Aluminum recycling is an important activity that allows returning this metal to the market saving energy and resources. This activity generates slag and dross, both hazardous materials, which are recovered by other in...Aluminum recycling is an important activity that allows returning this metal to the market saving energy and resources. This activity generates slag and dross, both hazardous materials, which are recovered by other industries (tertiary sector). In that process, new wastes are produced, but most of them are disposed in security storage facilities because of their hazardousness and scarce marketable value. In Spain, the statistical data analysis on waste reveals that this sector is increasing every year. This study aims to characterize the wastes generated by the tertiary aluminum industries in Spain. Samples were collected in different aluminum recycling industries and characterized by chemical analyses, X-ray fluorescence, X-ray diffraction and particle size determination. Wastes rich in aluminum oxide and alkaline elements also comprise metallic aluminum and aluminum nitride. Such components are the main responsible for the waste hazardousness since they generate toxic gases in the presence of water. Besides, their fine granulometry (x50 < 30 μm) also contributes highly to the hazardousness.展开更多
The dehydration process of gypsum rock was studied under concentrated solar energy by using a Fresnel lens with power density of 260 Wcm-2. Temperatures higher than 700。C were attained for 1 min of solar exposure. Th...The dehydration process of gypsum rock was studied under concentrated solar energy by using a Fresnel lens with power density of 260 Wcm-2. Temperatures higher than 700。C were attained for 1 min of solar exposure. The effect of grain size of sample and radiation exposure time on the formation of bassanite and anhydrite was studied by XRD. The complete transformation of dihydrate into hemihydrate and/or anhydrate phases is complete for the finer size sample. Plaster composed of 92.7% of anhydrite and 7.3% of bassanite was obtained for 5 min of solar exposure. Morphological and textural modifications were followed by SEM and interferometric/confocal profilometer.展开更多
文摘Aluminum recycling is an important activity that allows returning this metal to the market saving energy and resources. This activity generates slag and dross, both hazardous materials, which are recovered by other industries (tertiary sector). In that process, new wastes are produced, but most of them are disposed in security storage facilities because of their hazardousness and scarce marketable value. In Spain, the statistical data analysis on waste reveals that this sector is increasing every year. This study aims to characterize the wastes generated by the tertiary aluminum industries in Spain. Samples were collected in different aluminum recycling industries and characterized by chemical analyses, X-ray fluorescence, X-ray diffraction and particle size determination. Wastes rich in aluminum oxide and alkaline elements also comprise metallic aluminum and aluminum nitride. Such components are the main responsible for the waste hazardousness since they generate toxic gases in the presence of water. Besides, their fine granulometry (x50 < 30 μm) also contributes highly to the hazardousness.
文摘The dehydration process of gypsum rock was studied under concentrated solar energy by using a Fresnel lens with power density of 260 Wcm-2. Temperatures higher than 700。C were attained for 1 min of solar exposure. The effect of grain size of sample and radiation exposure time on the formation of bassanite and anhydrite was studied by XRD. The complete transformation of dihydrate into hemihydrate and/or anhydrate phases is complete for the finer size sample. Plaster composed of 92.7% of anhydrite and 7.3% of bassanite was obtained for 5 min of solar exposure. Morphological and textural modifications were followed by SEM and interferometric/confocal profilometer.
