Uso de taninos condensados das cascas de espécies arbóreas no tratamento de água

Abstract

Among the products that have attracted great commercial interest in recent years are tannin-based polymers, which are substances present in different parts of plants and have diverse applications. Tannin-based coagulants act directly in the coagulation and flocculation process in water treatment, this process being a pre-treatment that conditions the water for subsequent treatments. Thus, this work has the general objective of evaluating the potential for extracting tannins from tree species and evaluating their potential as coagulants for water treatment. Healthy trees of Acacia mangium Willd., Copaifera arenicola (Ducke) J. Costa & L. P. Queiroz, Hancornia speciosa Gomes and Terminalia catappa L. were selected, the tannins were extracted from the bark and the condensed tannin content was determined. After extraction, the cationization process was carried out. Then, coagulation tests were carried out at different concentrations and stirring times. Concentrations of 50 mg/L¹, 100 mg/L¹, 150 mg/L¹ and 200 mg/L¹ were used for each coagulant. Rapid stirring was performed for 2 min at 130 rpm followed by slow stirring for 10 min at 30 rpm (T1); fast stirring for 2 min at 130 rpm followed by slow stirring for 20 min at 30 rpm (T2). During the coagulation tests, the turbidity and pH values of the water from each treatment were evaluated after 2 min and every 10 minutes for a total of 60 minutes. The tannic extracts obtained from the bark of C. arenicola and H. speciosa showed condensed tannin content above 10%. The species of A. mangium and C. arenicola showed a high Stiasny index with values of 95.34% and 91.85%, respectively. The natural coagulant based on T. catappa treated the water efficiently, reaching the minimum values required for human consumption. The best concentration found was 200 mg/L¹ and T2 was the best stirring time. Which makes the coagulant indicative of use in water treatment systems.