## 3 Results and Discussion
### ICP Analysis  
The ICP analysis provides information on the elemental composition of a sample. The results of an ICP analysis can include elemental concentrations, elemental identifications, isotropic ratios, contaminant detection, and elemental speciation [69].  
Based on the results obtained, adsorption of 90.6% of As(V) and 96.3% of Cr(III) was achieved from synthetic solutions with known contents of each metal, after a process carried out for 60 min at room temperature. Similarly, for the evaluation of the joint adsorption of As(V) and Cr(III), the percentages obtained were 57% for As(V) and 75.1% for Cr(III).  
A discrepancy was noted in the adsorbed contents of As(V) and Cr(III) when the adsorption of each metal was evaluated individually versus simultaneously. In both scenarios, a higher percentage of Cr adsorption was observed compared with As, which is potentially attributed to the presence of Cu in the jarosite, which may have oxidized Cr(III) to Cr(VI), thereby enhancing its adsorption. Additionally, the presence of Zn, Al, and Si may have facilitated the formation of more reactive species with the Fe ions [65].  
The adsorption efficiency of 90.6% for As(V) and 96.3% for Cr(III) obtained in this study is remarkably high compared with that in previous studies that have used different adsorbent materials (natural and synthesized) [13; 16; 20; 70]. For example, previous studies have reported adsorption efficiencies for As(V) ranging from 40% to 80% using materials such as iron oxides, clays, and activated carbons [15; 71; 25; 72; 73]. The high adsorption efficiency observed in the present study can be attributed to the presence of functional groups on the surface of the industrial jarosite that can interact with As(V) and Cr(III) ions. More specifically, the adsorption of these ions on the decomposed jarosite particles, which are mainly composed of iron hydroxide with high porosity, may be due to adsorption on the surface due to electrostatic and Van der Waals interactions between the ions and the surface. An exchange of As and Cr ions with Fe ions on the surface of the material may also occur, which may be favored by the formation of reactive species that are formed with elements such as Zn, Al, and Si, or by the presence of Cu, which manages to oxidize Cr and thus favor the adsorption of this element. Likewise, precipitation of the ions on the surface of the material and diffusion toward the matrix through the pores of the material may occur.  
Additionally, the decomposition of industrial jarosite at alkaline pH may have released iron ions and other metals that may have contributed to the adsorption of As(V) and Cr(III) ions [74; 21; 75].  
These results are preliminary and require further in-depth studies. However, there appears to be competition between As(V) and Cr(III) when both ions are present simultaneously, and Cr apparently wins the location on the decomposed IJ when As is present. Nevertheless, the adsorption of Cr(III) appears to be more efficient than of As(V), which, as was discussed, could be due to the presence of elements such as Zn, Al, Si, and Cu in the decomposed jarosite. And despite everything, the efficiency of heavy metal adsorption using mining waste is a reality.  
Future studies should investigate the ability of industrial jarosite to adsorb other ions and contaminants, such as heavy metals and radionuclides. Additionally, it would be beneficial to study the stability and durability of industrial jarosite under different environmental conditions and uses. Finally, it is important to evaluate the economic and environmental viability of industrial jarosite as an adsorbent material compared with other materials available on the market.