An experimental study was conducted to investigate the ability of municipal solid waste bottom ash as a resource of cement. Bottom ash contains a large amount of chlorine, and insoluble chlorine such as Friedel’s salt in bottom ash has remained as a problem.
Friedel’s salt forms by a chemical reaction between C3A(3CaO&middit;Al₂O₃) and CaCl₂, and it has been reported as a “poorly understood phase in the CaO-Al₂O₃-CaCl₂-H₂O system”. The solubility of Friedel’s salt increases with increasing degree of carbonation and decreasing pH. In this study, the possibility of Friedel’s salt formation from compounds other than for C₃A, and Friedel’s salt decomposition by sulfuric acid ion are examined.
The conclusions of this study are as follows: 1) Bottom ash contain not less than two insoluble chlorines of Friedel’s salt (formed from C₃A) and hydrocalumite (formed from compounds except for C₃A). 2) Friedel’s salt in bottom ash converted to ettringite under a circumstance with a high sulfuric acid ion concentration.

View full abstract

Reusable and recyclable automobile parts and materials are recovered from waste, then the remaining scraps are shredded into automobile shredder residue (ASR). The ASR is either buried or incinerated. However, the components of ASR consist of metals, glass, rubber, and unrecoverable PVC wire coatings, ABS and other plastics. If ASR is incinerated with these components, it will generate hydrogen chloride, which will corrode the incinerator. To study a solution to this problem, we studied dehalogenation behavior by applying dechlorination procedures for flexible PVC. ASR was placed in 2 to 16mol/L NaOH aqueous solution, heated by microwave at 100 to 190°C for 0 to 60 minutes. When this procedure was applied to ASR containing roughly 22% Cl, we found that it was possible to remove 98% of chlorine, 99.3% of sulfur and 100% of bromine from ASR in 2mol/L NaOH, heated at 190°C for 30 minutes. When studying the gross calorific value of the low degraded dehalogenation residue, we found it to be roughly 8000Kcal/kg, which was equivalent to coal. The study indicates that roughly 52% of the residue was recoverable, and 10% turned to ash, and the study suggests that the waste can be used as a densified refuse-derived fuel.

View full abstract

This study clearly introduces the basic characteristics of a new material composed of post-consumer PET (polyethylene terephthalate) bottles and scallop shells as its raw materials. The influence of heat on the scallop shells and the organic substances contained in them was investigated. Comparisons were made regarding the degree of yellowing and the strength of the materials made from post-consumer PET bottles, scallop shells and also calcium carbonate. It was found that the degree of yellowing caused by thermolysis of the organic substances contained in the scallop shells is greater than that of the calcium carbonate. Moreover, no trace of foaming attributed to thermolysis gas of the organic substance was confirmed for those materials made from post-consumer PET bottles and scallop shells. The properties of these materials indicate that the composite of the scallop shell has a higher degree of yellowness and strength than that of calcium carbonate. These results show that the composite from post-consumer PET bottles and scallop shells could possibly be utilized.

View full abstract

The achievement of reclamation conditions suitable for waste stabilization is expected when controlling the amount of water permeation through the cover layer at final landfill sites. The structure of a capillary barrier, which is one method to control the amount of water permeation, was examined from the viewpoint of water permeation control. Based on this examination, it was found that analytical predictions accurately corresponded to measurement results, thus, the prediction of water permeation was quite reliable. Therefore, it was determined that capillary barriers are effective in controlling water permeation.

View full abstract

Domestic and bilateral recycling of post-consumer PET bottles, both inside Japan and between Japan and China, were compared from the viewpoints of energy consumption and quality of recycled resin. Recycling scenarios for post-consumer PET bottles were established based on the current situation, being investigated through the conducting of hearings and field surveys both in Japan and China. Significant differences between domestic and bilateral recycling were identified through a format designed for characterizing various recycling scenarios. These differences were linked to legal, technical, and economic constraints on PET bottle recycling in Japan and China.

View full abstract

Porous carbon samples were prepared from falcata (Albizia falcataria), which is a wood material that has become popular recently, at different carbonization temperatures, and their abilities to adsorb trichloroethylene (TCE) in aqueous solutions were evaluated. The iodine adsorption number of porous carbons prepared from falcata at 800°C was higher than the number for samples prepared at other temperatures. The specific surface area and pore volume were the largest at 900°C carbonization, 444m² g⁻¹ and 0.196mL g⁻¹, respectively. Porous carbon prepared from falcata at 800°C, which had the smallest mean pore diameter of all the prepared porous carbon samples, had the greatest TCE adsorption capacity. Its TCE adsorption capacity was higher than the capacity of activated carbons that are commercially available. The TCE isotherm data also suggest that porous carbon prepared from falcata at 800°C has more pores suitable for TCE adsorption than those of commercial activated carbons. Therefore, adsorption capacities of trace organic pollutants in aqueous solution cannot be predicted only from BET surface area or total pore volumes. These results showed that the porous carbons prepared from falcata can be used for the remediation of groundwater contaminated with TCE.

View full abstract

In order to investigate the dynamic behavior of a quinone biomarker in leachate from a final landfill site for municipal solid waste, leachate was collected continuously on fine and rainy days. Four samples from five fine-weather days did not have significant differences in quinone discharge and composition. On the other hand, on rainy-weather days, the quinone composition changed significantly before and after the peak flow of leachate, because bacteria containing Q-10, namely Alphaproteobacteria, was discharged in great amounts. Subsequently, quinone discharge increased remarkably. This increase can be explained as follows. Particulate matters had relatively more Alphaproteobacteria, resulting in the high contribution to the discharge. After the rain, the quinone discharge and composition returned to close to the original conditions before the rainfall.

View full abstract