No abstract

Aluminum Research SummaryAlumina red mud, a fi ne-textured, iron-rich, alkaline residue, is the major waste product of bauxite digestion with caustic soda to remove alumina. The high alkalinity and salinity as well as the poor nutrient status are considered to be the major constraints of red mud revegetation. This research was conducted to evaluate the ameliorating effect of gypsum, sewage sludge, ferrous sulfate, ammonium sulfate, ammonium nitrate, and calcium phosphate on alumina red mud. The effectiveness of the mixtures was evaluated by applying extraction tests and performing experiments using six plant species. Gypsum amendment signifi cantly reduced the pH, electrical conductivity, and sodium and aluminum content of red mud. Sewage sludge application had an extended effect in improving both the soil structure and the nutrient status of the gypsum-amended red mud. Together with the gypsum and sewage sludge, calcium phosphate application into red mud enhanced plant growth and gave the most promising results.

No abstract

A detailed geotechnical and environmental laboratory investigation of phosphogypsum (a by-product of the phosphoric acid production industry) is presented in this paper. The aim of the investigation programme was to evaluate the potential of Greek phosphogypsum for alternative uses, such as in the rehabilitation of quarries and mines by filling voids on or within the ground and as secondary embankment roads. Based on the results, phosphogypsum classifies as low-plasticity silt that is easily compacted at different ranges of moisture content. When compacted, the material develops adequate strength and stiffness. The leachability of most major elements was found to be minimal and the material satisfies common criteria for waste acceptance in landfills. Long-term pilot-scale field tests are necessary in order to evaluate the long-term behaviour of the material in any proposed rehabilitation scheme.

No abstract