Iron-bearing clays are ubiquitously distributed as mineral dusts in the atmosphere. Bromophenols were reported as the major products from thermal decomposition of the widely used brominated flame retardants (BFRs). However, little information is available for the reactivity of iron associated with mineral dusts to interact with the atmospheric bromophenols and the subsequent toxic effects. Herein, three common clay minerals (montmorillonite, illite and kaolinite) were used to simulate mineral dusts, and the reactions with gaseous 2-bromophenol were systematically investigated under environmentally relevant atmospheric conditions. Our results demonstrate that structural Fe(III) in montmorillonite and Fe(III) from iron oxide in illite mediated the dimerization of 2-bromophenol to form hydroxylated polybrominated biphenyl and hydroxylated polybrominated diphenyl ether. The surface reaction is favored to occur at moisture environment, since water molecules formed complex with 2-bromophenol and the reaction intermediates via hydrogen bond to significantly lower the reaction energy and promote the dimerization reaction. More importantly, the formed dioxin-like products on clay mineral dust increased the toxicity of the particles to A549 lung cell by decreasing cell survival and damaging cellular membrane and proteins. The results of this study indicate that not only mineral dust itself but also the associated surface reaction should be fully considered to accurately evaluate the toxic effect of mineral dust on human health.

A massive and dense textured layer (ca. 35–50 cm thick) of hardpan was uncovered at the top layer, which capped the unweathered sulfidic Cu-Pb-Zn tailings in depth and physically supported gravelly soil root zones sustaining native vegetation for more than a decade. For the purpose of understanding functional roles of the hardpan layer in the cover profile, the present study has characterized the microstructures of the hardpan profile at different depth compared with the tailings underneath the hardpans. A suit of microspectroscopic technologies was deployed to examine the hardpan samples, including field emission-scanning electron microscopy coupled with energy dispersive spectroscopy (FE-SEM-EDS), X-ray diffraction (XRD) and synchrotron-based X-ray absorption fine structure spectroscopy (XAFS). The XRD and Fe K-edge XAFS analysis revealed that pyrite in the tailings had been largely oxidised, while goethite and ferrihydrite had extensively accumulated in the hardpan. The percentage of Fe-phyllosilicates (e.g., biotite and illite) decreased within the hardpan profile compared to the unweathered tailings beneath the hardpan. The FE-SEM-EDS analysis showed that the fine-grained Ca-sulfate (possibly gypsum) evaporites appeared as platelet-shaped that deposited around pyrite, dolomite, and crystalline gypsum particles, while Fe-Si gels exhibited a needle-like texture that aggregated minerals together and produced contiguous coating on pyrite surfaces. These microstructural findings suggest that the weathering of pyrite and Fe-phyllosilicates coupled with dolomite dissolution may have contributed to the formation of Ca-sulfate/gypsum evaporites and Fe-Si gels. These findings have among the first to uncover the microstructure of hardpan formed at the top layer of sulfidic Cu-Pb-Zn tailings, which physically capped the unweathered tailings in depth and supported root zones and native vegetation under semi-arid climatic conditions.

The removal of pesticide residues in soil is a research hotspot. The metolachlor (MET) adsorption by walnut shell biochar (BC) modified with montmorillonite (MBC), illite (IBC), and kaolinite (KBC), as well as the original BC (OBC) was investigated. The characteristics of samples were studied by scanning electron microscopy and mapping analysis, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, and chemical stability analysis. The effects of the dosage, ionic strength, and pH, and determined the adsorption kinetics and isotherms for MET with the BCs were analyzed. In addition, response surface methodology regression model analysis was conducted and the adsorption mechanisms were investigated. The results showed that the thermal stability and chemical stability of MBC, IBC, and KBC were higher than those of OBC, and MBC had the greatest stability. The MET adsorption rates of OBC, MBC, IBC, and KBC were 62.15%, 92.47%, 87.97%, and 83.31%, respectively. The kinetic fitting results and adsorption mechanisms showed that the modification of BC with minerals enhanced the physical adsorption of MET. The maximum MET adsorption capacities by OBC, MBC, IBC, and KBC were 39.68 mg g⁻¹, 68.49 mg g⁻¹, 65.79 mg g⁻¹, and 65.36 mg g⁻¹, respectively. Hydrogen bonds, π–π bonds, coordination bonds, and hydrophobic interactions were the key adsorption mechanisms. Therefore, the mineral-modified BCs were characterized by high adsorption rates and stability. This approach can make BC more efficient, with higher performance as a low cost soil amendment.

Elucidating the mechanisms of heavy metal (HM) adsorption on clay minerals is key to solving HM pollution in soil. In this study, the adsorption of four HM atoms (As, Cd, Cr, and Hg) on the illite(001) surface was investigated using density functional theory calculations. Different adsorption configurations were investigated and the electronic properties (i.e., adsorption energy (Eₐd) and electron transfer) were analyzed. The Eₐd values of the four HM atoms on the illite(001) surface were found to be As > Cr > Cd > Hg. The Eₐd values for the most stable adsorption configurations of As, Cr, Cd, and Hg were −1.8554, −0.7982, −0.3358, and −0.2678 eV, respectively. The As atoms show effective chemisorption at all six adsorption sites, while Cd, Cr, and Hg atoms mainly exhibited physisorption. The hollow and top (O) sites were more favorable than the top (K) sites for the adsorption of HM atoms. The Gibbs free energy results show that the illite(001) surface was energetically favorable for the adsorption of As and Cr atoms under the influence of 298 K and 1 atm. After adsorption, there was a redistribution of positions and reconfiguration of the chemical bonding of the surface atoms, with a non-negligible influence around the upper surface atoms. Bader charge analysis shows electrons were transferred from the surface to the HM atoms, and a strong correlation between the valence electron variations and the adsorption energy was observed. HM atoms had a high electronic state overlap with the surface O atoms near the Fermi energy level, indicating that the surface O atoms, though not the topmost atoms around the surface, significantly influence HM adsorption. The above results show illite(001) preferentially adsorbed As among all four investigated HM atoms, indicating that soils containing a high proportion of illite might be more prone to As pollution.

Natural media such as soil and sediment contain mineralogical and organic components with distinct chemical, surface, and electrostatic properties. To better understand the role of various soil and sediment components on particle transport, columns were packed with quartz sand and natural sediment with added Fe oxyhydroxide coating, illite clay, and peat moss to investigate how these added components influence nTiO₂ retention and transport in geochemically heterogeneous medium. Results showed that nTiO₂ transport was low at pH 5, attributable to the electrostatic attraction between positively-charged nTiO₂ and negatively-charged medium. While illite did not notably affect nTiO₂ transport at pH 5, Fe oxyhydroxide coating increased nTiO₂ transport due to electrostatic repulsion between Fe oxyhydroxide and nTiO₂. Peat moss also increased nTiO₂ transport at pH 5, attributable to the increased DOC concentration, which resulted in higher DOC adsorption to nTiO₂ and intensified electrostatic repulsion between nTiO₂ and the medium. At pH 9, nTiO₂ transport was high due to the electrostatic repulsion between negatively-charged nTiO₂ and medium surfaces. Fe oxyhydroxide coating at pH 9 slightly delayed nTiO₂ transport due to electrostatic attraction, while illite clay and peat moss substantially inhibited nTiO₂ transport via straining/entrapment or electrostatic attraction. Overall, this study demonstrated that pH has a considerable effect on how minerals and organic components of a medium influence nTiO₂ transport. At low pH, electrostatic attraction was the dominant mechanism, therefore, nTiO₂ mobility was low regardless of the differences in mineralogical and organic components. Conversely, nTiO₂ mobility was high at high pH and nTiO₂ retention was dominated by straining/entrapment and sensitive to the mineralogical and organic composition of the medium.

The adsorption characteristics of heavy metals: cadmium(II), chromium(III), copper(II), nickel(II), lead(II), and zinc(II) ions by kaolin (kaolinite) and ballclay (illite) from Thailand were studied. This research was focussed on the pH, adsorption isotherms of single-metal solutions at 30–60 °C by batch experiments, and on ion selectivityin mixed and binary combination solutions. It was found that, except Ni, metal adsorption increased with increased pH of the solutions and their adsorption followed both Langmuir and Freundlich isotherms. Adsorption of metals in the mixture solutions by kaolin was: Cr > Zn > Cu ≈ Cd ≈ Ni > Pb, and for ballclay was: Cr > Zn > Cu > Cd ≈ Pb > Ni. The adsorption of metals was endothermic, with the exception of Cd, Pb and Zn for kaolin, Cu and Zn for ballclay. Kaolin and ballclay exhibited relatively hard Lewis base adsorption site. The presence of other metals may reduce or promote the adsorption of heavy metals. The presence of Cr³⁺induced the greatest reduction of metal adsorptiononto kaolin, as did the presence of Cu²⁺for ballclay.

The world’s interest now is focusing on the applying of the principles of sustainable development in managing natural resources, especially in managing freshwater, which is one of the greatest challenges the whole world face. In this paper, the illite ore was tested to remove the excess of iron and manganese from groundwater which is used for drinking and household purposes in Assiut. To accomplish this goal, the study was based on two directions. The first direction focused on achieving a physicochemical analytical survey for all the groundwater produced by wells in Assiut governorate, and its averages are plotted on GIS maps, to illustrate the difference in the concentrations of iron and manganese. However, the second direction focused on the preparation and examination of the modified illite ore, and it was characterized by using XRD, SEM, FT-IR, and XRF techniques. The results showed that the sodalite-bearing modified illite (SBMI) was able to remove the excess of iron and manganese from raw groundwater with the efficiency of 99% and 97%, respectively.

The sediments were studied according to the granulometric characteristics, the geochemical analyses of the sediments (organic matter (OM), carbonate, and pH), the analyses of heavy metals (HM) characteristics, and their contamination status in the ecological system and the mineralogical analysis of the sediments at 8 sites spread over the Marchica lagoon (NE-Morocco). Our results showed that the opening of the new wide and deep pass affected the spatial distributions of the metals, which were closely related to fine fraction and sediment OM concentration. In the north and southeast lagoon zones presented low concentrations of the HM, fine particles (clay), OM, whereas the south and the center of the lagoon were heavily loaded with HM and OM, corresponding to the trapping zones by fine particles. The results of mineralogy analyses have revealed the predominance of non-clay minerals such as quartz and calcite, and for the clay fractions of sediments showed that they are formed of illite, kaolinite, smectite, and chlorite in highly variable proportions; illite was the most dominant clay in the north-western Marchica lagoon sediments. Therefore, the HMs are fixed by clay colloids having a high cation exchange capacity with smectite-chlorite-kaolinite assembly.

The desorption of radioactive cesium (Cs) in soil is influenced by the clay mineral type, adsorption site, and concentration of Cs. In this study, experiments to detect desorption of non-radioactive and radioactive Cs from illite using oxalic acid were performed for 2 days at 70 °C in hydrothermal conditions. The results showed that the ¹³³Cs removal efficiency by oxalic acid and inorganic acid treatment was similar at high concentration (22.86 mmol/kg) of non-radioactive ¹³³Cs. In the radioactive ¹³⁷Cs experiment, the removal efficiency by oxalic acid was higher than that by inorganic acid at low concentration (0.79 × 10⁻⁶ mmol/kg) of radioactive ¹³⁷Cs. Based on the illite hypothetical frayed edge site (FES) concentration of 0.612 mmol/kg, the results suggested that ¹³⁷Cs was preferentially adsorbed to FES on illite. The ¹³⁷Cs at low concentration was difficult to remove because it was irreversible adsorption to FES, while the non-radioactive Cs at high concentration was mainly adsorbed to planar sites, and so was easy to desorb by ion exchange. Based on the results of NMR, FTIR, and XPS analyses, we concluded that the higher efficiency of ¹³⁷Cs removal at low concentration by oxalic acid treatment than by treatment with inorganic acid was because of chelation effects associated with the complexation of oxalic acid (ligands) and metal ions in irreversible site (FES).

This work investigated the impact of a clay mineral on toxic waste. The Ivorian Anti-pollution Center discovered the toxic waste from Probo Koala boat on 21 August 2006. This boat had been used to refine oil named naphtha of cokéfaction by Trafigura firm in the sea. The process of refining consists of caustic sodium carbonate washing and produced toxic waste. These toxic wastes have been unloading in 13 zones of the Abidjan district: Akouédo, Abobo, Abobo Alépé road (Djibi village), civile prison road (MACA), industrial zone of Koumassi, Port-Bouët - Vridi CAP Logistic (Rue Saint-Sylvestre)… This situation caused a socio-political crisis and generated the death of many people. To solve this problem, one first part has been excavated and sent to France to be incinerated. A second part is used to be a biopile for bioremediation. After these two processes, the rest of toxic waste remained in the place where they have been unloaded. The analyses of these toxic wastes show that polycyclic aromatic hydrocarbons (PAHs), oxygenated polycyclic aromatic compounds (O-PACs), volatile aromatic compound (VAC), mercaptan and sulfur molecules, and also heavy metal and organometallic are the principal polluters of these contaminated soils. From a mineralogical viewpoint, the tropical climate soils of Ivory Coast in general and district of Abidjan in particular constituted of about 50% of kaolinite, 30 to 40% of smectite, and 10 to 20% of illite (OSTROM 1993). In this study, we want to show the impact of this local clay on toxic waste.