Bentonite; Environment; Ghassoul; Kaolin; Mobility; Clay mineralogy; Consumer applications; Environmental applications; Geochemicals; Moroccan clay; Naturally-occurring radionuclides; Potentially toxic elements; Water Science and Technology; Soil Science; Geochemistry and Petrology; Earth and Planetary Sciences (miscellaneous)
Abstract :
[en] Natural Moroccan clays such as bentonite, Ghassoul, and kaolin, are used extensively in consumer and environmental applications where their geochemical stability is critical. The potential release of potentially toxic elements (PTEs) and naturally occurring radionuclides from these raw materials remains poorly constrained, however. The present study investigated mineralogical controls on the leaching of potentially toxic elements (PTEs: Ag, As, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Se, Sn, V, and Zn) and radionuclides (Po, U, Th, Ra) from three raw Moroccan clays: a montmorillonite-rich clay (Mnt), kaolinite-rich clay (Kln), and stevensite-rich clay (Stv). A multidisciplinary methodology combined mineralogical (X-ray diffraction, XRD), chemical (X-ray fluorescence, XRF; inductively coupled plasma-optical emission spectroscopy, ICP-OES), and radioactivity spectrometry analyses with standardized leaching tests (EN 12457-4) to quantify elemental mobility and assess environmental risk. The results revealed distinct leaching signatures controlled by the clay mineralogy. The large cation exchange capacity of Mnt-rich clay favored cation release (e.g. Zn, exceeding inert waste limits), with moderate mobility of As (∼12%) and Mo (∼11%). In contrast, the Kln-rich clay exhibited low mobility of PTEs and radionuclides, consistent with its inert geochemical behavior and low specific surface area. Stevensite-rich clay exhibits significant mobility of molybdenum (∼91.3%) and moderate mobility of arsenic (∼22.6%) under mildly alkaline conditions. Despite the relatively high natural radioactivity of the Stv-rich clay, leachate concentrations of alphaemitting radionuclides remained limited (<15 Bq kg-1), causing negligible radiological risk. These findings demonstrate that the clay mineralogy, rather than total contaminant concentration, is the primary factor dictating leaching behavior. This underscores the necessity of mineralogy-specific risk assessments for the safe management and application of industrial clays, particularly the Stv-rich Ghassoul clay, in consumer and environmental contexts.
Research Center/Unit :
Geology - ULiège
Disciplines :
Earth sciences & physical geography
Author, co-author :
Harrou, Achraf ; Université de Liège - ULiège > Geology ; Geology and Sustainable Mining Institute (GSMI), Mohammed VI Polytechnic University (UM6P), Benguerir, Morocco ; Laboratory of Applied Chemistry and Environment, Faculty of Sciences, Mohammed First University, Oujda, Morocco
Dira, Abdelouassia ; Laboratory of Applied Chemistry and Environment, Faculty of Sciences, Mohammed First University, Oujda, Morocco ; Materiales Polifuncionales Basados en Carbono (UGR-Carbon), Dpto. Química Inorganica, Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente, Universidad de Granada (UEQ-UGR), Granada, Spain
Jouini, Marouen ; Geology and Sustainable Mining Institute (GSMI), Mohammed VI Polytechnic University (UM6P), Benguerir, Morocco
Elghali, Abdellatif; Geology and Sustainable Mining Institute (GSMI), Mohammed VI Polytechnic University (UM6P), Benguerir, Morocco
Raya, Juan Pedro Bolívar; Center On Natural Resources, Health and the Environment (RENSMA), University of Huelva, Huelva, Spain
Fagel, Nathalie ; Université de Liège - ULiège > Département de géologie > Argiles, géochimie et environnements sédimentaires
El Ouahabi, Meriam ; Université de Liège - ULiège > Département de géologie > Argiles, géochimie et environnements sédimentaires
Gharibi, ElKhadir; Laboratory of Applied Chemistry and Environment, Faculty of Sciences, Mohammed First University, Oujda, Morocco
Language :
English
Title :
Mineralogical control on the leaching of potentially toxic elements and radionuclides from raw Moroccan clays
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