Kinetic and thermodynamic studies are carried out at low initial cadmium concentration on a soil sample
extracted from Aspach le Bas in Eastern France. It can be concluded from kinetic experiments that the implied
process is of pseudo‐second order. Rate constants, relaxation times and activation energy are calculated. The
energy value determined in this study (40 kJ mol−1
) shows that the process implies both physisorption and
chemisorption.
The influence of soil particle size (i.e. of the initial soil and its different fractions: sand, coarse silt, fine silt and
clay), organic matter and temperature on the cadmium sorption capacity is also investigated. The Langmuir
and the Dubinin–Radushkevich models are chosen to analyze these thermodynamic experiments. The
isotherms have revealed that the Cd2+ sorption is enhanced by increasing temperature and organic matter
for all the fraction but the sand (in this last case, no temperature or organic matter have changed Cd2+
sorption). Thermodynamics parameters (ΔG, ΔH and ΔS) are determined from experimental isotherms
fitting following three methods used in the literature. It can be deduced from the different results that
adsorption (exo or endothermic according to the fraction). Finally, a mean free energy of adsorption is
obtained via Dubinin–Radushkevich model and confirms that the two types of sorption (physical and
chemical) act in the whole process.
Kinetic and thermodynamic studies are carried out at low initial cadmium concentration on a soil sampleextracted from Aspach le Bas in Eastern France. It can be concluded from kinetic experiments that the impliedprocess is of pseudo‐second order. Rate constants, relaxation times and activation energy are calculated. Theenergy value determined in this study (40 kJ mol−1) shows that the process implies both physisorption andchemisorption.The influence of soil particle size (i.e. of the initial soil and its different fractions: sand, coarse silt, fine silt andclay), organic matter and temperature on the cadmium sorption capacity is also investigated. The Langmuirand the Dubinin–Radushkevich models are chosen to analyze these thermodynamic experiments. Theisotherms have revealed that the Cd2+ sorption is enhanced by increasing temperature and organic matterfor all the fraction but the sand (in this last case, no temperature or organic matter have changed Cd2+sorption). Thermodynamics parameters (ΔG, ΔH and ΔS) are determined from experimental isothermsfitting following three methods used in the literature. It can be deduced from the different results thatadsorption (exo or endothermic according to the fraction). Finally, a mean free energy of adsorption isobtained via Dubinin–Radushkevich model and confirms that the two types of sorption (physical andchemical) act in the whole process.
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