Studies in Electrokinetic Migration Rates of Dyes in Sand and Clay

Self-designed electrokinetic setups were constructed to examine the differences in electromigration and electroosmotic rates in both sand and clay. Two dyes were analyzed separately to measure these phenomena within these two media types. The dyes used were a red food coloring (primary compound Allura Red) and a green food coloring (referred to as a "blue dye,"as its migrating component was C-phycocyanin (C-PC) via Spirulina Blue extract). The power supply had a 30 V output with a measured 9.36 ± 0.04 mA current (0.054 mA/cm2) output. Electromigration was readily apparent for the red dye in both sand (9.12 ± 1.57 cm/d) and clay (0.93 ± 0.16) cm/d. It was also observed for the blue dye (C-PC) in sand (7.28 ± 0.57 cm/d) but not in clay. A confirmation experiment for the blue dye in sand was performed at an identical voltage but a slightly lower current output (0.040 mA/cm2), and the migration rate was found to be similar, at 6.60 ± 0.20 cm/d. For the blue dye in clay, the migration rate proceeded toward the cathode at 0.17 cm/d. Calculations indicate this phenomenon to be due to electroosmosis but may be due to a weak electromigration of the dye in protonated form.