Production of tannin-based adsorbents and their use for arsenic uptake from water

Tannins have been shown to be excellent candidates to produce biosorbents. These ubiquitous and inexpensive natural biopolymers are of easy extraction and conversion into insoluble matrices. Furthermore, it is somewhat easy to chemically modify a TBA (Tannin Based Adsorbent), in order to enhance its adsorption ability towards specific substances. In this work, a pine-tannin based adsorbent was modified with iron loading in order to assess its ability to uptake arsenic. Oxidation of the tannin gel prior to iron treatment was proven to be essential for the iron uptake. Moreover, the iron content of the tannin gel was shown to improve its affinity towards arsenic. It was achieved maximum adsorption capacities of 1.92 and 2.3 mg g⁻¹ of As(III) and As(V), respectively, at 20°C and pH 3.5. Hence, the adsorbent here synthesized presents itself as a potential alternative for arsenic removal from aqueous solutions through adsorption.