ADSORPTION OF AQUEOUS COPPER AND ZINC BY VARIOUS CLAY SUBSTRATES USING A MODIFIED COLUMN METHOD

Different soil types adsorb ions and filter solutions at different rates and strengths. In this experiment, we simulated filtration of aqueous zinc, a secondary contaminant, and copper, a primary contaminant, through kaolinite and red clay. Copper and zinc are often associated in nature and manufacturing, and they are important metals with the potential to contaminate groundwater. A modified column method was used to replicate subsurface conditions of aqueous metal adsorption by kaolinite and red clay. The starting concentrations for aqueous zinc and copper prepared from reagent grade nitrates were 9.25 + 0.01(SD) ppm and 5.11 + 0.00 ppm, respectively. Solution concentrations post filtration were determined using flame atomic absorption spectroscopy. The maximum contaminant level (MCL) for zinc in drinking water is 5 ppm according to the Environmental Protection Agency (EPA). Through this method, all of the aqueous zinc was adsorbed indicated by a value of 9.67 + 0.21 ppm in red clay, and most adsorbed by kaolinite as indicated by a value of 8.64 + 0.22 ppm. The MCL for copper in secondary drinking water is 1.3 ppm according to the EPA. The post filtration concentrations of copper in both red clay and kaolinite were below the maximum detectable limits, suggesting that both soil types adsorbed most, if not all, aqueous copper. An ANOVA was run to determine if there was significant difference in the concentration of the supernatant between soil types for zinc. The p-value for zinc adsorption was less than 0.05 indicating a significant difference between adsorption by red clay and kaolinite with red clay being more affective. Based on these results, red clay filters zinc significantly more than kaolinite, though both absorb zinc to levels below the MCL. Additionally, both red clay and kaolinite filter copper effectively to levels well below the MCL.