Removal of Heavy Metal Pollutants from Waters by Adsorption on Molecular Sieve Zeolite-A

An adsorbent of low production cost and simple synthesis technology,named Zeolite-A,was synthesized and its adsorption behavior towards heavy metals,and optimum conditions of the adsorption reaction (including pH of solution,concentration of the metal ions,time of adsorption process and etc.) were studied systematically. Besides possessing the prominent adsorptivity of natural Zeolite,the synthetic Zeolite-A was proved to have clean surface of its crystals,homogeneous grainity,regular shape and without the presence of any colloidal or amorphous substances,as shown by its scanning electron micrograph. It was found that efficiency of adsorption by Zeolite-A was dependent on the magnitude of radii of hydrated ions of heavy metals. Among the metal ions studied Fe(Ⅱ、Ⅲ),Cr(Ⅲ),Pb2+,Mn2+,Cu2+,Mg2+,Zn2+,Ni2+ and Cd2+,Pb2+ ion showed the best adsorptivity;and the efficiency of adsorption of Pb2+ ion was increased with the raise of pH of solution and with the increase of time of adsorption process. The experiments were done in a solution having the concentration of metal ions of 2×103mg·L-1,and the adsorptivity of Pb2+ ion achieved to a value of 99.6%. It was proposed that the synthetic Zeolite-A is suitable to be used in the removal of heavy metals from waters. Desorption of metal ions from Zeolite-A could be effectively done by soaking in a 0.1 mol·L-1 HCl solution.