Arsenic contamination of groundwater is recognized as a problem of global proportions. Conventional arsenic removal methods typically require centralized treatment facilities which may be inaccessible to poor rural communities. Further, these technologies have significant environmental impacts. Previously, cactus mucilage was shown to flocculate suspended solids and remove arsenic from water. Cactus mucilage is an extract from the Opuntia ficus-indica (also known as Nopal and Prickly Pear cactus). Currently, we are investigating the mechanism by which the mucilage removes arsenic from water, with the aim of optimizing the process for mucilage dosage, operating pH and mucilage extract. Batch kinetic and column-depth experiments were performed in which the mucilage was contacted with aqueous arsenic solutions. The arsenic concentration was detected with hydride generation atomic fluorescence spectroscopy. Our results suggest that a complex is formed between the sugars and carbohydrate compounds of the cactus mucilage and the solvated arsenic ions.