Influence of carbonation on the leaching characteristics of heavy metals in a co-processed cement product
碳酸化对模拟废物水泥窑共处置产品中重金属浸出的影响

Cement clinker was produced from a cement calcination simulation facility (heavy metals were mixed into the cement raw meal in a certain proportion) ,and concrete samples were then prepared. The samples were milled to diameters less than 1 mm,some of which were carbonated and others were used as the control group. Tests of the pH-dependence were carried out to study the influence of carbonation on the leaching behavior of heavy metals (Cr, Ni, As, Cd and Pb) and on the ANC (acid neutralizing capacity) of cement concrete. Under alkaline conditions (pH = 7～12) the ANC of the non-carbonated samples was larger, however in weak acid conditions (pH = 5～7) the ANC of the carbonated samples was larger. The leaching behavior of heavy metals including Cr, Ni, Cd and Pb was not influenced by carbonation,but the pH of the leaching liquid was changed. The adsorption phase of As was influenced by carbonation and the release rule changed obviously. The amounts of Cr, Ni, Cd and Pb leached from the concrete were reduced after carbonation,but at certain pH (pH = 3～7and pH >11), the amount of leached As increased. Consequently, the leaching behavior of As should be considered in risk assessment of concrete eoproducta.