Abstract
The aim of this work is to quantitatively characterize the structural response to a chemical disruption of saturated montmorillonite crystallites by organic molecules (tetracycline (TC)), derived from pharmaceutical waste. The chemical disturbance is performed by varying the surrounding soil solution pH. To show the effect of this chemical perturbation on the interlamellar space (IS) configuration and the hydration properties, an “in situ” XRD analysis, based on the modeling of the 00l reflections, is carried out. The “in situ” XRD analysis is performed by varying the relative humidity conditions (%RH). FTIR SEM and BET- (Brunauer-Emmett-Teller-) BJH (Barrett-Joyner-Halenda) analyses are used as complementary techniques to confirm the structural changes accompanying the intercalation process. Results showed a dependence between solution acid character and the TC adsorption mechanism. From pH values close to 7, the deprotonation of the TC molecule within IS is accelerated by an increasing %RH rate. IR spectroscopy shows that the structure is preserved versus pH value and only a shift of the water deformation bands ascribed to interlamellar water molecule abundance and TC conformation is observed. The surface morphology studied by SEM shows the increase in the surface porosity by increasing the pH value. BET-specific surface area and BJH pore size distribution (PSD) analyses confirm the SEM observations.
Highlights
The risks associated with the presence of industrial and household waste in the soil and the environment are multiplied with the great demand for everyday consumer products
The semiquantitative analysis is based on the reflection peak geometry interpretation and the investigation of the evolution of the FWHM parameter (Table 2)
The high FWHM value is obtained at 80%RH for pH = 5 and at 60%RH for pH = 6
Summary
The risks associated with the presence of industrial and household waste in the soil and the environment are multiplied with the great demand for everyday consumer products. Various conventional and modern technologies are used for reducing the organic pollutant effect on the human health (fauna and flora). Among these technologies, we can mention the ion exchange process which is in relation to the main properties of clay mineral and chemical precipitation and adsorption [1,2,3,4]. Recent studies investigated the adsorption/desorption of various organic matters on/from soil particles. These include, for example, the adsorption of antibodies, surfactants, fireretarding organics, and herbicides [5,6,7,8]. The use of these techniques is thwarted by the high cost of materials used for these purposes
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