<p>A study of the adsorption of the anionic blue textile dye Dianix was carried out in batch mode using a biomaterial made from calcined eggshells. FTIR analysis revealed the presence of Ca–O and HO–Ca–OH groups. BET analysis was used to determine the specific surface area and pore volume, which were found to be 251.71 m²/g and 5.058 cm³/g. The study focused on parameters such as the mass effect (0.04 g/50 mL) of the dye in aqueous solution at a concentration of 20 mg/L, at a pH of 7, and a removal rate of 95%.The adsorption kinetics follow the pseudo-second&#xa0;order model (<i>R</i>² = 0.99961) and the pseudo-first&#xa0;order model (<i>R</i>² = 0.99874). The study of the Freundlich, Langmuir and Temkin isotherms reveals that the adsorption amount is 451.77 mg/g.The adsorption process is of the physisorption type (Δ<i>H</i>° = 71.254 kJ/mol) and the negative values of the free energy (Δ<i>G</i>°) confirm that the adsorption is spontaneous and occurs via non-covalent cation-π and O…Ca²⁺… O and O…Ca²⁺…N. The mechanism of BD dye molecule binding to the surface of the biomaterial is a mixed parallel and vertical combination, with two different adsorption percentages, in the case 0.5 &lt; n &lt; 1.</p>