Lead(II) adsorption by raw and acid-activated vermiculite

Acid-activated vermiculite (AAV) was prepared by treating raw vermiculite (RV) at 80 degrees C with HCl solution. The surface properties and Pb(II) adsorption characteristics of RV and AAV were studied. The specific surface area (SSA), cation exchange capacity (CEC), pH at zero point of charge (pHzpc), and surface charge at pH 5.8 of AAV were 287.62 m(2)/g, 24.85 cmol/kg, pH 3.06, and -0.361 mmol/g, respectively. Compared to RV, the SSA, CEC and surface charge of AAV increased, but the value of pHzpc decreased. At pH 5.8, the maximum adsorption capacities (q(max)) for Pb(II) of RV and AAV were 10.72 and 18.53 mg/g, respectively. The adsorption data for Pb(II) by RV and AAV could be well fitted using Langmuir isotherm (R-2=0.990 and 0.995, respectively).