Behaviour of cerium(III) in the presence of components of soils and its humate complex

ABSTRACT

The behaviour of cerium, as a prototype of the lanthanide group, against the inorganic components of two types of soils (one from an Abisreligiosa forest (IM-F) and the other from a semiarid zone (IM-S)) was investigated. The pseudo-second order model applied to the kinetics adsorption data for both soils indicated chemical adsorption; the equilibrium was reached in less than 4 h, the adsorption of Ce(III) in these conditions were 15.6 and 3.5 mg g⁻¹ for IM-F and IM-S respectively. The adsorbents showed a buffer effect in alkali conditions, the adsorption was highest at 5 > pH_eq < 6 for both adsorbents. The adsorption isotherms showed that the IM-F surface is homogeneous with a maximum adsorption capacity of 15.7 mg g⁻¹ and that of IM-S is heterogeneous. IM-F is more efficient at low adsorbent dosage, whereas this parameter virtually does not affect the IM-S efficiency but the adsorption percentage increases as the dosage increases. The thermodynamic parameters showed an exothermic and chemical adsorption process using IM-F (ΔH⁰ = −96.6 KJ mol⁻¹) and an endothermic and physicochemical process using IM-S (ΔH⁰ = 29 KJ mol⁻¹). Finally, the competition of the adsorption by IM-F and the formation of the complex with humic acids showed the complex formation of Ce:(HA)n, (1:1) with a log ${\text{β}}_{Ce,HA}^{app}=5.2$.

GRAPHICAL ABSTRACT

KEYWORDS:

• Cerium (III)
• soils
• adsorption parameters
• humate complexes

Acknowledgments

The authors thank the technical support of the nuclear reactor staff and of Mr. Villa Tomasa and Miss I. Z. López Malpica. P.T.A.S. is supported by Catedras-CONACYT Fellowship – 2018.

Disclosure statement

No potential conflict of interest was reported by the author(s).