Premium
Temperature Effects on Nickel Sorption Kinetics at the Mineral–Water Interface
Author(s) -
Scheckel Kirk G.,
Sparks Donald L.
Publication year - 2001
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2001.653719x
Subject(s) - sorption , activation energy , gibbsite , arrhenius equation , enthalpy , nickel , thermodynamics , amorphous solid , chemistry , kinetics , metal , kaolinite , materials science , chemical engineering , mineralogy , adsorption , crystallography , organic chemistry , physics , quantum mechanics , engineering
In recent years, innovative studies have shown that sorption of metals onto natural materials results in the formation of new mineral‐like precipitate phases that increase in stability with aging time. While these findings have demonstrated the usefulness of current state‐of‐the‐art molecular‐scale methods for confirming macroscopic data and elucidating mechanisms, basic kinetic and thermodynamic parameters for the formation of the metal precipitates have not been examined. This study examined Ni‐sorption kinetics on pyrophyllite, talc, gibbsite, amorphous silica, and a mixture of gibbsite and amorphous silica over a temperature range of 9 to 35°C. Using the Arrhenius and Eyring equations, we calculated the energy of activation ( E a ) and enthalpy (ΔH ‡ ), entropy (ΔS ‡ ), and free energy of activation (ΔG ‡ ), related to the formation of the Ni precipitates. Based on values of E a (93.05 to 123.71 kJ mol −1 ) and ΔS ‡ (−27.51 to −38.70 J mol −1 ), Ni sorption on these sorbents was surface‐controlled and an associative mechanism. The ΔH ‡ values (90.60 to 121.26 kJ mol −1 ) suggest, as indicated by E a values, that an energy barrier was present for the system to overcome in order for the reaction to occur. Additionally, the large, positive ΔG ‡ values suggest there is an energy barrier for product formation. Although metal precipitation reactions often occur in the natural environment, this study shows that the rate of these reactions depends strongly on temperature.