Rajat S. Ghosh

POTENTIAL WATER-QUALITY EFFECTS FROM IRON CYANIDE ANTICAKING AGENTS IN ROAD SALT

Water-soluble iron cyanide compounds are widely used as anticaking agents in road salt, creating potential contamination of surface and groundwater with these compounds when the salt dissolves and is washed off roads in runoff. This paper presents a summary of available information on iron cyanide use in road salt and its potential effects on water quality. Estimates of total cyanide concentrations in snow-melt runoff from roadways are also presented as simple mass-balance calculations.

Subsurface fate and transport of cyanide species at a manufactured-gas plant site

Cyanide is present at manufactured-gas plant (MGP) sites in oxide-box residuals, which were often managed on-site as fill during active operations. Cyanide can leach from these materials, causing groundwater contamination. Speciation, fate, and transport of cyanide in a sand-gravel aquifer underlying an MGP site in the upper Midwest region of the United States were studied through characterization, monitoring, and modeling of a plume of cyanide-contaminated groundwater emanating from the site. Results indicate that cyanide in the groundwater is primarily in the form of iron-cyanide complexes (>98%), that these complexes are stable under the conditions of the aquifer, and that they are transported as nonreactive solutes in the sand-gravel aquifer material. Weak-acid-dissociable cyanide, which represents a minute fraction of total cyanide in the site groundwater, may undergo chemical-biological degradation in the sand-gravel aquifer. It seems that dilution may be the only natural attenuation mechanism for iron-cyanide complexes in sand-gravel aquifers at MGP sites.

Comparison of alkaline industrial wastes for aqueous mineral carbon sequestration through a parallel reactivity study.

Thirty-one alkaline industrial wastes from a wide range of industrial processes were acquired and screened for application in an aqueous carbon sequestration process. The wastes were evaluated for their potential to leach polyvalent cations and base species. Following mixing with a simple sodium bicarbonate solution, chemistries of the aqueous and solid phases were analyzed. Experimental results indicated that the most reactive materials were capable of sequestering between 77% and 93% of the available carbon under experimental conditions in four hours. These materials - cement kiln dust, spray dryer absorber ash, and circulating dry scrubber ash - are thus good candidates for detailed, process-oriented studies. Chemical equilibrium modeling indicated that amorphous calcium carbonate is likely responsible for the observed sequestration. High variability and low reactive fractions render many other materials less attractive for further pursuit without considering preprocessing or activation techniques.

Horizontal In-Duct Scrubbing of Sulfur-Dioxide from Flue Gas Exhausts

Alcoa has conducted multi-year concept validation, pilot and full-scale demonstration studies to assess the technical feasibility of an energy efficient, horizontal gas-flow, co-current in-duct scrubber. The in-duct scrubber was designed and developed with the aim to significantly reduce capital expenditures and operating costs while providing >90% reduction of SO2 emissions from aluminum smelters, anode bake furnaces, coke calciners and industrial boiler exhausts.