Study On Sorption Behavior Of Heavy Metal Ions On Rectorite

Rectorite is a kind of uncommon natural clay that is represented by regular (1:1) stacking of mica-like layers and montmorillonite-like layers. In this paper rectorite was characterized and its surface sites distribution was determined by FITEQL using potentiometric titration. Sorption behavior of rectorite with Th(IV) and Ni(II) as sorbates was studied under ambient conditions by using a batch technique. Effect of medium pH, ionic strength, soil humic acid (HA) and fulvic acid (FA), temperature on metal ions sorption were investigated. Instruments such as SEM, FT-IR, XPS were used to study the reaction between metal ions and rectorite. An interpretation for the results was attempted.The results of this paper showed that cation exchange site≡XNa and amphoteric hydroxyl site≡SOH were the main surface sites of rectorite. Na-rectorite had good sorption ability to heavy metal ions, and its inorganic modified sample Al-cross linked rectorite has advantage than Na-rectorite in treating high concentration metal ions. Sorption of Th(IV) and Ni(II) increased with increasing pH and decreasing ionic strength. The influence of soil HA/FA on sorption of metal ion varied with metal ion and pH. Sorption isotherms of metal ions on rectorite were followed Langmuir or Freundlich isotherm. The thermodynamic parameters (ΔH°,ΔS°andΔG°) for Th(IV) and Ni(II) sorption onto rectorite were calculated from the temperature dependence, and the results suggested that the sorption reaction was spontaneous with a high affinity. Considering the occurrence of different sorption mechanisms, surface complexation and cation competition exchange account for Th(IV) and Ni(II) sorption on rectorite.