Abstract

More and more efforts are being made to find efficient bio-based water and wastewater treatment products. Especially the use of tannin-based materials has become more prevalent in recent years due to the wide availability of sustainable tannin sources. This article provides an updated literature review on the potential for tannin use for coagulants and adsorbent synthesis and practical applicability in water purification. Tannin coagulants work well in many applications, especially in color, turbidity, and COD removal from industrial waters, and are often even better than conventional ones (e.g., metal salts). One of the most significant benefits of tannin coagulants is their small effect on the pH of the treated water. Also, tannin coagulants can work at a wide pH range, and sludge volume is typically smaller than with metal salts. However, it is worth noting that the performance varies widely among tannin coagulants. Tannin-derived resins and composites have been synthesized and evaluated as adsorbents for water purification. In general, tannin-derived adsorbents present good adsorption capacities for metals, antimony, cationic dyes, and uranium ions, owing to their chelating ability and negative surface charge in the pH conditions of interest and reducing power in the case of chromium(VI). With simple chemical modifications, tannin can be converted into effective sorbents for more challenging pollutants. More research is needed to test tannin materials on a larger scale and evaluate their overall benefits and cost-effectiveness.