Absorption and fixation rate of carbon dioxide by rock weathering

Abstract

The artificial weathering of alkaline rocks, which are abundant resources, is thought to be one possible countermeasure for CO2 problem by increasing carbon cycle on this planet. From the viewpoint of inorganic chemistry, net fixation of carbon is possible by this measure. However, the rate of fixation may be impracticably slow. In the present paper, the dissolution kinetics of various silicates for industrial applications was investigated. The dissolution kinetics of mineral ions from silicate rocks suspended in water saturated with carbon dioxide by sufficient flow was measured for 0-600 h at 25oC. The filtered aqueous samples were acidified and then analyzed for the main metal elements. After an initial rapid increase, the metal ion concentration increased linearly with time and then attained a plateau value. From the linear dissolution stage, the dissolution rate of the mineral was determined. The rate was found to be proportional to the surface area of the sample, irrespective of the ratio of sample amount to water, or its average diameter. It was concluded that the dissolution kinetics was controlled at the mineral surface. The calculated linear rates ranged from 2.1×10-5 to 7.3×10-4 mol/m2 · h. The dissolution rates of CaSiO3 and CaCO3 were found to be highest. © 2010 The Society of Chemical Engineers, Japan.