Mass transport process for adsorption of metal ions onto a new type adsorbent poly(vinyl alcohol)(PVA)/peat/clay composite bead

An innovative spherical poly(vinyl alcohol)(PVA)/peat/clay porous composite bead was prepared and shown to be suitable for use as an adsorbent. The mass transport process for the adsorption of metal ions onto this composite bead in an aqueous system was investigated. In the external mass transport process, the diffusion coefficient (D-1) of Cu+2 and Zn+2 ions increased with increasing initial metal ion concentration and the increasing effect was more pronounced in the initial metal ion concentrations range of 18x10(-3) to 22x10(-3)M. The diffusion rate of Zn+2 ions was faster than that of Cu+2 ions. In the intraparticle diffusion process, the diffusion coefficient (D-2) decreased with increasing initial metal ion concentration in the initial concentration range of 1x10(-3) to 4x10(-3)M, and the value of D-2 maintained an almost constant value in the initial concentration range of 8x10(-3) to 22x10(-3)M. The rate of ion diffusion within the adsorbent for Cu+2 ions was faster than that for Zn+2 ions. The adsorption mechanism was controlled by the intraparticle diffusion process. The adsorption followed the Langmuir adsorption isotherm model. The maximum amount of adsorbed metal ions for Cu+2 and Zn+2 ions were 22.57 and 13.62 mg/g composite bead, respectively.