Phosphorus movement through sands modified by red mud
Field and laboratory column experiments show that red mud (waste from bauxite refining) neutralised with gypsum increases Phosphorus (P) sorption capacity of sandy soils. Some 1.68 g P/ kg RMG (red mud neutralised by 50% gypsum) was sorbed from 9.5 mg/ L P solution during a continuous flow of 50 cm/d for 750 pore volumes. Batch tests indicate almost no desorption of sorbed P, however during continuous flow leaching, a total of 14% of the sorbed P was desorbed. During flooding – drying cycles of laboratory columns, with secondary effluent, 91% P removal occurred through 30% RMG (30% RMG, 70% Bassendean sand mixture), and 63% removal through 20% RMG, both with some more capacity to sorb P; whereas 10% RMG continued to sorb P at 50% efficiency even after the calculated sorption capacity was exhausted. Initially previously sorbed P in soil would be leached out by the alkaline leachate from red mud incorporated above it. In general the potential for P removal by renovated soils seems high.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Environmental Science|
|Publisher:||Australian Water Association|
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