Formaldehyde reduction with scallop shell powders fired at high temperatures: Identification of the effective ingredient.

The volatile organic compound (VOC) reduction activity of scallop shell powders fired at 300, 600 and 900 degrees C was examined using formaldehyde (HCHO). Raw shells as well as fired shells immediately after firing at several temperatures, except for 600 degrees C, were found to gradually remove HCHO from the air. In the case of shell powders stored for 3 months after firing, the HCHO reduction activity of the powder fired at 900 degrees C was obviously improved, with the HCHO concentrations rapidly reaching zero within 20 min. It has been found by X-ray diffraction measurements that shell powder stored for 3 months after firing at 900 degrees C contains a small amount of calcium hydroxide (Ca(OH)2) generated from calcium oxide (CaO). Our results suggest that Ca(OH)2 may be the effective ingredient in the HCHO reduction.