Doctor of Philosophy (PhD)
School of Plant, Environmental, and Soil Sciences
This study investigated the competitive sorption of Ni, Pb, and Zn as well as synergistic interactions between Ni and phosphate (P) in soils and Mn oxide-coated sand. During stirred-flow experiments, the sorption of heavy metal cations by Olivier soil was mutually reduced when applied simultaneously. When applied consecutively, the cation of higher affinity was able to displace the cation of lower affinity from the soil surface, however, no evidence for the reverse case was observed. A novel general exchange kinetics model was able to correctly describe such displacement. Competition between Ni and Zn mutually increased mobility in Olivier and Windsor soils. A new Freundlich-type competitive isotherm (CDI) and kinetic model (CDIT) were introduced and described the observed data well. The sorption of Ni and Zn by Mn oxide-coated sand was investigated at pH 4.0-7.0, where sorption and reaction nonequilibrium increased with increasing pH. Two novel pH-dependent isotherms were introduced and described the sorption data well. Moreover, competitive sorption kinetics were well described by two pH-dependent, multicomponent kinetic models. The sorption of Ni by Mahan and Windsor soils increased in the presence of P, and vice versa. The Freundlich and Langmuir isotherms were extended based on the assumption of the formation of a ternary complex to produce two novel multicomponent isotherms that described Ni and P sorption data well. These isotherms were incorporated into kinetic expressions and described the sorption kinetics of Ni and P in single ion and multicomponent systems. The sorption and transport of Ni and P in Mn oxide-coated sand was evaluated at pH 4.0-8.0 in both single and multicomponent systems. The presence of P substantially increased Ni sorption at pH 4.0 but had no effect at pH 8.0. The sorption of P increased in the presence of Ni across the range of pH, however, the greatest increases occurred at pH 8.0. A pH-dependent, multicomponent isotherm was introduced and provided a reasonable description of the observed sorption data, and a corresponding kinetic model was used to describe transport experiments with varying success. Overall, six novel isotherms and seven kinetic models were introduced and used to describe experimental data.
Padilla, Joshua Tyler, "Competitive Sorption and Transport of Heavy Metals in Soil and Mn Oxide-Coated Sand" (2022). LSU Doctoral Dissertations. 5790.