Novel tannin-based adsorbents were tested on heavy metals removal. Up to 10 heavy metals (Cd2+, Cr3+, Pb2+, Hg2+, Co2+, Ni2+, Cu2+, Zn2+, UO22+, and Mn2+) were removed with different adsorbents that involved tannins from Acacia mearnsii de Wild, Schinopsis balansae, Cupressus sempervivens,, and Pinus pinaster. These tannin extracts were gelified with formaldehyde in basic medium. The whole study was conducted from a statistical point of view, so ANOVA tests were carried out in order to evaluate the optimum concentration of formaldehyde, the most reactive tannin extract, and the metals most easily removed. These considerations pointed to the optimum tanningel derived from cypress, concentrated formaldehyde, with a high affinity to UO22+, Hg2+ and Pb2+. Lastly, equilibrium and kinetic studies were carried out on these systems.