Ti3C2Tx MXene@MOF decorated polyvinylidene fluoride membrane for the remediation of heavy metals ions and desalination

Recent advances of MXene@MOF composites for catalytic water splitting and wastewater treatment approaches

MXenes are a group of 2D material which have been derived from the layered transition metal nitrides and carbides and have the characteristics like electrical conductivity, high surface area and variable surface chemical composition. Self-assembly of clusters/metal ions and organic linkers forms metal organic framework (MOF). Their advantages of ultrahigh porosity, highly exposed active sites and many pore architectures have garnered them a lot of attention. But poor conductivity and instability plague several conventional MOF. To address the issue, MOF can be linked with MXenes that have rich surface functional groups and excellent electrical conductivity. In this review, different etching methods for exfoliation of MXene along with the synthesis methods of MXene/MOF composites are reviewed, including hydrothermal method, solvothermal method, in-situ growth method, and self-assembly method. Moreover, application of these MXene/MOF composites for catalytic water splitting and wastewater treatment were also discussed in details. In addition to increasing a single MOF conductivity and stability, MXenes can add a variety of new features, such the template effect. Due to these benefits, MXene/MOF composites can be effectively used in several applications, including photocatalytic/electrocatalytic water splitting, adsorption and degradation of pollutants from wastewater. Finally, the authors explored the current challenges and the future opportunities to improve the efficiency of MXene/MOF composites.

Design and application of metal organic frameworks for heavy metals adsorption in water: a review

The growing apprehension surrounding heavy metal pollution in both environmental and industrial contexts has spurred extensive research into adsorption materials aimed at efficient remediation. Among these materials, Metal-Organic Frameworks (MOFs) have risen as versatile and promising contenders due to their adjustable properties, expansive surface areas, and sustainable characteristics, compared to traditional options like activated carbon and zeolites. This exhaustive review delves into the synthesis techniques, structural diversity, and adsorption capabilities of MOFs for the effective removal of heavy metals. The article explores the evolution of MOF design and fabrication methods, highlighting pivotal parameters influencing their adsorption performance, such as pore size, surface area, and the presence of functional groups. In this perspective review, a thorough analysis of various MOFs is presented, emphasizing the crucial role of ligands and metal nodes in adapting MOF properties for heavy metal removal. Moreover, the review delves into recent advancements in MOF-based composites and hybrid materials, shedding light on their heightened adsorption capacities, recyclability, and potential for regeneration. Challenges for optimization, regeneration efficiency and minimizing costs for large-scale applications are discussed.

Application of Ag nanoparticles decorated on graphene nanosheets for electrochemical sensing of CEA as an important cancer biomarker

In this research, a novel biosensing platform is described based on graphene nano-sheets decorated with Ag nano-particles (GNSs@Ag NPs). The designed electrochemical aptasensor was employed to determine carcinoembryonic antigen (CEA), an important cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity for CEA tumor marker because of the high specific surface area and excellent conductivity of the prepared GNSs@Ag NPs composite. The established assay demonstrated a wide linear range from 0.001 pg/mL to 10 pg/mL with a correlation coefficient of 0.9958 and low detection limit (DL) of 0.5 fg/mL based on S/N = 3 protocol. The derived biosensor illustrated acceptable selectivity towards common interfering species including HER2, VEGF, IgG, MUC1 and CFP10. In addition, the aptsensor showed good reproducibility and fast response time. The applicability of the suggested strategy in human serum samples was also examined and compared to the commercial enzyme-linked immunosorbent assay (ELISA). Based on the experimental data, it was found that the discussed sensing platform can be exerted in the monitoring of CEA in different cancers for early diagnosis.

Photoelectrocatalytic modification of nanofiltration membranes with SrF2/Ti3C2Tx to simultaneously enhance heavy metal ions rejection and permeability

Heavy metal pollution can significantly harm water systems and human health. Combining photoelectrocatalytic (PEC) and nanofiltration (NF) membrane separation technologies can effectively remove heavy metal ions from wastewater. In this study, a water bath method was used to form SrF2/Ti3C2Tx (ST) nanoparticles on the surface of polyvinylidene fluoride (PVDF) membranes and an additional polyamide (PA) functional layer was formed at the interface by crosslinking. ST@PA composite NF membranes (STPP) with good photocatalytic performance were obtained. The separation and catalytic properties of the STPP membranes were controlled by the ST content, which modifies the surface structure and properties of the membranes. The membrane with optimal ST crosslinking exhibited a water contact angle of 50.8°, pure water flux of 24.6 L·m-2·h-1·bar-1, and rejection rates of Mn2+, Ni2+, Cu2+, and Zn2+ of 98.8%, 95.3%, 95.7%, and 97.3%, respectively, under PEC-assisted separation with visible light illumination from a Xe lamp (300 W) and an applied voltage (2 V). The STPP membranes showed improved rejection rates of heavy metal ions under PEC-assisted operation. The mechanism for the improved membrane performance under PEC conditions was preliminarily clarified considering the relationship between the photocatalytic and filtration properties of STPP membranes along with the influence of light irradiation and an external voltage on the heavy metal ions. The generation of electrons, holes, superoxide radicals, and hydroxyl radicals during membrane operation enhances the rejection rates of heavy metal ions. Based on these results, STPP membranes are considered a promising technology for industrial applications in heavy metal removal.

ZnO/PDA/Mesoporous Cellular Foam Functionalized Thin-Film Nanocomposite Membrane towards Enhanced Nanofiltration Performance

Thin-film nanocomposite (TFN) membranes are the third-generation membranes being explored for nanofiltration applications. Incorporating nanofillers in the dense selective polyamide (PA) layer improves the permeability-selectivity trade-off. The mesoporous cellular foam composite Zn-PDA-MCF-5 was used as a hydrophilic filler in this study to prepare TFN membranes. Incorporating the nanomaterial onto the TFN-2 membrane resulted in a decrease in the water contact angle and suppression of the membrane surface roughness. The pure water permeability of 6.40 LMH bar^-1 at the optimal loading ratio of 0.25 wt.% obtained was higher than the TFN-0 (4.20 LMH bar^-1). The optimal TFN-2 demonstrated a high rejection of small-sized organics (>95% rejection for 2,4-dichlorophenol over five cycles) and salts-Na₂SO₄ (≈95%) > MgCl₂ (≈88%) > NaCl (86%) through size sieving and Donnan exclusion mechanisms. Furthermore, the flux recovery ratio for TFN-2 increased from 78.9 to 94.2% when challenged with a model protein foulant (bovine serum albumin), indicating improved anti-fouling abilities. Overall, these findings provided a concrete step forward in fabricating TFN membranes that are highly suitable for wastewater treatment and desalination applications.