ABSTRACT
Municipal solid waste incineration (MSWI) fly ashes are hazardous waste since they contain organic pollutants, heavy metals and an important amount of various soluble salts. However their chemical composition is interesting for their valorization in cement production. The objective of this paper is to assess the possibility of MSWI fly ashes reuse as cement raw meal, after pre-treatment, at a laboratory scale. The environmental impact has also been studied (analyses of the metals, of dioxins and furans and leaching tests on clinker produced). Experimental results show that the replacement of MSWI fly ash could be taken up to 30% in the raw mixes, according to the chemical composition of the MSWI fly ashes. This substitution is also to be refined according to the content of hazardous elements contents. This study also shows that the pre-treatment must be well carried out in order to limit the alkaline contents which may affect the quality of the cementitious phases.
Subject(s)
Metals, Heavy , Refuse Disposal , Carbon , Coal Ash , Incineration , Particulate Matter , Solid WasteABSTRACT
Petroleum industries continuously consume catalysts on very large scales. The recycling of spent catalysts is thus of major economic and environmental importance and its first step consists of the characterization of the valuable metal content. Wavelength dispersive X-ray fluorescence (WDXRF) analysis is compared with inductively coupled plasma atomic emission spectrometry (ICP-AES) for the analysis of five samples of spent hydrodesulphurization (HDS) and hydrodemetallization (HDM) catalysts. The elements are considered for their economic interest (Co, Ni, Mo, and V) or for the problems that can arise when they are present in the sample in significant quantities (Al, As, P, Fe). First, the systematic comparison of the analysis of known synthetic samples was performed. The originality here is that the samples were first beaded with lithium tetraborate (Li2B4O7) for WDXRF analysis and then dissolved in hot HCl 6M for ICP-AES measurements. With this processing, we were able to clearly identify the origin of analytical problems when they arose. Second, the semi-quantitative protocol of WDXRF is compared with the quantitative procedure. Finally, the analysis of the spent catalysts is presented and the information gained by the systematic comparison of ICP-AES and WDXRF is shared. The interest of the simultaneous determination by the two techniques when such complicated heterogeneous matrices are involved is clearly demonstrated.
ABSTRACT
Major uses of thermoelectricity concern refrigeration purposes, using Peltier devices, mainly composed of antimony, bismuth and tellurium. Antimony was identified as a critical raw material by EU and resources of bismuth and tellurium are not inexhaustible, so it is necessary to imagine the recycling of thermoelectric devices. That for, a complete characterization is needed, which is the aim of this work. Peltier devices were manually dismantled in three parts: the thermoelectric legs, the alumina plates on which remain the electrical contacts and the silicone paste used to connect the plates. The characterization was performed using five Peltier devices. It includes mass balances of the components, X-ray diffraction analysis of the thermoelectric legs and elemental analysis of each part of the device. It appears that alumina represents 45% of a Peltier device in weight. The electrical contacts are mainly composed of copper and tin, and the thermoelectric legs of bismuth, tellurium and antimony. Thermoelectric legs appear to be Se-doped Bi2Te3 and (Bi0,5Sb1,5)Te3 for n type and p type semiconductors, respectively. This work shows that Peltier devices can be considered as a copper ore and that thermoelectric legs contain high amounts of bismuth, tellurium and antimony compared to their traditional resources.
