Up to four tannin extracts from different natural vegetal sources were gelified with formaldehyde and
acetaldehyde. The feasible combinations were tested in the removal of Zn2+, methylene blue (MB) and
cetyltrimethylammonium bromide (CTAB) in aqueous solutions. So-called tanningels resulted highly
effective in the elimination of these pollutants, although the best combinations of tannin and aldehyde
involved those from cypress and pine and formaldehyde in a ratio of 3.68 mmol g−1. Maximum capacity
values of Pinus tannin gel (PTG) regarding dye and detergent removal reached 1.56 mmol g−1 and
1.91 mmol g−1, respectively, and followed a Langmuir isotherm. These capacity values are similar or even
higher to those obtained in previous research works where activated carbon or other raw materials were
used as adsorbents