Daniele Malferrari

Heavy metals in sediments from canals for water supplying and drainage: mobilization and control strategies.

One of the most critical aspects of the maintenance of canals for water supplying and drainage is the managing of deposited sediments, which must be periodically removed. Deposited sediments, if containing anthropogenic pollutants with a concentration exceeding specific law limits, must be stored as industrial wastes, thus raising additional economic and logistic problems to deal with. Our research considers polluted sediments from an area close to the south side of Po river, in order to characterize heavy metals associated with different mineral species, thus defining effective treatments for their inertization, and suggesting a possible process for their recycle. Our results demonstrate that the composition of these sediments is suitable for the production of tiles and bricks. Several tests were thus performed to optimize sample treatment and other process parameters, finally giving very encouraging results. Releasing tests on fired products reveal that all the heavy metals are well retained.

Crystal chemistry of trioctahedral micas in alkaline and subalkaline volcanic rocks: A case study from Mt. Sassetto (Tolfa district, Latium, central Italy)

Abstract This work provides a crystal-chemical description of trioctahedral micas from volcanic rocks (lavas, tuffs, ignimbrites, and xenoliths) outcropping at Mt. Sassetto (Tolfa district, Tuscan Province, central Italy). Mica crystals vary in composition from ferroan phlogopite to magnesian annite. Heterovalent octahedral substitutions are mainly related to Al3+, Ti4+, and, only in a few samples, to Fe3+. The two main mechanisms regulating Ti inlet into the mica structure are the Ti-oxy [VITi4+VI(Mg,Fe)2+-1(OH)--2O2-2] and Ti-vacancy [VITi4+VI □VI(Mg,Fe)2+-2] substitutions. In these micas, Ti content is the predominant crystal-chemical parameter and significantly affects octahedral and interlayer topology as well. Micas with the highest Ti contents deviate from the expected fractional crystallization trend in the Ti vs. Mg/(Mg + Fetot) diagram, possibly as a consequence of a variation in intensive parameters (T, P, fH₂, fO₂, fH₂O) during crystallization in the magmatic chamber. In micas with significant Fe3+ contents, the layer charge balance is accomplished by the following mechanisms: VIFe2+-3VIFe23+VI□, VIFe2+-1VIFe3+(OH)--1O2-, and VIFe2+-1VIFe3+IVSi-14+IVAl3+. These micas show mean electron counts greater for the octahedral M2 site than for M1, and unit-cell parameters signifcantly smaller than usual for other micas. Atmospheric weathering is unlikely to produce the observed Fe oxidation. The Fe3+-vacancy and Fe-oxy substitutions could represent secondary, re-equilibration effects related to post-eruptive water-rock hydrothermal processes (acid-sulfate alteration).

Characterization of Cu-complexes in smectite with different layer charge location: chemical, thermal and EXAFS studies

Abstract The retention of Cu and Cu-amino acid complexes by montmorillonite and beidellite, before and after repeated acidified aqueous solution treatments, was studied using X-ray diffraction, chemical and thermal analyses, mass spectrometry and synchrotron-based X-ray absorption spectroscopy (XAS). The results indicate that the extraction of metal complexes from smectites depends on the nature of the layer charge and on the kind of organic species. Cu-cysteine complexes are strongly retained in the interlayer position, whereas Cu-glycine complexes are mostly adsorbed in cationic form which can be easily removed from the silicate layer. The layer periodicity for Cu-smectites treated with glycine shows little or no layer expansion, whereas significant swelling of the layer periodicity is observed in smectites treated with cysteine. Thermal decomposition of both smectites with sorbed Cu-amino acid species shows the evolution of H 2 O, NO, CH 3 CH 3 , and CO 2 . In Cu-cysteine treated smectites, the release of H 2 S, NO 2 , SO 2 , and N 2 O 3 also occurs. X-ray absorption spectroscopy (XAS) was used to assess the relationships between the structure of the Cu complexes and their desorption from smectites. In Cu-exchanged smectites, the first coordination shell agrees with the hypothesis that the Cu coordinates to oxygen atoms to form monomer and/or dimer complexes. The first coordination shell of Cu in smectites treated with glycine shows four atoms at distances of ∼2 A. Two of these bonds are with nitrogen and two with oxygen atoms. For copper-cysteine complexes XAS data are compatible with the existence of Cu-N clusters, thus suggesting that Cu links to the amino acid by the aminic group.

Single-crystal X-ray studies of trioctahedral micas coexisting with dioctahedral micas in metamorphic sequences from western Maine

Abstract A crystal-chemical study of thirteen biotite (twelve of 1M polytype and one of 2M1 polytype) and four muscovite samples was made. The biotite coexists with the muscovite. Samples are from metamorphic terranes and from granitic and granodioritic bodies occurring in three areas of western Maine. The metamorphic mineral zones identified by mineral compatibilities are, in order of increasing metamorphic grade: the Lower Sillimanite Zone (LSZ), the Upper Sillimanite Zone (USZ), and the K-feldspar + Sillimanite Zone (K + SZ). The muscovite compositions cluster near ideal muscovite and display a small celadonite substitution and a small, but variable, paragonite substitution. The biotite composition has values of VIMg2+/ VI(Mg2+ + Fe2+) ranging from 0.26 to 0.54 and significant octahedral Al content (0.48 ≤ VIAl ≤ 0.72 apfu in metamorphic biotite samples, 0.51 ≤ VIAl ≤ 0.67 in those from granites). In trioctahedral micas from western Maine and especially in those with graphite, there are a greater number of interlayer vacancies than in common micas. Interlayer vacancies have an increase in interlayer cation-basal oxygen atom distances and a decrease in tetrahedral flattening angle τ, thus suggesting a reduced interlayer charge. With a few exceptions, tetrahedral rotation angle α is related to crystallization temperature. In particular, α decreases with a temperature increase, and α is also related to octahedral chemical substitutions. Results tentatively suggest, for micas from metamorphic environments, a direct influence of genetic parameters (T and fO₂) on mica crystal structure, and not just chemical composition.

Sorption of Cd–cysteine complexes by kaolinite

The effect of cysteine on the adsorption of Cd(II) by kaolinite was examined at 25 °C using a low-defect kaolinite from Minas Gerais (Brazil) and a high-defect kaolinite from Berici Hills (Italy). The chemical data demonstrated that the amount of Cd–cysteine detected on kaolinite increases rapidly during the first few hours with a first-order reaction, thereafter adsorption becomes linear with time for low-defect kaolinite and slows rapidly for high-defect kaolinite. In low-ordered kaolinite, the Cd–cysteine is intercalated in the structure. Evidence of these changes was also observed by differential thermal analysis (DTA). The thermal decomposition of the Cd–cysteine adsorbed on the kaolinites was studied by analysing the evolved gases. The mass spectra of both samples show the evolution of NO (or CH3CH3, m/z=30), CO2 (m/z=44), and SO2 (m/z=64) between 150 and 300 °C and of H2O (m/z=18), CO2 (m/z=44) and SO2 (m/z=64) in the temperature range between 400 and 700 °C. The high-defect kaolinite also caused the evolution of molecular units with m/z=34 (H2S) and m/z=76 (N2O3).

Crystal chemistry of apatites from the Tapira carbonatite complex, Brazil

The crystal chemistry of ten hydroxyl fluorapatite crystals from the Tapira alkaline carbonatitic complex (Brazil) was investigated by electron microprobe, ion microprobe, infrared spectroscopy and single crystal X-ray diffraction. Apatite crystals are characterized by modest REE and a very low Cl content. They exhibit the following compositional range in atoms per formula unit 9.935 ≤ Ca ≤ 10.024, 5.926 ≤ P ≤ 6.006, 0.005 ≤ REE ≤ 0.046, 0.422 ≤ F ≤ 0.914, 0.003 ≤ Cl ≤ 0.008, 0.003 ≤ Si ≤ 0.038; Na is present in trace. Crystal structure refinements were carried out in space group P 6 3 / m , ( R values varies between 0.016 and 0.028). The REE for Ca substitution requires two different exchange mechanisms producing an increase in the bond valence on the X anionic site: the deprotonation of OH and/or the substitution of CO 2- 3 for OH. The CO 2- 3 substitution in the anionic sites of investigated structures was related to great CO 2 activity of the melt whereas deprotonation of the apatite crystals could be related to the highly oxidizing nature of the Tapira carbonatitic magma. The very low Cl/F ratio suggests that the crystallization of Tapira pluton was relatively shallow. The determination of REE partitioning between the Ca1 and Ca2 sites is difficult because of the low REE content. A proportional increase in the size of the Ca1 and Ca2 sites was observed with increasing REE content as well as an overall increase of a parameter.

Interlayer potassium and its neighboring atoms in micas: Crystal-chemical modeling and XANES spectroscopy

Abstract A detailed description of the interlayer site in trioctahedral true micas is presented based on a statistical appraisal of crystal-chemical, structural, and spectroscopic data determined on two sets of trioctahedral micas extensively studied by both X-ray diffraction refinement on single crystals (SCXRD) and X-ray absorption fine spectroscopy (XAFS) at the potassium K-edge. Spectroscopy was carried out on both random powders and oriented cleavage flakes, the latter setting taking advantage of the polarized character of synchrotron radiation. Such an approach (AXANES) is shown to be complementary to crystal-chemical investigation based on SC-XRD refinement. However, the results are not definitive as they focus on few samples having extreme features only (e.g., end-members, unusual compositions, and samples with extreme and well-identified substitution mechanisms). The experimental absorption K-edge (XANES) for potassium was decomposed by calculation and extrapolated into a full in-plane absorption component (σ||) and a full out-of-plane absorption component (σ⊥). These two patterns reflect different structural features: σ|| represents the arrangement of the atoms located in the mica interlayer space and facing tetrahedral sheets; σ⊥ is associated with multiple-scattering interactions entering deep into the mica structure, thus also reflecting interactions with the heavy atoms (essentially Fe) located in the octahedral sheet. The out-of-plane patterns also provide insights into the electronic properties of the octahedral cations, such as their oxidation states (e.g., Fe2+ and Fe3+) and their ordering (e.g., trans- vs. cis-setting). It is also possible to distinguish between F- and OH-rich micas due to peculiar absorption features originating from the F vs. OH occupancy of the O4 octahedral site. Thus, combining crystal-chemical, structural, and spectroscopic information is shown to be a practical method that allows, on one hand, assignment of the observed spectroscopic features to precise structural pathways followed by the photoelectron within the mica structure and, on the other hand, clarification of the amount of electronic interactions and forces acting onto the individual atoms at the various structural sites.

Crystal structure and chemical composition of Li-, Fe-, and Mn-rich micas

Abstract The crystal chemistry of three Li-, Fe-, and Mn-rich trioctahedral micas has been characterized by single-crystal X-ray diffraction. The samples are from Hirukawa mine, Japan: (Si3.43Al0.57)(Al1.00 Fe0.38Mg0.01Mn0.17Li1.44)(Na0.05K0.95)O10F1.88(OH)0.12; from Mokrusha mine, Russia: (Si3.30Al0.70)(Al1.00Fe0.36 Mg0.01Mn0.31Li1.32)(Ca0.01Na0.04K0.94)O10F1.91(OH)0.09; and from Sawtooth Mountains, Boise County, Idaho, U.S.A.: (Si3.11Al0.89)(Al0.91Ti0.02Fe0.46Mg0.03Mn0.52Li1.06)(Na0.05K0.92Rb0.02)O10F1.89(OH)0.11. Our crystals belong to the 1M polytype with layer symmetry C121(1) and show M1 and M3 sites much larger in size than M2. Mean electron-count (m.e.c.) values are more variable for the M1 and M3 sites than for M2. With the exception of the sample from Sawtooth Mountains, all tetrahedral mean bond lengths appear to be smaller for T1 than for T11 site. When compared to the Li- and Fe-rich series, crystals show similar crystal-chemical trends, thus suggesting that the layer structure is affected in a similar way by Fe and Mn cations

Rossiantonite, Al3(PO4)(SO4)2(OH)2(H2O)10•4H2O, a new hydrated aluminum phosphate-sulfate mineral from Chimanta massif, Venezuela: Description and crystal structure

Abstract Rossiantonite, ideally Al3(PO4)(SO4)2(OH)2(H2O)10·4H2O, triclinic (space group P1̄), a = 10.3410(5), b = 10.9600(5), c = 11.1446(5) Å, a = 86.985(2), b = 65.727(2), g = 75.064(2)°, V = 1110.5(1) Å3, Z = 2, is a new mineral from the Akopan-Dal Cin cave system in the Chimanta massif (Guyana Shield, Venezuela). The mineral occurs as small (≤0.15 mm) and transparent crystals in a white to slightly pink fine-grained sand, filling spaces between boulders of weathered quartz sandstone. Associated phases are gypsum, sanjuanite, rare alunite, quartz and micro-spherules of amorphous silica. Rossiantonite is colorless with a white streak and vitreous luster. The mineral is brittle with irregular to sub-conchoidal fracture and it shows a poorly developed cleavage. Rossiantonite is biaxial and not pleochroic, with mean refractive index of 1.504. The calculated density is 1.958 g/cm3. Electron microprobe analyses, with H2O measured by thermogravimetric analysis, provided the following empirical formula based on 28 O apfu: Al2.96Fe0.03P1.01S2H30.02O28. The five strongest lines in the X‑ray powder diffraction pattern, expressed as d (Å), I, (hkl) are: 4.647, 100, (210); 9.12, 56, (100); 4.006, 53, (220); 8.02, 40, (110); 7.12, 33, (011). The crystal structure, refined using 3550 unique reflections to R = 0.0292, is built of PO4 and AlO6 polyhedral rings, creating complex chains parallel b by sharing the OH-OH edge belonging to the Al(3) polyhedron. Three symmetrically independent Al sites can be identified, namely: Al(1), Al(2), and Al(3). Tetrahedral sites, occupied by P, share all their apexes with AlO6 octahedra. Unshared octahedral apexes are occupied by water molecules. Four additional water molecules are placed in between the previously identified chains. Two oxygen tetrahedra, occupied by S atoms, are connected along the chains by means of weak hydrogen bonding. The rossiantonite structure shows similarities with minerals belonging to the sanjuanite-destinezite group.

CRYSTALLOGRAPHIC FEATURES AND CLEAVAGE NANOMORPHOLOGY OF CHLINOCHLORE: SPECIFIC APPLICATIONS

Natural and synthetic micas have been used widely as substrates to study biological systems; but, as in the case of negatively charged DNA, anionic charge repulsion may render micas a less than ideal templating surface for many biological systems. The purpose of this study was to investigate the potential for the chlorite clinoclore, which contains a positively charged interlayer octahedral sheet, to serve as a substrate for DNA adsorption. The relationships between clinochlore cleavage characteristics, in terms of nano-morphology, and surface potential are investigated, as are its average crystal chemistry and topology. That the structural features of clinochlore can be used successfully to condense, order, and self assemble complex biomolecules, such as DNA is also proven.A natural IIb-4 clinochlore [