This research was carried out to determine the effectiveness of freeze-dried calcium alginate hydrogels in the form of beads for removing the azo dye, Eriochrome Black T (EBT), from an aqueous solution. After achieving standardization of the biosorbent preparation process, the influence of the following factors on dye sorption was analyzed: pH, dye concentration, and biosorbent dosage. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize biosorbent material. In addition, the sorbent point of zero charge (PZC) was determined. The experimental data fitting level to the linearized forms of pseudo-first and -second order, intra-particle (IP) diffusion, and the Elovich adsorption models was analyzed, finding that they better fit a pseudo-second order model. The results showed that PZC confirmed that calcium alginate beads are a feasible material for EBT at pH 4 with 60% adsorption and FTIR showed that the absorption occurred by electrostatic interactions between the biosorbent and dye. Also, adsorption isotherms fitting showed that the Freundlich model was the most optimal to describe the absorption mechanism. According to the research results, the biosorbent material used has a good potential for future research focused on contaminants removal from water.
Toledo-Guillén et al. (2026) studied this question.