Determination of biosorption capacity of microalgae biomass using the Boehm method

Many algae biomass has been successfully employed for treating metals and dyes from contaminated effluents. Microalgae have been described as a potential biosorbent for the treatment of industrial dilute aqueous solutions containing lanthanides. This study aims to assess the potential for biosorption of Chlorella vulgaris and Ankistrodesmus falcatus through a prior characterization of its surfaces using Boehm titration. Biosorption depends on the protonation or deprotonation of the functional groups on the surface of the biosorbent. The Boehm method is a technique that allowed characterizing the acid and basic sites of the different adsorbent materials in base to selective neutralization. The values found evidence that the biomass presents acidic and basic groups, which is fundamental to the biosorptive process. In the quantification of basic groups, the biomass of C. vulgaris showed a larger number of groups, being this 1654.36 mEq.g-1, while the A. falcatus biomass contained 734.52 mEq.g-1. The results indicated that the surface of both biomasses has a higher number of basic groups than of acidic groups. The lactonic groups were not detected by the methodology used, only phenolic groups and carboxylic acids in similar amounts for both C. vulgaris and A. falcatus. The carboxyl groups were found in a higher proportion (54 mEq.g-1) about the phenolic groups (14 mEq.g-1). These results showed a good capacity and efficiency of biosorption of both microalgae biomasses for the ions Ln3+, which can improve lanthanides recovery strategies using biotechnological processes.