Bartolomeo Megna

Photocatalytic conversion of glucose in aqueous suspensions of heteropolyacid-TiO2 composites.

Commercial and home prepared TiO2 samples were functionalized with a commercial Keggin heteropolyacid (HPA) H3PW12O40 (PW12) or with a hydrothermally home prepared K7PW11O39 salt (PW11). All the materials were characterized by specific surface area measurements (BET), XRD analyses, Raman, DRS along with SEM observations and they have been used for glucose photocatalytic conversion in an aqueous suspension. Different reaction extents and distribution of intermediate oxidation products were observed depending on the photocatalyst. Gluconic acid, arabinose, erythrose and formic acid were observed as oxidation products when bare TiO2 or HPA/TiO2 composite materials were used. Glucose isomerization to form fructose was also observed and in some runs traces of glucaric acid and glyceraldehyde were also found. The carbon mass balance was accomplished in the presence of the commercial Evonik P25 TiO2 powder and the composites where TiO2 was present, whereas the presence of the solvothermically prepared TiO2 gave rise to a carbon unbalance, due to strong adsorption of the products on the photocatalyst surface. No reactivity was observed in the presence of PW12 alone while PW11 induced only isomerization of the glucose.

Measure of a limestone weathering degree using Laser Scanner.

The weathering degree of the building materials and natural stones is generally quantified as the decrement of some mechanical features that can be measured experimentally by means of compressive tests or point load tests in the laboratory or Schmidt hammer tests carried out in situ. Such destructive or damaging tests are unacceptable in case of cultural heritage since even small amounts of damage must be avoided. This work shows a correlation between Schmidt hammer rebound values and the reflectivity that is detected by means of terrestrial scanner laser; therefore it allows assessing the weathering degree of buildings or stones in situ. The results demonstrate that such an investigation could be a significant alternative representing an innovative and non-destructive technique.

The open metastable structure of a collapsible sand: fabric and bonding

This paper deals with the compositional and textural characteristics determining open metastable structures in the pleistocenic sand outcropping in the Agrigento district (Sicily). The aim of the study was to individuate the bonding types occurring between grains that could generate matric suction phenomena. The composition and microfabric were characterised by means of granulometry, porosimetry, permeability, optical and ESEM-EDS microscopy, thermogravimetry and XR diffractometry, electric conductivity, and ionic chromatography. The data thus acquired show that the skeleton of the sand is constituted mostly by bioclasts and microfossils, calcite and quartz monocrystalline grains. Moreover, assemblages of silt and clay minerals are interposed among them. Cementation is generally absent even at the sites of contact between grains. Porosity is due mainly to interparticle voids. The spatial arrangement of sand, silt and limey grains, the pore geometry, volume and size distribution and network connectivity allow both capillary condensation and effective capillary transport of water. It appears that bonding is due mainly to capillary forces related to the texture and to the type of pores rather than being ruled by composition.