Ecotoxicity of 2-mercaptobenzotiazole (2-MBT) at free and nanoengineered forms to embryos of the sand dollar Mellita quinquiesperforata

Abstract

Corrosion is one of the main causes of degradation of metallic structures in contact with the marine environment. For this reason, corrosion inhibitors (CI), chemical additives used to slow or prevent the progress of this phenomenon in metals, are routinely applied to such structures. 2-Mercaptobenzothiazole (2-MBT) is advantageous for use in structures exposed to atmospheric and aquatic corrosion, due to its low production cost and high performance in acidic media. However, the disposal and release of this compound in the marine environment can lead to high toxicity to aquatic biota, which creates the need for technological innovation, in the sense of developing environmentally friendly ICs in order to reduce the associated environmental impacts. A technological alternative developed by researchers from the University of Aveiro (UA), in Portugal, in partnership with a company (Smallmatek Ltda) is the encapsulation of 2-MBT in manufactured nanomaterials (NM), such as mesoporous silica nanocapsules (SiNC) and hydroxides lamellar doubles (LDH). This technology optimizes the use of active compounds through the controlled release mechanism, however, its ecotoxicological potential in aquatic organisms has not yet been studied. The objective of this research is to carry out an evaluation of the ecotoxicity and environmental hazard of free and nanostructured 2-MBT, through its impact on the embryonic development of a neotropical echinoderm, the sand dollar. To this end, toxicity tests will be performed with Mellita quinquiesperforata embryos to determine toxicity indexes (CEO, CENO, CLE50) of 2-MBT in its free, (b) nanostructured SiNC and (c) immobilized by LDH forms. In parallel, bioassays will be performed with (d) SiNC and (e) empty LDH to determine the toxicity of these nanomaterials in the absence of the corrosion inhibitor. Results will also be classified as: Extremely toxic: <0.1 mg/L; Very toxic: 0.1 - 1 mg/L; Toxic: 1 - 10 mg/L; Harmful: 10 - 100 mg/L and Non-toxic: > 100 mg/L, to define safe concentrations of the tested substances. The data obtained in this IC project will be incorporated into a larger international project (NANOGREEN), being used to generate the specific sensitivity distribution curves (SSD curves), which will be used to estimate the environmental hazard of 2-MBT, in the forms free and nanostructured.