Surfactant-Aided Remediation of Pesticide Contamination in Soils and Transport of Soil Colloids Within Porous Media
Surfactant-aided soil remediation technologies, such as surfactant-aided soil washing and in situ surfactant-enhanced sorption zone systems, have received considerable research attention recently in remediating hydrophobic organic compound (HOC) contamination. Soil particle-size dependent sorption of surfactants and its effect on HOCs partitioning within soil-water-surfactant systems, although critical in understanding the mechanisms by which the HOCs are removed by these systems, has not been studied well. This dissertation systematically investigated the sorption behavior of three surfactants with different charge properties (TritonRTM X-100 (TX), a nonionic surfactant; linear alkylbenzene sodium (LAS); benzalkonium chloride (BC), a cationic surfactant) and two HOCs, represented by the two most commonly used hydrophobic pesticides (atrazine and diuron), onto soils and soil primary size fractions (clay (50mum) size fractions). Special attention was paid to the effect of surfactant sorption on pesticide sorption and desorption. As relevant to HOC fate and transport in soils, soil colloids transport and deposition within porous media was also examined in this study. The results showed that the surfactant and pesticide sorption in all cases were highly soil particle-size dependent. The sorption capacities of the nonionic surfactant (TX) and cationic surfactant (BC) onto the soils and their size fractions was determined by soil cation exchange capacity (CEC), while the total soil system hardness, defined as the total amount of soluble and exchangeable divalent cations (Ca2+, Mg2+) associated with the soils and the size fractions, determined the anionic surfactant (LAS) pseudo-sorption capacity. Surfactant sorption capacity determined overall treatment efficiency of surfactant-aided soil washing systems and desorption of pesticides out of the clay fractions was found to be the limiting factor in these systems. For surfactant-enhanced sorption zone the treatment efficiency can be optimized by controlling the amount of cationic surfactant sorbed onto the size fractions. Within a certain sub-saturation BC sorption range, the coarse size fractions (e.g., sand fractions) became more effective sorbent for the pesticides than the finer size fractions, resulting in more pesticide being immobilized permanently. The transport and deposition of the soil colloids are found to be very sensitive to both the species of the cations in bulk solutions and on the cation exchangeable sites on the colloidal surfaces. The results of this research serve to better select appropriate surfactants for a specific surfactant-aided soil remediation application according to soil and HOC properties, which leads to improved treatment efficiency. The findings of the soil colloid transport and deposition contribute to colloid transport theory.
- Paperback | 170 pages
- 203 x 254 x 11mm | 349g
- 02 Sep 2011
- Proquest, Umi Dissertation Publishing
- United States
- colour illustrations