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Characterization of clay-based adsorbents for the removal of pentachlorophenol and other organic contaminants from water
xiv, 138 leaves : illustrations ; 28 cm.
Pentachlorophenol (PCP) is a common contaminant of groundwater. Selected clays were investigated to determine their ability to adsorb PCP. All clays were exchanged with cetylpyridinium chloride (CP) in excess of their cation exchange capacities. Preliminary studies indicated base clays did not sorb PCP well, but CP-exchanged clays adsorbed between 86-96% of the PCP over 96 h. A CP-modified clay, CP/LPHM, retained the PCP, and isothermal analyses indicated CP/LPHM had a high capacity for PCP. Groundwater from a contaminated site was used to determine the efficacy of CP/LPHM in adsorbing components of a complex mixture. A sensitive bioassay with chicken embryos showed this water to be toxic in ovo, but this toxicity was diminished with 0.5% w/w CP/LPHM treatment to levels that were not significantly different from control groups. Samples were examined by GC/MS to determine the identity and concentrations of contaminants present before and after treatment with CP/LPHM. Baseline PCP levels exceeded 10 ppm; in CP/LPHM treatment groups, PCP levels were non-detectable. Concentrations of those PAHs in the baseline analysis showed a decrease after treatment. The organoclay was immobilized to sand and packed in columns. Breakthrough capacity studies with 10 ppm PCP were performed on the sorbent, termed Claypac Immobilized Organoclay (Claypac[][][]) , and sigmoidal breakthrough curves were generated. The breakthrough capacity was reached at ~.845ml/mg sorbent with10 ppm PCP, which surpassed granulated activated carbon (GAC). To prevent desorption of CP, the base clay was immobilized to sand for Claypac Immobilized Parent Clay (Claypac[][][]). Columns were prepared with 200 mg Claypac[][][] followed by an equal weight of Claypac[][][]. Effluent from the CP/LPHM columns alone was toxic in the CP-sensitive Hydra bioassay. No adverse effects were observed with Claypac[][][] and Claypac[][][] columns. Larger columns of 100 g Claypac[][][] followed by equivalent columns of Claypac[][][] were tested at a bioremediation facility as a polishing step for effluent. Naphthalene broke through at three sampling intervals. Other PAHs broke through at some intervals, but without a pattern. PCP concentrations following treatment were below detection limits for all intervals. The columns were effective in reducing concentrations of many of the remaining PAHs below the levels of detection which improved effluent quality.
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Includes bibliographical references (leaves 105-136).