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The process of cement matrix solidification of a hazardous inorganic waste mixture containing As(2)O(3), CrCl(3).6H(2)O, K(2)CrO(4), CdCl(2), HgO and Pb(NO(3))(2) compounds has been evaluated by performing leach experiments in both static and dynamic water conditions. Improved physical characteristics of the matrix (i.e. compressive strength, and total porosity) are observed when 12% of waste is blended in cement. In the static leach test the released concentrations of As(III), Cd(II) and Cr(VI) metals are substantially reduced compared with previous investigations, in which a single compound of each of As(III), Cd(II), Cr(III) and Cr(VI) was immobilised separately in cement. The leachate concentrations of As(III), Cd(II) and Cr(III) are much below their permissible limits as reported in the literature for drinking water quality. Chromium (III) is found to be completely stabilised in the cement matrix. The hydrolysed compound Cr(OH)(3).nH(2)O is believed to influence also the leaching rates of other metals by limiting their ionic mobility within the solidified matrix. The sequence of the release of different elements has been compared with that given by previous authors. The discrepancies are related to the use of different specimen preparation technology and the different leaching procedures. The cumulative fraction release of some elements (Pb and Hg) is found to depend on the square root of t, so that a diffusion coefficient D(e) based on Fick's theory is calculated.

Additional information

Authors: ZAMORANI E, JRC Ispra (IT);SERRINI G, JRC Ispra (IT)
Bibliographic Reference: Paper presented: International Symposium on Cement Industry Solutions to Waste Management, Calgary (CA), October 7-9, 1992
Availability: Available from (1) as Paper EN 36993 ORA
Record Number: 199211014 / Last updated on: 1994-12-02
Original language: en
Available languages: en
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