Kinetics and thermodynamics of nickel sorption to calcium-palygorskite and calcium-sepiolite: a batch study.

摘要

Knowing thermodynamic features of sorption/desorption of metals to/from soil minerals is a very efficient tool to assess and control the fate of these chemicals in the environment. In this batch experiment, we assessed the sorption of nickel (Ni) onto palygorskite and sepiolite at temperatures of 25, 35 and 45 degrees C. Nickel sorption onto both minerals at the three temperatures was adequately described by the Langmuir sorption model (R2m) and the Langmuir sorption coefficient (K_L), indicating the enhanced sorption potential and stronger bonding of Ni to the minerals. Positive values of enthalpy ( Delta H) revealed the endothermic nature of Ni sorption and negative free energy Delta G degrees indicated that sorption of Ni to palygorskite and sepiolite under standard conditions (25 degrees C) is spontaneous. Time-dependent sorption data at the three temperatures were adequately described by the first order kinetic model (R2a) for sepiolite compared with palygorskite indicated that Ni was more readily sorbed onto sepiolite.