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Hybrid materials based on clays and polyamines are supposed to be efficient heavy metals sorbents due to the well-known adsorption behaviour of the clay matrix and to the coordination properties of un-protonated amino groups. For this purpose, a montmorillonite clay was modified with three different aliphatic polyamines: L6 and L10 have a linear structure with six and ten amino groups, respectively, while B14 is a branched polyamine with fourteen amino groups. Initial amine concentration was the main parameter investigated and data were fitted with Langmuir and Freundlich models. Interaction mechanisms between clay and amines were deeply investigated by different experimental techniques such as X-ray powder diffraction (XRD), thermal analysis measurements (DTG), Fourier Transform Infrared Spectroscopy (FT-IR) and diffuse reflectance (NIR) spectroscopy. Experimental results showed that the amount of amines efficiently immobilized in the solid phase can be increased by increasing the initial concentration of polyamines in the clay modification process. These data were best fitted by Freundlich model, indicating a presence of surface sites of different nature. In the resulting hybrid materials, neither the accessibility of the NH/NH2 groups of the amines, nor the accessibility of the structural OH of the clay was hindered. Several preliminary tests in La ions’ uptake and release from aqueous solution were also carried out. In the conditions used for this study, total metal ion removal was achieved at sufficiently low linear amine loadings (i.e., 0.45 mmol/gclay for the small L6 amine), suggesting that these hybrid materials are promising for the proposed application in environmental remediation.

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The recovery of precious metals through hydrometallurgical techniques is one of the most active research areas on recovery of metals from electronic scraps. In this perspective, a pilot plant was designed for the treatment of small WEEE (Waste Electrical and Electronic Equipment) via hydrometallurgy. The process is based on two different leaching steps, in nitric acid and in aqua regia, followed by electrodeposition processes, to mainly recover copper, silver and gold. Two adsorption steps were also carried out to recover nickel and tin.The goal of the present study is to assess the environmental impacts associated with the designed hydrometallurgical treatment of the small WEEE through Life Cycle Assessment (LCA) methodology. The approach considered is cradle-to-gate, i.e., from the collected WEEE entering the collection centre to the secondary metals obtained from the hydrometallurgical treatment.Results obtained by SimaPro software and CML-IA method show that the nitric acid leaching contributes mostly to the impacts of the hydrometallurgical process (from 40% to 80%), followed by the adsorption steps. From an environmental perspective, the latter can still be improved at the design phase by increasing the lifetime of the sorbents

In this work, Ca-montmorillonite (STx), natural and modified (STx-L6) with a linear penta-ethylene-hexamine (L6), were tested as sorbents in a liquid/solid process for La and Cu capture in bionic model solutions. Twelve La/Cu ratios in solution were set and analyzed with the final target of investigating the capture mechanisms when both Cu and La are present. The liquid phase was characterized via inductively coupled plasmaoptical emission spectroscopy (ICP-OES), while the solids were studied by means of X-ray powder diffraction (XRPD). No direct competition between Cu and La ions for the capture sites was found but rather the modification of the acid−base condition of the solution and the related equilibria due to aquo-and hydroxycopper complexes formation. Cu complexes are responsible for pH modification and the related influence on the capture of La ions. Three distinct mechanisms were identified to be active in the capture process, i.e., ion exchange, surface adsorption, and coordination of the metal by the polyamine, when present. Only La is involved in the ionic exchange process, since no Cu was captured by pristine clays, while only Cu is coordinated to the polyamine, in view of its preferential interaction with amino groups. The different capture mechanisms are responsible for the higher efficiency of the organoclay, with respect to the pristine one. This study lays the groundwork for the development of an efficient method for rare earths (REs) and precious metal recovery from waste electrical and electronical equipment (WEEE) by a liquid/solid process.

Two montmorillonitic clays were modified with N-(methoxy-polyethylene glycol) ethylene diamine and tested as sorbents for removal of Rare Earths (REs) from aqueous solutions. Lanthanum was chosen as representing element of REs family and adsorption tests were performed with the aim of selecting a system with good uptake efficiency for the pollutant abatement in wastewaters. The effects of pH were studied and the properties of the obtained final materials were evaluated with simple model systems of the final application. The modified clays were characterized before and after the intercalation, combining the results of X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR), whereas the solutions were analysed by means of Chemical Oxygen Demand to quantify the amount of intercalated polymer and by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) to quantify the metal ions concentration. The results showed that the organo-clays have been efficiently prepared while the characterization techniques showed that the intercalation mechanism was strongly dependent on the pH of the preparation procedure, affecting the protonation of the amino groups.