The role of the diffuse double layer in leaching of calcium from the surface of flyash particles

A 1:25 ratio of flyash:water was stirred in an unbaffled reactor and the ca lcium that was leached into the bulk solution was measured over time. This experiment was conducted for two different flyashes differing in surface ch arge and calcium content. In both cases calcium accounted for nearly 92% of the total ions leached into the bulk phase. Since flyash particles are neg atively charged, the overall mass transfer coefficient for the leaching of calcium from the surface of flyash into the bulk was calculated assuming th e ions diffuse across a diffuse double layer. A steady state was assumed to exist across the diffuse double layer-bulk interface and the calcium is pa rtitioned between the two phases. It was found that the overall mass transf er coefficient was influenced by the mass transfer from the flyash surface to the diffuse double layer. This novel approach explains the role of, thr diffuse double layer in leaching of calcium from flyashes (C) 2001 Elsevier Science B.V. All rights reserved.