Removal of lead ions from acid aqueous solutions and acid mine drainage using zeolite bearing tuff

The adsorption of lead ions onto a zeolite bearing tuff (stilbite) from synthetic acid aqueous solution and acid mine drainage taken from Sasa mine, Macedonia, is elaborated in this paper. The results present that adsorption occurs effi ciently in both of cases. The physical and chemical properties of the used natural material, zeolite bearing tuff, are characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy. The concentration of metal ions in solution before and after treatment is obtained by AES-ICP. The effectivity of zeolite bearing tuff is determined through a series of experiments under batch conditions from single ion solutions, whereby the main parameters are the effects of initial pH of solution, mass of adsorbent, initial metal concentration in solution, contacting time and competing cations. The maximum capacity of zeolite bearing tuff for removal of lead ions from solution is determined by equilibrium studies. The experimental obtained data are fi tted with Freundlich and Langmuir adsorption models. The experimental data are better fi tted with Langmuir adsorption isotherm. Zeolite bearing tuff is effective adsorbent for treating acid mine drainage. The results showed that 99% of lead ions are removed from acid mine drainage, i.e. the concentration of lead ions from 0.329 mg/dm3 decrease to 0.002 mg/dm3. The pH value of acid mine drainage from 3.90 after treatment with zeolite bearing tuff increases to 5.36. 88 A. Zendelska, M. Golomeova, B. Golomeov, B. Krstev Material and methods Analytical methods Particle characterization reveals information on the physical and chemical nature of zeolite bearing tuff particles, which is related to its ability to remove lead ions from solution. The used adsorbent, zeolite bearing tuff, was studied using X-ray Diffractometer 6100 from Shimadzu to investigate the mineralogical structure of the sample. This technique is based on observing the scattering intensity of an X-Ray beam hitting a sample as a function of incident and scattered angle, polarization, and wavelength or energy. The diffraction data obtained are compared to the database maintained by the International Centre for Diffraction Data, in order to identify the material in the solid samples. The surface morphology of sample was studied using a scanning electron microscope, VEGA3 LMU. This particular microscope is also fi tted with an Inca 250 EDS system. EDS stands for Energy Dispersive Spectroscopy, it is an analytical technique used for the elemental analysis of a sample based on the emission of characteristic X-Rays by the sample when subjected to a high energy beam of charged particles such as electrons or protons. ICP-AES Agilent was used to analyze the concentration of metal ions in solution before and after treatment. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) is an analytical technique used for the detection of trace metals. It is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element. The intensity of this emission is indicative of the concentration of the element within the sample. Based on material balance, the adsorption capacity was calculated by using the following expression: