Diversity 2022, 14, 931. https://doi.org/10.3390/d14110931 www.mdpi.com/journal/diversity Article Ecotoxicological Evaluation of Dye Degradation and Photodegradation by Peracetic Acid with Sodium Carbonate Leydiane Barbosa Bezerra 1 , Thayrine Dias Carlos 2 , Aline Silvestre Pereira Dornelas 3 , Warlyton Silva Martins 3 , Miréia Aparecida Bezerra Pereira 3 , Aline Karla de Souza Nolberto 4 , Gil Rodrigues dos Santos 3 , Ildon Rodrigues do Nascimento 3 , Rodrigo Ribeiro Fidelis 3 , Nelson Luis Gonçalves Dias de Souza 4 , Douglas Henrique Pereira 4 , Renato Almeida Sarmento 3 and Grasiele Soares Cavallini 4, * 1 Curso de Química Ambiental, Universidade Federal do Tocantins, Gurupi 77.402-970, Tocantins, Brazil 2 Programa de Pós-Graduação em Biodiversidade e Biotecnologia da Amazônia Legal, Universidade Federal do Tocantins, Gurupi 77.402-970, Tocantins, Brazil 3 Programa de Pós-Graduação em Produção Vegetal, Universidade Federal do Tocantins, Gurupi 77.402-970, Tocantins, Brazil 4 Programa de Pós-Graduação em Química, Universidade Federal do Tocantins, Gurupi 77.402-970, Tocantins, Brazil * Correspondence: grasiele@uft.edu.br Abstract: Advanced oxidative processes (AOPs) are procedures used for the treatment of wastewater based on the generation of free radicals, such as hydroxyl (•OH) and carbonate anion (CO3 •− ) radicals. However, although contaminants are degraded in these processes, the by-products generated in this transformation can be a greater source of toxicity than the original compound, making ecotoxicological tests essential for monitoring the efficacy of these treatment processes. In this study, we examined the ecotoxicity of AOP by-products generated using peracetic acid (PAA) and sodium carbonate, with and without solar radiation, for the degradation of methylene blue dye, using the planarian Girardia tigrina as a test organism. Ecotoxicological tests evaluated the acute toxicity of the generated by-product in terms of lethal concentrations (LC50). Although in both as- says the degradation of the dye was greater than 99%, higher toxicity was observed in the assay using PAA and carbonate in the absence of radiation. From the results obtained, we conclude that the by-product generated from the degradation of methylene blue dye by peracetic acid and sodium carbonate, with and without solar radiation, can pose risks to aquatic ecosystems if released directly into water bodies. Keywords: photochemical; carbonate anion radical; planaria; by-product toxicity 1. Introduction Textile industries are among the main polluters of water bodies and the largest con- sumers of water. Raw materials and inputs, such as dyes and other chemical products, are used in several production stages. The sector’s washing stage generates large volumes of wastewater, which, when inappropriately treated, causes damage to the environment [1]. The presence of these dyes in aquatic ecosystems, in addition to causing visual pollution, is also detrimental to aquatic biota and human health, as some classes of dyes can be car- cinogenic and mutagenic, and concentrations of 1 mg/L can cause such damage [2]. Efficient alternatives for the treatment of industrial effluents are the so-called ad- vanced oxidative processes (AOPs), which are primarily characterized by the changes they produce in the chemical structure of contaminants present in water and effluents [3]. The basic principle of AOP is the formation of free radicals, such as the hydroxyl (•OH) and hydroperoxyl (•OOH) radicals, based on chemical, electrochemical, or photochemi- cal methods [4]. In the latter, •OH radicals are generated by a combination of strong Citation: Bezerra, L.B.; Carlos, T.D.; Dornelas, A.S.P.; Martins, W.S.; Pereira, M.A.B.; Nolberto, A.K.d.S.; Santos, G.R.d.; Nascimento, I.R.d.; Fidelis, R.R.; Souza, N.L.G.D.d.; et al. Ecotoxicological Evaluation of Dye Degradation and Photodegradation by Peracetic Acid with Sodium Carbonate. Diversity 2022, 14, 931. https://doi.org/10.3390/d14110931 Academic Editors: Aleš Gregorc and Letizia Marsili Received: 5 July 2022 Accepted: 25 October 2022 Published: 29 October 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).