Experimental study on washing of coal fly ashes by water with carbon dioxide - washing effects on chromium (VI) and boron

Coal fly ashes discharged from coal-fired power plants are expected are anticipated for use in the Japanese industrial world. However, they contain trace amount of the toxic substances, e.g. chromium (VI) and boron. In light of this fact, this study is intended to develop a washing method for reducing the environmental impact of coal fly ashes. The authors’ preliminary study revealed the possibility of eliminate chromium (VI) and boron; their concentrations decreased on the condition that the water quality of washing solution changed from alkali to neutral. On the basis of this fact, we have obtained a new washing technology of coal fly ashes that uses water with carbon dioxide. This study investigated the possibility of eliminating of chromium (VI) and boron from coal fly ashes by washing using water with carbon dioxide in a laboratory. Experimental results demonstrate the possibility of eliminating these substances.