Recently, two-dimensional (2D) materials have been representing wide applications such as sensing devices, catalysis, optoelectronic applications, and medicine [[1], [2], [3], [4]]. Besides, there have been many studies on a new class of 2D materials, carbide-nitride (MXenes), with interesting properties [[5], [6], [7], [8]]. MXenes are also successfully synthesized by the elements of group IIIA or IVA and a carbon or nitrogen. Similar to the 2D transition metal dichalcogenides, MXenes can be semiconducting or metallic [[9], [10], [11], [12], [13], [14], [15]]. Furthermore, these novel 2D materials show much higher conductivity than the graphene layer [16,17]. High performance of the 2D MXene layers have been verified in divers’ fields such as bio-sensors [18] and hydrogen storage applications [[19], [20], [21], [22], [23], [24]]. For instance, Liu et al. [25,26] investigated the application of 2D Ti3C2 in the hydrogen sorption behavior of MgH2. Motivated by the successful synthesis [27,28] of the 2D MXene monolayers with calcium and chromium carbide compositions (Ca2C and Cr2C), in this work we investigate the application of the Ca2C and Cr2C monolayers as adsorbent for use in next generation removal heavy metals (HMs). While the interesting properties of the considered Ca2C and Cr2C MXenes attract high attentions, research on the applications of the considered 2D materials to remove toxic HM ions are still scarce.

Capture of HMs from wastewater is a vital process in the industrial procedures [[29], [30], [31], [32], [33], [34], [35], [36]]. Previously, divers techniques for removing of HMs from wastewater have been proposed. Among these techniques, adsorption is known as a low-cost approach for eliminating the HMs from wastewater [[37], [38], [39]]. As a fascinating experimental research, various isotherms of HMs adsorption on the nanomaterials were recently investigated [40]. While diverse materials have been explored to eliminate of HMs from wastewater [[38], [39], [40], [41], [42]], it has not been performed a comprehensive study to remove the HMs using Ca2C and Cr2C MXene monolayers. Therefore, previous fascinating studies have inspired us for examining the application of synthesized Ca2C and Cr2C [27,28] MXene monolayers as adsorbents to capture toxic HMs. In another word, this research is conducted to explore the performance of Ca2C and Cr2C MXene layers to capture Cd2+, Hg2+, and Pb2+ from wastewater.