Eduardo Domínguez

Ecological bricks made with clays and steel dust pollutants

Abstract More than 27,000 tons of steel dust containing Zn, Pb, Cd, Ni and Cr are generated each year by two steel mills in Argentina. The waste can be classified as low-zinc carbon dust and its treatment is governed by environmental rather than economical considerations. The aim of this work was to test the use of clays in the formulation of a ceramic body that could incorporate steel dust and met environmental regulations. Once the raw materials were characterised, a ceramic body was prepared in the laboratory and subjected to the EP-TOXIC leaching test. The ceramic body passed this test. Based on these promising results a prototype of commercial brick incorporating 20% steel dust was produced. The brick meets standard commercial regulations being inert to the EP-TOXIC and full TCLP leaching tests and the ceramic process has low emission of dangerous gases. The addition of steel dust, reduces the firing temperature of the ceramic process meeting the recycling EPA requirements for the disposal of hazardous waste.

Genesis and applications of the Cerro Rubio kaolin deposit, Patagonia (Argentina)

Abstract At Cerro Rubio area, the stratigraphic position and the origin of kaolinization have been a matter of controversy. Most of the residual kaolin deposits of Patagonia, Argentina are related to a paleoweathered surface developed over the rhyolitic Bahia Laura Group during the Upper Jurassic–Lower Cretaceous. In the nearby areas and in the same type of rocks, there are Au–Ag epithermal deposits that show argillic alteration, therefore determining the origin of the alteration (weathering or hydrothermal) is essential in exploring new areas for either gold or kaolin. The source rocks are tilted tuffs where the ash-shards and biotites were transformed to kaolinite. A positive cerium anomaly as well as the high δ 18 O isotopic composition of the kaolinite of 23–24‰ suggest that the kaolinite was formed under weathering conditions. Field and fossil evidence indicate that the source rocks were Middle Jurassic in age. All these evidences suggest that the Cerro Rubio is part of the Paleoweathered surface of Patagonia where almost all the kaolin deposits of Argentina occur. Preliminary studies indicate that, because of its high crude brightness of 79.8, Cerro Rubio kaolin can be used in the manufacture PVC and white paints. In mixtures with other kaolins of the area of less viscosity, it could be used in dinnerware and sanitaryware ceramic, thus increasing the kaolin reserves in Patagonia. Its high viscosity and abrasiveness limited its use without an industrial treatment mainly in the paper industry.