The global population growth has led to a significant increase in the demand for freshwater, straining traditional sources like rivers, lakes, and groundwater. Industrial development has further exacerbated the issue by polluting these sources with heavy metals like lead, copper, chromium, and arsenic, posing environmental and health risks (Jaishankar et al., 2014; Mitra et al., 2022). Therefore, it is essential to treat industrial and municipal wastewater to protect our conventional water sources. The severity of clean water scarcity especially in the deserts and rural areas of some developing countries cannot be overemphasized.
Arsenic is a naturally occurring heavy metal found in the environment, ranking 20th in natural abundance (Tchounwou et al., 2012). Arsenic is considered one of the most harmful trace elements in the environment and it exists in both inorganic (iAs) and organic (oAs) forms, with its chemical form and concentration affecting its solubility, mobility, reactivity, bioavailability, and toxicity (Mlangeni et al., 2023). Increases in arsenic levels in the soil over time are primarily caused by human activities such as uncontrolled industrial processes, using arsenic in the production of tools, cosmetics, ornaments, pigments, coal-fired furnaces, glass, tanneries, medicine, mirror manufacturing, and its use in pesticides during the 20th century (Patel et al., 2023). In water, arsenic presence is associated with natural processes including soil erosion, leaching from rocks, chemical reactions, biological activity, volcanic emissions, and industrial activities (Nordstrom, 2002; Smedley & Kinniburgh, 2002).
Arsenic contamination in water is a widespread issue globally. Groundwater and drinking water in many countries (Shaji et al., 2021; Smedley, 1996), including India, Bangladesh, Malaysia, Mexico, Hungary, New Zealand, the USA, Spain, Japan, Canada, Taiwan, and Mainland China, have been impacted by arsenic pollution. Long-term exposure to arsenic in drinking water can increase the incidence of cancer of the skin, lung, liver, bladder, arsenicosis, dermal lesions, peripheral neuropathy, kidney, and prostate (Islam et al., 2023; Smith et al., 1992). Given the global extent of arsenic contamination, it is essential to research and develop methods to understand arsenic chemistry and remove it from water. Common methods for removing arsenic include coagulation, flocculation, adsorption, ion exchange, membrane filtration, bioremediation, solar oxidation, and electrochemical treatments. Adsorption is particularly effective and cost-efficient due to its simplicity (Gao et al., 2020; Guisela B et al., 2022; Koomson et al., 2023; Pincus et al., 2021; Wei et al., 2019; Xing et al., 2022; Younas et al., 2024). Several adsorbents, such as clay, polymers, biological materials, metal oxides, and composite materials, have shown potential for removing arsenic. Despite these advancements, there are still limitations to their use. As a result, there is a pressing need to create new and effective adsorbents that can efficiently remove arsenic from water.
The literature surveys have revealed that numerous researchers consistently strive to develop effective and efficient materials for eliminating hea(Gao et al., 2020; Pincus et al., 2021; Wei et al., 2019)vy metals, including arsenic pollutants, from wastewater often discharged by industrial production processes. Some of these works explored the use of metal-organic frameworks (Dechdacho et al., 2023; Du et al., 2024), biochar (Din et al., 2024; Mon et al., 2024; Wei et al., 2019), and other carbon-based materials (Egbosiuba et al., 2020; Gao et al., 2020; Karić et al., 2022; Pincus et al., 2021; Tolkou & Kyzas, 2023; Wierońska-Wiśniewska et al., 2024). Among the works is Mojiri et al.(2024) that used mineral or clay-based adsorbents like bentonites and zeolites to eliminate arsenic from polluted water, which was similar to the work of Egbosiuba et al. (2024), which used kaolin clay to eliminate arsenic from wastewater with an adsorption capability of 337.22 mg/g. Another is Hua (2018) that confirms the effectiveness of modified bentonite using manganese oxide and poly-dimethyl diallyl ammonium-chloride for eliminating arsenic from wastewater. A biobased adsorbent was also synthesized by Guisela et al. (2022) from eucalyptus bark (a cheaply available material) using an acid treatment, which shows an adsorption capacity of 0.944 mg/g in their studies. The bulk of the works in the literature have consistently focused more on the deployment of experimental approaches in their studies for arsenic elimination from wastewater. Only a few of the works (Yan et al., 2024; S. Zhang et al., 2011; Y. Zhang & Liu, 2019) deployed either computational or hybrid approaches in their investigation. Some of these theoretical studies explored metallic oxides like calcium oxides, iron oxides, and other related sorbents. Wijaj et al. (2016) studied the interaction trends of doping elements on the periodic table with graphene sheets. However, a detailed report for the adsorption mechanism is not reported in the report.
Among the few computational studies that explored arsenic adsorption, there are insignificant reports accounting for the molecular-scale details of arsenic adsorption on graphene-based surfaces or membranes. In this study, we explore the different arsenic adsorption mechanisms on a pristine graphene sheet, which was investigated in a vacuum and aqueous (filled with water) systems using quantum mechanic calculation methods to unravel the effect of solvent on the arsenic adsorption capacity of the pristine graphene. In a nutshell, this study focuses on investigating graphene's adsorption capabilities and its potential for removing arsenic, a major pollutant in wastewater.