Zn uptake by illite and argillaceous rocks

The uptake of Zn by Illite du Puy (IdP) and two argillaceous rocks, Opalinus Clay (OPA) Boda Claystone (BODA) was investigated. illite studied in 0.1 M NaCl at near-neutral pH loadings varying from 2.1 to 42 mmol/kg. the rock systems carried out 7.2 their respective porewaters 8.0 evaluate influence porewater composition. varied 1.8 86 mmol/kg 1.7 60 for OPA BODA, respectively. simplified “bottom-up approach” predict natural rocks with different clay mineral contents compositions tested. This approach found be applicable low equilibrium ([Zn]eql) concentrations below 10−7 M. However, [Zn]eql above M, model calculations clearly underpredicted sorption data. extended X-ray absorption fine structure (EXAFS) results support findings based on wet chemistry using 2 site protolysis non-electrostatic surface complexation cation exchange (2SPNE SC/CE) model. In IdP system prolonged reaction times up years, formation precipitates not observed. indicates that complexes are stable over a time period dissolution recrystallization processes might play significant role Zn-IdP process. addition, EXAFS corroborate previous existence weak strong sites types dioctahedral minerals, as assumed 2SPNE SC/CE BODA systems, precipitation could start begin metal 16 24 mmol/kg, differences between samples prepared modest indicating case minerals predominant process, effects originating minor. Furthermore, despite mineralogy, both show same behaviour, predominantly responsible higher concentrations. study demonstrates how “pure” such can transferred sorbate