D-amygdalin is a toxic compound found in the kernels of some bitter almond cultivars.This compound is toxic because of its potential to release poisonous hydrogen cyanide. The D-amygdalin contents of the kernels of 18 commercial almond cultivars (Prunus dulcis Mill. = Amygdalus communis L.) and three wild genotypes (Amygdalus webbii Spach.) were determined by HPLC. In initial tests, two extraction procedures [100% (v/v) methanol or 4% (w/v) citric acid)], two different kernel cutting sizes (powdered or roughly-cut pieces), and two shaking techniques (mechanical shaking or sonication) were assessed. The results obtained showed that the method of extraction can have a strong effect on the extent of recovery of the potentially toxic compound, which varied by a factor of approx. 20-fold across the different extraction techniques.The greatest recovery of D-amygdalin from wild almond kernels was achieved with mechanical shaking of roughly-cut kernels in 100% (v/v) methanol, and this procedure was applied for all subsequent analyses of the D-amygdalin contents of all genotypes. The highest amounts of D-amygdalin were found in “bitter” cultivars and wild genotypes (716 – 23,025 mg kg–1), with lower values in “sweet” cultivars (0 – 158 mg kg–1). High levels of variability were observed both among the 18 almond cultivars and the A. webbii genotypes tested.

The aim of this work is to investigate the efficiency of the phyllomanganate birnessite in degrading catechol after mechanochemical treatments. A synthesized birnessite and the organic molecule were grounded together in a high energy mill and the xenobiotic-mineral surface reactions induced by the grinding treatment have been investigated by means of X-ray powder diffraction, X-ray fluorescence, thermal analysis and spectroscopic techniques as well as high-performance liquid chromatography and voltammetric techniques. If compared to the simple contact between the birnessite and the organic molecule, mechanochemical treatments have revealed to be highly efficient in degrading catechol molecules, in terms both of time and extent. Due to the two phenolic groups of catechol and the small steric hindrance of the molecule, the extent of the mechanochemically induced degradation of catechol onto birnessite surfaces is quite high. The degradation mechanism mainly occurs via a redox reaction. It implies the formation of a surface bidentate inner-sphere complex between the phenolic group of the organic molecules and the Mn(IV) from the birnessite structure. Structural changes occur on the MnO6 layers of birnessite as due to the mechanically induced surface reactions: reduction of Mn(IV), consequent formation of Mn(III) and new vacancies, and free Mn2+ ions production.

The existence of a lot of worldwide pentachlorophenol-contaminated sites has induced scientists to concentrate their effort in finding ways to degrade it. Therefore, an effective tool to decompose it from soil mixtures is needed. In this work the efficiency of the phyllomanganate birnessite (KBi) in degrading pentachlorophenol (PCP) through mechanochemical treatments was investigated. To this purpose, a synthesized birnessite and the pollutant were ground together in a high energy mill. The ground KBi-PCP mixtures and the liquid extracts were analyzed to demonstrate that mechanochemical treatments are more efficient in removing PCP than a simple contact between the synthesized birnessite and the pollutant, both in terms of time and extent. The mechanochemically induced PCP degradation mainly occurs through the formation of a surface monodentate inner-sphere complex between the phenolic group of the organic molecules and the structural Mn(IV). This is indicated by the changes induced in birnessite MnO6 layers as a consequence of the prolonged milling with the pollutant. This mechanism includes the Mn(IV) reduction, the consequent formation of Mn(III) and new vacancies, and free Mn2+ ions release. The PCP degradation extent is limited by the presence of chloro-substituents on the aromatic ring.

Clay minerals have revealed highly potential in soil remediation due to their low cost, availability, and low toxicity. Mechanochemical processes allow to activate chemical reactions by inducing different kinds of mechanical stress and without any other energy supply. This study investigated the effect of dry milling on the ability of dioctahedral and trioctahedral smectites to immobilize heavy metals cations. To this purpose a dioctahedral smectite “bentolite L” and a trioctahedral one “laponite RD” were ground with different amount of copper(II) chloride in dry conditions into a zirconia planetary ball mill (mechanochemical treatment). Increasing milling time and Cu/clay minerals mass ratio were selected for experimental tests. From the ground mixtures two different kinds of samples were extracted using the following procedures: 1) with deionised water; 2) with 1 M MgCl2 solution. Copper immobilization degree was evaluated by ICP/OES analysis of exstracts as difference between the amount of Cu(II) spiked in the mixture and the amount of Cu(II) ions present in the extracted fraction. The analyses showed an increased Cu retention as time increases for both bentolite L and laponite RD. Mechanochemical treatments, depending on time and different mass ratio, induced the increase of retention efficiency. The solid phases were also characterized by means of solid-state NMR and spectroscopic techniques such as FTIR and XPS, to investigate the mechanisms of the “mechanochemical retention” of copper by both the clay minerals

Abstract—The pollution of soils by organic contaminants, such as phenols, is a serious problem because of the high toxicity and persistence in the environment. Mechanochemical treatments (MTs) of polluted soils with minerals, such as clays and oxides, which have surfaces that exhibit catalytic properties, have been suggested to be a new useful strategy to promote both organic and inorganic pollutant degradation. Nevertheless, much still remains to be studied about the capability of clays to promote pollutant removal by means of the mechanochemical activation of the mineral surfaces. This work investigates the efficiency of the mineral kaolinite in promoting the sequestration of catechol (CAT) and pentachlorophenol (PCP) by MT. A well crystallized kaolinite (KGa-1b) was milled for prolonged times with different amounts of organic molecules so as to obtain two different clay:organic compound ratios. Prolonged grinding and a higher clay mineral:organic compound ratio were found to be more effective in promoting a stronger removal than simple contact. After 1 h of mechanochemical treatment, the PCP and CAT removal percentages were 32% and 20%, respectively. Additionally, a 7-day undisturbed incubation of the milled mixtures produced a trend for increased CAT removal (up to 40%). The interaction mechanism between kaolinite and each organic compound (i.e. CAT and PCP) after a MT was inferred by integrating information from spectroscopic, diffractometric, and chromatographic analyses. X-ray diffraction and Fourier-transform infrared data suggested a strong interaction between CAT and KGa-1b. This interaction mechanism likely occurs through the formation of an inner-sphere complex by H-bonding between the organic molecules and the oxygens of the kaolinite tetrahedral sheet. On the other hand, a weak interaction (i.e. van der Waals type) can occur between the KGa-1b O-planes and the PCP molecules, which likely bind to the external surfaces of KGa-1b.

The presence of heavy metals in the environment is a potential risk for the ecosystem due to their toxicity to plant, animals and human life. Lots of technologies and treatments have been developed to remove them from aqueous solutions, employing natural or synthetic sorbents. Among them, clay minerals have revealed interesting properties in soil remediation due to their natural occurrence, low toxicity, and low cost. Moreover, mechanochemical processes allow to activate chemical reactions by inducing different kinds of mechanical stress and without any other energy supply. In this study the effect of mechanochemical treatments on the ability of dioctahedral and trioctahedral smectites to “entrap” heavy metals is investigated. To this purpose a dioctahedral smectite “bentolite L” and a trioctahedral one “laponite RD” were ground with different distinct amounts of copper and cadmium chloride in dry conditions by means of zirconia planetary ball mill. Experimental tests were performed modifying the milling time and metal/clay minerals mass ratio, whereas grinding energy and ball to powder ratio were kept constant. The efficiency of the mechanochemical process to promote the interaction between smectites and heavy metals was evaluated by means of different analytical techniques: the immobilization degree was evaluated by ICP/OES analyses and expressed by the leachable fraction of metal ions. While the investigation on the main adsorption sites of the heavy metals on the ground surfaces was tested by means of solid-state measurements through the combined use of X-ray Fluorescence Spectroscopy, Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Nuclear Magnetic Resonance and X-ray Photoelectron Spectroscopy.

The risk related to the presence of hydrophobic contaminants in soil is mainly due to their availability, influenced by aging processes and the amount and quality of organic matter An improper estimation of the risk of a pollutant in soil. could affect whatever remediation action Therefore, integrated approaches are needed for a realistic evaluation of the contaminant availability. This work aims to correlate chemical extraction methods and bioassays to assess the bioaccessibility, bioavailability and toxicity of phenanthrene (PHE). Bioaccessibility and bioavailability of PHE in an agricultural soil polluted with 15 and 150 mg kg(-1) of PHE have been studied in relation to aging. effects (up to 240 days) and compost amendments (10 and 30 t ha(-1)). The bioaccessibility, evaluated by means of the PHE amount desorbed by Tenax TA resin, evidenced a decrease in PHE amount extracted at 240 days, with respect to that extracted at 20 days (aging effect) in the presence of 15 mg kg PHE, and at 10 t ha(-1) of compost addition. The addition of higher doses of compost (30 t ha(-1)) evidenced a reduction of the bioaccessible PHE fraction after only 20 days of aging. No differences were observed in samples contaminated with 150 mg kg(-1) of PHE. The bioavailability was assessed by PHE uptake in Eisenia andret (Annelida. Lumbricidae) exposed for 14 days to soil samples This parameter showed a marked reduction with ailing and compost amendment both at 15 and 150 mg kg(-1) of PHE concentration. A reduction of the acute toxicity (mortality of individual earthworms) and of morphological alterations in immune system cells were observed after 240 days of aging in all samples. Results evidenced that the toxicity of PHE was well correlated with the bioavailability. However, the relationships between the bioaccessibility and the two above-mentioned parameters were less clear.