Design and Construction of a Cell to Model the Stabilization of Toxic Waste Solids to Residuals by Means of an Encapsulated Process

Abstract

The residuals from galvanization processes, production of electronic components, paintings, electroplating, steel production, etc., are considered dangerous due to their high content of heavy metals such as lead and chromium. In this work, we designed and built a quartz cell which is able to resist the high temperatures at which the cement type, Portland, is obtained, with the purpose of exploring the stabilization of these elements when incorporating them into the process of production of the cement, and evaluating various quantities added as ingredients. The influence of this addition in the primary product, the clinker, is evaluated, as well as the retention of the metals and their possible incorporation into the rotational oven. The clinker production process is simulated by coupling the cell built into a laboratory device mounted to model the process. Temperature is controlled and the heating ramps represent the real process of production. Tests of leached material were performed on the product, under the norm governed by the Environmental Protection Agency (EPA), to verify the incorporation and retention of the metals studied in the structure of the clinker. Compression tests were carried out to verify that the addition of the metals does not affect the mechanical properties of the final product. Samples were prepared by additions of from 5 to 20 wt% of each element and the clinkering process was simulated in a laboratory device. Leaching tests were performed with the produced clinker samples in order to verify the incorporation of the studied metals in the clinker structure and the 28‐day compressive strength test in order to verify mechanical properties of the product. Scanning electron microscopic analysis revealed the effectiveness of the encapsulation among the clinker crystalline phases. The results led to the conclusion that additions of up to 20 wt% of lead and up to 5 wt% of chromium to clinker raw‐material are totally incorporated and do not affect the maximum compressive strength.