Static Die-away of a Nonylphenol Ethoxylate Surfactant in Estuarine Water Samples

Abstract

The static die-away of the nonylphenol ethoxylate (NPE) surfactant used to stabilize the bitumen−water emulsion in the fuel Orimulsion was studied using estuarine water samples collected at four stations in Tampa Bay, FL. Incubations were in the dark at 28 °C for 183 days. Primary degradation was complete in 4−24 days with lag periods between 0 and 12 days. The concentration of five NPE intermediate degradation products and total surfactant were monitored at 4−8-day intervals for the first 89 days and at 30-day intervals thereafter. The intermediates detected included nonylphenol diethoxylate (NP2EO) and nonylphenoxy ethoxy acetic acid (NP2EC). Much smaller amounts of nonylphenoxy acetic acid (NP1EC) and nonylphenol monoethoxylate (NP1EO) were detected. The completely deethoxylated metabolite nonylphenol (NP) was not detected. On a molar basis, NP2EC accounted for 66.0−93.3% of degradation products and for 22.7−75.6% of the starting material at the termination of the experiment. The sequence of degradatio...