Optimization of Turbidity Removal in Water Using Chemically Modified Tannins From Brazilian Species

Cationized tannins are natural coagulants with great potential for sustainable water treatment. This study investigated the performance of chemically modified tannins extracted from Stryphnodendron adstringens and Mimosa tenuiflora barks for turbidity removal and optimization of coagulation conditions. Tannins were extracted using Na₂SO₃ at 70°C and chemically cationized to enhance their positive charge density. We hypothesized that the cationization process would improve particle destabilization by promoting electrostatic attraction and hydrogen bonding with negatively charged colloids. Coagulation efficiency was evaluated through a 2³ factorial design, considering coagulant dosage (50-150 mg) and rapid/slow mixing times (1-3 min; 10-30 min). Optimal conditions for S. adstringens were obtained with 150 mg of coagulant, 1 min of rapid mixing, and 10 min of slow mixing, whereas Mimosa tenuiflora performed best with 50 mg, 3 min of rapid mixing, and 30 min of slow mixing. Although these results were obtained under controlled laboratory conditions, challenges related to large-scale application and raw water variability remain to be addressed. Overall, this study demonstrates the promising potential of Brazilian tannins as renewable coagulants, providing evidence-based insights into the mechanisms and influencing factors governing natural polymer-based coagulation and flocculation processes.