Vzájemné interakce mezi huminovými látkami bentonitem a olovem

Abstract

Introduced dissertation work deals with experiments targeted to clarify the behavior of humic substances (HS) in the contact with natural bentonite (type Bentonit 75, B75) at various conditions. It was found out, that the valence of cations present in the solution has the greatest influence at HS interactions with B75. Therefore all another factors were investigated in the presence of both monovalent and divalent cations. From the sight of contact time it was found out, that the adsorbed amount of HS was stabilized much faster in the presence of divalent cations then in the presence of monovalent cations. Further the influence of the pH value on the HS sorption was investigated. It was stated, that the adsorbed amount of HS decreases with increasing pH value. This influence appears mainly in the presence of monovalent cations, in the case of divalent cations the influence of pH value was negligible. Last factor mentioned in this work is the value of ionic strength. It was found out, that the adsorbed amount of HS on the B75 arises with increasing ionic strength, again the effect of ionic strength is greater in the presence of monovalent cations then in the presence of divalent cations. Generally it was found out, that divalent cations increase adsorbed amount of HS and also they increase strength of bonds between B75 and HS or between molecules of HS to each other, which is probably caused by cation bridges formation. It was stated from analyses of prepared materials, that the HS are adsorbed on the surface of B75, where they can form higher layers at the covered B75 surface in the presence of divalent cations. The intercalation of HS to the interlayer doesn’t take place. Due to high affinity of HS to the metal cations, the influence of HS to Pb(II) capture at B75 was investigated at various pH values and ionic strength values (adjusted by NaCl as background electrolyte). It was found out, that HS can increase the captured amount of Pb(II) against B75 alone, but it is mainly due to the formation of higher layers of HS at the covered clay surface. Pb(II) cations form probably cation bridges between HS and B75 surface. Captured amount of Pb(II) increases with increasing pH value and it decreases with increasing ionic strength of background electrolyte. Also there are observed strongly bound and immobilized Pb(II) cations in the Pb-HS/B75 complex, also after huge change of solution parameters (pH value, ionic strength value). This is probably one of the mechanisms of Pb(II) removing from environment. From the sight of HS, there are both monovalent (Na) and divalent (Pb) cations present in the solution and adsorption of HS shows behavior as in the presence of divalent cations. So it can be stated, that HS prefer divalent cations during binding to B75 surface or to another HS molecule.