NGWA Event and Education Recordings Archive

Fluoride occurrence in underground water is a significant health concern because it is faced by millions around the world. We used Moringa oleifera (MO) seed extract coupled with electrocoagulation (EC) for fluoride removal from water. MO extract was prepared with 1 g of MO seed flour added into 100 mL (6.6 mM) NaCl solution, stirred 30 min and filtered. The experiments were performed using either deionized (DI) or tap water containing 10 mg L^-1 fluoride (NaF, Aldrich). Different MO extract volumes (0.5-2.5 mL of MO extract per 100 mL of water) were used in batch and semi-continuous experiments coupled with EC (3.3 mA cm^-2) and different electrode separation (1- 4 cm), all experiments were performed in duplicates. For fluoride quantification, 2 mL of SPANDS fluoride reagent (Hach) were added to 10 mL of water sample and stirred for 1 minute. Fluoride concentration in the water samples was measured by UV-vis spectrophotometry (550 nm). Control experiments were performed with 1.25 mL of MO extract and 3.3 mA cm^-2 current density, achieving 5 and 54% water defluoridation, respectively. Best experimental conditions with the batch MO/EC system with DI water produced > 90% fluoride removal using 1.25 mL of MO extract followed by EC (3.3 mA cm^-2) with 1 cm electrode separation after 15 minutes. Considering these conditions, the design of a semi-continuous EC reactor for process upscaling was completed. Semi-continuous experiments with the MO/EC were performed using DI and tap water ̶ mimicking field conditions ̶ using 1 cm electrode separation, 1.25 mL of MO extract, and different current densities (J = 0.7-3.3 mA cm^-2). Over 90% fluoride removal was achieved after 20 minutes, using 3.3 mA cm^-2, in both DI and tap water. The MO/EC processes reduced fluoride concentration in water from 10 mg L^-1 to below 1.5 mg L^-1.