(706d) Mechanism of Arsenic Removal From Water by Interaction with Cactus Mucilage

Arsenic contamination of groundwater and the consequent health issues in exposed populations remains a global public health and environmental crisis. The communities worst affected by chronic arsenic exposure are in the developing world where, in some instances, access to conventional water treatment facilities is limited or non-existent. This has fueled research into innovative methods to remove arsenic from drinking water which would be accessible to and sustainable in developing communities. Cactus mucilage is an extract from the Opuntia ficus-indica (also known as Nopal and Prickly Pear cactus). The mucilage is a natural flocculant and has shown an interaction with arsenic which can be harnessed to remove these arsenic species from drinking water. In previous work, the mucilage from Opuntia ficus-indica (also known as Nopal and Prickly Pear) has been shown to interact with arsenate through the use of carbonyl and carboxyl functional groups on the carbohydrate polymer. In this work, we seek to determine the removal mechanisms by comparing macroscopic experiments with molecular level spectroscopic methods. Time-resolved FTIR was used to monitor the kinetics of the interaction between cactus mucilage and arsenate. The effects of solution pH, ionic strength and mucilage fraction were examined. The findings suggest that charge mediation through pH manipulation is a control variable for the interaction, indicating that pH control will optimize water treatment using this material.