Breakthrough studies with mono-, binary- and ternary-ion systems comprised of Fe(II), F⁻ and As(III) using river sand packed columns for groundwater treatment

Groundwater in Assam, India, contains excessive amounts of arsenic (As(III)), fluoride (F⁻) and iron (Fe(II)). The rural and semi-urban population of Assam uses indigenous iron filters fabricated using processed sand (PS) as one of the chief constituents to reduce Fe(II) concentration; however, no efforts have been made to reduce As(III) or F⁻ concentrations before use. The present work is directed towards assessing the potential of PS for removal of these ions from mono-, binary- and ternary-ion systems through continuous mode column studies. Synthetic water samples containing fixed concentration of ions were prepared using deionized water. The observed order of breakthrough of ions was: As(III) followed by Fe(II) and F⁻ followed by Fe(II) in the case of the binary ion systems of Fe(II) + As(III) and Fe(II) + F⁻. The throughput volume for As(III) in the (Fe(II) + As(III)) system and for F⁻ in the (Fe(II) + F⁻) system is termed the critical breakthrough throughput volume. In the ternary ion system (Fe(II) + As(III) + F⁻), the order of breakthrough of ions observed was F⁻, then As(III) and then Fe(II) and hence the throughput volume F⁻ is termed the critical breakthrough throughput volume. Results of column studies also indicate the impact on the uptake of the selected ion by the presence of the other ion present in the binary- and ternary-ion systems.