“Previous studies have noted the relationship between shallow groundwater rich in sodium (Na) and bicarbonate (HCO3) and elevated levels of dissolved arsenic. However, most experimental work on arsenic adsorption in the presence of HCO3 and differing Na/Ca ratios has proven difficult to extrapolate to natural systems because of differences in tested mineral compositions and component concentrations. In this study, I performed a series of adsorption experiments using river sediments to evaluate the influence of HCO3 and monovalent/divalent cations on the extent of arsenic adsorption onto natural sediment in groundwater.
Batch adsorption (kinetics, equilibrium, and metal loading) experiments were conducted using river sediments with anions salts (0.1 or 0.01M Na HCO3, NaCl, CaCl2, or MgCl2) amended with arsenate and in some cases with natural organic matter (NOM). Arsenate [As(V)] adsorbed strongly onto sediment under all conditions, but the experiments with HCO3 increased the mobility of arsenic (i.e., less adsorption was observed) relative to systems with chloride (Cl). Systems with divalent cations (e.g., Ca or Mg) adsorbed substantially more arsenic (≥ 20%) than Na-Cl or Na- HCO3 systems. This may be attributable to the presence of ternary As(V)-divalent cation-mineral surface complexes and/or an electrostatic effect that promotes additional adsorption of arsenic. This study suggests that changes in the bulk chemistry of groundwater, such as the amount of HCO3 and the ratio of Na/Ca can measurably influence the extent of arsenic adsorption onto river sediments”--Abstract, page iii.
Borrok, David M.
Wronkiewicz, David J.
Grote, Katherine R.
Geosciences and Geological and Petroleum Engineering
M.S. in Geology and Geophysics
Missouri University of Science and Technology
ix, 64 pages
© 2022 Leticia Augusta Dos Santos Ferreira, All rights reserved.
Thesis - Open Access
Dos Santos Ferreira, Leticia Augusta, "Adsorption of arsenic onto river sediments" (2022). Masters Theses. 8085.