Red mud treated with KOH: synthesis of sustainable materials from waste for water treatment.

Solid waste resulting from bauxite ore (red mud) was converted into useful products consisting in hydrogarnet together with zeolite. Red mud (RM) transformation from disposal material into new source was carried out using potassium hydroxide as an activator and hydrothermal process (HY) or vapor phase crystallization (VPC) approach. HY process was performed at 60, 90, and 130 °C whereas during the VPC method, red mud was contacted only with vapor from the distilled water heated at 60 and 90 °C. The results indicate the formation of katoite and zeolite L (LTL topology) with both approaches. All the synthetic products display magnetic properties. In addition, a preliminary investigation on arsenic removal from drinking water (from 59 to 86%), makes the synthetic materials appealing for environmental applications. Finally, the synthesis of a large amount of very useful newly-formed phases using vapor molecules confirms the efficiency of the innovative and green VPC process in waste material transformation.

Surface Nanotexturing of Boron-Doped Diamond Films by Ultrashort Laser Pulses.

Polycrystalline boron-doped diamond (BDD) films were surface nanotextured by femtosecond pulsed laser irradiation (100 fs duration, 800 nm wavelength, 1.44 J cm-2 single pulse fluence) to analyse the evolution of induced alterations on the surface morphology and structural properties. The aim was to identify the occurrence of laser-induced periodic surface structures (LIPSS) as a function of the number of pulses released on the unit area. Micro-Raman spectroscopy pointed out an increase in the graphite surface content of the films following the laser irradiation due to the formation of ordered carbon sites with respect to the pristine sample. SEM and AFM surface morphology studies allowed the determination of two different types of surface patterning: narrow but highly irregular ripples without a definite spatial periodicity or long-range order for irradiations with relatively low accumulated fluences (<14.4 J cm-2) and coarse but highly regular LIPSS with a spatial periodicity of approximately 630 nm ± 30 nm for higher fluences up to 230.4 J cm-2.

Apportioning PM1 in a contrasting receptor site in the Mediterranean region: Aerosol sources with an updated sulfur speciation.

A multi-parametric experimental campaign was performed in Agri Valley (Basilicata, southern Italy) from July 2017 to January 2018. The investigated area, though basically rural and devoted to agricultural activities, hosts a huge on-shore oil reservoir, i.e. Centro Olio Val d'Agri (COVA), bringing substantial environmental modifications and impacts to the district landscape. Daily concentrations of PM1 aerosol samples, Equivalent Black Carbon and number size distributions were evaluated. Chemical aerosol speciation based on elemental and ion analyses were carried out and source apportionment by Positive Matrix Factorization (PMF) was applied to reconstruct PM1 source profile. The most significant emission sources found are torches from the oil treatment facility (37 % w/w), an unresolved factor constituted by soil resuspension, Saharan dust, and biomass burning (24 % w/w), ammonium sulphate (23 % w/w), emissions from the oil desulfurization (Claus process) (13 % w/w), and traffic + road dust (3 % w/w). SEM analysis on PM1 single particles allowed to confirm the finding from PMF including the occurrence of elemental sulfur associated with the Claus process. The novelty of the present study consists in the identification of this latter fingerprint.

Mobility of trace metals in serpentinite-derived soils of the Pollino Massif (Southern Italy): insights on bioavailability and toxicity.

This paper deals with the evaluation of geo- and bioavailability of trace elements, including heavy metals, present in a typical serpentinite-derived soil of the Pollino Massif (Southern Italy). Precisely, the research was aimed to (1) assess processes and factors controlling the mobility of metals in the soil in order to identify the elements "potentially harmful" for the human health, (2) estimate possible metals accumulation in horticultural crops, and (3) evaluate phyto- and genotoxicity of Cr naturally present in soils and water. The studied profile has a homogeneous mineralogical composition consisting of metal-rich phases as prevailing minerals. The three-step sequential extraction was performed on soil samples from which four fractions (exchangeable, reducible, oxidizable, and residual) were obtained and analysed by ICP-MS. The lowest contents of metals are in the exchangeable and oxidizable fractions suggesting a metal contamination is unlikely for the studied soil. Conversely, the residual and reducible fractions are the more metal enriched fractions. Among heavy metals, mainly Pb and Cd and subordinately Ni, Cr, Cu, and Zn are associated with Fe- and Mn-oxi/hydroxides that, under acidic conditions, may release the adsorbed metals in circulating water. The high contents of heavy metals, including Cr and Ni, of analysed vegetables suggest a metal transfer from soil to plant. However, no significant effects on Vicia faba seeds were observed by in vivo phyto- and genotoxicity tests. Conversely in vitro genotoxicity tests, performed on HepG2 human cell line, showed that DNA damage and cytotoxic effect depending on Cr concentration may occur.

Soil Moisture Retrieval by Integrating TASI-600 Airborne Thermal Data, WorldView 2 Satellite Data and Field Measurements: Petacciato Case Study.

Soil moisture (SM) plays a fundamental role in the terrestrial water cycle and in agriculture, with key applications such as the monitoring of crop growing and hydrogeological management. In this study, a calibration procedure was applied to estimate SM based on the integration of in situ and airborne thermal remote sensing data. To this aim, on April 2018, two airborne campaigns were carried out with the TASI-600 multispectral thermal sensor on the Petacciato (Molise, Italy) area. Simultaneously, soil samples were collected in different agricultural fields of the study area to determine their moisture content and the granulometric composition. A WorldView 2 high-resolution visible-near infrared (VNIR) multispectral satellite image was acquired to calculate the albedo of the study area to be used together with the TASI images for the estimation of the apparent thermal inertia (ATI). Results show a good correlation (R² = 0.62) between the estimated ATI and the SM of the soil samples measured in the laboratory. The proposed methodology has allowed us to obtain a SM map for bare and scarcely vegetated soils in a wide agricultural area in Italy which concerns cyclical hydrogeological instability phenomena.

Influence of Synthesis Method on LTA Time-Dependent Stability.

Time-stability of LTA zeolite formed by hydrothermal method with or without the action of ultrasonic irradiation was investigated by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The results show that 6 months after the synthesis by hydrothermal process with continuous sonication, LTA evolves into a more stable sodalite, whereas no differences are detected 12 months after LTA synthesis by conventional pre-fused hydrothermal process. These data confirm that using the two approaches, different mechanisms control both zeolite crystallization and time-stability of the newly-formed mineral at solid state. The results are particularly important in the light of the synthetic zeolite application.

Environmental risk induced by TiO2 dispersions in waters and sediments: a case study.

A southern Italian area that is characterized by large outcrops of rocks that are rich in titanium oxide (TiO2) phases were investigated to determine the mineralogical risk induced by the natural dispersion of TiO2 minerals. Rock, sediment and surface water samples were collected to determine the physicochemical and mineralogical factors (i.e., size distribution, morphology and alteration) indicative of potential TiO2 toxicity. X-ray diffraction data suggested that titanium oxides were present as rutile and anatase. Scanning electron microscopy images showed elongated TiO2 morphologies; fibres were found as either isolated or embedded/enclosed in flake-like phyllosilicates. The concentration of fibres in stream water ranged from 1.7 to 4.6 million fibres per litre. The highest fibre amounts in the sediments were in the <8-µm fraction, while single fibres were primarily concentrated in the <2-µm fraction. The results indicate that titanium oxide minerals represent a natural source of environmental risk and that the geomineralogical characterization of rich TiO2 areas is indispensable for understanding their geoavailability, dispersion and distribution.

Removal of Mn from aqueous solution using fly ash and its hydrothermal synthetic zeolite.

A number of water purification processes have been developed in recent years based on the utilisation of low-cost materials with high pollutant removal efficiency. Among these materials, fly ash and zeolite synthesised from fly ash are two examples of high-efficiency adsorbents. Column absorption tests were performed in order to compare the manganese sorption behaviour of an Italian coal fly ash and zeolite synthesised from it. Different masses of both materials (10-60 g) were exposed to solutions containing a total metal concentration of 10 mg/L. Batch adsorption studies were also conducted to determine the effect of time on the removal on Mn sequestration. The results indicate that both materials are effective for the removal of Mn from aqueous solution by precipitation due to the high pH of the solid/liquid mixtures. However, the leaching tests reveal that the amount of Mn removed from the fly ash was greater than that leached from the zeolite, thereby indicating that the metal is partially sequestrated by zeolite.

Provenance of inorganic aerosol using single-particle analysis: a case study.

A total of 137 samples of airborne particulates with an aerodynamic equivalent diameter of 10 µm or less (PM10) were collected from April 2007 to July 2008 in four different areas (Potenza, Lavello, Viggiano, Matera) of the Basilicata region in southern Italy. A total of approximately 140,000 particles were analysed using a Field Emission Scanning Electron Microscope (FESEM) equipped with an Energy-Dispersive X-ray Spectrometer (EDS). To formulate a hypothesis on the origin of particles, the dataset was numerically reduced using mineralogical criteria. Eight particle groups were established (Silicate, Silica, Carbonate, Sea Salt, Polymineral, Industrial, Sulphur, and Biogenic Particles) among which Silicate, Sulphur and Industrial Particles were found to be the most abundant. Among the Silicate Particles, the alumosilicates were the most commonly occurring particles (mineral and fly ash particles), and the presence of a small metallurgical factory located in the industrial area of Potenza significantly affects the presence of metal particles (mainly Fe-Zn spinels). The anthropogenic pressure exerted by different types of Sulphur-rich (e.g., Na-Ca-Sulphates, S-only) Particles in the other areas is most likely linked to industrial combustion processes, i.e., waste incinerator oil and oil extraction. Significant differences were found in the particulate concentrations and the compositions of samples collected in different seasons as well as during the night and daytime periods. Crustal Particles were the most abundant in spring-summer, and both Sulphur-rich Particles and Industrial Particles increased in autumn-winter. The proportion of latter category of particles increases in the samples collected during the night periods due to weather conditions (atmospheric stability, thermal inversion, etc.). Sulphur-rich Particles were observed to be more abundant during the daytime due to anthropogenic processes (combustion) and solar radiation. In summary, mineralogical and geochemical approaches are fundamental to delineate the human and natural contributions from automated microscopic analyses.

Effects of ultrasonic treatment on zeolite synthesized from coal fly ash.

The synthesis of zeolites from three samples of fly ash was carried out through a low-temperature (25-60°C) hydrothermal process with a NaOH pre-fusion treatment preceded by sonication. The results were compared with those of conventional hydrothermal syntheses. XRD and SEM investigations demonstrate that the application of ultrasonic treatment facilitates the formation of zeolites at a lower-temperature (25°C) than syntheses not preceded by sonication. No significant difference in type, temperature of crystallization, or amount of zeolites synthesized was noted between the three different samples of fly ash, implying that the chemical composition of fly ash had little influence on the zeolite product within the compositional range of these fly ash precursors. Although there appears to be a correlation between the SiO(2)/Al(2)O(3) ratio of the fly ash and the temperature of zeolite formation by conventional synthesis, no correlation was apparent when ultrasonic pre-treatment was used at low-temperatures.