# Enhanced Performance of nZVI/MXene@CNTs for Rapid As(III) Removal from Aqueous Solutions
## 1 Introduction  
Arsenic (As(III)) poses a serious ecological concern due to its toxicity and prevalence in the environment [1, 2]. The metalloid properties of arsenic mean that when talking about the environmental problems that it causes, heavy metal pollution is commonly brought up. Arsenic-containing wastewater is widely sourced from industrial activities, such as electroplating, chemical, mining and smelting with poisonous, migratory, and carcinogenic, causing substantial environmental issues and even considerable human health risk [3]. To prevent the negative effects of As(III) on the environment, the World Health Organization set a maximum of 10 \(\mu\)g/L for arsenic in the international drinking-water standards [4]. Thus, purifying arsenic-containing wastewater is one of the most critical environmental issues that needs immediate attention. There are various forms of As(III) in industrial wastewater, including AsO\({}_{3}\)\({}^{-}\),AsO\({}_{4}\)[5] and the crystal shape of arsenite [5, 6]. Because of being more toxic than its oxidized formin wastewater, As(III) has drawn greater attention [7]. The conventional methods were employed for the removal of As(III) from industrial wastewater, including coagulation precipitation [8], electro flocculation [9], ion exchange [10], membrane separation [11], biological methods [12] and adsorption [13]. Adsorption technology, due to its wide adaptability, environmental friendliness and economic characteristics, is regarded as a simple and effective strategy [14; 15]. Consequently, attention has shifted to the innovative synthesis and application of adsorbent materials [16; 17]. [PERSON] [18] et al. investigated kaolinite, montmorillonite and nontronites for As(III) wastewater treatment, and discovered that nontronite with a greater iron concentration (37.63%) had the highest As(III) adsorption capability (0.68 mg/g), compared to montmorillonite (0.26 mg/g) and kaolinite (0.24 mg/g). [PERSON] [19] et al. developed a Leonardite activated-carbon as an adsorbent for the removal of As(III) with an adsorption capacity of 4.5 mg/g, which realized the resource utilization of mine waste. [PERSON] [20] et al. produced pyrolyzed oakwood BC with 3.16 mg/g As(III) removal capacity and revealed that a large BC surface area (475 m\({}^{2}\)/g) and pore volume (0.2 cm\({}^{3}\)/g) could be formed after high temperatures of 500 \({}^{\circ}\)C. Although many natural materials were used for the adsorption of heavy metals due to their low cost, easy access and quick adsorption, the poor removal capability limited their widespread application [21]. Recently, nanotechnology has attracted interest for the potential to address various environmental challenges by manipulating the particle size and surface modifiers [22; 23]. Many of the nanomaterials have been synthesized effectively for the purification of heavy metal wastewater, for instance, carbon nanomaterials [24], nanoscale metal-organic frameworks and their derivatives [25] and transition metal composite nanomaterial, such as iron nanoparticles [26], transition metal oxides [27] (e.g., Fe\({}_{3}\)O\({}_{4}\), Ag\({}_{2}\)O) and transition metal nanocomplex [28; 29] (e.g., Co\({}_{3}\)O\({}_{4}\)/GO, MnO\({}_{2}\)/Fe\({}_{2}\)O\({}_{3}\)@AC). [PERSON] [30] et al. reported that nanoscale zero-valent iron (nZVI) for As(III) adsorption quickly saturated within minutes, with a maximum adsorption capacity of 3.5 mg/g. [PERSON] [31] et al. synthesized bimetallic oxide magnetic nanoparticles (MnFe\({}_{2}\)O\({}_{4}\) and CoFe\({}_{2}\)O\({}_{4}\)) for the purification of low-concentration arsenic solutions, demonstrating that MnFe\({}_{2}\)O\({}_{4}\) and CoFe\({}_{2}\)O\({}_{4}\) had maximum As(III) adsorption capacities of 94.00 mg/g and 100 mg/g, respectively, and the nanoparticles could be reused well by desorption. [PERSON] [32] et al.