Strontium (Sr) ions in aqueous solutions could be absorbed by root tissue powders of Amaranthus spinosus, a common weed found in the fields. The adsorption isotherm could be fitted by either the Langmuir or the Freundlich model with the maximum adsorption capacity being 12.89 mg/g from the Langmuir isotherm. The maximum adsorption capacity of rite biosorbent decreased with increasing temperature, whereas alkaline pretreatment enhanced the adsorption capacity 1.9 fold. Alginate gel beads (I mm diameter) containing the root tissue powders were prepared and packed in a column for continuous adsorption/desorption of Sr in solution. Efficient desorption of Sr could be carried out with 0.1 M CaCl2 to give a concentrated Sr solution with 94% recovery. (C) 1997 Elsevier Science Ltd.