Aplicação dos taninos de Stryphdodendron adstringens e Mimosa tenuiflora como coagulantes no tratamento de água

Abstract

For drinking water to reach human consumption it is necessary to go through a treatment process, however the inorganic coagulants that are used cause health and environmental problems. Thus, it has been sought to produce coagulants alternative to those commonly used, being renewable, biodegradable and of low cost. Thus, the objective is to develop natural renewable coagulants based on tannins of the native species barbatimão (Stryphnodendron adstringens) and jurema-preta (Mimosa tenuiflora) and to test them in the treatment of water for supply. The tannins used in the water treatment were extracted from the husks of the two species, which were air-dried, ground, classified, extracted and, subsequently, the extract was sieved, filtered and concentrated, to determine the Stiasny index, content of condensed tannins and total solids content. The obtained tannins went through chemical modifications in their structure, with and without the use of formaldehyde, to later go through the water treatment process, using the jar-test equipment. Different concentration variables and agitation speeds were used to find the best combination of variables. The initial and final pH and turbidity were measured. It was possible to observe that the jurema-preta showed a better coagulant activity, when compared to the barbatimão, using a concentration of 50 mg and a rapid stirring time of 3 min and a slow stirring of 30 min, optimizing the amount of product used in the cleaning process of the water. In addition, it was observed that the cationization of the tannins without the use of formaldehyde, did not present an effective removal of the turbidity of the water, being necessary to make modifications in the applied methodology.