Calcium carbonate as sorbent for lead removal from wastewaters.

Low-cost and largely available industrial by-products such as calcite (CaCO3) have been considered as sorbents to remediate wastewaters from toxic elements, such as lead, in compliance with the European circular economy strategy. To date few articles are reporting results on lead sorption at the calcite-water solution interface by X-ray photoelectron spectroscopy (XPS) and this investigation aims to clarifying the mechanism of the interaction of Pb2+ model solutions over a wide concentration range, from 0.1 µM to 80 mM, with commercial calcite. X-ray powder diffraction (XRPD), scanning electron microscopy (SEM, EDX) and XPS analysis indicate that when CaCO3 particles are soaked in Pb2+ 0.1 mM and 1 mM solutions, hexagonal platelets of hydrocerussite [(PbCO3)2 Pb(OH)2] precipitate on its surface. When the concentration of Pb2+ is equal or higher than 40 mM, prismatic acicula of cerussite [PbCO3] precipitate. Solution analysis by atomic emission spectroscopy (ICP-AES) and ICP-mass spectrometry (ICP-MS) indicate that Pb2+ removal efficiency is nearly 100%; when the initial Pb2+ concentration was equal to 0.1 µM it was below the limit of detection (LOD) and the efficiency could not be determined. The sorption capacity (qe) increases linearly with increasing initial Pb2+ concentration up to a value of 1680 (20) mg/g when the initial Pb2+concentration is 80 mM. These findings suggest that heterogeneous nucleation and surface co-precipitation occur and calcite can be well considered a very promising sorbent for Pb2+ removal from wastewaters within a wide initial concentration range.

Arsenopyrite and pyrite bioleaching: evidence from XPS, XRD and ICP techniques.

In this work, a multi-technical bulk and surface analytical approach was used to investigate the bioleaching of a pyrite and arsenopyrite flotation concentrate with a mixed microflora mainly consisting of Acidithiobacillus ferrooxidans. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy mineral surfaces investigations, along with inductively coupled plasma-atomic emission spectroscopy and carbon, hydrogen, nitrogen and sulphur determination (CHNS) analyses, were carried out prior and after bioleaching. The flotation concentrate was a mixture of pyrite (FeS(2)) and arsenopyrite (FeAsS); after bioleaching, 95% of the initial content of pyrite and 85% of arsenopyrite were dissolved. The chemical state of the main elements (Fe, As and S) at the surface of the bioreactor feed particles and of the residue after bioleaching was investigated by X-ray photoelectron and X-ray excited Auger electron spectroscopy. After bioleaching, no signals of iron, arsenic and sulphur originating from pyrite and arsenopyrite were detected, confirming a strong oxidation and the dissolution of the particles. On the surfaces of the mineral residue particles, elemental sulphur as reaction intermediate of the leaching process and precipitated secondary phases (Fe-OOH and jarosite), together with adsorbed arsenates, was detected. Evidence of microbial cells adhesion at mineral surfaces was also produced: carbon and nitrogen were revealed by CHNS, and nitrogen was also detected on the bioleached surfaces by XPS. This was attributed to the deposition, on the mineral surfaces, of the remnants of a bio-film consisting of an extra-cellular polymer layer that had favoured the bacterial action.

Combined use of X-ray photoelectron and Mössbauer spectroscopic techniques in the analytical characterization of iron oxidation state in amphibole asbestos.

Asbestos fibers are an important cause of serious health problems and respiratory diseases. The presence, structural coordination, and oxidation state of iron at the fiber surface are potentially important for the biological effects of asbestos because iron can catalyze the Haber-Weiss reaction, generating the reactive oxygen species *OH. Literature results indicate that the surface concentration of Fe(III) may play an important role in fiber-related radical formation. Amphibole asbestos were analyzed by X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy, with the aim of determining the surface vs. bulk Fe(III)/Fe(tot) ratios. A standard reference asbestos (Union Internationale Contre le Cancer crocidolite from South Africa) and three fibrous tremolite samples (from Italy and USA) were investigated. In addition to the Mössbauer spectroscopy study of bulk Fe(III)/Fe(tot) ratios, much work was dedicated to the interpretation of the XPS Fe2p signal and to the quantification of surface Fe(III)/Fe(tot) ratios. Results confirmed the importance of surface properties because this showed that fiber surfaces are always more oxidized than the bulk and that Fe(III) is present as oxide and oxyhydroxide species. Notably, the highest difference of surface/bulk Fe oxidation was found for San Mango tremolite--the sample that in preliminary cytotoxicity tests (MTT assay) had revealed a cell mortality delayed with respect to the other samples.

The chemical state of arsenic in minerals of environmental interest--an XPS and an XAES study.

A systematic analytical study using X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) has been carried out to characterize the chemical state of arsenic in complex environmental samples. The conventional approach, which relies on the chemical shift of the core levels As3d, provides ambiguous results in determining the chemical environment of arsenic. A more accurate approach, based on the Auger parameter and on the Wagner (Chemical State) plot, which combines AsLMM kinetic energy and As3d binding energy, was adopted. This novel method for determining the chemical state of arsenic was employed to completely characterize arsenic in complex environmental samples.

Quantitative evaluation of oxidative stress, chronic inflammatory indices and leptin in cancer patients: correlation with stage and performance status.

In advanced cancer patients, the oxidative stress could take place either at the onset of disease or as a function of disease progression. To test this hypothesis, the following parameters were investigated: the erythrocyte activity of the enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), the serum activity of glutathione reductase (GR) and the serum total antioxidant status (TAS). The total antioxidant capacity of plasma LMWA was evaluated by the cyclic voltammetry methodology. We further determined the serum levels of proinflammatory cytokines (IL-6 and TNFalpha), IL-2, leptin and C-reactive protein (CRP). All of these parameters have been correlated with the most important clinical indices of patients such as Stage of disease, ECOG PS and clinical response. Eighty-two advanced stage cancer patients and 36 healthy individuals used as controls were included in the study. Our findings show that SOD activity was significantly higher in cancer patients than in controls and GPx activity was significantly lower in cancer patients than in controls. Serum values of IL-6, TNFalpha and CRP were significantly higher in patients than in controls. Serum leptin values of cancer patients were significantly lower than controls. SOD activity increased significantly from Stage II/ECOG 0-1 to Stage IV/ECOG 0-1, whereas it decreased significantly in Stage IV/ECOG 3. GPx activity decreased significantly in Stage IV/ECOG 2-3. An inverse correlation between ECOG PS and serum leptin levels was found. Serum levels of IL-2 decreased from Stage II/ECOG 0-1 to Stage IV/ECOG 2-3. A direct correlation between Stage/ECOG PS and serum levels of both IL-6 and CRP was observed. Cisplatin administration induced a significant increase of GPx after 24 hr. In conclusion, this is the first study that shows that several "biological" parameters of cancer patients such as antioxidant enzyme activity, cytokines, leptin and CRP strictly correlate with the most important clinical parameters of disease such as Stage and ECOG PS.