Removal of Cu(II) and Zn(II) ions by sorption onto bone char using batch agitation

The sorption rate of copper and zinc ions onto bone char around pH 5 has been studied using a batch agitation system. The calcium hydroxyapatite, which is the main composition in bone char, removes the metal ions by means of adsorption and ion exchange from the solutions. When the pH values of solutions are adjusted to pH 4 or below, the X-ray desorption patterns show the degrees of the crystalline of hydroxyapatite in the bone char reducing. Therefore, the sorption process for the metal ions removal from effluent is recommended to control around pH 5 or above to reduce the loss of the sorbent. In addition, the experimental data from the adsorption isotherms and batch kinetics studied were correlated using the Langmuir equation and a film-pore diffusion mass transport model. The Langmuir parameters were incorporated into the film-pore diffusion model to correlate the batch kinetic data. The constant pore diffusivities for the sorption of copper and zinc ions onto bone char are equivalent to 6.67 × 10^-7 and 6.32 × 10^-7 cm²/s, respectively. The film-pore diffusion model shows slight deviation to the experimental data when the solution is in high concentration or when the volume-to-mass ratio is low.