The increasing global population and the deterioration of water sources are leading to a rise in water consumption worldwide [1], Surface water and groundwater pollution are primarily caused by contaminants from municipal, industrial, and agricultural activities [2]. This degradation in water quality poses a severe threat to the availability of freshwater for human use. Water covers around 70 % of the Earth's surface [3], with the majority being saltwater in oceans and seas [4]. In response to the growing demand driven by population growth [5], agricultural development [6], and industrial expansion, many arid regions and countries are turning to desalination to supplement their water supply.

In today's world, the issue of heavy metal contamination is a matter of great concern, mainly due to industrial production generating substantial amounts of wastewater containing these pollutants [7]. Heavy metals present serious hazards to human health and the environment, as they are non-biodegradable, toxic, and have a tendency to accumulate in living organisms [8]. Nitrate and nitrite are inorganic nitrogen-containing ions, present as groundwater contaminants from industrial and natural sources. They can also be found in food products and drinking water [9], posing health risks such as the formation of potentially carcinogenic nitroamides and nitrosamines [10], as well as causing methemoglobinemia, especially in infants. Numerous techniques, encompassing both efficient biological processes and physicochemical procedures, have been suggested to remove nitrogen compounds from water intended for human consumption [11]. Reverse osmosis (RO) is a physical process that uses external pressure to push water through a semi-permeable membrane, effectively trapping dissolved materials [12]. RO is capable of simultaneously separating multiple contaminants, producing high-quality water regardless of the initial water quality [13].

In the realm of water filtration technologies, novel two-dimensional (2D) nanomaterials are being increasingly utilized owing to their unique properties, including nano-sized pores [14], atomic-scale thickness [15,16], high surface area [17], and stability [18,19]. Remarkably, their atomic-scale thickness enables high liquid permeability, surpassing that of commercial nanofiltration (NF) membranes by several times [[18], [19], [20]]. Their atomic-scale thickness contributes to their exceptional liquid permeability, which exceeds that of commercial nanofiltration (NF) membranes by several times [21,22]. Graphene, which is a million times thinner than paper and almost transparent, has very high thermal conductivity, excellent optical properties [23,24], and is believed to be the most robust material in the world [25]. Graphene's remarkable properties and single-layer structure make it highly versatile for various applications [23,26], including field-effect transistors [27], flexible electronics [28], optical detectors, composite materials, energy storage, precision sensors, and drug delivery [29,30].

In this type of 2D material, the thickness is significantly less than that in the other two dimensions, leading to significant changes in the electronic structure and network dynamics [31]. In contrast, graphene analogs share the atomic layer structure of graphene, their physical properties differ, giving rise to unique characteristics. Graphene is characterized by its direct zero band gap and metallic properties in terms of electronic properties. In contrast, various other 2D crystals display a diverse range of band structures. The structure of graphene replaces C–C aromatic bonds in graphene with acetylene chains. In addition, graphene structures show attractive semi-conducting properties that enable their use in electronic devices [32]. It is also thought that these structures are possible candidates for gas separation, filtration and water desalination due to inherent nanopores [32,33].

Chalcogenides are an emerging class of 2D materials, represented by the transition metal dichalcogenide (TMDC) MX2. For MX2, the intermediate metal atom layer M (Mo, W, Ta, Nb) is surrounded by two layers of chalcogen atoms S (S, Se, Te) [34]. MX2 has two typical phases: 2H and 1T; 2h phases have been studied more than 1T. GaS, GaSe and InSe are chalcogenides with a double metal layer that is placed between two chalcogen layers and forms a vertical X-M-M-X structure. MXene is produced by A-group element etching of ternary layered metal carbides, nitrides, or carbonitrides (max phases), where M represents a primary, intermediate metal, such as titanium (Ti), scandium (Sc), vanadium (V), niobium (Nb), titanium (Ta) [35]. A represents an element of group A (group three or four), and X represents C, or N is represented by the general formula Mn+1AXn (n = 1–3) and the resulting MXene as Mn+1XnTx, where Tx is the surface caused by hydrofluoric acid (HF) etching or a mixture of lithium It is fluoride and hydrochloric acid (LiF/HCl). Some computational studies have highlighted the potential of carbon nitride and artificial channels [36] for water purification and ion removal [[37], [38], [39], [40]].

In a recent study, Mao et al. [41], explored the transport of two typical ions, namely Cl− and NO3− through a carbon nanotube-based nano-channel by using an all-atom molecular dynamics simulation. The results indicate that ion dehydration is crucial for selectivity with complicated dependency on pore size and electronic potential, as well as ion geometry. Meidani et al. [42] discussed an in-depth study on a class of MXenes known as titanium carbides (Tin+1 Cn) by employing extensive molecular dynamics simulations. Their research revealed that the 50 Å2 nanopores on Ti3C2 membranes have the remarkable ability to reject >99 % of ions, demonstrating a 20−55 % higher permeation rate compared to graphene, MoS2, and other MXene membranes. Majidi et al. [43] performed a study utilizing all-atom molecular dynamics simulation to assess the effectiveness of g-C3N4 and C2N nano-sheets in separating nitrite and nitrate pollutants from aqueous solutions. The findings demonstrated that these membranes exhibit high rejection capability for nitrate and nitrite ions under high-pressure conditions, with water flux being enhanced by hydrogen bonding dynamics.

In this study, we investigate the performance of MXene membrane in removing pollutants such as nitrite or nitrate from water. For this purpose, the effect of various parameters such as the size of the pores, the structure of the MXene, characteristics of the cavities, applied pressure, flux, etc. This study underscores the significance of 2D materials in achieving efficient filtration of anionic compounds while maintaining high water permeance. The structure of MXene is Mn2C, Ti2C, and V2C. Based on the obtained results, Ti2C provided the best performance for removing nitride and nitrate. This phenomenon is due to the differences in electronegativity radii of Ti atoms, titanium, vanadium, and manganese. Titanium has a larger covalent radius and lower electronegativity. The charge distribution in the Ti2C structure is higher than in other structures.