INNOVATIVE OXIDATION PATHWAYS FOR THE TREATMENT OF TRADITIONAL AND EMERGING CONTAMINANTS

Mushtaque Ahmad

Three different topics related to the activation of persulfate, and the application of reactive peroxygen system for recalcitrant contaminant remediation, and regeneration of used activated carbon were studied. An introduction that covers theory and motivation for the research is presented in the first chapter. The second chapter examines the degradation of a recalcitrant fluorocarbon, perfluorooctanoic acid (PFOA), by reactive species generated through catalyzed hydrogen peroxide propagation (CHP) reactions. The results of this research demonstrate that CHP formulation is effective degrading PFOA. Although hydroxyl radical does not degrade PFOA, CHP systems are effective in treating PFOA via nucleophilic attack by superoxide and hydroperoxide. In addition, PFOA degradation products included short chain fluorocarbons, such as 2,2-difluoropropane, which is an indication of a nucleophilic attack and the generation of fluoride confirms PFOA destruction. An innovative technique for persulfate activation is discussed in the third chapter of this dissertation. The potential for glucose as a persulfate activator was investigated at both acidic pH (3) and basic pH (12.5). The results of this research demonstrate that glucose can activate persulfate in both acidic and basic pH regimes; however, the rates of oxidant and reductant generation are higher at basic pH (12.5), most likely due to the higher ionization of glucose (pKa= 12.28). The results of this research also demonstrate that depending on the pH and persulfate concentration, a minimum concentration of glucose is needed for the effective generation of oxidants and reductants. The fourth chapter examines the regeneration potential of granular activated carbon (GAC) by two superoxide systems: hydrogen peroxide-bicarbonate system, and percarbonate system. Treatment efficiency of these systems increased with increasing oxidants (hydrogen peroxide, and percarbonate) concentration. Nearly complete desorption and destruction of toluene from GAC surface was achieved by 1 M hydrogen peroxide-bicarbonate, and 1 M percarbonate system at pH 12.5. However, the desorption and destruction of octanol-1 in 1 M hydrogen peroxide-bicarbonate, and 1 M percarbonate system at pH 12.5 was < 86%. Because 1-octanol is more hydrophobic than toluene, hydrophobicity might affect the regeneration of GAC. To investigate the effect of hydrophobicity of organic contaminants on the regeneration of GAC, 3 compounds of varying degree of hydrophobicity were evaluated: toluene, naphthalene, and phenanthrene. The desorption efficiency was inversely proportional to contaminants hydrophobicity. The results of this research demonstrate that hydrogen peroxide-bicarbonate system and percarbonate system are effective in regenerating GAC and may have potential for in situ carbon regeneration in full scale systems.

INNOVATIVE OXIDATION PATHWAYS FOR THE TREATMENT OF TRADITIONAL AND EMERGING CONTAMINANTS

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