Uso de taninos oriundos do angico-vermelho (Anadanenthera macrocarpa) para produção de coagulante orgânico no tratamento de água de abastecimento humano.

Abstract

In view of the advances in water treatment technologies, this work aimed to study the potential of water treatability of tannins extracted from the bark of angico-vermelho (Anandenanthera macrocarpa) by means of a Box-Behnken experimental design. The best tannin extraction conditions were evaluated, evaluating the concentration of the solvent used (sodium hydroxide), the extraction temperature and the heating time, being selected for the next step of treatability. Also using the Box-Behnken statistical method, the performance of aluminum sulphate, Tanfloc SL and Tannin Extracted from Angico Peel (TECA) were evaluated, varying the dosage of coagulant, pH and sedimentation rate as, evaluating by the variables absorbance-254 removal, apparent color removal and turbidity removal the best application conditions for each coagulant. Raw water from the Epitácio Pessoa reservoir was used, which is a natural water with low turbidity and low apparent color. All coagulants were applied under the same experimental conditions, simulating on a bench scale using a jartest. For the extraction, a greater influence of the solvent concentration on the result was verified, with the 2.5% NaOH solution being the best point for extraction, with a time of 60 minutes, at a temperature of 100 oC. As for treatability, coagulant dosage was the factor that most linearly influenced the dependent variables, most often in an inversely proportional way. The work obtained significant models for the three coagulants studied. The model obtained for TECA had satisfactory performance in removing turbidity in the clarification step, obtaining the bests values for dependent variables at dosage values of 10 mg/L, pH 7.75 and sedimentation speed of 1.5 cm/min, reaching a removal value turbidity of 10.18%.