Comparative study of differently treated animal bones for Co2+ removal

The objective of the present study was the evaluation of differently treated bovine bones for Co2+ removal from aqueous media. Powdered bones (B), as well as samples prepared by H2O2 oxidation (BH2O2) and annealing at 400-1000 °C (B400-B1000), were tested as sorbent materials. A combination of XRD, FTIR spectroscopies, DTA/TGA analyses, specific surface area (Sp) and point of zero charge (pHPZC) measurements was utilized for physicochemical characterization of sorbents. Sorption of Co2+ was studied in batch conditions as a function of pH, contact time and Co2+ concentration. Initial pH values in the range 4-8 were found optimal for sorption experiments. Equilibrium time of 24 h was required in all investigated systems. The maximum sorption capacities differ significantly from 0.078 to 0.495 mmol/g, whereas the affinity towards Co2+ decreased in the order: B400 > BH2O2 > B600 > B > B800 > B1000. The pseudo-second-order model and Langmuir theoretical equation were used for fitting the kinetic and equilibrium data, respectively. Ion-exchange with Ca2+ and specific cation sorption were identified as main removal mechanisms. The amounts of Co2+ desorbed from loaded bone sorbents increased with the decrease of pH as well as with the increase of Ca2+ concentration. Heating at 400 °C was found to be an optimal treatment for the production of the Co2+ removal agent.