As far as I understand you want to quantify the amounts of Hg(II) and Al(III) adsorbed from a solution on a solid material using UV-Vis spectroscopy. I would use the following procedure. Take a solution of Hg/Al, add the desired amount of an adsorbent, wait until equilibration, separate the solid with centrifuge or filter. Google for a colorimetric assay to determine the concentrations of Hg/Al in solution. Calibrate your assay with standard solutions of Hg/Al. The amount of adsorbed metal will be a difference between the solution before treatment with adsorbent and after the treatment. The key words for googling could be a "colorimetric analysis of Hg(II) or Al(III) in solutions"

Hello dear Geletii, thank you very much for the tips. Just one more doubt, when I use chromophores agent because these metals don't show bands in the uv-vis without them, how can I quantify by adsorption? Do I add it together with the chromophore agent to adsorb the metal, or do I add the agent after adsorption to quantify it?

I have also analyzed Cobalt adsorption through UV-vis Analysis, I have cited the paper in my research paper. You can read this paper {https://www.nature.com/articles/s41598-023-33902-9} to understand mathematical implementation and find the cited paper, there they have provided a lot of heavy metal concentration analysis using UV vis method search this in google {Sirotiak, M., Bartošová, A. & Blinová, L. UV-VIS spectrophotometric determinations of selected elements in modelled aqueous solutions. J. Environ. Prot. Saf. Educ. Manag. 2(3), 75–87 (2014)}