Adsorption Characteristics for Lead(II) by Fulvic Acid-Modified Vermiculite

Abstract

Fulvic acid-modified vermiculite (FA-Ver) was prepared by mixing vermiculite and fulvic acid in a suspension. The XRD patterns showed that the vermiculite in FA-Ver possesses an irregular stacking of layers supported and non-supported by fulvic acid particles. The specific surface area (SSA), cation exchange capacity (CEC), pH at zero point of charge (pHZPC), and surface charge at pH 6.0 of FA-Ver was 379.35 m2/g, 52.17 cmol/kg, pH 2.36, and -0.442 mmol/g, respectively. The SSA, CEC and surface negative charge of FA-Ver increased and the pHZPC decreased compared to the corresponding values of vermiculite. Langmuir and Freundlich isotherms fitted the adsorption data for Pb(II) by HA-vermiculite well (R2=0.988 and 0.982, respectively). The Freundlich correlation coefficient of vermiculite was low (R2=0.954) and that of FA-Ver was slightly higher (R2=0.980). At pH 6.0, the Langmuir maximum adsorption capacities for Pb(II) of vermiculite and FA-Ver were 11.86 and 19.41 mg/g, respectively.