Adsorbent biopolymers from tannin extracts for water treatment

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.