Adsorption of naturals hormones estrone, 17-estradiol, and estriol by rice husk: monocomponent and multicomponent kinetics and equilibrium.

In the present study, the use of the rice husk biomass as an alternative biosorbent for treating the estrone, 17 -estradiol, and estriol hormones in monocomponent and multicomponent systems was investigated. The high-performance liquid chromatography technique (HPLC-UV) was applied in order to quantify the hormones, validating this method according to ANVISA and INMETRO. The biosorbent presented functional groups typical of cellulose, hemicellulose, lignin, and proteins, with an amorphous, fibrous, and porous surface. The best performance was obtained with a neutral pH and at room temperature (25[Formula: see text]C). The equilibrium times in batch systems were 60  min for the estrone, and 120 min for 17 estradiol and estriol. The monocomponent kinetics of adsorption of estrone and estriol were adequately described by the pseudo-first-order model, whereas for the 17  estradiol both pseudo-first-order and pseudo-second-order models well described the experimental data. For the multicomponent system, the kinetics of adsorption was appropriately represented by the pseudo-first-order model, demonstrating that the number of active sites was the limiting factor of the process. The monocomponent adsorption isotherms were adequately fitted by the Langmuir model, reaching adsorption capacities of 2.698, 1.649, and 0.979 mg g for the estrone, 17 estradiol, and estriol hormones, respectively. The ternary isotherm models did not represent the experimental data, indicating that there was no competition among the hormones. The reactions presented favourable and spontaneous characteristics. The rice husk biomass showed a great potential as an adsorbent when treating effluents contaminated with hormones.