Optimizing the Production of a Condensed Tannin-Based Bioflocculant for Toxic Metal Remediation

Abstract Conventional water treatment typically employs chemical coagulants and flocculants, such as aluminum sulfate and iron salts. However, the intensive use of these products can lead to negative environmental impacts and pose significant health risks. In this context, bioflocculants derived from renewable sources, such as tannins extracted from açaí seeds (Euterpe oleracea), represent a promising alternative for sustainable production. This study investigated the efficiency of a cationic bioflocculant (BioTAC), developed from açaí seed tannins and chemically modified via the Mannich reaction, for the removal of toxic metals from aqueous media. Structural characterization of BioTAC was performed using mid-infrared Fourier transform spectroscopy (MIR-FTIR), and metal removal efficiency was assessed by inductively coupled plasma mass spectrometry (ICP-MS) at various bioflocculant concentrations (52–87 parts per billion, ppb) and pH values (4–10). The FTIR spectra revealed characteristic absorption bands in the ∼3300 cm–1 region, corresponding to O–H stretching, as well as peaks at ∼2930, ∼2880 cm–1, ∼1750 cm–1, and ∼1610 cm–1, and bands between 950 and 1150 cm–1. The high removal rates (91–100%) for aluminum (Al), titanium (Ti), iron (Fe), copper (Cu), zinc (Zn), and uranium (U) were achieved with concentrations between 69 and 87 ppb in an alkaline medium. Alkalinization was found to be crucial, as it promoted the deprotonation of the phenolic hydroxyl groups, thereby enhancing the chelation capacity for metal ions. Consequently, the application of BioTAC not only mitigates agro-industrial waste but also reduces dependence on chemical agents for treating water contaminated with toxic metals.