(715e) Application of Industrial Wastes to Absorption of Carbon Dioxide

Industrial wastes that have calcium silicates as main ingredients include steelmaking slag, wasted cement, fly ashes and so on. We separated and/or re-crystallized calcium oxide and silica from these wastes. The concentration of acetic acid as an extract, extraction time, and extraction temperature had significant influence on the composition of the extract or the raffinate. We found that more silica was extracted with lower temperature, higher concentration of acetic acid and shorter extraction time. Under the same conditions of extraction, silica in the slag was more extractable than that in waste cement. In the former, extracted silica was gelated out of the extract while the recrystallized solids on the gel showed very low CO2 absorptivity. On the other hand, porous solids recrystallized from the latter was more active for the absorption. The absorptivity was kept almost constant in their repeated use.