著者

佐伯 和利

出版者

日本粘土学会

雑誌

粘土科学 (ISSN:04706455)

巻号頁・発行日

vol.45, no.2, pp.90-94, 2006-03-06

被引用文献数

5

---

In order to understand the adsorptive selectivities of heavy metal species on constituents of soil, adsorptions of heavy metal ions (Cd^<2+>, Co^<2+>, Cu^<2+>, Ni^<2+>, Pb^<2+> and Zn^<2+>) on a variable charge material, silica which have a surface functional group, Si-OH, were investigated as a function of the solution pH,. The comparative sorption study with Ca^<2+> were also carried out in the similar manners. The adsorptive affinities of the divalent metal ions on silica were numbered with intrinsic surface complexation constants (K_m^1 (int)) calculated approximately from the adsorptive data using a constant capacitance model. Experiments of Cd and Pb adsorptions were carried out in a 0.1 mol L^<-1> (M) NaNO_3 background solution because a chemical speciation model, SOILCHEM estimated that each proportion of free ions of the metals would be low in a 0.1 M NaCl background solution. The other metal's adsorption experiments used a 0.1 M NaCl background solution. The higher pH the suspension raised, the more heavy metal ions were adsorbed. The adsorptions of the heavy metals increased rapidly from 0 to 100% in narrow pH range (about 2 pH units). The heavy metal ions differed from Ca^<2+> in their great adsorptions at higher pH. Judging from the K_m^1 (int) of each divalent metal ion, the selective order for the metal adsorption by silica was Pb > Cu > Zn > Ni > Cd > Co >> Ca. In addition of the data for Fe^<2+> and Mn^<2+> in my previous study (Saeki, 2004), the order of the nine metals was Pb > Cu > Fe > Zn > Ni > Cd > Mn > Co >> Ca.