Sorption of 17β-estradiol from aqueous solutions on to bone char derived from waste cattle bones: Kinetics and isotherms

This study is aimed at investigating the removal of 17β-estradiol (E2) from aqueous solutions using bone char derived from waste cattle bones. The cattle bones were surface treated with acetone and pyrolyzed in an oxygen depleted environment. The obtained bone char was then used for the adsorption of 17β-estradiol. This work involves studying the batch adsorption process with respect to the effect of contact time, initial concentration and role of dosage of adsorbent. The adsorption kinetic studies revealed that the adsorption of E2 on bone char obeys the pseudo second order kinetic model. In addition, the adsorption kinetics was also assessed for the intraparticle diffusion model. This study shows that the adsorption of E2 on bone char was a very complex mechanism involving the diffusion process. Increasing the bone char dosage led to an increase in the removal of E2. With a bone char dosage of 50 g L^-1, about 95.3% of E2 was removed from aqueous solutions. The experimental adsorption isotherm data were fitted to Langmuir and Freundlich isotherm models. The saturated bone char was regenerated using ethanol/water solution. The preliminary reusability study showed that the adsorption capacity was restored to 85% of its initial capacity in the third cycle.