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The ability of portland cement to stabilize/solidify organic wastes was evaluated by conducting column leaching tests on portland cement pastes containing phenol and trich loroethylene (TCE). Synthetic solidified waste was manufactured by mixing dilute aqueous solutions of phenol and TCE with Portland Type II cement at a 0.5 liquid-to-cement ratio. The liquid consisted of either 4000 mg/L phenol or 1100 mg/L TCE in purified water. The cement was cured for 3 days and 28 days at 100% humidity at room temperature. Thirty grams of particles approximately 5 to 10 mm in diameter were placed in an enclosed leaching ap paratus. Purified water was pumped upward through the column at a rate of 0.08 to 0.18 mL/ min. Every 48 h for eight days, samples of the leachate in the collection flask and samples of the vapor in the head spaces above the collection flask and leaching column were analyzed by gas chromatography. The concentrations of phenol and TCE found in these samples were used to calculate the total mass of the organic compound which was released from the solidified waste during eight days of leaching.
An empirical mathematical model was used to predict the long-term leaching characteristics of the stabilized phenol waste. The leachability indexes calculated for phenol in cement paste cured 3 days and 28 days were 7.7 and 8.2, respectively. This index rates the relative mobility of the contaminant on a uniform scale that varies from 5 (very mobile) to 15 (immobile). Similar leachability indexes could not be calculated for cement paste containing TCE due to unquantified losses of TCE by volatilization prior to the start of the leach tests and suspected decomposition of TCE in the highly alkaline environment. Gas chromatograms of the TCE waste leachates contained unidentified peaks which were thought to represent the products of TCE decomposition.
cement stabilization, leach test, phenol, solidification, stabilization, trichloroethylene
Environmental engineer, University of New HampshireRoy F. Weston, Inc., DurhamConcord, NHNH
Professor, University of New Hampshire, Durham, NH