Cu-Zn powders as potential Cr(VI) adsorbents for drinking water.

This work examines the possibility of applying CuZn alloys as a reducing medium for the efficient removal of hexavalent chromium from drinking water. In an effort to develop a route for producing powders of CuZn alloys under mild conditions and investigate the optimum composition for such application, a series of alloys in the form of powders were prepared, by a sequence of Cu and Zn ball-milling and low temperature annealing. Batch Cr(VI) removal tests, performed to evaluate and compare the efficiency of the products under typical natural water parameters (pH 7 and natural-like water), indicated that the best performing material have a composition around 50 wt% Cu. The dominant reduction mechanisms are both the corrosion of the alloy surface and the electron transfer to the solution. The behavior of granulated CuZn media was tested in rapid-scale column tests using the commercial KDF which verified the high potential of CuZn alloys in Cr(VI) removal. Nevertheless, Cu and Zn leaching problems should be also considered.

Glass-ceramic materials from electric arc furnace dust.

Electric arc furnace dust (EAFD) was vitrified with SiO2, Na2CO3 and CaCO3 powders in an electric furnace at ambient atmosphere. Vitreous products were transformed into glass-ceramic materials by two-stage heat treatment, at temperatures determined by differential thermal analysis. Both vitreous and glass-ceramic materials were chemically stable. Wollastonite (CaSiO3) was separated from the parent matrix as the dominant crystalline phase, verified by X-ray diffraction analysis and energy dispersive spectrometry. Transmission electron microscopy revealed that wollastonite crystallizes mainly in its monoclinic form. Knoop microhardness was measured with the static indentation test method in all initial vitreous products and the microhardness values were in the region of 5.0-5.5 GPa. Devitrification resulted in glass-ceramic materials with microhardness values strongly dependent on the morphology and orientation of the separated crystal phase.

Vitrification of lead-rich solid ashes from incineration of hazardous industrial wastes.

Lead-rich solid industrial wastes were vitrified by the addition of glass formers in various concentrations, to produce non-toxic vitreous stabilized products that can be freely disposed or used as construction materials. Toxicity of both the as-received industrial solid waste and the stabilized products was determined using standard leaching test procedures. The chemically stable vitreous products were subjected to thermal annealing in order to investigate the extent of crystal separation that could occur during cooling of large pieces of glass. Leaching tests were repeated to investigate the relation between annealing process and chemical stability. X-ray, scanning and transmission electron microscopy techniques were employed to identify the microstructure of stabilized products before and after thermal treatment. Relation between synthesis and processing, chemical stability and microstructure was investigated.