Sensitivity of Freundlich equation constant 1/n for zinc sorption on changes induced in calcite by mechanical activation

This work presents an attempt to modify the properties of calcite by mechanical activation in order to enhance its capacity for heavy metal removal. The equilibrium isotherms of zinc adsorption onto the mineral show the data correlate well with Freundlich model. Experiments with temperature changes in sorption tests proved that chemisorption plays the main role in zinc sorption on calcite. The solid-state properties of calcite (surface area, particle size, particle morphology and crystallinity) has been modified by mechanical activation (high-energy milling) and the structure sensitivity parameter, SA/X (SA: specific surface area and X: crystallinity) has been used for the characterization of mechanically activated calcite. The good linear correlation (R = 0.92) between Freundlich parameter 1/n and log(SA/X) has been found. The experimental results proved that the mechanically activated calcite is an effective sorbent for Zn removal from water solutions.