## 1 Introduction
Physical methods, meanwhile, rely on techniques such as reverse osmosis, employing semi-permeable membranes to eliminate contaminants, but it is necessary to consider that the applicability of this technique, the treatment performance, and its cost are necessary factors in determining the most appropriate technology for treating contaminated water [24]. Furthermore, adsorption processes are utilized, primarily involving materials like activated carbon, zeolites, clays, biogenic compounds and porous materials, which effectively retain arsenic and chromium ions [25; 26; 27; 28; 29; 30; 31; 32]. Also, some synthetic minerals are used for the removal of heavy metals, such as schwertmannite, which is synthesized by a modified chemical oxidation process to obtain nanoparticles of this compound and which has been adequately used for the adsorption of As [33; 34; 35; 36]. This synthesized compound again shows the affinity of Fe(III) for As, since increasing the Fe content in the synthesized material improves the adsorption of As(V). Thus, the use of iron hydroxides can improve the adsorption of As(III) and As(V), when used together with the addition of an adsorbent such as calcium contained in calcite [37], which does not seem to occur with Cr, since the presence of this element in the adsorbent apparently decreases the amount of adsorbed Cr ions [38]. On the other hand, the simultaneous removal of As(V) and Cr(VI) was possible with the use of a graphene oxide functionalized ferrohydrite. Here, the greater affinity of As for Fe than Cr is clearly noted [39]. Similarly, in nature, there are groups of related minerals that are the product of oxidative and reductive processes involving iron as the main active element in the adsorption of heavy metals. Examples of minerals that could act like adsorbents for As and Cr could be be beundatite [40; 41], scorodite [42; 43], alunite [44; 45; 46], goethite [47; 48], and jarosite [49; 50; 51; 52; 53; 54; 55], among others. Based on the above, arsenic adsorption was achieved at room temperature with synthetic potassium jarosite, with encouraging results [14]. Therefore, this study demonstrates the possibility of using industrial jarosite, considered a toxic waste, for the adsorption of As and Cr. This preliminary study demonstrates the potential of a harmful waste like jarosite to adsorb arsenic and chromium, offering a promising solution for the removal of these contaminants from polluted water. The innovation lies in the possibility that this residue can adsorb heavy metals, then desorb or isolate them, and repeatedly adsorb and desorb them several times, which can reduce costs and improve efficiency by using a waste already considered toxic and hazardous. While this breakthrough holds great promise, its implementation may face challenges related to its scalability, cost-effectiveness, and environmental sustainability. Nevertheless, this research paves the way for further investigations and potential applications of using a toxic waste in water remediation. In both situations, the full impact could be significant for communities affected by water pollution and for the places where these toxic wastes are produced from mining activities, and this could now be a solution to eliminate any As and Cr contained in water. So, in this study, the hypothesis is that industrial jarosite, considered a toxic waste, can be effectively used for the repeated adsorption and desorption of arsenic and chromium in contaminated water, reducing costs and improving efficiency in water remediation. Then, to investigate the proposed hypothesis, a preliminary study was conducted in which the ability of industrial jarosite to adsorb arsenic and chromium in synthetic solutions at room temperature was evaluated.