Bone charcoal is a carbonaceous substance, which is derived from the carbonization of selected grades of animal bones by heating dry bones in an airtight iron retort at 500-700℃ for about 4-6 hours. Comparing the capacity of metal ions removal with activated carbon, bone charcoal not only provides a porous carbon surface for physical adsorption, but also provides a hydroxyapatite lattice - Ca_l0(PO₄)(OH)₂ for ion exchange of metal ions. Based on these properties, this sorbent should have excellent adsorption capacities for metal ions....[ Read more ]

Bone charcoal is a carbonaceous substance, which is derived from the carbonization of selected grades of animal bones by heating dry bones in an airtight iron retort at 500-700℃ for about 4-6 hours. Comparing the capacity of metal ions removal with activated carbon, bone charcoal not only provides a porous carbon surface for physical adsorption, but also provides a hydroxyapatite lattice - Ca_l0(PO₄)(OH)₂ for ion exchange of metal ions. Based on these properties, this sorbent should have excellent adsorption capacities for metal ions.

In this research, the sorption equilibrium and the sorption kinetics of metal ions from solution onto bone charcoal were studied. To study the sorption capacity, the sorption equilibrium of cadmium, copper and zinc ions onto bone char has been investigated. The pH of metal ion solutions were controlled at 4.8 ± 0.1. The test temperature was controlled at 20 ± 2℃. The experimental results were substituted into several single component isotherm equations (the Langmuir, Freundlich, Langmuir-Freundlich and Redlich-Peterson equations) and the Langmuir-Freundlich equation was found to be the most appropriate isotherm model to describe the sorption equilibrium of metal ions onto bone char. The sorption capacity of bone char for cadmium, copper and zinc at an equilibrium metal concentration of 3.0 mmole/dm³ was found to be 0.57 mmole/g, 0.79 mmole/g and 0.56 mmole/g, respectively.

To study the kinetics of metal ion removal, the commonly accepted method of using an agitated batch sorber was adopted. The solution containing metal ions was agitated by the high-speed agitator. The sorbent was added into the sorber to remove the metal ion. The removal rate of metal ions by the adsorbent can be determined and plotted against time. The experimental data were analyzed by four reaction kinetic equations (Pseudo-first order, Pseudo-second order, Elovich and Modified second order equation). Based on the single component test results, the most appropriate reaction kinetic model can be determined by mathematical modeling and comparing theoretically predicted data with the experimental data points. In this research, the Elovich equation was found to be the best fitting equation to describe the sorption kinetics of metal ions onto bone char.