No abstract

The application limits of the laser-cleaning technique for different types of building stones have been investigated by measuring colour variations. The selected stones differ in their chemical and mineralogical composition, colour, texture and crystallinity degree. The experimentation was carried out with a Q-switched Nd:YAG laser. The colour variations on stones associated with different operative fluences were measured using a colorimeter. Further, surface morphological changes were examined under SEM. From the calculation of colour differences, a damage threshold fluence was established for each stone type. The response of the stones to laser radiation at a particular fluence was found to be mainly conditioned by their chemical and mineralogical composition and, to a less extent, by their textural characteristics.

Hydrochloric acid from exhausted pickling baths is a residue that has to be managed adequately because of its high pollutant potential. In this work, an ion exchange treatment for removing iron from the spent acid was studied in an attempt to make the re-utilization of said acid viable for industry while reducing the amount of waste generated. Several cationic, anionic, and chelating resins were tested. Cationic and chelating resins are able to remove Fe(II) that is present as a cation in the acid, whereas anionic resins are able to remove Fe(III) that forms anionic complexes with the chloride anion. The capacity of the cationic and chelating resins, although not high, does improve as the iron concentration in the hydrochloric acid increases and when the acid concentration decreases, because there is less competition between the ferrous cation and the protons. The anionic resins showed higher capacity for removing iron, especially the Lewatit MP-500, and this capacity also increased with iron concentration.

This article presents the effect of laser radiation on the color of ornamental granites used for external cladding. The laboratory experimentation was undertaken on a widely used coarse-grain granite commercially known as Rosa Porriñ o. The irradiation was carried out with a Q-switched Nd:YAG laser at 1064 nm and several energy densities (fluences) on polished surfaces, dry and wet, uncoated, and artificially coated-simulating a black crust. Laser effects on the granite surface were determined by color measurements with a colorimeter. These measurements made possible to determine probable damage due to laser radiation and the diverse response of different minerals.

Pine-bark sawdust was oxidized with nitric acid (5-20% by weight) and further ammoniated with NH3 or NH40H. Ammoniation with NH, was carried out in a fluidized bed reactor at 100 and 250°C and a NH, flow of 126 L/h (0°C; 101.3 kPa). Ammoniation with NH40H was carried out in a batch reactor by reacting the oxidized sample with NH40H (2 kmol/m3) at total reflux. Data on total nitrogen, ammonia nitrogen and KMn04 soluble nitrogen content are reported for the resulting product.On a oxyd6 de la sciure d'6core de pin avec de I'acide nitrique (5 h 20% en poids), puis on I'a ammoniaquke avec NH, ou NH,OH. On a fait le traitement avec NH, dans un r6acteur h lit fluidis6 h 100 et 250°C et un debit de NH, de 126 L/h (O"C, 101.3 kPa). On a fait I'ammoniation avec NH40H dans un r6acteur discontinu, en faisant r6agir 1'Cchantillon oxyd6 avec NH40H (2 kmol/m') h reflux total. On rapporte, pour le produit rksultant, les donnkes obtenues pour I'azote total, I'azote ammoniacal et la teneur en azote soluble dans KMn04. ood wastes produced from forest lumbering are a po-838 THE