Abstract
Waste green tuff powder produced by cutting Towada stone has been utilized to eliminate formaldehyde related to greenhouse gases. The green tuff contains TiO2 on zeolite as observed by scanning electron microscope (SEM)t. The green tuff is a natural catalyst that can produce hydrogen peroxide with moisture and oxygen with light. The optimum temperature for calcination of the green tuff powder has been investigated in order to produce hydroxyl radicals from the decomposition of hydrogen peroxide using ultraviolet light (UV) and no light. The green tuff calcined at 800 °C showed a high decomposition rate of hydrogen peroxide with no UV light under high alkaline conditions when measured by using ESR. With UV light, the optimum temperature for calcination of green tuff powder in order to reduce the hydroxyl radical was also 800 °C. Next, the powder calcined at 800 °C was used to produce the tile by compression and heating, and then the formaldehyde adsorption rate was measured. The green tuff powder calcined at 800 °C showed a high adsorption rate, similar to that of the activated carbon. The tiles formed at 40 MPa and heated at 1100 °C were the strongest and also showed adsorption with respect to formaldehyde. The adsorbed formaldehyde on the green tuff tile and powder was possibility decomposed by the hydroxyl radical produced by photocatalysis.
Highlights
For sustainable development, it is necessary to reduce greenhouse gases, CO2 and other related gases and to recycle waste materials
As the produced hydroxyl radical can react to formaldehyde, the better hydrogen peroxide decomposition conditions are examined after the calcination of green tuff at various temperatures
Green tuff powder calcined at 800 ◦C shows a large ESR spectrum of hydroxyl radical even if it is not ultraviolet light (UV) irradiated
Summary
It is necessary to reduce greenhouse gases, CO2 and other related gases and to recycle waste materials. By utilizing rock (green tuff) cutting waste powders, the possibility of reducing formaldehyde [1,2], which is a volatile organic compound recognized by WHO, was investigated. Sugai et al produced several boards of green tuff aggregate (1-3 mm and less than 1 mm in size) using a mixture with 40 wt% of white Portland cement at 20 ◦C for 10 days They measured the adsorption capacity of toluene and formaldehyde in the air using these boards and reported that the adsorption was similar to the board used in diatomaceous earth [8]. LIXIL Co. produced the “ECOCARAT” tile to adsorb the toluene and acetaldehyde [9] Both articles explained that the reason for volatile chemical substance removal in the air was adsorption onto porous materials. It is suggested that the photocatalyst can decompose the adsorbed formaldehyde, due to the presence of the hydroxyl radical on calcined green tuff or tile
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