Electrocatalytic oxidation of antidiabetic drug metformin adsorbed on intercalated MXene

Understanding the potential role of microbial electrolysis cells in promoting electron transfer and microbial metabolism during the drying period in treating metformin-containing wastewater with an adsorption-biological coupling system

Effective removal of metformin from wastewater through biological treatment technology has been a challenging issue. Enhancing electron transfer was demonstrated to be an effective measure to improve the removal of refractory pollutants from wastewater. In this study, the effects of a microbial electrolysis cell (MEC) in strengthening an adsorption-biological coupling reactor during the drying period in treating metformin wastewater were investigated, along with its microbial community and metabolism. Compared to without a MEC, the removal rates of chemical oxygen demand (COD), total phosphorus (TP), ammonia-nitrogen, and metformin all increased with the increase of voltage; at 1.0 V, their removal rates were 77.26 %-91.45 %, 59.22 %-75.85 %, 79.52 %-91.56 %, and 57.45 %-70.15 % respectively. The main dominant bacteria in the two groups were Pseudomonadota (28.14 %-75.72 % and 13.51 %-84.79 %, respectively) and Actinobacteria (16.27 %-67.10 % and 6.11 %-84.27 %). The MEC increased the relative abundance of glycolytic glucokinase and pyruvate kinase genes. In nitrogen metabolism, dissimilar nitrate reduction was strengthened. In addition, the relative abundance of the functional genes involved in phosphate translocation, electron transport-linked phosphorylation, and phosphate metabolism were all increased after voltage addition, which promoted microbial activity and increased the TP removal rate.

Effective radioactive strontium removal using lithium titanate decorated Ti3C2Tx MXene/polyacrylonitrile beads

A lithium titanate-decorated Ti3C2Tx MXene (LTO-MX) composite was synthesized through etching and alkali processes, and subsequently immobilized using polyacrylonitrile (PAN) polymer via a phase inversion method. In the batch study, the strontium adsorption behavior followed the Redlich-Peterson isotherm and the pseudo-second-order kinetic models. The maximum adsorption capacity for strontium reached 24.05 mg/g. Furthermore, a continuous fixed-bed column study was performed using the LTO-MX PAN beads to remove strontium from aqueous solutions. The dynamic behavior of column adsorption was examined under various operating parameters such as initial strontium concentration, flow rate, and bed height. Dynamic modeling was employed to describe adsorption breakthrough properties based on these experimental data. Both the Thomas and Yoon-Nelson models accurately simulated the breakthrough curves. The proposed mechanisms for strontium adsorption included encapsulation, electrostatic attraction, cation exchange, and surface complexation. These results demonstrate the effectiveness of LTO-MX PAN beads as adsorbents for the continuous removal of strontium from radioactive wastewater.

MXenes as emerging adsorbents for removal of environmental pollutants

MXenes are a recently emerging class of two-dimensional nanomaterials that have gained considerable interest in the field of environmental protection. Owing to their high surface area, abundant terminal groups, and unique two-dimensional layered structures, MXenes have demonstrated high efficacy as adsorbents for various pollutants. Here we focused on the latest developments in the field of MXene-based adsorbents, including the structure and properties of MXenes, their synthesis and modification methods, and their adsorption performance and mechanisms for various pollutants. Among the pollutants that have been reported to be adsorbed by MXenes are radionuclides (U(VI), Sr(II), Cs(I), Eu(III), Ba(II), Th(IV), and Tc(VII)/Re(VII)), heavy metals (Hg(II), Cu(II), Cr(VI), and Pb(II)), dyes, per- and polyfluoroalkyl substances (PFAS), antibiotics (tetracycline, ciprofloxacin, and sulfonamides), antibiotic resistance genes (ARGs), and other contaminates. Moreover, future directions in MXene research are also suggested in this review.