Co-impacts of cation type and humic acid on migration of polystyrene microplastics in saturated porous media.

The aging process of microplastics (MPs) could significantly change their physical and chemical characteristics and impact their migration behavior in soil. However, the complex effects of different cations and humic acids (HA) on the migration of aged MPs through saturated media are not clear. In this research, the migration and retention of pristine/aged PSMPs (polystyrene microplastics) under combined effects of cations (Na+, Ca2+) (ionic strength = 10 mM) and HA (0, 5, 15 mg/L) were investigated and analyzed in conjunction with the two-site kinetic retention model and DLVO theory. The findings showed that the aging process accelerated PSMPs migration under all tested conditions. Aged PSMPs were less susceptible to Ca2+ than pristine PSMPs. Under Ca2+ conditions, pristine/aged PSMPs showed higher retention than under Na+ conditions in the absence of HA. Furthermore, under Na+ conditions, the migration of aged PSMPs significantly increased at higher concentrations of HA. However, under Ca2+ conditions, the migration of aged PSMPs decreased significantly at higher concentrations of HA. In higher HA conditions, HA, Ca2+, and PSMPs interact to cause larger aggregations, resulting in the sedimentation of aged PSMPs. The DLVO calculations and two-site kinetic retention models' results showed the detention of PSMPs was irreversible under higher HA conditions (15 mg/L) with Ca2+, and aged PSMPs were more susceptible to clogging. These findings may help to understand the potential risk of migration behavior of PSMPs in the soil-groundwater environment.

Multifunctional Edge-Activated Carbon Nitride Nanosheet-Wrapped Polydimethylsiloxane Sponge Skeleton for Selective Oil Absorption and Photocatalysis.

Developing green 3D porous materials integrating multitasking environmental remediation with high efficiency and reusability is considered to be a promising sustainable approach and is urgently required. Herein, we have successfully prepared a facile, ecofriendly, and robust multifunctional composite sponge of carbon nitride (CN) nanosheets wrapping an elastomer polydimethylsiloxane (PDMS) skeleton without harsh treatments. The composite sponge (CN@PDMS) exhibits excellent hydrophobic and superoleophilic properties with a water contact angle of 133.2°. This sponge also shows high selective absorption of organic solvents and oils with high recyclability after 10 absorption cycles. Furthermore, the CN@PDMS sponge has a high ability for demulsification of the oil-in-water emulsion as well. The as-prepared sponge displays high thermal stability, retaining 82.16% of its original weight up to 550 °C, and extraordinary prolonged stability in harsh corrosive solutions over 35 h compared with the pristine PDMS sponge. Additionally, the CN@PDMS sponge exhibits a high ability for adsorption and photodegradation of rhodamine B under visible light irradiation with self-cleaning and high reusability over 5 runs. Such a sustainable strategy would provide new ways for broad environmental applications.

Amorphous nickel phosphide as a noble metal-free cathode for electrochemical dechlorination.

Nickel phosphide (Ni2P) is an emerging efficient catalyst for the hydrogen evolution and water splitting. Herein, we report that Ni2P is also a promising catalyst for enhancing electrochemical dechlorination of chlorinated disinfection byproducts (DBPs). Amorphous Ni2P (ANP) mini-nanorod arrays were in-situ fabricated on nickel foam (NF) via a facile phosphidation process, and then used as a binder-free cathode for electrochemical dechlorination of trichloroacetic acid (TCAA). Results showed that ANP exhibited superior performance on electrochemical dechlorination of TCAA than other metal cathodes (e.g., NF and Pd/C). Scavenging experiments and electron spin resonance (ESR) technique indicated that atomic H* was generated from water reduction through ANP catalysis, and primarily contributed to TCAA dechlorination. Indeed, the superhydrophilic surface of ANP favored electrocatalyst/electrolyte contact, and its low impedance further afforded rapid electron transport from the electrode to water or protons for atomic H* generation. The kinetic modelling and mass balance evaluation revealed the transformation mechanism of TCAA dechlorination. This study is among the first to develop ANP as a binder-free cathode for electrochemical dechlorination, and have important implications for eliminating chlorinated DBPs in water.