MXenes are a family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides with many attractive properties. Two-dimensional Ti3C2Tx (MXene) has been recently explored for applications in water desalination/purification membranes. A major success indicator for any water treatment membrane is the resistance to biofouling. To validate this and to understand better the health and environmental impacts of the new 2D carbides, we investigated the antibacterial properties of single- and few-layer Ti3C2Tx MXene flakes in colloidal solution. The antibacterial properties of Ti3C2Tx were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Ti3C2Tx shows a higher antibacterial efficiency toward both Gram-negative E. coli and Gram-positive B. subtilis compared with graphene oxide (GO), which has been widely reported as an antibacterial agent. Concentration dependent antibacterial activity was observed and more than 98% bacterial cell viability loss was found at 200 μg/mL Ti3C2Tx for both bacterial cells within 4 h of exposure, as confirmed by colony forming unit (CFU) and regrowth curve. Antibacterial mechanism investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with lactate dehydrogenase (LDH) release assay indicated the damage to the cell membrane, which resulted in release of cytoplasmic materials from the bacterial cells. Reactive oxygen species (ROS) dependent and independent stress induction by Ti3C2Tx was investigated in two separate abiotic assays. MXenes are expected to be resistant to biofouling and offer bactericidal properties.

The 21% Ag@MXene composite membrane demonstrated an ultra-high water flux of 420 L m−2h−1bar−1and high rejection efficiency for organic molecules with excellent flux recovery.

Advanced membranes that enable ultrafast water flux while demonstrating anti-biofouling characteristics can facilitate sustainable water/wastewater treatment processes. MXenes, two-dimensional (2D) metal carbides and nitrides, have attracted attention for applications in water/wastewater treatment. In this work, we reported the antibacterial properties of micrometer-thick titanium carbide (Ti3C2Tx) MXene membranes prepared by filtration on a polyvinylidene fluoride (PVDF) support. The bactericidal properties of Ti3C2Tx modified membranes were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by bacterial growth on the membrane surface and its exposure to bacterial suspensions. The antibacterial rate of fresh Ti3C2Tx MXene membranes reaches more than 73% against B. subtilis and 67% against E. coli as compared with that of control PVDF, while aged Ti3C2Tx membrane showed over 99% growth inhibition of both bacteria under same conditions. Flow cytometry showed about 70% population of dead and compromised cells after 24 h of exposure of both bacterial strains. The damage of the cell surfaces was also revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis, respectively. The demonstrated antibacterial activity of MXene coated membranes against common waterborne bacteria, promotes their potential application as anti-biofouling membrane in water and wastewater treatment processes.

No abstract

The performance of two-dimensional (2D) Ti3C2T x MXene nanosheets in the adsorption and copper removal from aqueous media was investigated. Delaminated (DL)-Ti3C2T x exhibited excellent Cu removal ability, because of their large specific surface area, hydrophilicity, and unique surface functional properties. Scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analyses were performed to analyze the structural changes in Ti3C2T x MXene and its interaction with Cu ions. Oxygenated moieties in the layered structure of MXene facilitated reductive adsorption of Cu2+ forming Cu2O and CuO species. DL-Ti3C2T x exhibited a higher and faster Cu uptake, compared to multilayer (ML)-Ti3C2T x . The maximum experimental adsorption capacity (Q exp,max) was 78.45 mg g–1, and 80% of the total content of metal ions was adsorbed within 1 min. A pseudo-second-order kinetic model and the Freundlich adsorption isotherm accurately describe the equilibrium time and maximum Cu uptake onto the adsorbent material, respectively. Thermodynamic analysis revealed that the adsorption process was endothermic. The adsorption capacity (Q e) of DL-Ti3C2T x was 2.7 times higher than that of a commercially available activated carbon. The present results illustrate the promising potential of 2D MXene nanosheets for the removal of toxic metals from water.

Raw municipal wastewater from five wastewater treatment plants representing the vast majority of the Qatar population was sampled between the third week of June 2020 and the end of August 2020, during the period of declining cases after the peak of the first wave of infection in May 2020. The N1 region of the SARS-CoV-2 genome was used to quantify the viral load in the wastewater using RT-qPCR. The trend in Ct values in the wastewater samples mirrored the number of new daily positive cases officially reported for the country, confirmed by RT-qPCR testing of naso-pharyngeal swabs. SARS-CoV-2 RNA was detected in 100% of the influent wastewater samples (7,889 ± 1,421 copy/L – 542,056 ± 25,775 copy/L, based on the N1 assay). A mathematical model for wastewater-based epidemiology was developed and used to estimate the number of people in the population infected with COVID-19 from the N1 Ct values in the wastewater samples. The estimated number of infected people in the population on any given day using the wastewater-based epidemiology approach declined from 542,313 ± 51,159 to 31,181 ± 3,081 over the course of the sampling period, which was significantly higher than the officially reported numbers. However, seroprevalence data from Qatar indicates that diagnosed infections represented only about 10% of actual cases. The model estimates were lower than the corrected numbers based on application of a static diagnosis ratio of 10% to the RT-qPCR identified cases, which is assumed to be due to the difficulty in quantifying RNA losses as a model term. However, these results indicate that the presented WBE modelling approach allows for realistic assessment of incidence trend in a given population, with a more reliable estimation of the number of infected people in a population at any given point in time than can be achieved using human biomonitoring alone.

No abstract

We studied the biocompatibility of Ti3C2TxMXene sheets by analyzing their potential toxicityin vivoand their potential risks on marine biota and ecosystems using a zebrafish embryo model.