| Widely distributed soil and water pollution by heavy metals thretan the human lives and ecological balance. This paper is designated to investigate the adsorption behavior and mechanism of four heavy metals (Cd, Cu, Pb, Zn) on three materials (Kaolin, Ca-bentonite and activated Firmiana Simplex Leaf) on the basis of laboratory experiments. Several factors have been studied with regarding their effects on adsorption characteristics, and the relevant mechanisms have been studied with assistance of FT-IR and XRD pattern. Then, we mixed the betonite with activated Firmiana Simplex Leaf to make composite material and studied its adsorption behavior. The main conclusions are as follows:1) As the clay mineral composed of silicate and sillico aluminate, Kaolinite as well as bentonite can react with heavy metals in the form of surface complexes to give rise to the adsorption capacity of soils. The magnesite and white mica in Kaolin was found greatly responsible for adsorption of Pb(â…¡) and Cu(â…¡).2) There are lots of amine group, carbonate and phosphate in activated Firmiana Simplex Leaf, which provide beneficial adsorption site towards heavy metals. The quartz was found for the first time responsible for adsorption of Cd(â…¡) in the form of cadmium metasilicate.3) Compared to Freundlich and D-R model, Langmuir model is more suitable to describe the adsorption behavior. According to kinetics,40 min and 3-4 h are needed to reach equilibrium for activated Firmiana Simplex Leaf and bentonite, but more than 50 h for Kaolin.4) Firmiana Simplex Leaf-bentonite composite material have amine group, carbonate and phosphate together with some complex site towards heavy metals. And the adsorption process often complete in several hours, in addition,85%of heavy metals can be removed in weak acid condition, showing industrial applicance potential.
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