Improving the extraction of Anacardium occidentale bark tannins by alkaline and sulphitation processes and their efficiency in coagulation: chemical characterization by HPLC

  • Paula Evanyn Pessoa do Nascimento Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • Tatiane Kelly Barbosa de Azevedo Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • Kayo Lucas Batista de Paiva Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • Denys Santos de Souza Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • Fernando Hermínio Ferreira Milheiros Nunes Departamento de Química. Universidade de Trás-os-Montes e Alto Douro (UTAD), Quinta de Prados - Folhadela, 5000-801, Vila Real, Portugal.
  • Elisa de Lurdes Matos da Costa Departamento de Química. Universidade de Trás-os-Montes e Alto Douro (UTAD), Quinta de Prados - Folhadela, 5000-801, Vila Real, Portugal.
  • Elaine Cristina Alves da Silva Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • Alexandre Santos Pimenta Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • Neyton de Oliveira Miranda Escola Agrícola de Jundiaí. Universidade Federal do Rio Grande do Norte (UFRN), RN 160, Km 03, Cx. Postal 07, CEP: 59280-000, Macaíba, RN, Brazil.
  • João Gilberto Ucella Meza Filho Departamento de Engenharia Florestal. Universidade Federal Viçosa (UFV), Avenida Peter Henry Rolfs, s/n, Campus Universitário, CEP: 36570-900, Viçosa, MG, Brazil.
DOI: https://doi.org/10.4136/ambi-agua.3145

Resumen

Tannins extracted from several forest species can be successfully used as coagulants in water treatment. This study employs a high-yield tannin extract from cashew tree (Anacardium occidentale) bark as an eco-friendly alternative for water treatment. First, ground bark was hot-water-extracted for tannins, using two adjuvants (NaOH and Na2SO3) at three concentrations for each. The total solids content (TST), Stiasny index (I), and condensed tannins content (TTC) were determined in the tannic extracts. The proanthocyanidins extracted from the bark were separated by solid-phase extraction into oligomeric and polymeric fractions. Total phenolic compounds were measured using the Prussian blue test method. The phenolic compounds present in the original extract and in the oligomeric and polymeric procyanidin fractions were analyzed by HPLC-MSn. The extracted tannins were cationized and applied in water treatment. The results showed that reagent-assisted extraction efficiently enhanced tannin yields and quality compared with pure hot-water extraction, with NaOH as the most effective. Total phenolic compounds and total condensed tannins in the Cashew tree bark were 154.18 mg GAE g-1 and 164.59 mg g-1, respectively. Phenolic compounds corresponded to catechin gallate, gallic acid, catechin, epigallocatechin, epicatechin, ellagic acid glycoside, triterpenoids, and anacardic acid. Other phenolics included prodelphinidins and procyanidins, in both oligomeric and polymeric forms. Cationized tannins used as coagulants effectively decreased water turbidity. The study demonstrated the potential of Cashew tree bark tannins as a sustainable alternative for water treatment. Results showed the potential of tannins as eco-friendly coagulant bases in water treatment.

Keywords: natural flocculant, natural products, non-wood forest products, tannins, water treatment.

Publicado
18/06/2026
Número
Vol. 21 (2026)
Sección
Articulos

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