Two dimensional MXenes as emerging paradigm for adsorptive removal of toxic metallic pollutants from wastewater

A critical review of MXene-based composites in the adsorptive and photocatalysis of hexavalent chromium removal from industrial wastewater

The growing concern of water pollution is a critical issue stemming from industrialization and urbanization. One of the specific concerns within this broader problem is the toxicity associated with chromium (Cr), especially in its Cr (VI) form. Transition metal carbides/nitrides (MXenes) are attractive materials for the treatment of water due to their unique properties such as layered structure, high surface area, conductivity, flexibility, scalable manufacture, and surface functions. Adsorption and photocatalysis reactions are the two promising methods for the removal of Cr (VI) by using MXenes. Still, most of the previous reviews were limited to the single application area. Hence, this review covers recent developments in MXene-based composites, highlighting their dual role as both adsorbents and photocatalysts in the removal of Cr (VI). MXene-based composites are found to be effective in both adsorption and photodegradation of Cr (VI). Most MXene-based composites have demonstrated exceptional removal efficiency for Cr (VI), achieving impressive adsorption capacities ranging from 100 to 1500 mg g-1 and degradation percentages between 80% and 100% in a relatively short period. The active functional groups present on the surface of MXene have a viable impact on the adsorption and photodegradation performance. The mechanism of Cr (VI) removal is explained, with MXenes playing a key role in electrostatic attraction for adsorption and as co-catalysts in photocatalysis. However, MXene-based composites have limitations such as instability, competition with co-existing ions, and regeneration challenges. Further research is needed to address these limitations. Additionally, MXene-based composites hold promise for addressing water contamination, heavy metal removal, hydrogen production, energy storage, gas sensing, and biomedical applications.

2D sheet structure of zinc molybdate decorated on MXene for highly selective and sensitive electrochemical detection of the arsenic drug Roxarsone in water samples

Water contamination is a serious environmental issue posing a significant global challenge. Roxarsone (ROX), a widely used anticoccidial drug is excreted in urine and feces, potentially disrupting natural habitats. Therefore, rapid and cost-effective ROX detection is essential. In this study, we developed a 2D sheet structure of zinc molybdate decorated on MXene (ZnMoO4/MXene) for detecting ROX using electrochemical methods. The materials were characterized using appropriate spectrophotometric and voltammetric techniques. The ZnMoO4/MXene hybrid exhibited excellent electrocatalytic performance due to its rapid electron transfer rate and higher electrical conductivity. The ZnMoO4/MXene-modified GCE (ZnMoO4/MXene/GCE) showed a broad linear range with high sensitivity (10.413 μA μМ-1 cm-2) and appreciable limit of detection (LOD) as low as 0.0081 μM. It also demonstrated significant anti-interference capabilities, excellent storage stability, and remarkable reproducibility. Furthermore, the feasibility of utilizing ZnMoO4/MXene/GCE for monitoring ROX in water samples was confirmed, achieving satisfactory recoveries.

Unveiling the power of MXenes: Solid lubrication perspectives and future directions

The interaction between two surfaces leads to the generation of friction and wear of material. Friction and wear are some of the major challenges that may readily be overcome by the third part of tribology called lubrication. Utilizing solid lubricants including polymers, carbon-based materials, soft metals, transition metal dichalcogenides, along with their potential benefits and drawbacks in dry environments can reduce friction. Recently, an emerging class of two-dimensional (2D) transition metal nitrides, carbides or carbonitrides commonly known as MXenes have emerged as an attractive alternative for solid lubrication because of their ability to establish wear-resistant tribo layers and well as low friction and shear strength. Furthermore, the inherent hydrophilic nature of these substances has led to limited dispersion stability and phase compatibility when combined with pure base oils. As a result, their potential use as solid lubricants and lubricant additives has been impeded. To address this issue and enhance the applicability of MXenes as solid lubricants, their surface modification can be an attractive tool. Therefore, this review provides a succinct summary of the current state-of-the-art in surface functionalization of MXenes, a subject that has not yet been thoroughly addressed. Further, the mechanical behavior of MXenes and composites has been discussed, followed by the potential of MXenes as a solid lubricant at micro- and macro-scale. Finally, the existing opportunities and challenges of the research area have been discussed with possible future research directions. We believe, this article will be a valuable resource for MXenes and opens the door to improve the chemical, physical and mechanical properties of MXenes in various applications, such as solid lubrication.

Remediation of Safranin-O and Acid Fuchsin by Using Ti3C2 MXene /rGo-Cu2O Nanocomposite: Preparation, Characterization, Isotherm, Kinetics and Thermodynamic Studies

In recent years, MXene has become one of the most intriguing two-dimensional layered (2Dl) materials extensively explored for various applications. In this study, a Ti3C2 MXene/rGo-Cu2O Nanocomposite (TGCNCs) was developed to eliminate Safranin-O effectively (SO) and Acid Fuchsin (AF) as cationic dyes from the aquatic environment. Multistep was involved in the preparation of the adsorbent system, including the Preparation of Ti3C2, after that, GO synthesis by the Humer method, followed by rGO production, then added CuSO4 to obtain a final Nanocomposite (NCs) called "TGCNCs". The structure of TGCNCs can be varied in several ways, including FTIR, SEM, TGA, Zeta, EDX, XRD, and BET, to affirm the efficacious preparation of TGCNCs. A novel adsorbent system was developed to remove SO and AF, both cationic dyes. Various adsorption conditions have been optimized through batch adsorption tests, including the pH of the solution (4-12), the effect of dosage (0.003-0.03 g), the impact of the contact time (5-30 min), and the effect of beginning dye concentration (25-250 mg/L). Accordingly, the TGCNCs exhibited excellent fitting for Freundlich isotherm mode, resulting in maximum AF and SO adsorption capacities of 909.09 and 769.23 mg.g-1. This research on adsorption kinetics suggests that a pseudo-second-order (PSO) model would fit well with the experimental data ( = 0.998 and = 0.990). It is evident from the thermodynamic parameters that adsorption is an endothermic process that is spontaneous and favourable. During the adsorption of SO and AF onto NCs, it is hypothesized that these molecules interact intramolecularly through stacking interactions, H-bond interactions, electrostatic interactions, and entrapment within the polymeric Poros structure nanocomposite. Regeneration studies lasting up to five cycles were the most effective for both organic dyes under study.

Cutting-edge developments in MXene-derived functional hybrid nanostructures: A promising frontier for next-generation water purification membranes

A novel family of multifunctional nanomaterials called MXenes is quickly evolving, and it has potential applications that are comparable to those of graphene. This article provides a current explanation of the design and performance assessment of MXene-based membranes. The production of MXenes nanosheets are first described, with an emphasis on exfoliation, dispersion stability, and processability, which are essential elements for membrane construction. Further, critical discussion is also given to MXenes potential applications in Vacuum assisted filtration, casting method, Hot press method, electrospinning and electrochemical deposition and layer-by-layer assembly for the creation of MXene and MXene derived nanocomposite membranes. Additionally, the discussion is carried forward to give an insight to the modification methods for the construction of MXene-based membrane are described in the literature, including pure or intercalated nanomaterials, surface modifiers and miscellaneous two-dimensional nanomaterials. Furthermore, the review article highlights the potential utilization of MXene and MXene based membranes in separation and purification processes including removal of small organic molecules, heavy metals, oil-water separation and desalination. Finally, the perspective use of MXenes strong catalytic activity and electrical conductivity for specialized applications that are difficult for other nanomaterials to accomplish are discussed in conclusion and future prospectus section of the manuscript. Overall, important information is given to help the communities of materials science and membranes to better understand the potential of MXenes for creating cutting-edge separation and purification membranes.

Environmental remediation of hazardous pollutants using MXene-perovskite-based photocatalysts: A review

Photocatalysis utilizing semiconductors offer a cost-effective and promising solution for the removal of pollutants. MXene and perovskites, which possess desirable properties such as a suitable bandgap, stability, and affordability, have emerged as a highly promising material for photocatalytic activity. However, the efficiency of MXene and perovskites is limited by their fast recombination rates and inadequate light harvesting abilities. Nonetheless, several additional modifications have been shown to enhance their performance, thereby warranting further exploration. This study delves into the fundamental principles of reactive species for MXene-perovskites. Various methods of modification of MXene-perovskite-based photocatalysts, including Schottky junction, Z-scheme and S-scheme are analyzed with regard to their operation, differences, identification techniques and reusability. The assemblance of heterojunctions is demonstrated to enhance photocatalytic activity while also suppressing charge carrier recombination. Furthermore, the separation of photocatalysts through magnetic-based methods is also investigated. Consequently, MXene-perovskite-based photocatalysts are seen as an exciting emerging technology that necessitates further research and development.

Graphitic carbon nitride derived probes for the recognition of heavy metal pollutants of environmental concern in water bodies

Graphitic carbon nitride (g-CN) has a number of valuable features that have been recognized during the studies related to its photocatalytic activity enhancement derived by visible light. Because of these characteristics, g-CN can be used as a detecting signal transducer with different transmission modalities. The latest up-to-date detection capabilities of modified g-CN nanoarchitectures are covered in this study. The structural features and synthetic methodologies have been discussed in a number of reports. Herein, employment of the g-CN as a promising probing modality for the recognition of different toxic heavy metals is the promising feature of the present study.

Can MXene be the Effective Nanomaterial Family for the Membrane and Adsorption Technologies to Reach a Sustainable Green World?

Environmental pollution has intensified and accelerated due to a steady increase in the number of industries, and exploring methods to remove hazardous contaminants, which can be typically divided into inorganic and organic compounds, have become inevitable. Therefore, the development of efficacious technology for the separation processes is of paramount importance to ensure the environmental remediation. Membrane and adsorption technologies garnered attention, especially with the use of novel and high performing nanomaterials, which provide a target-specific solution. Specifically, widespread use of MXene nanomaterials in membrane and adsorption technologies has emerged due to their intriguing characteristics, combined with outstanding separation performance. In this review, we demonstrated the intrinsic properties of the MXene family for several separation applications, namely, gas separation, solvent dehydration, dye removal, separation of oil-in-water emulsions, heavy metal ion removal, removal of radionuclides, desalination, and other prominent separation applications. We highlighted the recent advancements used to tune separation potential of the MXene family such as the manipulation of surface chemistry, delamination or intercalation methods, and fabrication of composite or nanocomposite materials. Moreover, we focused on the aspects of stability, fouling, regenerability, and swelling, which deserve special attention when the MXene family is implemented in membrane and adsorption-based separation applications.

"One-can" strategy for the synthesis of hydrothermal biochar modified with phosphate groups and efficient removal of uranium(VI)

Significant selectivity, reasonable surface modification and increased structural porosity were three key factors to improve the competitiveness of biochar in the adsorption field. In this study, a hydrothermal bamboo-derived biochar modified with phosphate groups (HPBC) was synthesized using "one-can" strategy. BET showed that this method could effectively increase the specific surface area (137.32 m2 g-1) and simulation of wastewater experiments indicated HPBC had an excellent selectivity for U(VI) (70.35%), which was conducive to removal of U(VI) in real and complex environments. The accurate matchings of pseudo-second-order kinetic model, thermodynamic model and Langmuir isotherm showed that at 298 K, pH = 4.0, the adsorption process dominated by chemical complexation and monolayer adsorption was spontaneous, endothermic and disordered. Saturated adsorption capacity of HPBC could reach 781.02 mg g-1 within 2 h. The introduction of phosphoric acid and citric acid by "one-can" method not only provided abundant -PO4 to assist adsorption, but also activated oxygen-containing groups on the surface of the bamboo matrix. Results showed that adsorption mechanism of U(VI) by HPBC included electrostatic action and chemical complexation involving P-O, PO and ample oxygen-containing functional groups. Therefore, HPBC with high phosphorus content, outstanding adsorption performance, excellent regeneration, remarkable selectivity and green value provided a novel solution for the field of radioactive wastewater treatment.

Hybrid Polymer-Silica Nanostructured Materials for Environmental Remediation

Due to the ever-growing global population, it is necessary to develop highly effective processes that minimize the impact of human activities and consumption on the environment. The levels of organic and inorganic contaminants have rapidly increased in recent years, posing a threat to ecosystems. Removing these toxic pollutants from the environment is a challenging task that requires physical, chemical, and biological methods. An effective solution involves the use of novel engineered materials, such as silica-based nanostructured materials, which exhibit a high removal capacity for various pollutants. The starting materials are also thermally and mechanically stable, allowing for easy design and development at the nanoscale through versatile functionalization procedures, enabling their effective use in pollutant capture. However, improvements concerning mechanical properties or applicability for repeated cycles may be required to refine their structural features. This review focuses on hybrid/composite polymer-silica nanostructured materials. The state of the art in nanomaterial synthesis, different techniques of functionalization, and polymer grafting are described. Furthermore, it explores the application of polymer-modified nanostructured materials for the capture of heavy metals, dyes, hydrocarbons and petroleum derivatives, drugs, and other organic compounds. The paper concludes by offering recommendations for future research aimed at advancing the application of polymer-silica nanostructured materials in the efficiency of pollutant uptake.

Organic Covalent Interaction-based Frameworks as Emerging Catalysts for Environment and Energy Applications: Current Scenario and Opportunities

The term "covalent organic framework" (COF) refers to a class of porous organic polymeric materials made from organic building blocks that have been covalently bonded. The preplanned and predetermined bonding of the monomer linkers allow them to demonstrate directional flexibility in two- or three-dimensional spaces. COFs are modern materials, and the discovery of new synthesis and linking techniques has made it possible to prepare them with a variety of favorable features and use them in a range of applications. Additionally, they can be post-synthetically altered or transformed into other materials of particular interest to produce compounds with enhanced chemical and physical properties. Because of its tunability in different chemical and physical states, post-synthetic modifications, high stability, functionality, high porosity and ordered geometry, COFs are regarded as one of the most promising materials for catalysis and environmental applications. This study highlights the basic advancements in establishing the stable COFs structures and various post-synthetic modification approaches. Further, the photocatalytic applications, such as organic transformations, degradation of emerging pollutants and removal of heavy metals, production of hydrogen and Conversion of carbon dioxide (CO₂ ) to useful products have also been presented. Finally, the future research directions and probable outcomes have also been summarized, by focusing their promises for specialists in a variety of research fields.

Strategic analysis on development of simultaneous adsorption and catalytic biodegradation over advanced bio-carriers for zero-liquid discharge of industrial wastewater

With rapid industrial development, millions of tons of industrial wastewater are produced that contain highly toxic, carcinogenic, mutagenic compounds. These compounds may consist of high concentration of refractory organics with plentiful carbon and nitrogen. To date, a substantial proportion of industrial wastewater is discharged directly to precious water bodies due to the high operational costs associated with selective treatment methods. For example, many existing treatment processes rely on activated sludge-based treatments that only target readily available carbon using conventional microbes, with limited capacity for nitrogen and other nutrient removal. Therefore, an additional set-up is often required in the treatment chain to address residual nitrogen, but even after treatment, refractory organics persist in the effluents due to their low biodegradability. With the advancements in nanotechnology and biotechnology, novel processes such as adsorption and biodegradation have been developed, and one promising approach is integration of adsorption and biodegradation over porous substrates (bio-carriers). Regardless of recent focus in a few applied researches, the process assessment and critical analysis of this approach is still missing, and it highlights the urgency and importance of this review. This review paper discussed the development of the simultaneous adsorption and catalytic biodegradation (SACB) over a bio-carrier for the sustainable treatment of refractory organics. It provides insights into the physico-chemical characteristics of the bio-carrier, the development mechanism of SACB, stabilization techniques, and process optimization strategies. Furthermore, the most efficient treatment chain is proposed, and its technical aspects are critically analysed based on updated research. It is anticipated that this review will contribute to the knowledge of academia and industrialist for sustainable upgradation of existing industrial wastewater treatment plants.

Applications of advanced MXene-based composite membranes for sustainable water desalination

MXenes are an innovative class of 2D nanostructured materials gaining popularity for various uses in medicine, chemistry, and the environment. A larger outer layer area, exceptional stability and conductivity of heat, high porosity, and environmental friendliness are all characteristics of MXenes and their composites. As a result, MXenes have been used to produce Li-ion batteries, semiconductors, water desalination membranes, and hydrogen storage. MXenes have recently been used in many environmental remediations, frequently surpassing conventional materials, to treat groundwater contamination, surface waters, industrial and municipal wastewaters, and desalination. Due to their outstanding structural characteristics and the enormous specific surface area, they are widely utilized as adsorbents or membrane materials for the desalination of seawater. When used for electrochemical applications, MXene-composites can deionize via Faradaic capacitive deionization (CDI) and adsorb various organic and inorganic pollutants to treat the water. In general, as compared to other 2D nanomaterials, MXene has superb characteristics; because of their magnificent characteristics and they exhibit strong desalination capability. The current review paper discusses the desalination capability of MXenes and their composites. Focusing on the desalination capacity of MXene-based nanomaterials, this study discusses the characteristics and synthesis techniques of MXenes their composites along with their ion-rejection capability and pervaporation desalination of water via MXene-based membranes, capacitive deionization capability, solar desalination capability. Furthermore, the challenges and prospects of MXenes and their composites are highlighted.

Recent advances in carbon-based nanomaterials for the treatment of toxic inorganic pollutants in wastewater

Wastewater contains inorganic pollutants, generated by industrial and domestic sources, such as heavy metals, antibiotics, and chemical pesticides, and these pollutants cause many environmental problems.

Rapid growth of MXene-based membranes for sustainable environmental pollution remediation

Water consumption has grown in recent years due to rising urbanization and industry. As a result, global water stocks are steadily depleting. As a result, it is critical to seek strategies for removing harmful elements from wastewater once it has been cleaned. In recent years, many studies have been conducted to develop new materials and innovative pathways for water purification and environmental remediation. Due to low energy consumption, low operating cost, and integrated facilities, membrane separation has gained significant attention as a potential technique for water treatment. In these directions, MXene which is the advanced 2D material has been explored and many applications were reported. However, research on MXene-based membranes is still in its early stages and reported applications are scatter. This review provides a broad overview of MXenes and their perspectives, including their synthesis, surface chemistry, interlayer tuning, membrane construction, and uses for water purification. Application of MXene based membrane for extracting pollutants such as heavy metals, organic contaminants, and radionuclides from the aqueous water bodies were briefly discussed. Furthermore, the performance of MXene-based separation membranes is compared to that of other nano-based membranes, and outcomes are very promising. In order to shed more light on the advancement of MXene-based membranes and their operational separation applications, significant advances in the fabrication of MXene-based membranes is also encapsulated. Finally, future prospects of MXene-based materials for diverse applications were discussed.

Advances in 2D MXenes-based materials for water purification and disinfection: Synthesis approaches and photocatalytic mechanistic pathways

MXenes two-dimensional materials have recently excited researchers' curiosity for various industrial applications. MXenes are promising materials for environmental remediation technologies to sense and mitigate various intractable hazardous pollutants from the atmosphere due to their inherent mechanical and physicochemical properties, such as high surface area, increased hydrophilicity, high conductivity, changing band gaps, and robust electrochemistry. This review discusses the versatile applications of MXenes and MXene-based nanocomposites in various environmental remediation processes. A brief description of synthetic procedures of MXenes nanocomposites and their different properties are highlighted. Afterward, the photocatalytic abilities of MXene-based nanocomposites for degrading organic pollutants, removal of heavy metals, and inactivation of microorganisms are discussed. In addition, the role of MXenes anti-corrosion support in the lifetime of some semiconductors was addressed. Current challenges and future perspectives toward the application of MXene materials for environmental remediation and energy production are summarized for plausible real-world use.

Graphitic carbon nitride nanosheets as promising candidates for the detection of hazardous contaminants of environmental and biological concern in aqueous matrices

Monitoring of pollutant and toxic substances is essential for cleaner environment and healthy life. Sensing of various environmental contaminants and biomolecules such as heavy metals, pharmaceutics, toxic gases, volatile organic compounds, food toxins, and pathogens is of high importance to guaranty the good health and sustainable environment to community. In recent years, graphitic carbon nitride (g-CN) has drawn a significant amount of interest as a sensor due to its large surface area and unique electrochemical properties, low bandgap energy, high thermal and chemical stability, facile synthesis, nontoxicity, and electron rich property. Furthermore, the binary and ternary nanocomposites of graphitic carbon nitride further enhance their performance as a sensor making it a cost effective, fast, and reliable gadget for the purpose, and opens a wide area of research. Numerous reviews addressing a variety of applications including photocatalytic energy conversion, photoelectrochemical detection, and hydrogen evolution of graphitic carbon nitride have been documented to date. But a lesser attention has been devoted to the mechanistic approaches towards sensing of variety of pollutants concerned with environmental and biological aspects. Herein, we present the sensing features of graphitic carbon nitride towards the detection of various analytes including toxic heavy metals, pharmaceuticals, phenolic compounds, nitroaromatic compounds, volatile organic molecules, toxic gases, and foodborne pathogens. This review will undoubtedly provide future insights for researchers working in the field of sensors, allowing them to investigate the intriguing graphitic carbon nitride material as a sensing platform that is comparable to several other nanomaterials documented in the literature. Therefore, we hope that this study could reveal some intriguing sensing properties of graphitic carbon nitride, which may help researchers better understand how it interacts with contaminants of environmental and biological concern. Graphitic carbon nitride Nanosheets as Promising Analytical Tool for Environmental and Biological Monitoring of Hazardous Substances.

Facet engineering of ultrathin two-dimensional materials

Ultrathin two-dimensional (2D) materials exhibit broad application prospects in many fields due to the enhanced specific surface area to volume ratio and quantum confinement effect. Because of the atomic thickness and various orientations, ultrathin 2D materials exposing specific facets have drawn great attention for various applications in catalysis, batteries, optoelectronics, magnetism, epitaxial template for material growth, etc. Though maintaining the atomic thickness of 2D materials while controlling crystal facets is an enormous challenge, breakthroughs are being made. This review provides a comprehensive overview of the recent advances in the facet engineering of 2D materials, ranging from a basic understanding of facets and the corresponding approaches and the significance of facet engineering. We also propose current challenges and forecast future development directions including the establishment of a facet database, the fabrication of new 2D materials, the design of specific substrates, and the introduction of theoretical calculations and in situ characterization techniques. This review can guide researchers to design ultrathin 2D materials with unique and distinct facets and provide an insight into the applications of energy, magnetism, optics, biomedicine, and other fields.

Covalent organic frameworks as promising adsorbent paradigm for environmental pollutants from aqueous matrices: Perspective and challenges

Covalent organic frameworks (COFs) are an emerging class of new porous crystalline polymers materials having robust framework, outstanding structural regularity, highly ordered aperture size, inherent porosity, and chemical stability with designer properties, making them an ideal material for adsorbing a variety of contaminants from water bodies. Presented study focusses on the current advances and progress of pristine COFs as well as COFs based composites as an emerging substitute for the adsorption and removal of a variety of pollutants including water desalination technique, heavy metals, pharmaceuticals, dyes and organic pollutants. The absorption capabilities of COFs-derived architecture are evaluated and equated with those of other commonly used adsorbents. The interaction between sorption ability and structural property as well as some regularly utilized ways to improve the adsorption performance of COFs-based materials are also reviewed. Finally, perspective and a summary about the challenges and opportunities of COFs and COFs-derived materials are discussed to deliver some exciting data for fabricating and designing of COFs and COFs-derived materials for remediation of environmental pollutants.

Covalent Organic Frameworks-Based Membranes as Promising Modalities from Preparation to Separation Applications: An Overview

Covalent organic frameworks (COFs) are a promising class of porous crystalline materials made up of covalently connected and periodically protracted network topologies through organic linkers. The tailorability of organic linker and intrinsic structures endow COFs with a tunable porosity and structure, low density, facilely-tailored functionality, and large surface area, attracting increasing amount of interests in variety of research areas of membrane separations. COF-based membranes have spawned a slew of new research projects, ranging from fabrication methodologies to separation applications. Herein, we tried to emphasis the major developments in the synthetic approaches of COFs based membranes for a variety of separation applications such as, separation of gaseous mixtures, water treatment as well as separation of isomeric and chiral organic compounds. The proposed methods for fabricating COF-based continuous membranes and columns for real world applications are also thoroughly explored. Finally, a viewpoint on the future directions and remaining challenges for COF research in the area of separation is provided.

Removal of Malachite Green Dye from Water Using MXene (Ti3C2) Nanosheets

In the present study, new emerging 2D Mxene nanosheets (MXNSs) were synthesized from MAX phase powders of Ti3AlC2 and then characterized using a scanning electron microscope (SEM) and X-ray diffraction (XRD) to explore the chemical and physical properties of the prepared MXNS. The characterization of the synthesized MXNS indicated the formation of exfoliated 2D MXene nanosheets (Ti3C2) as a result of the HF treatment of the MAX phase, which was confirmed by XRD measurements, as the characteristic peaks of 2D MXene nanosheets were only observed. The synthesized MXNS was then used as a solid adsorbent for removing malachite green dye (MG) from water. The effects of different operational factors such as MXNS dose, solution temperature, time, MG concentration, solution pH, and ionic strength have also been evaluated. The adsorption results showed that the temperature of the solution, as well as its pH, significantly influenced MG removal when using MXNS. The optimum removal was obtained within 150 min, with 20 mg of MXNS at ambient temperature and a pH value of 6.0. The maximum removal capacity obtained was 4.6 mg MG per g of MXNS using 5 mg of MXNS with a removal efficacy of 46.0%, and the minimum removal capacity obtained was 2.5 mg MG per g of MXNS using 20 mg of MXNS with a removal efficacy of 99.1%. Finally, the results displayed that the MXNS solid adsorbent was able to absorb a high percentage of MG and maintained reasonable efficiency for four consecutive cycles, indicating that MXNS could be a promising adsorbent in wastewater remediation and environmental sustainability.

Salt Removal by Chemically Modified Graphene in Capacitive Deionization (CDI)

Obtaining clean water from salt water by capacitive deionization (CDI) with chemically modified graphene (rGO) was explored in this study. Strong acid (HNO3:H2SO4 = 2:1) was employed to modify rGO to enhance its hydrophilicity and electrochemical properties. Characteristics of rGO with/without acid modification were analyzed by XRD, SEM, FTIR, contact angle, BET, and cyclic voltammetry (CV). Contributions of sulfonic acid groups, hydroxyl groups, and NO2 stretching after acid modification resulted in better wettability and higher specific capacitance of rGO. The contact angle for rGO dropped from 84.9° to 35.1° (am-rGO), indicating improved hydrophilicity of rGO with acid modification. The specific capacitance of am-rGO can reach 150.2 F/g at the scan rate of 1 mV/s. The average NaCl electrosorption capacity of the CDI process with am-rGO was 0.63 mg NaCl/g electrode (10.86 μmol NaCl/g electrode), which indicated rGO with acid modification can enhance the electrosorption capacity by 3.9 times. This study demonstrated that chemical modification can significantly improve the hydrophilicity, electrochemical properties, and electrosorption performance of rGO, which has potential for applications to other carbon-based materials for CDI systems to improve salt removal efficiency.

Thermodynamic and kinetic coupling modeling for thallium(I) sorption at a heterogeneous titanium dioxide interface

The transformations of monovalent thallium (Tl) in an aqueous environment may be affected significantly by Tl(I) partitioning at the solid-water interface during sorption. Models used to quantify the kinetics of Tl(I) adsorption on heterogeneous adsorbents and formation of multiple complexes under a wide range of water chemistry conditions can accurately predict the environmental fate of thallium. In this study, Tl(I) sorption on representative titanium dioxide at different solution pH values and loading concentrations was investigated with two unified adsorption models, diffuse layer modeling and kinetics modeling. Three Tl(I) surface complexes, TiOTl, TiOHTl⁺, and TiOTlOH^-, were used in the diffuse layer model and successfully described batch adsorption and the results of spectroscopic analyses. The contribution of TiOHTl⁺ to the adsorption capacity was much higher than those of TiOTl and TiOTlOH^- under neutral and weakly alkaline conditions, while the species TiOTlOH^- predominated among Tl(I) complexes in strongly alkaline environments. The adsorption and desorption rate coefficients derived from thermodynamics and kinetics coupling modeling suggested the influence of different complex characteristics on adsorption and desorption of Tl(I). Our results provide a comprehensive model for predicting the dynamic binding behavior of Tl at heterogeneous solid-water interfaces.

Novel synthesis methods and applications of MXene-based nanomaterials (MBNs) for hazardous pollutants degradation: Future perspectives

MXenes are a quickly growing and extended group of two-dimensional (2D) substances that have earned unbelievable analysis credits for various application areas within different manufacturing areas. Due to novel essential architectural and physicochemical properties shows good properties, such as elevated exterior area, living adaptability, strong electrochemistry, and great hydrophilicity. Given the fast progress within the structure and synthesis of MBNs for water treatment, quick updates on this research field are required to remove toxic substances, such as production approaches and characterization methods for the advantages and constraints of MXenes for pollutant degradation. MXenes are determined as a proposed road toward atmosphere-clean-up machinery to identify and decrease a pattern of hazardous resistant pollutants from environmental forms. Here, in this review article, we have been focused on describing the overview, novel synthesis methods, and characteristics of the MXene-based nanomaterials (MBNs) in the field for removing hazardous contaminants from environmental conditions. In the last, the utilizations of MBNs in water sanitization, organic solvent filtration, antibiotics degradation, pesticide degradation, heavy metals degradation, ions removal, bacterial pathogens degradation, along with the conclusion, challenges, and prospects in this field, have been discussed.

MXene-laden bacteriophage: A new antibacterial candidate to control bacterial contamination in water

In this study, Ti₃C₂ MXene nanofragments with a size distribution of about 20 nm were laden on the well-characterized bacteriophages via electrostatic bonding, introducing a new antibacterial agent as a modified virus vector to be used in high-risk bacterial environment. At > MIC of MXene, the MXene-functionalized bacteriophage would be much more active in attacking the bacteria because of the high specificity for host receptors' recognition and targeting ability of bacteriophage and bacterial surface negative charge when comparing to the phage alone. Also, the induced positive surface moieties drive MXene nanofragments toward the negative surface charge of bacteria. The main mechanisms are the specific targeting capacity of bacteriophages, often by lysing the host and bursting out, and the physical interaction of MXene nanofragments with the bacterial cell membrane, which may rupture the cell wall in microbial death. The results described that the Ti₃C₂ MXene significantly enhanced the bacteriophage adsorption rate and stability over long-standing cultivation in aquatic environments providing superior antibacterial efficacy against the bacterial cells target. The Ti₃C₂ MXene-laden bacteriophage demonstrated a fast, efficient attaching to bacterial host cells, high antibacterial potential, and reduced 99.99% of the artificial contamination in water samples. Interestingly, no re-growth of target bacteria was observed in the samples during the experiment period, and the count of bacteria constantly remained below the detection threshold. This research raises attention in proposing a novel antibacterial agent to be synthesized through a simple one-step technique devoid of shortcomings of post-treatments in conventional antibacterial treatments.