## 英文概要

## Summery

In Japan, 50 million tons of municipal solid wastes (MSW) are generated per year and those wastes are incinerated to keep sanitary and to reduce those volume and mass. The mass reduction in incineration is about 90% and 10% of residual incineration ashes have been buried in landfills. However, landfills for incineration ashes are becoming difficult and problematic due to high cost, environmental issues, lack of available land and strict laws. At present, some municipal waste treatment plants in Japan, incineration ashes are melted to make a molten slag to promote recycling as a construction materials or aggregates. The energy cost to heat up to around 1400 • is preventing its becoming popular. The molten slug also has the problem in strength as the aggregate materials. Another way to promote recycling is to use the incineration ash as a raw material for cement plants. Since the chemical composition of incineration ashes is similar to cement, the quantity going into landfills can be reduced. However, incineration ashes usually contain high chloride ion content, which causes metal erosion especially in reinforced concrete. Therefore, the amount of incinerated ashes accepted is limited by the high cost and huge consumption of energy of the chlorine by-pass system typically used for controlling the chloride content of the incinerated ashes. Alternative method to remove chloride is by washing the incineration ashes with water. This method requires large quantities of water for rinsing which then must be treated for re-use. Reverse osmosis (RO) is the most popular water treatment technology for this purpose. However, RO requires the pre-treatment of its membrane to prevent clogging by the sludge in the liquid. The process also uses a large quantity of energy and the high cost of the fabrication as well as the maintenance can be prohibitive. The capacitive deionization (CDI) technique could be used as an alternative to other water treatment technologies.

In this study capacitive deionization technique, having higher efficiency and lower operation cost in comparison with the reverse osmosis technique, for regeneration of rinse water used for dechlorination of incineration ashes is investigated. Activated charcoal-based electrodes were developed and characterized for their capacity to remove the chlorine ions dissolved in rinse water for incineration ashes. The mass ratio of rinse water to incineration ashes was also investigated to realize the most efficient removal of chloride from rinse water and minimize the regeneration load of the rinse water. The electrochemical properties of the developed electrode were characterized using a cyclic voltammetry system and it was demonstrated that the hydrophilic carbon electrode containing PVA as a binder showed higher capacitance and higher ion-adsorption potential in comparison to that of PVdF binder. An asymmetrical distribution of capacities of both electrodes was found to be ideal wherein no electrochemical reactions took place at the electrode surface. The electrode capacities were defined based on the difference between the rest potential of the electrodes and the oxidation-reduction potential of the solution. Furthermore, using the prepared municipal solid waste incinerator bottom ash rinse water, the ion conductivity and chloride concentration ion removal capacity of the developed PVA-bonded carbon electrode indicated 0.067 mol/m² and 0.09 mol/m², respectively, by switching the batch and flow through operation.

In this study, energy recovering by applying the charged/discharge energy to ion adsorption/desorption process of another cell, recycle concentrated chlorine solution to hypochlorous acid for sewage sterilization, and application of the CDI system to real incineration facilities have also been discussed. It is concluded that the washing system with the developed CDI for chlorine ion will promote the economic recycling of incineration ash to cement material.