Adsorvente baseado em biomassa de camarão para a remoção de corantes sintéticos de soluções aquosas

Abstract

The use of adsorbent materials prepared from shrimp shell biomass for the removal of dyes from aqueous solutions represents a promising approach in the field of environmental remediation. Shrimp shell, an abundant and sustainable source of biomass, stands out in the production of low-cost and highly efficient adsorbent materials. The contaminant removal process, such as dye removal using adsorbent materials, involves the transfer of substances present in the aqueous solution to the active sites of the material. These materials, with porous structures — exhibiting a surface area of 2.32 m²/g, a pore volume of 0.0105 cm³/g, and an average pore size of 16.98 nm — have the capacity to retain unwanted compounds through physical and/or chemical interactions. This master's dissertation aims to produce an adsorbent material from the biomass of the shrimp species Farfantepenaeus paulensis. For this, a methodology was adopted using the raw material, which was dried, washed, and crushed. After preparing the adsorbent material, it was characterized through physical, chemical, and morphological techniques. It was then applied to the removal of two synthetic dyes, Reactive Green 19 (VR-19) and Acid Red 114 (AR-114), from aqueous solutions. The tests were conducted in solutions with concentrations ranging from 10 to 400 mg/L, demonstrating a removal efficiency of approximately 95% for both dyes, achieved within 328 minutes for VR-19 and 389 minutes for AR-114, at pH 2.0. The experimental adsorption results were fitted to the Langmuir, Freundlich, and Liu isotherm models, providing a detailed understanding of the material's adsorption capacity. For the adsorption kinetic studies, pseudo-first order, pseudo-second order, and Avrami fractional order models were applied, allowing the identification of the most suitable adsorption mechanisms. The non-linear pseudo-second order model best described the adsorption kinetics of VR-19, while for AR-114, the Avrami fractional order model presented the best fit to the experimental data. In the isothermal studies, the Freundlich and Liu models were most appropriate for describing the adsorption of VR-19, while the Freundlich model best fit the AR-114 adsorption data. Based on the adsorption studies and the characteristics of the dyes and the adsorbent, an adsorption mechanism was proposed, considering electrostatic attraction between the sulfonate (-SO₃⁻) and azo (- N=N-) groups of the negatively charged dyes and the positively charged surface of the adsorbent at pH 2.0. This study presents an innovative approach by using in natura shrimp shell, without chemical modification, as an adsorbent for synthetic dye removal, combined with the valorization of local fishery waste and the application of rigorous analytical methodologies. The development of this project resulted in an adsorbent with suitable textural properties for the removal of synthetic dyes from an underutilized biomass. Furthermore, the study contributes to reducing environmental impacts by promoting the reuse of fishery industry residues, adding value to this biomass and offering a sustainable alternative for the treatment of industrial effluents.