Effect of humic acid on sorption of trace metal ions by sodium aluminosilicate Original Research Article

Sorption of trace metal ions (Pb2+, Zn2+ and Hg2+) on synthesized sodium aluminosilicate (Na–AS), an important clay mineral, was carried out in the presence and absence of humic acid (Aldrich) at different pH (3 to 10). The material was synthesized by solution route method and it was characterized by using different techniques such as X-ray diffraction, FT-IR, zeta potential measurement, BET surface area analysis and site density measurement. A series of experiments were made to find out the effect of ionic strength, calcium ions, sorbent dose, metal ions concentration and temperature on the sorption of divalent metal ions by Na–AS. The sorption was found to be dependent on pH as well as humic acid. At lower pH (< pH 6) sorption was observed to be enhanced in the presence of humic acid. Ionic strength played an important role in the sorption of metal ions. Sorption was observed to be decreased with increase in metal ion concentration (10−5 M to 10−2 M) and data was fitted well in Freundlich isotherm. Thermodynamic study showed endothermic, entropy favorable and spontaneous sorption behavior of metal ions by sodium aluminosilicate.