPF and microplastics, and provide a theoretical basis for assessing the ecological risk of microplastics in water.

Effects of solution chemistry and humic acid on the transport of polystyrene microplastics in manganese oxides coated sand.

Microplastics as the emerging persistent pollutants have attracted more attention in the terrestrial environments. In this study, the transport behavior of polystyrene microplastics (PSMPs) in manganese oxides coated sand (MOCS) was examined under different pH, ionic strength (IS), cationic type and humic acid (HA) conditions. Compared with the transport behavior of PSMPs in the bare sand, the mobility of PSMPs in MOCS was significantly lower and less affected by pH, IS and cation type, which can be attributed to the existence of attractive electrostatic force and rougher collector surfaces of MOCS. Specifically, the transport of PSMPs was inhibited when cotransport with Cd2+. Furthermore, the HA significantly increased the transport of PSMPs in the MOCS, and the mobility increased with the increase of HA concentration ranged from 0 to 10 mg L-1. The results can contribute to the further understanding of the migration mechanism and fate of microplastics in the soil system.