Marine microplastics enhance release of arsenic in coastal aquifer during seawater intrusion process.

Microplastics (MPs), omnipresent contaminants in the ocean, could be carried by seawater intrusion into coastal aquifers, which might affect the fate of heavy metals existing in aquifers. Herein, we investigated the release behavior of arsenic (As) in coastal aquifers during MPs-containing seawater intrusion by applying laboratory experiment and numerical simulation. We found that seawater with marine MPs enhanced the release of As in aquifers, especially for dissolved As(V) and colloidal As. Negatively charged MPs competed with As(V) for the adsorption sites on iron (hydr)oxides in aquifers, resulting in the desorption of As(V). In addition, MPs could promote the release of Fe-rich colloids by imparting negative charge to its surface and providing it with sufficient repulsive force to detach from the matrix, thereby leading to the release of As associated with Fe-rich colloid. We also developed a modeling approach that well described the transport of As in coastal aquifer under the impact of MPs, which coupled variable density flow and kinetically controlled colloids transport with multicomponent reactive transport model. Our findings elucidated the enhancement of MPs on the release of As in aquifers during seawater intrusion, which provides new insights into the risk assessment of MPs in coastal zones.

Ethyl cellulose based self-healing adhesives synthesized via RAFT and aromatic schiff-base chemistry.

In this work, reversible addition-fragmentation chain transfer (RAFT) polymerization and Schiff base chemistry was combined to fabricate self-healing adhesives. An esterification reaction was first performed to prepare ethyl cellulose based macroinitiators. Then, a "grafting from" RAFT of vanillin methacrylate and lauryl methacrylate was used to obtain graft copolymers. DSC result showed that the glass transition temperature was manipulated via changing the ratio of vanillin and fatty acids moieties. NMR spectrum analysis demonstrated the presence of aldehyde groups, which were available for the dynamic crosslinking to generate a network as self-healing adhesives. The adhesive test showed that the shear strength could reach 0.81 MPa with a self-healing efficiency of 98.7 %. The bottlebrush structures of copolymers and reversibility of Schiff base chemistry might collaboratively contribute to the high self-healing efficiency. This study provides a facile way to fabricate high-performance self-healing adhesives from ethyl cellulose and renewable resources.

Preparation and Characterization of DOPO-ITA Modified Ethyl Cellulose and Its Application in Phenolic Foams.

In order to improve the performance of phenolic foam, an additive compound of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and Itaconic acid (ITA) were attached on the backbone of ethyl cellulose (EC) and obtained DOPO-ITA modified EC (DIMEC), which was used to modify phenolic resin and composite phenolic foams (CPFs). The structures of DOPO-ITA were verified by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (¹H NMR). The molecular structure and microstructure were characterized by FT-IR spectra and SEM, respectively. Compared with EC, the crystallinity of DIMEC was dramatically decreased, and the diffraction peak positions were basically unchanged. Additionally, thermal stability was decreased and Ti decreased by 24 °C. The residual carbon (600 °C) was increased by 25.7%. With the dosage of DIMEC/P increased, the Ea values of DIMEC composite phenolic resins were increased gradually. The reaction orders were all non-integers. Compared with PF, the mechanical properties, flame retardancy, and the residual carbon (800 °C) of CPFs were increased. The cell size of CPFs was less and the cell distribution was relatively regular. By comprehensive analysis, the suitable dosage of DIMEC/P was no more than 15%.