Distribution behavior of inorganic constituents in chemical recycling processes of a municipal waste slag

AbstractA chemical recycling process of inorganic wastes has been developed, where after vitrifying wastes, the glasses were heat-treated and soaked in an acid, obtaining colorless and transparent SiO2-abundant glasses. In the present study, distribution behavior of the constituents such as Si, P, Ti, Al and so on present in a municipal waste slag was examined. According to compositional analyses, the recovered solids after acid treatment consisted of SiO2, P2O5 and TiO2, suggesting the preferential distribution of P and Ti atoms into SiO2-rich phase during phase separation. In high resolution microscopic analyses, however, it was observed that P and Ti atoms were distributed separately from Si atoms, and they were present in the different particles insoluble in the acid. It was finally concluded that the insoluble solids were produced by a dissolution–reprecipitation process, that is, once all the constituents of the vitrified slag were dissolved in the acid, P2O5 and TiO2 coprecipitated as particles, and TiO2 was indispensable for the precipitation of P2O5. SiO2 also precipitated as particles separately from P- and Ti-containing particles

Material recycling of inorganic slag by wet ball milling

The possibility of material recycling of inorganic slag by wet ball milling with distilled water and an ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA·2Na·2H2O) reagent was investigated. The wet ball milling of the simulated waste slag powder was performed using a ball mill pot and balls in air for 10 - 100 h at room temperature with the rotational speed fixed at 200 rpm. The fractions of CaO and Fe2O3 in the specimens obtained by wet-ball-milling the simulated waste slag powder decreased, that of SiO2 increased, and those of Al2O3 and Na2O hardly changed. These specimens contained 0.1 – 0.8mass% ZrO2. Appropriate solution and time for wet ball milling were 300 ml distilled water and 20 h, respectively. When the wet ball milling of the simulated waste slag powder was performed twice, the fractions of CaO, Al2O3 and Fe2O3 in the specimen obtained after repeated wet ball milling decreased, those of SiO2 and ZrO2 increased and that of Na2O hardly changed in comparison with those in the specimen wet-ball-milled once. The insoluble end product obtained by soaking the specimen wet-ball-milled once in 6M HCl for 20 hours was composed of 98.5mass% SiO2 and 0.6mass% or less other oxides and is usable as glass material

鉛フリー光学ガラスとしてのSnO-B(2)O(3)ガラスの光学特性

The preparation of SnO-B(2)O(3) and SnO-SiO(2) glasses by melting in Ar atomosphere was performed. The prepared SnO-B(2)O(3) glasses were large enough to measure optical properties whereas the vitrification in SnO-SiO(2) system was very difficult. PbO-B(2)O(3) and BiO1.5-B(2)O(3) glasses were also prepared for comparison with SnO-B(2)O(3) glasses. The densities, glass transition temperatures, and optical properties such as refractive indices, dispersion, and transmission spectra of SnO-B(2)O(3), PbO-B(2)O(3), and BiO(1.5)-B(2)O(3) glasses were measured. On the basis of the obtained results, the potential for SnO-B(2)O(3) glasses as lead-free glasses is particularly discussed from the viewpoint of optical properties

Material recycling of inorganic sludge by wet ball milling

The possibility of material recycling of inorgamic sludge by wet ball milling with distrilled water and an ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA・2Na・2H(2)O)reagent was investigated. The inorganic sludge consisted of 14.1mass% of the heat-treated sludge obtained after drying and heat treatment, 20.1mass% of active carbon, and 65.9mass% of water. The wet ball milling of the heat-treated sludge was performed using a ball pot and balls in air for 40 h at room temperature with the rotational speed fixed at 200rpm. The fractions of Mn, Fe, Ni, Cu, and Zr in the specimens obtained by wet-ball-milling the heat-treated sludge decreased and those of Si and Al increased. Appropriate content of distilled water and weight of the heat-treated sludge for wet ball milling were 150-250 ml and 4.5 g or less, respectively. When the wet ball milling of the heat-treated sludge was perfomed twice,the fractions of Mn, Fe, Ni, Cu, and Zr in the specimen obtained after repeated wet ball milling remarkably decreased and that of Si increased in comparison with those in the specimens wet-ball-milled once. This suggests that the repeat of wet ball milling of the heat-treated sludge leads to a colorless specimen without colored ions such as Mn, Fe, Ni, and Cu

Material design for the ceramics coating with high mold releasability by using molecular orbital calculations

　To explore the ceramic materials appropriate for the coatings with high mold releasability, molecular orbital (MO) calculations have been applied to the ceramics with NaCl structure, such as TiN, TiC, CrN, etc. Chemical bonding characters were evaluated based on the MO calculations, which were correlated to the experimental surface free energy. The dispersion and polar components of surface free energy indicated high correlation with the bond overlap population of the surface bonds and the net charge of inside atoms of the cluster models, respectively. Among the ceramic materials investigated, MoN had the lowest surface free energy, being expected to be most suitable as the ceramic coating material with high releasabilit

Studies on optical properties of SnO-based glasses as lead-free glasses

The preparation of SnO-SiO(2), SnO-B(2)O(3), and SnO-GeO(2) glasses by melting in air was performed. The prepared SnO-GeO(2) glasses were large enough to measure optical properties whereas the vitrification in SnO-SiO(2) and SnO-B(2)O(3) systems was difficult. PbO-GeO(2) and BiO(1.5)-GeO(2) glasses were also prepared for comparison with SnO-GeO(2) glasses. The densities, glass transition temperatures, and optical properties such as refractive indices, dispersion, and transmission spectra of SnO-GeO(2), PbO-GeO(2), and BiO(1.5)-GeO(2) glasses were measured. On the basis of the results, the potential for SnO-GeO(2) glasses as lead-free glasses is particularly discussed from the viewpoint of optical properties

Material Recycling of Municipal Waste Slags by Using Phase Separation of Glass

A novel recycling process of municipal waste slags obtaining Fe-free colorless materials was developed by using a phase separation of borosilicate glass. B(2)O(3) was added to a simulated waste slag to promote the phase separation. The slag glasses were heat-treated above glass transition temperatures, from which phase separation was successfully induced. The phase-separated slag glasses were still colored in black due to Fe ions, and after soaking in acid, they were successfully bleached, obtaining colorless solids. According to compositional analyses, no Fe ions were confirmed in the remaining insolubles, indicating that Fe ions were preferentially incorporated into the borate-rich phases soluble in acid. The main constituent of the colorless solids was SiO(2) and the end products obtained in the present process were expected as an alternative of pure silica glass